Genotoxic effects of nonylphenol and bisphenol A exposure in aquatic biomonitoring species: freshwater crustacean, Daphnia magna, and aquatic midge, Chironomus riparius

Multiple-biomarker approach in the assessment of bisphenol A effect on the grooved carpet clam Ruditapes decussatus (Linnaeus, 1758)

BACKGROUND

Bisphenol A (BPA), a plastic additive monomer, is among the most highly produced chemicals worldwide, and is broadly used in many industries, such as food and beverage containers, milk bottles, and paper products. Previous studies demonstrated that BPA has potential toxicity to aquatic organisms, causing endocrine disturbance and behavioural disorders. The current work aimed to determine the toxic impacts of BPA on the edible marine clam Ruditapes decussatus considering a multi-biomarker approach (mortality, biochemical studies, DNA strand breaks using comet assay, and histopathological examinations with semi-quantitative and quantitative histopathological analyses). The clams were exposed under laboratory conditions to three concentrations of BPA (0 "control", 1, and 5 µg/L) for a period of 21 days. After the exposure period, BPA impacts were assessed in the digestive gland as a versatile and environmentally relevant organ for ecotoxicological studies.

RESULTS

In BPA-treated clams, mortality (10%) occurred only at the highest BPA concentration (5 µg/L). Biochemical impairments were detected in a concentration-dependent manner as a consequence of BPA exposure. There were significant increases in malondialdehyde (MDA) and glutathione (GSH) levels, while catalase (CAT) activity was significantly reduced. Our results revealed that BPA induced neurotoxicity in R. decussatus, as evidenced by the inhibition of acetylcholinesterase (AChE) activity in a dose-dependent manner. Furthermore, DNA damage was strongly induced as BPA levels increased. Additionally, our results have been affirmed by alterations in digestive gland tissues at BPA treatments, which consequently can impair the clam's ability for food absorption; these alterations included mainly atrophic and necrotic digestive tubules, epithelial cell vacuolization, hemocyte infiltration, and intertubular fibrosis. Based on the data obtained from the semi-quantitative and quantitative histopathological analyses, the exposure of the clam's digestive gland to BPA with concentrations of 1 and 5 µg/L for 21 days showed significant histopathological alterations compared with the control clams.

CONCLUSION

The multi-biomarker approach used in the current study proved to be a useful tool for assessing the impact of diphenylmethane compounds, such as BPA. Water-borne BPA causes oxidative stress, neurotoxicity, genotoxicity, and deleterious effects on the clam digestive gland; all of these could deteriorate clam performance and health, causing tissue dysfunction.

Single-use take-away cups of paper are as toxic to aquatic midge larvae as plastic cups

Single-use plastics and food packaging are the most common items polluting the environment, commonly identified in surveys and litter monitoring campaigns. There are pushes to ban these products from production and use in different regions, and to replace them with other materials viewed as "safer" or "more sustainable". Here, we address the potential environmental impacts of take-away cups and lids used for hot and cold beverages, consisting of plastic or paper. We produced leachates from plastic cups (polypropylene), lids (polystyrene), and paper cups (lined with polylactic acid), under conditions representative of plastic leaching in the environment. The packaging items were placed and left to leach in sediment and freshwater for up to four weeks, and we tested the toxicity of contaminated water and sediment separately. We used the model aquatic invertebrate Chironomus riparius and assessed multiple endpoints both on larval stages and on emergence to the adult phase. We observed a significant growth inhibition with all the materials tested when the larvae were exposed in contaminated sediment. Developmental delays were also observed for all materials, both in contaminated water and sediment. We investigated teratogenic effects via the analysis of mouthpart deformities in chironomid larvae, and observed significant effects on larvae exposed to polystyrene lid leachates (in sediment). Finally, a significant delay in time to emergence was observed for females exposed to paper cups leachates (in sediment). Overall, our results indicate that all the tested food packaging materials can have adverse effects on chironomids. These effects can be observed from one week of material leaching in environmental conditions, and tend to increase with increasing leaching time. Moreover, more effects were observed in contaminated sediment, indicating that benthic organisms might be especially at risk. This study highlights the risk posed by take-away packaging and their associated chemicals, once discarded into the environment.

Alkylphenols cause cytotoxicity and genotoxicity induced by oxidative stress in RTG-2 cell line

Alkylphenols ethoxylates are industrial surfactants, and the release in the environmental matrices produces degraded products, of which nonylphenol (NP) and octylphenol (OP) were the most common. They can be classified as endocrine disruptors since the estrogenic potential is widely recognized, but some others toxic aspects are in discussion. This study aimed to evaluate the toxicity of NP, OP, and mixtures of both through cellular, biochemical and genetic biomarkers in fish gonadal cell line RTG-2 exposed to nominal concentrations of 0.05; 0.5; 5; 50, and 100 μg mL^-1 of each chemical and their mixtures of 0.05, 0.5; 5 μg mL^-1 concentrations. After 24 h, the cells were collected for cytotoxic (neutral red - NR; crystal violet - CV, resazurin assay - RA and lactate-dehydrogenase - LDH), antioxidant system (glutathione-s-transferase - GST; superoxide-dismutase - SOD; glutathione-peroxidase - GPx and malondialdehyde - MDA) and genotoxic assays (alkaline comet assay and Fpg-modified alkaline comet assay). The chemicals and their mixtures were cytotoxic at 50 and 100 μg mL^-1, in general aspect, but LDH showed cytotoxicity since 0.05 μg mL^-1. The GST and SOD showed an activity increase trend in most tested groups, while GPx decreased at 5 μg mL^-1 of the mixture. The MDA increase in all groups resulted in lipid peroxidation. The reactive oxygen species caused DNA damage for all groups. The tested chemicals and concentrations have been found in the freshwater systems. They can induce cell toxicity in several parameters that could impair the gonadal tissues considering the RTG-2 responses.

DNA Damage and Repair in different Tissues of Fresh Water Fish, <i>Channa punctata</i> after Acute and Subchronic Exposure to bisphenol A

The present study was conducted to investigate the genotoxic effect of Bis-Phenol A (BPA) after acute and subchronic exposure in different tissues of Channa punctata. The recovery in DNA damage was also ascertained after 30 days of cessation of exposure. Fish were exposed to different sublethal concentrations of BPA along with two controls i.e., with positive (acetone) and negative (water) controls for 96h (acute exposure) and 60 days (subchronic exposure) and after that fish were allowed to recover for 30 days in freshwater. The blood, liver, and gill tissue samples were collected at 24, 48, 72 and 96h for acute exposure and after 20, 40, and 60 days post-exposure for subchronic exposure. Exposed groups showed significantly higher DNA damage in both acute and subchronic exposure as compared to control groups. In the case of acute exposure, the highest damage was observed at 24 h of exposure followed by a decline in the value of all the parameters, while in the later hours of exposure these values further increased. On the other hand, in the case of sub-chronic exposure, the highest damage was observed after 60 days of exposure. Recovery experiment showed a decrease in the values of all the parameters studied. The result of the study clearly showed that BPA caused DNA damage in Channa punctata after acute as well as subchronic exposure.

Genotoxic potential of bisphenol A: A review

Bisphenol A (BPA), as a major component of some plastic products, is abundant environmental pollutant. Due to its ability to bind to several types of estrogen receptors, it can trigger multiple cellular responses, which can contribute to various manifestations at the organism level. The most studied effect of BPA is endocrine disruption, but recently its prooxidative potential has been confirmed. BPA ability to induce oxidative stress through increased ROS production, altered activity of antioxidant enzymes, or accumulation of oxidation products of biomacromolecules is observed in a wide range of organisms - estrogen receptor-positive and -negative. Subsequently, increased intracellular oxidation can lead to DNA damage induction, represented by oxidative damage, single- and double-strand DNA breaks. Importantly, BPA shows several mechanisms of action and can trigger adverse effects on all organisms inhabiting a wide variety of ecosystem types. Therefore, the main aim of this review is to summarize the genotoxic effects of BPA on organisms across all taxa.

Damages to biological macromolecules in gonadal subcellular fractions of scallop Chlamys farreri following benzo[a]pyrene exposure: Contribution to inhibiting gonadal development and reducing fertility

Benzo[a]pyrene (B[a]P), a representative polycyclic aromatic hydrocarbon (PAH) compound in marine ecosystem, has great potential for chronic toxicity to marine animals. It is becoming increasingly apparent that reproductive system is the major target of B[a]P, but the adverse effects of B[a]P on subcellular fractions in bivalve gonads have not been elucidated. Scallops Chlamys farreri are used as the experimental species since they are sensitive to environmental pollutants. This study was conducted to investigate how B[a]P affected the gonadal subcellular fractions, including plasma membrane, nucleus, mitochondria and microsome in scallops, and whether subcellular damages were related to reproductive toxicity. The results showed that mature gametes' counts were significantly decreased in B[a]P-treated scallops. Three biological macromolecules (viz., DNA, lipids and proteins) in gonadal subcellular fractions obtained by differential centrifugation suffered damages, including DNA damage, lipid peroxidation and protein carbonylation in B[a]P treatment groups. Interestingly, mitochondria and microsome were more vulnerable to lipid peroxidation and protein carbonylation than plasma membrane and nucleus, meanwhile males were more susceptible to DNA damage than females under B[a]P exposure. In addition, histological analysis showed that B[a]P delayed gonadal development in C. farreri. To summarize, our results indicated that B[a]P caused damages to biological macromolecules in gonadal subcellular fractions and then induced damages to gonadal tissues of C. farreri, which further inhibited gonadal development and ultimately leaded to reduction in fertility. This study firstly reports the impacts of PAHs on subcellular fractions in bivalves and their relationship with reproductive toxicity. Moreover, exposure of reproductive scallops to B[a]P leads to defects in reproduction, raising concerns on the possible long-term consequences of PAHs for natural populations of bivalves.

Bisphenol A induced toxicity in blood cells of freshwater fish Channa punctatus after acute exposure

The widespread use of bisphenol A (BPA) has led to its ubiquity in the natural environment. It is extensively incorporated into different industrial products and is associated with deleterious health effects on both public and wildlife. The current trial was conducted to determine the toxic potential of bisphenol A using various parameters viz haematological, biochemical, and cytological in freshwater fish Channa punctatus. For this purpose, fish were exposed to 1.81 mg/l (1/4 of LC₅₀) and 3.81 mg/l (1/2 of LC₅₀) of BPA along with positive (acetone) and negative controls (water) for 96 h. The blood samples were collected at 24, 48, 72, and 96 h post-exposure. Compared to the control group, fish after acute exposure to BPA showed a significant decrease in HB content, number of red blood cells, PCV values whereas a significant increase in WBCs count was recorded with an increase in the exposure period. Besides, oxidative stress (determined as malondialdehyde content) increased as BPA concentration increased. Further, the activity of different antioxidant enzymes like catalase, and superoxide dismutase decreased significantly after treatment. Results also showed significantly increased frequency of morphological alterations, nuclear changes, and increased DNA damage potential of BPA in red blood cells. Further structural analysis of erythrocytes in maximally damaged group using Scanning Electron Microscopy was performed. The study concludes that BPA exhibits genotoxic activity and oxidative stress could be one of the mechanisms leading to genetic toxicity.

Controlling micropollutants in tertiary municipal wastewater by O3/H2O2, granular biofiltration and UV254/H2O2 for potable reuse applications

A comprehensive pilot study was carried out to experimentally assess the potential of newly developed treatment trains integrating two-stage AOPs and biofiltration to reach potable reuse water quality standards from municipal wastewater. The processes consisted of a two-stage AOPs with (carbon or limestone) biofiltration, the first AOP (O₃/H₂O₂) serving as pre-treatment to biofiltration and the second AOP (UV₂₅₄/H₂O₂) serving as post-biofiltration finishing step to ensure advanced disinfection. A comprehensive monitoring campaign was put in place resulting from the combination of targeted, non-targeted and suspect screening measurements. It was found that 13 organic micropollutants were detected from a list of 219 suspects although at ng/L level only. For the treatment conditions piloted in this study (O₃ = 13 ± 0.5 mg/L, H₂O₂ = 11 ± 0.4 mg/L for the O₃/H₂O₂ process, and UV = 410 ± 63.5 mJ/cm², H₂O₂ = 5 mg/l for the UV₂₅₄/H₂O₂ process), it was possible to estimate the overall removal efficacy for each unit process, which was found to follow this order: RO (99%)  > BAC (87%) > O₃-H₂O₂ (78%)  > BAL (67%)  > UV/H₂O₂ (43%)  > AOP contact chamber (19%)  > UF(0%), with the treatment train integrating two AOPs and granular biofiltration with activated carbon (O₃/H₂O₂ + BAC + UV₂₅₄/H₂O₂) showing superior performance with a 99% abatement in total micropollutants. No ecotoxicologically-positive response was generally observed for any of the effluent samples from the tested trains, even when pre-concentration factors up to 100-1000 times were employed to increase the sensitivity of the bioassay methods.

Potential Health Risks Linked to Emerging Contaminants in Major Rivers and Treated Waters

The presence of endocrine-disrupting chemicals (EDCs) in our local waterways is becoming an increasing threat to the surrounding population. These compounds and their degradation products (found in pesticides, herbicides, and plastic waste) are known to interfere with a range of biological functions from reproduction to differentiation. To better understand these effects, we used an in silico ontological pathway analysis to identify the genes affected by the most commonly detected EDCs in large river water supplies, which we grouped together based on four common functions: Organismal injuries, cell death, cancer, and behavior. In addition to EDCs, we included the opioid buprenorphine in our study, as this similar ecological threat has become increasingly detected in river water supplies. Through the identification of the pleiotropic biological effects associated with both the acute and chronic exposure to EDCs and opioids in local water supplies, our results highlight a serious health threat worthy of additional investigations with a potential emphasis on the effects linked to increased DNA damage.

Amitraz toxicity to the midge Chironomus riparius: Life-history and biochemical responses

Acute and chronic toxicity of the formamidine pesticide amitraz to the midge Chironomus riparius was assessed using conventional ecotoxicological tests and biochemical approaches (biomarkers). Amitraz is mainly used as an ectoparasiticide in veterinary medicine, but also in agriculture and apiculture. However, information of amitraz toxicity to non-target invertebrates is limited. Besides the impairment of developmental and emergence rates (reduced larval growth, emergence, and delayed development time) caused by chronic exposure to amitraz, acute exposures induced alterations in the antioxidant enzymes glutathione peroxidase (GPx) and catalase (CAT), and in energetic metabolism biomarkers, lactate dehydrogenase (LDH) and electron transport system (ETS) activities. Moreover, lipid peroxidation (LPO) increased by amitraz exposure. Our results reveal potential secondary effects of amitraz to invertebrates and biomarkers that may aid in the interpretation of sub-lethal toxic responses to amitraz. These results add information concerning the potential outcomes of amitraz exposure to freshwater invertebrates underlining the importance of risk assessment studies of formamidine pesticides.

Evaluation of 4-nonylphenol and bisphenol A toxicity using multiple molecular biomarkers in the water flea Daphnia magna

Alkylphenols are well-known endocrine disruptors and may cause developmental and reproductive disorders in aquatic organisms. Daphnia magna is commonly used in ecotoxicological studies as a promising model species to investigate the effects of endocrine distruptors. In the present study, transcriptional modulation of eleven potential molecular indicators related to detoxification, antioxidant, development, and cellular stress was analyzed in D. magna exposed to different concentrations of bisphenol A (BPA) and 4-nonylphenol (4-NP) for 24 h and 48 h, using real-time qPCR. A hierarchical clustering analysis was applied to investigate relations among molecular markers depending on the compound, exposure duration, and concentration. Our findings suggested that GSH-related systems and stress proteins may be involved in cellular defense against BPA and 4-NP-mediated toxicity with different modes of action. Furthermore, these compounds may interrupt molting and reproduction in daphnids. In particular, D. magna GSH-related genes seem to be strongly affected by 4-NP exposure, indicating their potential as molecular biomarkers.

Genotoxic effects of combined multiple stressors on Gammarus locusta haemocytes: Interactions between temperature, pCO2 and the synthetic progestin levonorgestrel

Climate change and pharmaceutical contamination are two priority research topics due to their impacts in the aquatic ecosystems and in the food chain structure. In the bottom of many food chains are the invertebrates, like the amphipods, which are important environmental and ecotoxicological models. In this study, we combined the increase of temperature [ambient and warming temperature], pCO₂ [normocapnia and hypercapnia] and the synthetic progestin levonorgestrel (LNG) [environmentally relevant concentration (10 ng L^-1) and 100-fold higher (1000 ng L^-1)] to evaluate the genotoxic effects on the amphipod Gammarus locusta haemocytes, using the comet assay technique. Additionally, the study examined protective/potentiating effects of the three tested factors against hydrogen peroxide (H₂O₂)-induced DNA damage in haemocytes after ex vivo exposure. Our data revealed no significant effects of any of the three stressors on DNA damage of G. locusta haemocytes or protection against H₂O₂-induced DNA damage after twenty-one days exposure. Only a significant effect of the solvent was visible, since it was able to induce higher DNA damage (i.e. strand breaks) on exposed individuals. On the other hand, LNG exposure seemed to induce a slight increase of DNA damage after H₂O₂ exposure. Our findings suggest that more short-term studies to conclude about the genotoxicity and/or protective effects of the stress factors in G. locusta should be made, attending to the fast turnover rate of repairing cells that could have masked impacts seen only after the end of the experiment.

Immunotoxic effects of 4-nonylphenol on Clarias gariepinus: Cytopathological changes in hepatic melanomacrophages

Melanomacrophage centres (MMCs) play a key role in the immune response in fish. They are considered sensitive bio-monitoring structures with roles in the assessment of toxicant impacts. The aim of this study was to examine the potential histopathological effect of 4-nonylphenol (4-NP) on hepatic MMCs in Clarias gariepinus. To achieve this objective, adult male fish were divided randomly and equally into two groups: a control group and a group that was exposed to 4-NP (dissolved in water at a dose of 0.1 mg/L) for 21 days. The 4-NP-intoxicated hepatic MMCs contained numerous necrotic macrophages. Superoxide dismutase 2 was immuno-expressed in the hepatic MMCs in both groups, with no significant difference. Histomorphometric examination revealed that the sizes and numbers of MMCs were dramatically higher in the livers of 4-NP-exposed C. gariepinus than in control fish. Following 4-NP challenge, in the liver, the abundance of lipofuscin and haemosiderin pigments increased, and single-pigmented macrophages, aggregated groups of deformed red blood cells (RBCs) and macrophages were present near blood vessels and hepatic sinusoids. These results reveal that 4-NP exerts immunological effects on hepatic MMCs in C. gariepinus and support the utility of MMCs as a cytological biomarker for aquatic exposure to 4-NP.

Integrated approach of eco-epigenetics and eco-metabolomics on the stress response of bisphenol-A exposure in the aquatic midge Chironomus riparius

The stress response mechanisms of Bisphenol A (BPA), an endocrine disrupting compound, remain to be elucidated. In this study, we explored the effects of BPA on the non-biting midge Chironomus riparius through basic ecotoxicity assays, DNA damage (comet assay), eco-epigenetics (global DNA and histone methylations) and non-targeted global metabolomics (NMR based) approaches. The reproduction failure, increase in DNA damage, global DNA hyper-methylation, and increased global histone modification (H3K36) status were evident due to BPA exposure at 10% lethal concentration (LC₁₀: 1 mg/L, based on 48 h acute toxicity). Moreover, non-targeted global metabolomics followed by pathway analysis identified alterations of energy metabolism, amino acids, and methionine metabolisms etc. Most importantly, we found a potential cross-talk between altered epigenetics and metabolites, such as, increase in methionine and o-phosphocholine metabolites corresponds with the phenomena of global hyper-methylation in DNA and H3K36 mark. Overall, our results suggests that the crosstalk of global metabolomics and epigenetic modification was fundamental of the underlying mechanisms in BPA-induced stress response in C. riparius.

Oxidative stress and genotoxic effect of deltamethrin exposure on the Chinese mitten crab, Eriocheir sinensis

The oxidative stress and genotoxic effect of deltamethrin on the Chinese mitten crab Eriocheir sinensis were assessed using several commonly used biomarkers in this study. The results showed that the 48 h and 96 h LC₅₀ values of deltamethrin to E. sinensis were 2.319 and 1.164 μg/L, respectively, and the safe concentration was 0.293 μg/L. According to these results, deltamethrin was applied at concentrations of 1/16, 1/8, 1/4, 1/2 and 1/1 96 h LC₅₀ for 8 d in an exposure experiment. The activity of superoxide dismutase (SOD) increased remarkably at 1 d, but decreased at 4 d in concentration group of 1/4, 1/2 and 1/1 LC50, whereas catalase (CAT) activity decreased during the exposure. The total antioxidant capacity (T-AOC) at the concentrations of 1/4, 1/8 and 1/16 LC50 increased significantly at 1 d or 2 d respectively, whereas it decreased gradually until the end of the experiment under the concentrations above 1/4 LC50. The oxidative stress products malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) in serum increased significantly at each concentration except H₂O₂ at concentration of 1/16 LC50. Additionally, the micronucleus (MN) frequency of haemocytes increased at the concentrations of 1/4, 1/2 and 1/1 LC50 throughout the exposure, similar trend was observed in the comet ratio and percentage of tail-DNA (%DNA) in haemocytes. These results revealed that deltamethrin had a prominent toxic effect on E. sinensis based on antioxidative response inhibition and genotoxicity that was possibly due to lipid peroxidation (LPO) induced by oxidative products, and the accumulation of peroxide, even under a sublethal concentration.

The possible DNA damage induced by environmental organic compounds: The case of Nonylphenol

Human impact on the environment leads to the release of many pollutants that produce artificial compounds, which can have harmful effects on the body's endocrine system; these are known as endocrine disruptors (EDs). Nonylphenol (NP) is a chemical compound with a nonyl group that is attached to a phenol ring. NP-induced H₂AX is a sensitive genotoxic biomarker for detecting possible DNA damage; it also causes male infertility and carcinogenesis. We attempt to comprehensively review all the available evidence about the different ways with descriptive mechanisms for explaining the possible DNA damage that is induced by NP. We systematically searched several databases, including PubMed, Scopus, Web of Science, and gray literature, such as Google Scholar by using medical subheading (MeSH) terms and various combinations of selected keywords from January 1970 to August 2017. The initial search identified 62,737 potentially eligible studies; of these studies, 33 were included according to the established inclusion criteria. Thirty-three selected studies, include the topics of animal model (n = 21), cell line (n = 6), human model (n = 4), microorganisms (n = 1), solid DNA (n = 1), infertility (n = 4), apoptosis (n = 6), and carcinogenesis (n = 3). This review highlighted the possible deleterious effects of NP on DNA damage through the ability to produce ROS/RNS. Finally, it is significant to observe caution at this stage with the continued use of environmental pollutants such as NP, which may induce DNA damage and apoptosis.

Genotoxic effects of vinclozolin on the aquatic insect Chironomus riparius (Diptera, Chironomidae)

Vinclozolin (Vz) is a pollutant found in aquatic environments whose antiandrogenic effects in reproduction are well known in mammals. Although its reproductive effects have been less studied in invertebrates, other effects, including genotoxicity, have been described. Therefore, in this work, we studied the genotoxic effects of Vz in the freshwater benthic invertebrate Chironomus riparius. DNA damage was evaluated with the comet assay (tail area, olive moment, tail moment and % DNA in tail), and the transcriptional levels of different genes involved in DNA repair (ATM, NLK and XRCC1) and apoptosis (DECAY) were measured by RT-PCR. Fourth instar larvae of C. riparius, were exposed to Vz for 24 h at 20 and 200 μg/L. The Vz exposures affected the DNA integrity in this organism, since a dose-response relationship occurred, with DNA strand breaks significantly increased with increased dose for tail area, olive moment and tail moment parameters. Additionally, the lower concentration of Vz produced a significant induction of the transcripts of three genes under study (ATM, NLK and XRCC1) showing the activation of the cellular repair mechanism. In contrast, the expression of these genes with the highest concentration were downregulated, indicating failure of the cellular repair mechanism, which would explain the higher DNA damage. These data report for the first time the alterations of Vz on gene transcription of an insect and confirm the potential genotoxicity of this compound on freshwater invertebrates.

Individual and binary mixture effects of bisphenol A and lignin-derived bisphenol in Daphnia magna under chronic exposure

In recent years, many new chemicals have been synthesized from biomass with an aim for sustainable development by replacing the existing toxic chemicals with those having similar properties and applications. However, the effects of these new chemicals on aquatic organisms remain relatively unknown. In this study, the effects of bisphenol A (BPA) and lignin-derived bisphenol (LD-BP, a BPA analogue) on Daphnia magna were evaluated. The animals were exposed to BPA, LD-BP, and their binary mixture at concentrations (2-2000 μg L^-1) for 21 days. The expression of various biochemical markers and the effects on growth, molting, and reproduction parameters were examined. The results showed that the weight of daphnids significantly increased after exposure to BPA, LD-BP, and the binary mixture relative to that of the control animals. The activity of superoxide dismutase was significantly inhibited by LD-BP and the binary mixture. At the highest exposure concentration of the binary mixture, the activities of acetylcholinesterase and α-glucosidase, fecundity, and the number of neonates per brood were significantly altered. Our results showed that the effects of BPA and LD-BP on D. magna were generally comparable, except for the effect on the weight at their environmentally relevant concentrations (e.g., <20 μg L^-1). The effects on the reproduction of D. magna could be mainly due to the shift in energy redistribution under BPA and LD-BP exposures. Our results implied that exposures to both BPA and LD-BP could potentially cause deleterious effects at the population level in D. magna.

Effects of glyphosate on immune responses and haemocyte DNA damage of Chinese mitten crab, Eriocheir sinensis

As a broad-spectrum organophosphorus herbicide, glyphosate is widely utilized around the world. The toxic effects of glyphosate on Chinese mitten crab, Eriocheir sinensis, were assessed using immunotoxicity and genotoxicity biomarkers in this study. The results showed that 24 h and 96 h LC50 values of glyphosate for E. sinensis were estimated as 461.54 and 97.89 mg/L, respectively, and the safe concentration was 4.4 mg/L. According to the results above, glyphosate was applied at concentrations of 0, 4.4, 9.8, 44 and 98 mg/L, for 96 h in the exposure experiment. Total haemocyte count (THC) and percentage of granulocytes decreased significantly following 6 h exposure to each concentration of glyphosate and tended to gradually stabilize after 12 h except in 4.4 mg/L, which rapidly recovered to a normal level in 12 h. Phagocytic activity in all treatments decreased dramatically at 6 h and maintained stability until the 96-h mark. Comet tail has been observed early at 24 h in each treatment, and the comet ratio and percentage of DNA (% DNA) in the tail increased as the exposure experiment progressed. Immune-related enzyme activity varied during the experiment. Acid phosphatase (ACP) and alkaline phosphatase (AKP) activities in 44 and 98 mg/L treatments decreased significantly after 48 h exposure, while AKP activities in all concentrations increased markedly at the beginning of exposure. The superoxide dismutase (SOD) and peroxidase (POD) activities increased significantly after 6 h exposure to 44 and 98 mg/L of glyphosates but decreased at 24 h. In addition, the β-glucuronidase (β-GD) activities in the 9.8, 44 and 98 mg/L groups, increased after 6-h exposure and were significantly higher than those in the control at 96 h. These results indicated that glyphosate has evident toxic effect on E. sinensis by immune inhibition that is possibly due to the haemocyte DNA damage and a sharp decline in haemocyte numbers, which subsequently induced changes in activities of immune-related enzymes and haemocyte phagocytosis.

An insight into the genotoxicity assessment studies in dipterans

The dipterans have been widely utilized in genotoxicity assessment studies. Short life span, easy maintenance, production of large number of offspring in a single generation and the tissues with appropriate cell populations make these flies ideal for studies associated to developmental biology, diseases, genetics, genetic toxicology and stress biology in the group. Moreover, their cosmopolitan presence makes them suitable candidate for ecological bio-monitoring. An attempt has been made in the present review to reveal the significance of dipteran flies for assessing alterations in genetic content through various genotoxicity biomarkers and to summarize the gradual advancement in these studies. Recent studies on genotoxicity assays in dipterans have opened up a broader perspective for DNA repair related mechanistic studies, pre-screening of chemicals and environmental bio-monitoring. Studies in dipterans, other than Drosophila may be helpful in using them as an alternative model system for assessment of genotoxicity, especially at the gene level and further extension of these studies give a future insight to develop new strategies for maintaining environment friendly limits of the toxicants.

Bi-directional effects of vitamin B12 and methotrexate on Daphnia magna fitness and genomic methylation

Here we interrogated, using three separate but complementary experimental approaches, the impact of vitamin B12 availability and methotrexate exposure on Daphnia magna, which we hypothesised should have an opposite effect on One carbon metabolism (OCM). OCM is a vital biological process supporting a variety of physiological processes, including DNA methylation. Contrary to mammalian models, this process remains largely unexplored in invertebrates. The purpose of this study was to elucidate the impact of OCM short-term alteration on the fitness and epigenome of the keystone species, Daphnia. We used maternal age at reproduction, brood size and survival rates in combination with DNA methylation sensitive comet assay to determine the effects of vitamin B12 or MTX on fitness and the epigenome. Vitamin B12 had a positive influence on Daphnia fitness and we provide evidence demonstrating that this may be associated with an increased level of genome-wide DNA methylation. Conversely, exposing D. magna to MTX negatively influenced the fitness of the animals and was associated with loss of global DNA methylation, translating in decreased fitness. These results highlight the potential importance of OCM in invertebrates, providing novel evidence supporting a potential role for epigenetic modifications to the genome in D. magna environmental adaptability.

Evaluation of toxic and genotoxic potential of a wet gas scrubber effluent obtained from wooden-based biomass furnaces: A case study in the red ceramic industry in southern Brazil

Red ceramic industry in southern Brazil commonly uses wood biomass as furnace fuel generating great amounts of gas emissions and ash. To avoid their impact on atmospheric environment, wet scrubbing is currently being applied in several plants. However, the water leachate formed could be potentially toxic and not managed as a common water-based effluent, since the resulting wastewater could carry many toxic compounds derived from wood pyrolysis. There is a lack of studies regarding this kind of effluent obtained specifically and strictly from wooden-based biomass furnaces. Therefore, we conducted an evaluation of toxic and genotoxic potentials of this particular type of wet gas scrubber effluent. Physical-chemical analysis showed high contents of several contaminants, including phenols, sulphates and ammoniacal nitrogen, as well as the total and suspended solids. The effluent cause significant toxicity towards microcrustacean Artemia sp. (LC50 = 34.4%) and Daphnia magna (Toxicity Factor = 6 on average) and to higher plants (Lactuca sativa L. and Allium cepa L.) with acute and sub-acute effects in several parameters. Besides, using plasmid DNA, significant damage was observed in concentrations 12.5% and higher. In cellular DNA, concentrations starting from 12.5% and 6.25% showed significant increase in Damage Index (DI) and Damage Frequency (DF), respectively. The results altogether suggest that the effluent components, such phenols, produced by wood combustion can be volatilized, water scrubbed, resulting in a toxic and genotoxic effluent which could contaminate the environment.

Polybrominated diphenyl ethers (PBDEs) effects on Chironomus sancticaroli larvae after short-term exposure

In-vivo effects of polybrominated diphenyl ethers (PBDEs) containing 3, 4 and 5 bromine atoms were tested on fourth-instar larvae of Chironomus sancticaroli (Diptera: Chironomidae) after 48h of exposure, by measuring the activity of the acetyl cholinesterase, alpha and beta esterases and glutathione S-transferase. The PBDE congeners 2,2',4-triBDE (BDE-17), 2,2',4,4'-tetraBDE (BDE-47) and 2,2',4,4',5-pentaBDE (BDE-99) were evaluated at 0.5, 1.0, 2.0 and 3.0ngmL^-1. Acetyl cholinesterase activity decreased significantly (p≤0.05) at all evaluated concentrations of the three PBDE congeners, except for larvae exposed to BDE-17 at 1.0 and 2.0ngmL^-1. The significant inhibition of acetyl cholinesterase activity ranged from 18% (BDE-47 at 0.5ngmL^-1) to 72% (BDE-47 at 2.0ngmL^-1). The enzymes alpha and beta esterase were also affected by the three congeners, reducing their activity from 14% (BDE-99 at 1.0ngmL^-1) to 52% (BDE-47 at 2.0ngmL^-1) and from 7% (BDE-99 at 2.0ngmL^-1) to 34% (BDE-47 at 3.0ngmL^-1) respectively. Substantial increments in glutathione S-transferase activity were similarly observed, varying from 138% (BDE-99 2.0 at ng mL^-1) to 346% (BDE-17 at 1.0ngmL^-1). DNA strand breaks were detected exclusively in larvae exposed to BDE-99 at 2.0 and 3.0ngmL^-1 (H=11.7, p=0.019). These results showed that C. sancticaroli larvae were sensitive to the PBDEs treatments under the experimental conditions.

Whole-organism and biomarker endpoints in Daphnia magna show uncoupling of oxidative stress and endocrine disruption in phenolic derivatives

During the past century, the amount of chemicals released into water bodies has increased, with particular emphasis being attributed to xenobiotics with endocrine disruption properties and/or pro-oxidant effects. Among these, it is possible to identify a specific chemical class, alkylphenols, which are of widespread use, and include a variety of chemicals with multiple uses. Bisphenol A is an important chemical used in industrial production of plastics, and has been extensively described as an endocrine disruptor. Paracetamol is a pharmaceutical compound used in human medicine, known for its therapeutic action but also for its evident pro-oxidant features. Additionally, previous studies have suggested that paracetamol may also exert endocrine disruption. The main goal of this study was to assess the effects of both paracetamol and bisphenol A as endocrine disruptors, and as promoters of oxidative stress and damage, on the freshwater microcrustacean Daphnia magna. The obtained results showed that bisphenol A was capable of altering population traits of exposed organisms, by impairing molting. On the contrary, paracetamol was not causative of any significant change in this parameter, despite having caused extensive oxidative stress.

Toward the Design of Less Hazardous Chemicals: Exploring Comparative Oxidative Stress in Two Common Animal Models

Sustainable molecular design of less hazardous chemicals presents a potentially transformative approach to protect public health and the environment. Relationships between molecular descriptors and toxicity thresholds previously identified the octanol-water distribution coefficient, log D, and the HOMO-LUMO energy gap, ΔE, as two useful properties in the identification of reduced aquatic toxicity. To determine whether these two property-based guidelines are applicable to sublethal oxidative stress (OS) responses, two common aquatic in vivo models, the fathead minnow (Pimephales promelas) and zebrafish (Danio rerio), were employed to examine traditional biochemical biomarkers (lipid peroxidation, DNA damage, and total glutathione) and antioxidant gene activation following exposure to eight structurally diverse industrial chemicals (bisphenol A, cumene hydroperoxide, dinoseb, hydroquinone, indene, perfluorooctanoic acid, R-(-)-carvone, and tert-butyl hydroperoxide). Bisphenol A, cumene hydroperoxide, dinoseb, and hydroquinone were consistent inducers of OS. Glutathione was the most consistently affected biomarker, suggesting its utility as a sensitivity response to support the design of less hazardous chemicals. Antioxidant gene expression (changes in nrf2, gclc, gst, and sod) was most significantly (p < 0.05) altered by R-(-)-carvone, cumene hydroperoxide, and bisphenol A. Results from the present study indicate that metabolism of parent chemicals and the role of their metabolites in molecular initiating events should be considered during the design of less hazardous chemicals. Current empirical and computational findings identify the need for future derivation of sustainable molecular design guidelines for electrophilic reactive chemicals (e.g., SN2 nucleophilic substitution and Michael addition reactivity) to reduce OS related adverse outcomes in vivo.

Prediction and assessment of ecogenotoxicity of antineoplastic drugs in binary mixtures

The combined genotoxic effects of four anticancer drugs (5-fluorouracil [5-FU], cisplatin [CDDP], etoposide [ET], and imatinib mesylate [IM]) were studied testing their binary mixtures in two crustaceans that are part of the freshwater food chain, namely Daphnia magna and Ceriodaphnia dubia. Genotoxicity was assessed using the in vivo comet assay. Assessment was based on two distinct effect sizes determined from dose-response experiments. Doses for single and combined exposures expected to result in these effect sizes were computed based on Bliss independence as reference model. Statistical comparison by analysis of variance of single and combined toxicities allowed accepting or rejecting the independency hypothesis. The results obtained for D. magna showed independent action for all mixtures except for IM+5-FU that showed an antagonistic interaction. In C. dubia, most mixtures had antagonist interactions except IM+5-FU and IM+CDDP that showed Bliss independence. Despite the antagonistic interactions, our results demonstrated that combinations of anticancer drugs could be of environmental concern because effects occur at very low concentrations that are in the range of concentrations encountered in aquatic systems.

Effects of nonylphenol on key hormonal balances and histopathology of the endangered Caspian brown trout (Salmo trutta caspius)

Endocrine disruptor chemicals (EDCs) potentially pose a hazard to endangered species. Evaluation of the sensitivity of these species to EDCs could be helpful for protecting their populations. So, the present study investigated the adverse effects of nonylphenol, an EDC, on the endocrine hormones and histopathology of male and female juvenile Caspian brown trout (Salmo trutta caspius) following 21 days of exposure to nominal concentrations of 1, 10 and 100 μg/l. The results showed that the HSI and plasma total calcium of male and female fishes exposed to 100 μg/l nonylphenol were significantly increased compared with the control groups (P<0.001). The male plasma T3 level was significantly decreased in 10 (P<0.01) and 100 (P<0.001) μg/l nonylphenol. The female T3 level increased in 1 μg/l nonylphenol concentration (P<0.05). The plasma T4 of males showed significant elevation in fishes exposed to 100 μg/l nonylphenol (P<0.05), but no change for females in any of treatment groups relative to controls (P>0.05). No significant effect of nonylphenol exposure was observed on male plasma TSH levels (P>0.05), whereas, in females, nonylphenol at all concentrations significantly reduced TSH levels. A bell-shaped response was observed in male and female plasma GH levels. Moreover, various histopathological lesions were observed in gill and intestine tissues of fishes exposed to different nonylphenol concentrations. These results demonstrate the high sensitivity of this endangered species to even environmentally relevant concentrations of nonylphenol. Furthermore, Caspian brown trout could be used as bioindicators reflecting the toxicity of nonylphenol.

Genotoxicity assessment of membrane concentrates of landfill leachate treated with Fenton reagent and UV-Fenton reagent using human hepatoma cell line

Membrane concentrates of landfill leachates contain organic and inorganic contaminants that could be highly toxic and carcinogenic. In this paper, the genotoxicity of membrane concentrates before and after Fenton and UV-Fenton reagent was assessed. The cytotoxicity and genotoxicity was determined by using the methods of methyltetrazolium (MTT), cytokinesis-block micronucleus (CBMN) and comet assay in human hepatoma cells. MTT assay showed a cytotoxicity of 75% after 24h of exposure to the highest tested concentration of untreated concentrates, and no cytotoxocity for UV-Fenton and Fenton treated concentrates. Both CBMN and comet assays showed increased levels of genotoxicity in cells exposed to untreated concentrates, compared to those occurred in cells exposed to UV-Fenton and Fenton reagent treated concentrates. There was no significant difference between negative control and UV-Fenton treated concentrates for micronucleus and comet assay parameters. UV-Fenton and Fenton treatment, especially the former, were effective methods for degradation of bisphenol A and nonylphenol in concentrates. These findings showed UV-Fenton and Fenton reaction were effective methods for treatment of such complex concentrates, UV-Fenton reagent provided toxicological safety of the treated effluent, and the genotoxicity assays were found to be feasible tools for assessment of toxicity risks of complex concentrates.

Metabolomics reveals energetic impairments in Daphnia magna exposed to diazinon, malathion and bisphenol-A

(1)H nuclear magnetic resonance (NMR)-based metabolomics was used to study the response of Daphnia magna to increasing sub-lethal concentrations of either an organophosphate (diazinon or malathion) or bisphenol-A (BPA). Principal component analysis (PCA) of (1)H NMR spectra were used to screen metabolome changes after 48h of contaminant exposure. The PCA scores plots showed that diazinon exposures resulted in aberrant metabolomic profiles at all exposure concentrations tested (0.009-0.135 μg/L), while for malathion the second lowest (0.08μg/L) and two highest exposure concentrations (0.32μg/L and 0.47μg/L) caused significant shifts from the control. Individual metabolite changes for both organophosphates indicated that the response to increasing exposure was non-linear and described perturbations in the metabolome that were characteristic of the severity of exposure. For example, intermediate concentrations of diazinon (0.045μg/L and 0.09μg/L) and malathion (0.08μg/L) elicited a decrease in amino acids such as leucine, valine, arginine, glycine, lysine, glutamate, glutamine, phenylalanine and tyrosine, with concurrent increases in glucose and lactate, suggesting a mobilization of energy resources to combat stress. At the highest exposure concentrations for both organophosphates there was evidence of a cessation in metabolic activity, where the same amino acids increased and glucose and lactate decreased, suggesting a slowdown in protein synthesis and depletion of energy stocks. This demonstrated a similar response in the metabolome between two organophosphates but also that intermediate and severe stress levels could be differentiated by changes in the metabolome. For BPA exposures, the PCA scores plot showed a significant change in metabolome at 0.1mg/L, 1.4mg/L and 2.1mg/L of exposure. Individual metabolite changes from 0.7 to 2.1mg/L of BPA exposure showed increases in amino acids such as alanine, valine, isoleucine, leucine, arginine, phenylalanine and tyrosine. These metabolite changes were correlated with decreases in glucose and lactate. This pattern of response was also seen in the highest organophosphate exposures and suggested a generalized stress response that could be related to altered energy dynamics in D. magna. Through studying increasing exposure responses, we have demonstrated the ability of metabolomics to identify discrete differences between intermediate and severe stress, and also to characterize how systemic stress is manifested in the metabolome.

The Comet assay in insects--Status, prospects and benefits for science

The Comet assay has been recently adapted to investigate DNA damage in insects. The first reports of its use in Drosophila melanogaster appeared in 2002. Since then, the interest in the application of the Comet assay to studies of insects has been rapidly increasing. Many authors see substantial potential in the use of the Comet assay in D. melanogaster for medical toxicology studies. This application could allow the testing of drugs and result in an understanding of the mechanisms of action of toxins, which could significantly influence the limited research that has been performed on vertebrates. The possible perspectives and benefits for science are considered in this review. In the last decade, the use of the Comet assay has been described in insects other than D. melanogaster. Specifically, methods to prepare a cell suspension from insect tissues, which is a difficult task, were analyzed and compared in detail. Furthermore, attention was paid to any differences and modifications in the research protocols, such as the buffer composition and electrophoresis conditions. Various scientific fields in addition to toxicological and ecotoxicological research were considered. We expect the Comet assay to be used in environmental risk assessments and to improve our understanding of many important phenomena of insect life, such as metamorphosis, molting, diapause and quiescence. The use of this method to study species that are of key importance to humans, such as pests and beneficial insects, appears to be highly probable and very promising. The use of the Comet assay for DNA stability testing in insects will most likely rapidly increase in the future.

Eco-genotoxicity of six anticancer drugs using comet assay in daphnids

The eco-genotoxicity of six anti-neoplastic drugs, 5-fluorouracil, capecitabine, cisplatin, doxorubicin, etoposide, and imatinib, belonging to five classes of anatomical therapeutic classification (ATC), was studied applying the in vivo comet assay on cells from whole organisms of Daphnia magna and Ceriodaphnia dubia. For the first time, this test was performed in C. dubia. In addition, to have a wider genotoxic/mutagenic profile of the anticancer drugs selected, SOS chromotest and Salmonella mutagenicity assay were performed. The comet results showed that all drugs induced DNA damage, in both Cladocerans, with environmental concern; indeed Doxorubicin induced DNA damage in the order of tens of ng L(-1) in both crustaceans, as well as 5-flurouracil in C. dubia and cisplatin in D. magna. In the SOS Chromotest all drugs, except imatinib, were able to activate the repair system in Escherichia coli PQ37 while in the Salmonella mutagenicity assay, doxorubicin was the only drug able to cause direct and indirect frameshift and base-pair substitution mutations. Comet assay was the most sensitive tool of genotoxic exposure assessment, able to detect in vivo the adverse effects at concentration lower than those evaluated in vitro by bacterial assays.

Monitoring of genotoxicity in marine zooplankton induced by toxic metals in Ennore estuary, Southeast coast of India

The present study provides preliminary in-situ data on genetic integrity of marine zooplankton. Paracalanus parvus, Oithona rigida and Euterpina acutifrons were collected during four different seasons (summer, pre-monsoon, monsoon and post-monsoon) from 2011 to 2012 in Ennore and Kovalum estuaries. DNA damage levels in different zooplankton were analyzed by comet assay and were correlated with different environmental stressors. Spatial and temporal variations in DNA damage was observed in all the species. Zooplankton from Ennore estuary showed significantly lower genetic integrity. Particulate, sediment, and zooplankton fractions of Pb, Ni, Cu, Cr and Co were associated with high DNA damage during the period of lowest pH, salinity and dissolved oxygen. Zn and Cd showed lower genotoxic impact than the other metals. Feeding modes strongly influenced the genetic integrity in the zooplankton species studied. These results support the use of comet assay as a tool in effectively monitoring genotoxicity in marine plankton communities.

Comet Assay on Daphnia magna in eco-genotoxicity testing

Detection of potentially hazardous compounds in water bodies is a priority in environmental risk assessment. For the evaluation and monitoring of water quality, a series of methodologies may be applied. Among them, the worldwide used toxicity tests with organisms of the genus Daphnia is one of the most powerful. In recent years, some attempts were made to utilize Daphnia magna in genotoxicity testing as many of the new environmental contaminants are described as DNA-damaging agents in aquatic organisms. The aim of this research was to develop a highly standardized protocol of the Comet Assay adapted for D. magna, especially regarding the isolation of cells derived from the same tissue (haemolymph) from newborn organisms exposed in vivo. Several methods for haemolymph extraction and different Comet Assay parameters were compared. Electrophoretic conditions were adapted in order to obtain minimum DNA migration in cells derived from untreated organisms and, at the same time, maximum sensitivity in specimens treated with known genotoxicants (CdCl2 and H2O2). Additional tests were performed to investigate if life-history traits of the cladoceran (such as the age of adult organisms that provide newborns, the clutch size of origin, the number of generations reared in standard conditions) and the water composition as well, might influence the response of the assay. This study confirms the potential application of the Comet Assay in D. magna for assessing genotoxic loads in aqueous solution. The newly developed protocol could integrate the acute toxicity bioassay, thus expanding the possibility of using this model species in freshwater monitoring (waters, sediment and soil elutriates) and is in line with the spirit of the EU Water Framework Directive in reducing the number of bioassays that involve medium-sized species.

Biochemical and morphological responses in Chironomus riparius (Diptera, Chironomidae) larvae exposed to lead-spiked sediment

The aim of the present study was to assess the potential use of biochemical markers and mentum deformities as indicators of long-term exposure to lead (Pb) in Chironomus riparius larvae. To do this, the authors measured 3 biochemical markers (i.e., malondialdehyde level, metallothionein concentration, and energy reserve content) as well as larval growth and mentum deformities after 16-d exposure to sediment containing Pb. The concentrations studied ranged from 3.5 mg/kg to 505.5 mg/kg dry weight. Despite the bioaccumulation of Pb in C. riparius bodies, frequencies of both mentum deformities and the dry weight were not significantly different between the control and stressed groups. On the contrary, Pb exposure caused a significant increase of both malondialdehyde level and metallothionein concentration. The increase of body Pb concentrations did not significantly modify body copper and zinc concentrations. Moreover, we observed a decrease of total lipid content and an increase of glycogen content as a function of a dose-response relationship, while no variation in protein concentrations was observed. Despite the adverse effects observed at the biochemical level, larval development was not affected. These results suggested that measurements of malondialdehyde level, metallothionein concentration, and energy reserve content can be used as relevant biomarkers of long-term sublethal exposure to Pb in C. riparius larvae.

Antioxidant responses and whole-organism changes in Daphnia magna acutely and chronically exposed to endocrine disruptor bisphenol A

Bisphenol A (BPA) is a well known endocrine disruptor. Significantly less is known about its ability to induce antioxidant defense and oxidative stress in aquatic organisms. This is an interesting subject because BPA can act both as a prooxidant (induces the formation of reactive oxygen species) and an antioxidant. The aim of the present study was to elucidate if BPA induces changes in the activities of antioxidant enzymes catalase (CAT) and glutathione S-transferases (GSTs) and the level of lipid peroxidation in crustacean Daphnia magna. These biomarkers were followed after acute (48h) and chronic (21d) exposure period. Interestingly, CAT and GSTs were changed in the same manner after both exposure durations. The most observable change in daphnids was the increase of GSTs activities, measured with 1,2-chloro-4-dinitrobenzene as a substrate. No GSTs activities with ethacrynic acid and 1,2-dichloro-4-nitrobenzene as substrates were detected. The activity of CAT and the level of lipid peroxidation remained unchanged in daphnids exposed to sublethal concentrations of BPA. The reproduction rate was considerably affected already at 1.73mg/L while the growth was only affected at the highest concentration (13.8mg/L), where also significant mortality was observed.

DNA strand breaks detected in embryos of the adult snails, Potamopyrgus antipodarum, and in neonates exposed to genotoxic chemicals

We tested the freshwater mudsnail Potamopyrgus antipodarum, which is a species that has already been used for endocrine-disrupting compounds (EDCs) to determine whether early life stages of aquatic organisms are sensitive to genotoxic chemicals. For this purpose, we first developed the alkaline comet assay on adults, embryos, and neonates. The comet assay protocol was validated on both embryonic cells exposed in vitro to hydrogen peroxide and adult snails in the reproducing stage exposed to methyl methane sulfonate. During the latter experiment, DNA strand breaks were investigated on both embryonic cells and on adult gill cells. The second part of this study investigated the stability of DNA strand breaks in adult reproducing snails and neonates exposed to cadmium (Cd) and bisphenol A for 8 days. Hydrogen peroxide-induced DNA strand breaks in vitro in isolated embryonic cells. Exposure of adult reproducing snails to methyl methane sulfonate for 24h induced DNA strand breaks in embryos. Bisphenol A induced a significant increase in the DNA strand-break level in whole embryonic cells and whole neonate cells. Cd was genotoxic for both embryos and neonates during the exposure time and also after 7 days of depuration, suggesting that Cd could inhibit DNA repair enzymes. These preliminary results on this original model have encouraged us to consider the impact of genotoxic environmental contaminants on the F1 generation.

Characterization of a cytochrome P450 gene (CYP4G) and modulation under different exposures to xenobiotics (tributyltin, nonylphenol, bisphenol A) in Chironomus riparius aquatic larvae

Cytochrome P450 family members participate in xenobiotic transformation as a detoxification mechanism. We have characterized a CYP gene, assigned to the 4G family, in Chironomus riparius, a reference organism in aquatic toxicology. Due to the potential interest of CYP genes and P450 proteins for monitoring pollution effects at the molecular level, the alterations in the pattern of expression of this gene, induced by different xenobiotics, were analyzed. Different compounds, such as the biocide tributyltin (TBTO) and two other well-known endocrine disruptors, nonylphenol (NP) and bisphenol A (BPA), were tested at different concentrations and acute exposures. Upregulation of the CrCYP4G gene was found after exposures to TBTO (1 ng/L 24h-0.1 ng/L 96 h) and, as measured by RT-PCR mRNA quantification, its level was up to twofold that of controls. However, in contrast, NP (1, 10, 100 μg/L, 24h) and BPA (0.5mg/L 24h-3mg/L 96 h) downregulated the gene (by around a half of the control level) suggesting that this gene responds specifically to particular chemicals in the environment. Glutathione-S-transferase (GST) enzymatic activity was also evaluated for each condition. A fairly good correlation was found with CYP4G gene behavior, as it was activated by TBTO (96 h), but inhibited by NP and BPA (24h). Only the higher concentration of BPA tested activated GST, whereas it inhibited CYP4G activity. The results show that different xenobiotics can induce distinct responses in the detoxification pathway, suggesting multiple xenobiotic transduction mechanisms. This work confirms that specific P450 codifying genes, as well as GST enzyme activities, could be suitable biomarkers for ecotoxicological studies.

Genotoxicity of heavy metals to the larvae of Chironomuskiiensis Tokunaga after short-term exposure

The genotoxic effects of increasing concentrations (below lethal concentration [LC50]) of cadmium ([Cd] 0.1, 1 and 10 mg/L), copper ([Cu] 0.2, 2 and 20 mg/L) and zinc ([Zn] 0.5, 5 and 50 mg/L) on Chironomus kiiensis were evaluated using alkaline comet assay after exposure for 24 h. Both the tail moment and the olive tail moment showed significant differences between the control and different concentrations of Cd, Cu and Zn (Kruskal–Wallis, p < 0.05). The highest concentration of Cd was associated with higher DNA damage to C. kiiensis larvae compared with Cu and Zn. The potential genotoxicity of these metals to C. kiiensis was Cd > Cu > Zn.

Electrochemical enhancement of solar photocatalysis: degradation of endocrine disruptor bisphenol-A on Ti/TiO2 films

The photoelectrocatalytic oxidation over immobilized Ti/TiO(2) films in the presence of simulated solar light was investigated for the degradation of bisphenol-A (BPA) in water. The catalyst, consisting of 75:25 anatase:rutile, was prepared by a sol-gel method and characterized by cyclic voltammetry, X-ray diffraction and scanning electron microscopy. Experiments were conducted to assess the effect of applied current (0.02-0.32 mA/cm(2)), TiO(2) loading (1.3-9.2 mg), BPA concentration (120-820 μg/L), initial solution pH (1 and 7.5) and the aqueous matrix (pure water and treated effluent) on BPA photoelectrocatalytic degradation which was monitored by high performance liquid chromatography equipped with a fluorescence detector. The reaction was favored at anodic currents up to 0.04 mA/cm(2) and lower substrate concentrations, but it was hindered by the presence of residual organic matter and radical scavengers (e.g. bicarbonates) in treated effluents. Moreover, a pseudo-first order kinetic model could fit the experimental data well with the apparent reaction constant taking values between 2.9 and 32.4 10(-3)/min. The degradation of BPA by pure photocatalysis or electrochemical oxidation alone was also studied leading to partial substrate removal. In all cases, the contribution of applied potential to photocatalytic degradation was synergistic with the photocatalytic efficiency increasing between 24% and 97% possibly due to a more efficient separation and utilization of the photogenerated charge carriers. The effect of photoelectrocatalysis on the ecotoxic and estrogenic properties of BPA was also evaluated measuring the bioluminescence inhibition of Vibrio fischeri and performing the yeast estrogen screening assay, respectively.

Molecular effects of endocrine-disrupting chemicals on the Chironomus riparius estrogen-related receptor gene

Endocrine-disrupting chemicals (EDCs) mimic the action of endogenous estrogen hormones; consequently, they can interfere with the endocrine systems of a variety of organisms. There is global concern regarding the potential impacts of EDCs on the aquatic environment. To evaluate the effects of EDCs on the estrogen-related receptors (ERR) of Chironomus, we characterized full-length cDNA sequences of the ERR gene from Chironomus riparius. The complete cDNA sequence of the ERR gene was found to be 1332bp in length. The results of our phylogenetic analysis demonstrated that C. riparius ERR was most closely related to that of mosquitoes. The basal level of ERR mRNA was expressed abundantly during different life-history stages, with the exception of adult males. Additionally, ERR gene expression was upregulated significantly in C. riparius exposed to bisphenol A (BPA) and 4-nonylphenol (NP) at all concentrations assayed after 24h of exposure. The ERR gene was significantly upregulated following short periods of exposure to di(2-ethylhexyl)phthalate (DEHP) concentrations of only 50mgL(-1). However, under long-term exposure conditions, ERR expression was induced to a significant degree after BPA, NP, and DEHP exposure at all concentrations assayed. Furthermore, the luciferase reporter gene assay revealed increased ERR expression following exposure to these compounds. Collectively, these findings indicate that EDCs influence the expression of ERR in Chironomus species.