Toxicity of atrazine and nonylphenol in juvenile rainbow trout (Oncorhynchus mykiss): effects on general health, disease susceptibility and gene expression

Lufenuron treatment temporarily represses gene expression and affects the SUMO pathway in liver of Atlantic salmon

Lufenuron is a benzoylurea insecticide currently in use to combat sea lice infestation in salmon aquaculture in Chile. With pending approval in Norway, the aim of this work was to study the uptake and toxicity of lufenuron in liver tissue of Atlantic salmon. Juvenile salmon weighing 40 g were given a standard 7-day oral dose, and bioaccumulation and transcriptional responses in the liver were examined 1 day after the end-of-treatment (day 8) and after 1 week of elimination (day 14). Bioaccumulation levels of lufenuron were 29 ± 3 mg/kg at day 8 and 14 ± 1 mg/kg at day 14, indicating relatively rapid clearance. However, residues of lufenuron were still present in the liver after 513 days of depuration. The exposure gave a transient inhibition of transcription in the liver at day 8 (2437 significant DEGs, p-adj < .05), followed by a weaker compensatory response at day 14 (169 significant DEGs). Pathways associated with RNA metabolism such as the sumoylation pathway were most strongly affected at day 8, while the apelin pathway was most profoundly affected at day 14. In conclusion, this study shows that lufenuron easily bioaccumulates and that a standard 7-day oral dose induces a transient inhibition of transcription in liver of salmon.

Pesticides in the Great Barrier Reef catchment area: Plausible risks to fish populations

Waterways that drain the Great Barrier Reef catchment area (GBRCA) transport pollutants to marine habitats, provide a critical corridor between freshwater and marine habitats for migratory fish species, and are of high socioecological value. Some of these waterways contain concentrations of pesticide active ingredients (PAIs) that exceed Australian ecotoxicity threshold values (ETVs) for ecosystem protection. In this article, we use a "pathway to harm" model with five key criteria to assess whether the available information supports the hypothesis that PAIs are or could have harmful effects on fish and arthropod populations. Strong evidence of the first three criteria and circumstantial weaker evidence of the fourth and fifth criteria are presented. Specifically, we demonstrate that exceedances of Australian and New Zealand ETVs for ecosystem protection are widespread in the GBRCA, that the PAI contaminated water occurs (spatially and temporally) in important habitats for fisheries, and that there are clear direct and indirect mechanisms by which PAIs could cause harmful effects. The evidence of individuals and populations of fish and arthropods being adversely affected species is more circumstantial but consistent with PAIs causing harmful effects in the freshwater ecosystems of Great Barrier Reef waterways. We advocate strengthening the links between PAI concentrations and fish health because of the cultural values placed on the freshwater ecosystems by relevant stakeholders and Traditional Owners, with the aim that stronger links between elevated PAI concentrations and changes in recreationally and culturally important fish species will inspire improvements in water quality. Integr Environ Assess Manag 2024;00:1-24. © 2023 Commonwealth of Australia and The Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Studies of Endocrine Disruptors: Nonylphenol and Isomers in Biological Models

Certain emerging pollutants are among the most widely used chemicals globally, causing widespread concern in relation to their use in products devoted to cleaniness and asepsis. Nonylphenol ethoxylate (NPEOn) is one such contaminant, along with its degradation product, nonylphenol, an active ingredient presents in nonionic surfactants used as herbicides, cosmetics, paints, plastics, disinfectants, and detergents. These chemicals and their metabolites are commonly found in environmental matrices. Nonylphenol and NPEOn, used, are particularly concerning, given their role as endocrine disruptors chemical and possible neurotoxic effects recorded in several biological models, primarily aquatic organisms. Limiting and detecting these compounds remain of paramount importance. The objective of the present review was to evaluate the toxic effects of nonylphenol and NPEOn in different biological models. Environ Toxicol Chem 2023;00:1-12. © 2023 SETAC.

Transcriptome analysis reveals the mechanisms of hepatic injury caused by long-term environmental exposure to atrazine in juvenile common carp (Cyprinus carpio L.)

Atrazine (ATZ) is the second most commonly used herbicide worldwide, resulting in the pollution of water bodies and affecting the economic benefits of aquaculture. ATZ is known to cause liver damage in the common carp, Cyprinus carpio L., one of the most widely cultivated fish in China, but the underlying mechanisms are poorly understood. In this study, juvenile common carp Cyprinus carpio L. were exposed to three different environmental levels (0.4, 0.8, and 1.2 μg/L) of ATZ for 12 weeks and changes in the liver transcriptomes between the high-dose group and the control group were analyzed. The data showed that different levels of ATZ exposure caused hepatotoxicity in juvenile carp, shown by biochemical parameters and histopathological changes. Comparative transcriptomics showed that high-dose ATZ exposure led to alterations in the expression of various lipid metabolism-related gene changes, including genes associated with metabolic pathways, fatty acid metabolism, and fatty acid elongation. Furthermore, a connection network analysis of the top 100 differentially expressed genes (DEGs) showed a variety of associations between high-dose ATZ-induced liver damage and the principal DEGs, indicating the complexity of hepatotoxicity induced by ATZ. In conclusion, the molecular mechanisms underlying ATZ-triggered hepatotoxicity in juvenile carp are primarily related to impaired lipid metabolism.

Adverse effects of herbicides in freshwater Neotropical fish: A review

Although herbicides have been developed to act on the physiological processes of plants, they are responsible for causing deleterious effects on animals. These chemical compounds are widely used throughout the world, but especially in countries that export agricultural products such as Central and South America, their use has increased in recent years. Aquatic environments are natural reservoirs of herbicides, which after being applied on crops, run off through the soil reaching rivers, lakes, and oceans. Fish are among the many organisms affected by the contamination of aquatic environments caused by herbicides. These animals play an important ecological role and are a major source of food for humans. However, few studies address the effects of herbicides on fish in this region. Thus, in the present review we discuss the morphophysiological and molecular consequences of herbicide exposure in Neotropical fish systems as well as how the environmental and land use characteristics in this region can influence the toxicity of these pollutants. A toxicity pathway framework was developed summarizing the mechanisms by which herbicides act and endpoints that need to be further investigated.

Impacts of conventional and biodegradable microplastics on juvenile Lates calcarifer: Bioaccumulation, antioxidant response, microbiome, and proteome alteration

Discarded plastic bag is a main component of marine debris, posing potential threats to marine biota. This study was conducted to assess the potential effects of microplastics on juvenile Lates calcarifer. Fish were exposed via diet to two microplastic types from conventional polyethylene (PE) and biodegradable (Bio) plastic bags for 21 days. Antioxidative enzymes activity, intestinal microbiome and proteome were determined. PE and Bio microplastics were found to accumulate in gastrointestinal tracts, and no mortality was observed. Microplastics exposure did not induce significant antioxidant response except for the glutathione reductase (GR) modulation. Intestinal microbiome diversity decreased significantly in PE group based on Simpson index. Both types of microplastics induced proteome modulation by down-regulating proteins associated with immune homeostasis. Bio microplastics maintained higher intestinal microbial diversity and induced more proteins alteration than PE microplastics. This study provides toxicological insights into the impacts of conventional and biodegradable microplastics on juvenile L. calcarifer.

Chronic exposure to nonylphenol induces oxidative stress and liver damage in male zebrafish (Danio rerio): Mechanistic insight into cellular energy sensors, lipid accumulation and immune modulation

Nonylphenol (NP), an environmentally persistent and toxic endocrine-disrupting chemical with estrogenic properties, has severe implications on humans and wildlife. Accumulating evidence demonstrates the toxic response of NP on the developmental process, nervous system, and reproductive parameters. Although NP exposure has been implicated in chronic liver injury, the underlying events associated with hepatic pathophysiology remain less investigated. Using male zebrafish (Danio rerio) as the model, the present study investigates the impact of environmentally relevant concentrations of NP (50 and 100 μg/L, 21 days) on hepatic redox homeostasis vis-à-vis cellular energy sensors, inflammatory response, and cell death involving a mechanistic insight into estrogen receptor (ER) modulation. Our results demonstrate that congruent with significant alteration in transcript abundance of antioxidant enzymes (SOD1, SOD2, Catalase, GPx1a, GSTα1), chronic exposure to NP promotes ROS synthesis, more specifically superoxide anions and H₂O₂ levels, and lipid peroxidation potentially through elevated NOX4 expression. Importantly, NP perturbation of markers associated with fatty acid biosynthesis (srebf1/fasn) and cellular energy-sensing network (sirt1/ampkα/pgc1α) indicates dysregulated energy homeostasis, metabolic disruption, and macrovesicular steatosis, albeit with differential sensitivity at the dose level tested. Besides, elevated p38-MAPK phosphorylation (activation) together with loss of ER homeostasis at both mRNA (esr1, esr2a, esr2b) and protein (ERα, ERβ) levels suggest that NP modulation of ER abundance may have a significant influence on hepatic events. Elevated expression of inflammatory markers (TLR4, p-NF-κB, TNF-α, IL-6, IL-1β, and NOS2) and pro-apoptotic and necrotic regulators, e.g., Bax, caspase- 8, -9 and cleaved PARP1 (50 kDa), indicate chronic inflammation and hepatotoxicity in NP-exposed males. Collectively, elevated oxidative stress, metabolic dysregulation and immune modulation may lead to chronic liver injury in organisms exposed to metabolic disrupting chemicals.

Human Metabolism and Urinary Excretion Kinetics of Nonylphenol in Three Volunteers after a Single Oral Dose

Nonylphenol (NP) is an endocrine-disrupting anthropogenic chemical that is ubiquitous in the environment. Human biomonitoring data and knowledge on internal NP exposure are still sparse, and its human metabolism is largely unknown. Therefore, in this study, we investigated human metabolism and urinary excretion of NP. Three male volunteers received a single oral dose of 1 mg ¹³C₆-labeled NP (10.6-11.7 μg/kg body weight). Consecutive full urine voids were collected for 48 h. A metabolite screening identified nine ring- and/or side chain-oxidized metabolites. We chose the most promising hits, the alkyl chain-oxidized metabolites hydroxy-NP (OH-NP) and oxo-NP, for quantitative investigation next to the parent NP. For this purpose, we newly synthesized specific n - 1-oxidized monoisomeric analytical standards. Quantification of the polyisomeric metabolites was performed via online-solid phase extraction-LC-MS/MS with stable isotope dilution using a previously published consensus method. Alkyl chain hydroxylation (OH-NP) constituted the major metabolism pathway representing 43.7 or 62.2% (depending on the mass transition used for quantification) of the NP dose excreted in urine. The urinary excretion fraction (F_UE) for oxo-NP was 6.0 or 9.3%. The parent NP, quantified via an analogous isomeric ¹³C₆-NP standard, represented 6.6%. All target analytes were excreted predominately as glucuronic acid conjugates. Excretion was rather quick, with concentration maxima in urine 2.3-3.4 h after dosing and biphasic elimination kinetics (elimination half-times first phase: 1.0-1.5 h and second phase: 5.2-6.8 h). Due to its high F_UE and insusceptibility to external contamination (contrary to parent NP), OH-NP represents a robust and sensitive novel exposure biomarker for NP. The novel F_UEs enable to robustly back-calculate the overall NP intakes from urinary metabolite levels in population samples for a well-informed cumulative exposure and risk assessment.

Effects of diclofenac on sentinel species and aquatic communities in semi-natural conditions

Due to the potential hazard of diclofenac on aquatic organisms and the lack of higher-tier ecotoxicological studies, a long-term freshwater mesocosm experiment was set up to study the effects of this substance on primary producers and consumers at environmentally realistic nominal concentrations 0.1, 1 and 10 µg/L (average effective concentrations 0.041, 0.44 and 3.82 µg/L). During the six-month exposure period, the biovolume of two macrophyte species (Nasturtium officinale and Callitriche platycarpa) significantly decreased at the highest treatment level. Subsequently, a decrease in dissolved oxygen levels was observed. High mortality rates, effects on immunity, and high genotoxicity were found for encaged zebra mussels (Dreissena polymorpha) in all treatments. In the highest treatment level, one month after the beginning of the exposure, mortality of adult fish (Gasterosteus aculeatus) caused effects on the final population structure. Total abundance of fish and the percentage of juveniles decreased whereas the percentage of adults increased. This led to an overall shift in the length frequency distribution of the F₁ generation compared to the control. Consequently, indirect effects on the community structure of zooplankton and macroinvertebrates were observed in the highest treatment level. The No Observed Effect Concentration (NOEC) value at the individual level was < 0.1 µg/L and 1 µg/L at the population and community levels. Our study showed that in more natural conditions, diclofenac could cause more severe effects compared to those observed in laboratory conditions. The use of our results for regulatory matters is also discussed.

Transcriptomic analysis of nonylphenol effect on Saccharomyces cerevisiae

Nonylphenol (NP) is a bioaccumulative environmental estrogen that is widely used as a nonionic surfactant. We have previously examined short-term effects of NP on yeast cells using microarray technology. In the present study, we investigated the adaptive response of Saccharomyces cerevisiae BY4742 cells to NP exposure by analyzing genome-wide transcriptional profiles using RNA-sequencing. We used 2 mg/L NP concentration for 40 days of exposure. Gene expression analysis showed that a total of 948 genes were differentially expressed. Of these, 834 genes were downregulated, while 114 genes were significantly upregulated. GO enrichment analysis revealed that 369 GO terms were significantly affected by NP exposure. Further analysis showed that many of the differentially expressed genes were associated with oxidative phosphorylation, iron and copper acquisition, autophagy, pleiotropic drug resistance and cell cycle progression related processes such as DNA and mismatch repair, chromosome segregation, spindle checkpoint activity, and kinetochore organization. Overall, these results provide considerable information and a comprehensive understanding of the adaptive response to NP exposure at the gene expression level.

Emerging prospects of integrated bioanalytical systems in neuro-behavioral toxicology

Neurotoxicity effects of industrial contaminants are currently significantly under investigated and require innovative analytical approaches to assess health and environmental risks at individual, population and ecosystem levels. Behavioral changes assessed using small aquatic invertebrates as standard biological indicators of the aggregate toxic effects, have been broadly postulated as highly integrative indicators of neurotoxicity with physiological and ecological relevance. Despite recent increase in understanding of the emerging value of behavioral biotests, their wider implementation especially in high-throughput environmental risk assessment assays, is largely limited by the lack of advances in analytical technologies. To date, most of the behavioral biotests have only been performed with larger-volumes and lacked dynamic flow-through conditions. They also lack features necessary for development of higher throughput neuro-behavioral ecotoxicity assays such as miniaturization and integration of automated components. We postulate that some contemporary analytical limitations can be effectively addressed by innovative Lab-on-a-Chip (LOC) technologies, an emerging and multidisciplinary field poised to bring significant miniaturization to aquatic ecotoxicity testing. Recent developments in this emerging field demonstrate particular opportunities to study a plethora of behavioral responses of small model organisms in a high-throughput fashion. In this review, we highlight recent advances in this budding new interdisciplinary field of research. We also outline the existing challenges, barriers to development and provide a future outlook in the evolving field of neurobehavioral ecotoxicology.

The intersection of stress, sex and immunity in fishes

While sexual dimorphism in immune responses has been documented in other vertebrates, evidence for a similar phenomenon in fish is lacking. Here, we review the relationship between immunity, stress, spawning, and sex hormones in fish to gain a better understanding of sex-based differences in fish immune responses and its consequences for aquaculture. It is well known that there is a strong link between the stress response and immune function in fish. In addition, research to date has demonstrated that sexual dimorphism in the stress response exists in many species; yet, the relationship between the sexual dimorphic stress responses and immune function has rarely been explored together. Aside from stress, spawning is also known to trigger changes in fish immune responses. Estrogens and androgens have been shown to modulate the immune system which could account for differences between the two sexes of fish when spawning; however, evidence regarding the sexual dimorphism of these changes varies between fishes and is likely related to the spawning strategy employed by a given species. Sex hormones are also used in aquaculture practices to produce monosex populations, and exposure to these hormones early in development has been shown to impact the development of immune organs in several fishes. While female fish are generally thought to be more robust than males, aquaculture practices should also consider the role that maternal stress has on the immune function of the offspring and what role this plays in compromising the immune response of farmed fish.

Advancing the fathead minnow (Pimephales promelas) as a model for immunotoxicity testing: Characterization of the renal transcriptome following Yersinia ruckeri infection

Recent studies have utilized the fathead minnow (Pimephales promelas) to explore the immunotoxic effects associated with a variety of environmental contaminants in the absence of immunological stimuli. Though this approach allows for alterations in the resting immune system to be detected, previous evidence suggests that many immunotoxic effects may only manifest in the activated immune system. However, basic immune responses to pathogens have not been well described in this species. To expand the utility of the fathead minnow as a model for immunotoxicity testing, a more comprehensive understanding of the activated immune system is required. As such, the main goal of this study was to characterize the transcriptomic response to pathogen infection in the fathead minnow using RNA sequencing. To achieve this goal, female fathead minnows were intraperitoneally injected with either Hank's Balanced Salt Solution (sham-injected) or Yersinia ruckeri (pathogen-injected). Eight hours following injection, fish were sacrificed for the assessment of general morphological (i.e., mass, length, condition factor, hepatic index) and immunological (i.e., leukocyte counts, spleen index) endpoints. To assess the molecular immune response to Y. ruckeri, kidney tissue was collected for transcriptomic analysis. A comparison of sham- and pathogen-injected fish revealed that >1800 genes and >500 gene networks were differentially expressed.Gene networks associated with inflammation, innate immunity, complement, hemorrhaging and iron absorption are highlighted and their utility within the context of immunotoxicity is discussed. These data reveal pathogen-related molecular endpoints to improve data interpretation of future studies utilizing the fathead minnow as a model for immunotoxicity.

Contaminants of Emerging Concern Removal in an Effluent of Wastewater Treatment Plant under Biological and Continuous Mode Ultrafiltration Treatment

This work presents a case study of a wastewater treatment plant (WWTP), located in Biscay (Spain), in which the removal of high-occurrence contaminants of emerging concern (CEC) was studied. The existing biological treatment in the WWTP was complemented with a continuous ultrafiltration (c-UF) pilot plant, as a tertiary treatment. Thus, the effect on CEC removal of both treatments could be analyzed globally and after each operation. A total of 39 CEC were monitored, including pharmaceutical products, industrial additives, food additives, herbicides and personal care products. For evaluation of the efficiencies, the removal rates of the biological and of the c-UF treatments, including their variability over a day and a week in relation to the ammonium content, were examined in the influent of the WWTP. In the biological treatment, a wide range of different removal rates was obtained due to the different CEC’s biodegradability and concentration. In UF, lower, but more constant removal rates, were achieved. In addition, the reduction of the general toxicity by the UF treatment in terms of the Microtox® toxicity assay was also evaluated. After UF, all of the samples yielded values of TU50 lower than 1, confirming this result the UF effectiveness for toxicity removal.

Toxicity of nonylphenol and nonylphenol ethoxylate on Caenorhabditis elegans

Among the most used chemicals in the world are nonionic surfactants. One of these environmental pollutants is nonylphenol ethoxylate (NP-9), also known as Tergitol, and its degradation product, nonylphenol (NP). The objective of this work was to determine the toxicity of NP and NP-9 in Caenorhabditis elegans. Wild-type L4 larvae were exposed to different concentrations of the surfactants to measure functional endpoints. Mutant strains were employed to promote the activation of toxicity signaling pathways related to mtl-2, gst-1, gpx-4, gpx-6, sod-4, hsp-70 and hsp-4. Additionally, stress response was also assessed using a daf-16::GFP transgenic strain. The lethality was concentration dependent, with 24-h LC₅₀ of 122 μM and 3215 μM for NP and NP-9, respectively. Both compounds inhibited nematode growth, although NP was more potent; and at non-lethal concentrations, nematode locomotion was reduced. The increase in the expression of tested genes was significant at 10 μM for NP-9 and 0.001 μM for NP, implying a likely role for the activation of oxidative and cellular stress, as well as metabolism pathways. With the exception of glutathione peroxidase, which has a bimodal concentration-response curve for NP, typical of endocrine disruption, the other curves for this xenobiotic in the strains evaluated were almost flat for most concentrations, until reaching 50-100 μM, where the effect peaked. NP and NP-9 induced the activation and nuclear translocation of DAF-16, suggesting that transcription of stress-response genes may be mediated by the insulin/IGF-1 signaling pathway. In contrast, NP-9 induced a concentration-dependent response for the sod-4 and hsp-4 mutants, with greater fluorescence induction than NP at similar levels. In short, NP and NP-9 affect the physiology of C. elegans and modulate gene expression related to ROS production, cellular stress and metabolism of xenobiotics.

Modelling the effect of season, sex, and body size on the three-spined stickleback, Gasterosteus aculeatus, cellular innate immunomarkers: A proposition of laboratory reference ranges

Innate immunomarkers reflect both environmental contamination and fish health status, providing useful information in environmental risk assessment studies. Nevertheless, the lack of knowledge about the effect of confounding factors can lead to data misinterpretation and false diagnoses. The aim of this study was to evaluate the impact of three confounding factors (season, sex and body size) on three-spined stickleback innate immunomarkers in laboratory conditions. Results shown strong seasonal variations in stickleback innate immunomarkers, with higher immune capacities in late winter-early spring and a disturbance during the spawning period in late spring-summer. Sex and body size had a season dependant effect on almost all tested immunomarkers. Reference ranges were established in laboratory-controlled conditions (i.e. laboratory reference ranges) and compared with data obtained from in vivo chemical expositions. The predictive power of the statistical model depended on the immunomarker, but the control data of the in vivo experiments, realized in same laboratory conditions, were globally well include in the laboratory reference ranges. Moreover, some statistical effects of the in vivo exposures were correlated with an augmentation of values outside the reference ranges, indicating a possible harmful effect for the organisms. As confounding factors influence is a major limit to integrate immunomarkers in biomonitoring programs, modelling their influence on studied parameter may help to better evaluated environmental contaminations.

Transchem project - Part II: Transgenerational effects of long-term exposure to pendimethalin at environmental concentrations on the early development and viral pathogen susceptibility of rainbow trout (Oncorhynchus mykiss)

In the Transchem project, rainbow trout genitors were exposed to environmental concentrations of pendimethalin over a period of 18 months and two new first generations of offspring, F1_2013 and F1_2014, were obtained. We investigated the impact of direct chemical exposure on juveniles as well as the potential cumulative transgenerational and direct effects on the larval development and on the pathogen susceptibility of offspring. Depending on the chemical treatment or not of the adults, their offspring were distributed in the tanks of our experimental system, in two batches i.e. juveniles from the control genitors (G-) and others from the contaminated ones (G+), and then, half of the tanks were exposed daily to pendimethalin (Off+) while the others were used as controls (Off-). Viral challenges were performed on the offspring, before and after three months of direct chemical exposure, with strains of infectious hematopoietic necrosis virus (IHNV), viral haemorrhagic septicemia virus (VHSV) and sleeping disease alphavirus (SDV). Direct and transgenerational macroscopic effects were observed on offspring, with a percentage of abnormalities in offspring derived from the genitors exposed to pendimethalin (G+) significantly higher compared to those from the genitors from non-exposed group (G-). Before the direct chemical exposure, similar kinetics of mortality was observed between the offspring from the contaminated or control genitors after VHSV infection. With IHNV, the G+ group died in a slightly larger proportion compared to the G- group and seroconversion was greater for the G- group. For the SDV challenge, the mortality was delayed for the G+ offspring compared to the G- and seroconversion reached 65% in the G+ group compared to 45% in the G-, with similar antibody titres. After three months of direct chemical exposure, kinetics of mortality induced by IHNV infection were similar for all groups studied. Infection with SDV resulted in a cumulative mortality of 40% for the G- groups (Off- and Off+), significantly higher than those observed from the contaminated genitors G+. Proportion of seropositivity for SDV varied from 24 to 47% depending on the group, with very low quantities of secreted antibodies. Lastly, the direct exposure of offspring could impact the capacity of fish to adapt their haematological parameters to environmental and physiological changes, and underlines the potential toxic effects on the next generations.

Transcriptomic, lipid, and histological profiles suggest changes in health in fish from a pesticide hot spot

Barramundi (Lates calcarifer) were collected at the beginning (1st sampling) and end (2nd sampling) of the wet season from Sandy Creek, an agriculturally impacted catchment in the Mackay Whitsundays region of the Great Barrier Reef catchment area, and from Repulse Creek, located approximately 100 km north in Conway National Park, to assess the impacts of pesticide exposure. Gill and liver histology, lipid class composition in muscle, and the hepatic transcriptome were examined. The first sample of Repulse Creek fish showed little tissue damage and low transcript levels of xenobiotic metabolism enzymes. Sandy Creek fish showed altered transcriptomic patterns, including those that regulate lipid metabolism, xenobiotic metabolism, and immune response; gross histological alterations including lipidosis; and differences in some lipid classes. The second sampling of Repulse Creek fish showed similar alterations in hepatic transcriptome and tissue structure as fish from Sandy Creek. These changes may indicate a decrease in health of pesticide exposed fish.

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.

Immune response induced by major environmental pollutants through altering neutrophils in zebrafish larvae

Environmental pollutants may cause adverse effects on the immune system of aquatic organisms. However, the cellular effects of pollutants on fish immune system are largely unknown. Here, we exploited the transgenic zebrafish Tg(lysC:DsRed2) larva as a preliminary screening system to evaluate the potential inflammatory effects of environmental pollutants. Tg(lysC:DsRED2) larvae aged 7-day-postfertilization (7 dpf) were treated with selected environmental chemicals for 24 h (24 h) and the number of neutrophils were quantified using both image analysis and fluorescence activated cell sorting (FACS). We found that the numbers of neutrophils in the Tg(lysC:DsRED2) larvae were significantly increased by most of the organic chemicals tested, including E2 (17β-estradiol), BPA (Bisphenol-A), NDEA (N-nitrosodiethylamine), 4-NP (4-Nitrophenol) and Lindane (γ-hexachlorocyclohexane). Neutrophil numbers were also increased by all the metals tested (Na2HAsO4· 7H2O, Pb(NO3)2, HgCl₂, CdCl2, CuSO₄·5H₂O, ZnSO4, and K2Cr2O7). The only exception was TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), which significantly reduced the number of neutrophils after exposure. Additionally, the transcription of genes (lyz, mpo, tnfα and il8) related to fish immune system were significantly modulated upon exposure to some of the selected chemicals such as E2, TCDD, Cu and Cd. This study revealed that representatives of major categories of environmental pollutants could cause an acute inflammatory response in zebrafish larvae as shown by alterations in the neutrophils, which may imply a common immunotoxicity mechanism for most environmental pollutants. This study has also demonstrated that Tg(lyz:DsRed2) transgenic zebrafish is an excellent tool for screening environmental chemicals with potential inflammatory effects through FACS-facilitated neutrophil counting.

Effect of dietary supplementation with Spirulina platensis on Atrazine-induced oxidative stress- mediated hepatic damage and inflammation in the common carp (Cyprinus carpio L.)

The present study evaluated the potential modulatory effect(s) of dietary supplementation with Spirulina platensis (SP) on Atrazine (ATZ)-induced oxidative stress and inflammation in common carp (Cyprinus carpio L.). Common carp was exposed to ATZ (428μg/L) and SP (1%), either alone or in combination, for 40 days. Subsequently, the treatment groups were evaluated for ATZ-induced oxidative stress-mediated hepatic damage and the potential antioxidant effect(s) of SP supplementation. The results indicated that ATZ exposure led to a significant increase in the oxidative stress as suggested by the increased levels of lipid and DNA oxidative damage markers and the significant decline of antioxidant status biomarkers. Further, a real-time PCR analysis of the liver tissues revealed that the ATZ exposure resulted in the significant modulation of the mRNA expression of cytokines involved in the inflammatory response pathway in the liver, such as Interleukin (IL)-1ß and IL-10. The expression of IL-1ß mRNA was up-regulated while that of IL-10 mRNA was down-regulated. The group subjected to supplementation with SP exhibited a significant decrease in ATZ-induced oxidative stress-mediated hepatotoxic and inflammatory responses; however, these did not attain the levels of the control group. Owing to its ability for protecting against ATZ-induced oxidative stress-mediated hepatic damage in carps, SP could be a potentially effective and promising candidate as a feed additive for carps in aquaculture.

Immunotoxic responses of chronic exposure to cypermethrin in common carp

In the current study, laboratory evaluations were made to assess the immunomodulatory effect of cypermethrin on fingerlings of common carp (Cyprinus carpio L.). Results showed that 96-h LC50 of cypermethrin in common carp was estimated at 0.85 μg/L. Fish were exposed for 21 days to cypermethrin at three sub-lethal concentrations of 0.042, 0.085, and 0.17 μg/L that represented 5, 10, and 20%, respectively, of the 96-h LC50 of the pesticide for this fish species. Blood samples were taken after 7, 14, and 21 days of exposure. Immunological indices and resistance against bacterial infection were determined. Compared to the control group, the fish exposed to cypermethrin showed a significant increase in neutrophil ratio but exhibited a significant decrease in leukocyte number and lymphocyte ratio in treatments exposed to 0.17 and/or 0.085 μg/L after 21 days of exposure (p < 0.05). Serum protein level was significantly decreased in group exposed to 0.17 μg/L on day 14 and also in groups exposed to 0.085 and 0.17 μg/L on day 21 (p < 0.05). Immunoglobulin value was significantly reduced in groups exposed to 0.085 and 0.17 μg/L after 21 days of exposure (p < 0.05). Serum lysozyme activity and phagocytic activity were significantly decreased following exposure to 0.17 μg/L determined on days 14 and 21, post-exposure (p < 0.05). Mortality rate following the challenge with Aeromonas hydrophila significantly increased in fish exposed to 0.17 μg/L of cypermethrin. Overall, the present results indicate severe immunotoxicological effects of cypermethrin in common carp. Therefore, the use of cypermethrin in the proximities of common carp farms should be carefully considered.

Evaluation of chlorpyrifos effects, alone and combined with lipopolysaccharide stress, on DNA integrity and immune responses of the three-spined stickleback, Gasterosteus aculeatus

Organism immune defences might be weakened by pollutants, largely detected in aquatic ecosystems, leading to the facilitation for opportunistic pathogens to infect organisms. In this context, destabilization of fish non-specific immune parameters and erythrocyte DNA integrity was tested, on a model fish species, the three-spined stickleback (Gasterosteus aculeatus), after exposure to chlorpyrifos (CPF). Alone, pesticide exposure induced a genotoxic potential (chlorpyrifos at 1.75 and 0.88µg/L) in addition to a decrease in phagocytosis capacity and a stimulation of respiratory burst. Then, to mimic pathogenic infection, fish exposure to chlorpyrifos was combined with lipopolysaccharides (LPS) stress. In this second experiment, an increase of DNA damage was observed in fish exposed to a lower concentration of chlorpyrifos and LPS. Moreover, at the higher concentration of chlorpyrifos, an early destabilization of innate immunity was observed as suggested by the absence of an increase of lysosomal presence in fish injected with LPS. This study highlighted the usefulness of stress on stress responses to better understand the impact of contaminants on the organism's health.

Incorporating Transgenerational Epigenetic Inheritance into Ecological Risk Assessment Frameworks

Chronic exposure to environmental contaminants can induce heritable "transgenerational" modifications to organisms, potentially affecting future ecosystem health and functionality. Incorporating transgenerational epigenetic heritability into risk assessment procedures has been previously suggested. However, a critical review of existing literature yielded numerous studies claiming transgenerational impacts, with little compelling evidence. Therefore, contaminant-induced epigenetic inheritance may be less common than is reported in the literature. We identified a need for multigeneration epigenetic studies that extend beyond what could be deemed "direct exposure" to F1 and F2 gametes and also include subsequent multiple nonexposed generations to adequately evaluate transgenerational recovery times. Also, increased experimental replication is required to account for the highly variable nature of epigenetic responses and apparent irreproducibility of current studies. Further, epigenetic end points need to be correlated with observable detrimental organism changes before a need for risk management can be properly determined. We suggest that epigenetic-based contaminant studies include concentrations lower than current "EC_10-20" or "Lowest Observable Effect Concentrations" for the organism's most sensitive phenotypic end point, as higher concentrations are likely already regulated. Finally, we propose a regulatory framework and optimal experimental design that enables transgenerational epigenetic effects to be assessed and incorporated into conventional ecotoxicological testing.

Efficacy of Spirulina platensis diet supplements on disease resistance and immune-related gene expression in Cyprinus carpio L. exposed to herbicide atrazine

The present study evaluated the immunotoxicological effects of the herbicide atrazine (ATZ) at sub-lethal concentrations and the potential ameliorative influence of Spirulina platensis (SP) over a sub-chronic exposure period on Cyprinus carpio L., also known as common carp. Common carp was sampled after a 40-days exposure to ATZ (428 μg/L) and SP (1%), individually or in combination to assess the non-specific immune response, changes in mRNA expression of immune-related genes [lysozyme (LYZ), immunoglobulin M (IgM), and complement component 3 (C3)] in the spleen, and inflammatory cytokines (interleukins IL-1ß and IL-10) in the head kidney using real-time PCR. Additionally, disease resistance to Aeromonas sobria was evaluated. The results revealed that ATZ exposure caused a significant decline in most of the hematological variables, lymphocyte viability, and lysozyme and bactericidal activity. Moreover, ATZ increased the susceptibility to disease, reflected by a significantly lower post-challenge survival rate of the carp. ATZ may induce dysregulated expression of immune-related genes leading to downregulation of mRNA levels of IgM and LYZ in the spleen. However, expression of C3 remained unaffected. Of the cytokine-related genes examined, IL-1B was up-regulated in the head kidney. In contrast, the expression of IL-10 gene was down-regulated in the ATZ-exposed group. The SP supplementation resulted in a significant improvement in most indices; however, these values did not match with that of the controls. These results may conclude that ATZ affects both innate and adaptive immune responses through the negative transcriptional effect on genes involved in immunity and also due to the inflammation of the immune organs. In addition, dietary supplements with SP could be useful for modulation of the immunity in response to ATZ exposure, thereby presenting a promising feed additive for carps in aquaculture.

Hepatic transcriptomic profiles from barramundi, Lates calcarifer, as a means of assessing organism health and identifying stressors in rivers in northern Queensland

Resource managers need to differentiate between sites with and without contaminants and those where contaminants cause impacts. Potentially, transcriptomes could be used to evaluate sites where contaminant-induced effects may occur, to identify causative stressors of effects and potential adverse outcomes. To test this hypothesis, the hepatic transcriptomes in Barramundi, a perciforme teleost fish, (Lates calcarifer) from two reference sites, two agriculturally impacted sites sampled during the dry season, and an impacted site sampled during the wet season were compared. The hepatic transcriptome was profiled using RNA-Seq. Multivariate analysis showed that transcriptomes were clustered based on site and by inference water quality, but not sampling time. The largest differences in transcriptomic profile were between reference sites and a site sampled during high run-off, showing that impacted sites can be identified via RNA-Seq. Transcripts with altered abundance were linked to xenobiotic metabolism, peroxisome proliferation and stress responses, indicating putative stressors with the potential for adverse outcomes in barramundi.

Derivation of predicted no-effect concentration and ecological risk for atrazine better based on reproductive fitness

Atrazine (ATZ) is an herbicide most commonly used in China and other regions of the world. It is reported toxic to aquatic organisms, and frequently occurs at relatively high concentrations. Currently, ATZ has been proved to affect reproduction of aquatic species at much lower levels. So it is controversial to perform ecological risk assessment using predicted no-effect concentrations (PENCs) derived from traditional endpoints, which fail to provide adequate protection to aquatic organisms. In this study, PNECs of ATZ were derived based on six endpoints of survival, growth, behavior, biochemistry, genetics and reproduction. The PNEC derived from reproductive lesion was 0.044μg ATZ L^-1, which was obviously lower than that derived from other endpoints. In addition, a tiered ecological risk assessment was conducted in the Taizi River based on six PNECs derived from six categories of toxicity endpoints. Results of these two methods of ecological risk assessment were consistent with each other, and the risk level of ATZ to aquatic organisms reached highest as taking reproductive fitness into account. The joint probability indicated that severe ecological risk rooting in reproduction might exist 93.9% and 99.9% of surface water in the Taizi River, while 5% threshold (HC₅) and 1% threshold (HC₁) were set up to protect aquatic organisms, respectively. We hope the present work could provide valuable information to manage and control ATZ pollution.

How Does Reference Site Selection Influence Interpretation of Omics Data?: Evaluating Liver Transcriptome Responses in Male Rainbow Darter (Etheostoma caeruleum) across an Urban Environment

Studies quantifying the influence of reference site selection on transcriptomic profiles in aquatic organisms exposed to complex mixtures are lacking in the literature, despite the significant implications of such research for the interpretation of omics data sets. We measured hepatic transcriptomic responses in fish across an urban environment in the central Grand River watershed (Ontario, Canada). Adult male rainbow darter (RBD) (Etheostoma caeruleum) were collected from nine sites at varying distances from two major municipal wastewater treatment plants (MWWTPs) (Waterloo, Kitchener), including three upstream reference sites. The transcriptomic response in RBD was independently compared with that of fish from each of the three reference sites. Data collected in fish downstream of the Waterloo MWWTP (poorest effluent quality) suggested that ∼15.5% of the transcriptome response was influenced by reference site selection. In contrast, at sites where the impact of MWWTPs was less-pronounced and fish showed less of a transcriptome response, reference site selection had a greater influence (i.e., ∼56.9% of transcripts were different depending on the site used). This study highlights the importance of conducting transcriptomics studies that leverage more than one reference site, and it broadens our understanding of the molecular responses in fish in dynamic natural environments.

20 Years of fish immunotoxicology - what we know and where we are

Despite frequent field observations of impaired immune response and increased disease incidence in contaminant-exposed wildlife populations, immunotoxic effects are rarely considered in ecotoxicological risk assessment. The aim of this study was to review the literature on immunotoxic effects of chemicals in fish to quantitatively evaluate (i) which experimental approaches were used to assess immunotoxic effects, (ii) whether immune markers exist to screen for potential immunotoxic activities of chemicals, and (iii) how predictive those parameters are for adverse alterations of fish immunocompetence and disease resistance. A total of 241 publications on fish immunotoxicity were quantitatively analyzed. The main conclusions included: (i) To date, fish immunotoxicology focused mainly on innate immune responses and immunosuppressive effects. (ii) In numerous studies, the experimental conditions are poorly documented, as for instance age or sex of the fish or the rationale for the selected exposure conditions is often missing. (iii) Although a broad variety of parameters were used to assess immunotoxicity, the rationale for the choice of measured parameters was often not given, remaining unclear how they link to the suspected immunotoxic mode of action of the chemicals. (iv) At the current state of knowledge, it is impossible to identify a set of immune parameters that could reliably screen for immunotoxic potentials of chemicals. (v) Similarly, in fish immunotoxicology there is insufficient understanding of how and when chemical-induced modulations of molecular/cellular immune changes relate to adverse alterations of fish immunocompetence, although this would be crucial to include immunotoxicity in ecotoxicological risk assessment.

Performance of a novel atrazine-induced cerebellar toxicity in quail (Coturnix C. coturnix): Activating PXR/CAR pathway responses and disrupting cytochrome P450 homeostasis

Atrazine is well known to be a biologically hazardous substance with toxic effects, but atrazine-induced neurotoxicity remains unclear. The aim of this study was to investigate the mechanisms of atrazine-induced cerebellar toxicity. To determine atrazine-exerted potential neurotoxicity, quails were treated with 50, 250 and 500 mg/kg atrazine by gavage administration for 45 days. Notably, the changes of cytochrome P450 enzyme system (CYP450s) were observed in atrazine-exposed quails. The contents of cytochrome P450 (CYP450) and Cytochrome b5 (Cyt b5) and the activities of NADPH-cytochrome c reductase (NCR), aminopyrin N-demethylase (APND) and aniline-4-hydeoxylase (AH) were increased and erythromycin N-demethylase (ERND) was decreased in quail cerebellum. Nuclear xenobiotic receptors (NXRs) and the transcriptions of NXRs-related target molecules were influenced in cerebellum. Atrazine disrupted the CYP450s balance in quail cerebellum. These results suggested that atrazine-induced cerebellar toxicity in birds was associated with activating PXR/CAR pathway responses and disrupting cytochrome P450 homeostasis. This study provided novel evidences that atrazine exposure induced cerebellar toxicity.

Effect of environmentally-relevant concentrations of nonylphenol on sexual differentiation in zebrafish: a multi-generational study

Nonylphenol (NP) is a persistent environmental chemical that can disrupt the organism’s endocrine system, and is detected in the surface water and sea. In this study, we investigated whether NP can alter transcriptional expression of sexual differentiation-related genes. Three generations of zebrafish were exposed to 0, 2, 20 and 200 μg·L⁻¹ of NP, and transcriptional expression of sexual differentiation genes were assessed in 10, 20 and 40 dpf in the F1 and F2 generations. Growth of zebrafish exposed to 200 μg·L⁻¹ of NP was inhibited at 125 dpf in the F1 generation. 20 μg·L⁻¹ of NP resulted in 80% females in the F1 generation, but had no effect on the F2 generation. In terms of the sexual differentiation genes, the transcriptional expression of cyp19a1a and esr1 genes were upregulated in 20 μg·L⁻¹ of NP in the F1 generation. But expression of the sexual differentiation genes were not affected in the F2 generation. Overall, NP could affect sexual differentiation and gene transcriptional expression in the F1 generation. The tolerance of contaminant in the offsprings was improved at low concentration.

Estrogen-dependent seasonal adaptations in the immune response of fish

Clinical and experimental evidence shows that estrogens affect immunity in mammals. Less is known about this interaction in the evolutionary older, non-mammalian, vertebrates. Fish form an excellent model to identify evolutionary conserved neuroendocrine-immune interactions: i) they are the earliest vertebrates with fully developed innate and adaptive immunity, ii) immune and endocrine parameters vary with season, and iii) physiology is constantly disrupted by increasing contamination of the aquatic environment. Neuro-immuno-endocrine interactions enable adaption to changing internal and external environment and are based on shared signaling molecules and receptors. The presence of specific estrogen receptors on/in fish leukocytes, implies direct estrogen-mediated immunoregulation. Fish leukocytes most probably are also capable to produce estrogens as they express the cyp19a and cyp19b - genes, encoding aromatase cytochrome P450, the enzyme critical for conversion of C19 steroids to estrogens. Immunoregulatory actions of estrogens, vary among animal species, and also with dose, target cell type, or physiological condition (e.g., infected/non-infected, reproductive status). They moreover are multifaceted. Interestingly, season-dependent changes in immune status correlate with changes in the levels of circulating sex hormones. Whereas E2 circulating in the bloodstream is perhaps the most likely candidate to be the physiological mediator of systemic immune-reproductive trade-offs, leukocyte-derived hormones are hypothesized to be mainly involved in local tuning of the immune response. Contamination of the aquatic environment with estrogenic EDCs may violate the delicate and precise allostatic interactions between the endogenous estrogen system and the immune system. This has negative effects on fish health, but will also affect the physiology of its consumers.

Global transcriptomic profiling in barramundi (Lates calcarifer) from rivers impacted by differing agricultural land uses

Most catchments discharging into the Great Barrier Reef lagoon have elevated loads of suspended sediment, nutrients, and pesticides, including photosystem II inhibiting herbicides, associated with upstream agricultural land use. To investigate potential impacts of declining water quality on fish physiology, RNA sequencing (RNASeq) was used to characterize and compare the hepatic transcriptomes of barramundi (Lates calcarifer) captured from 2 of these tropical river catchments in Queensland, Australia. The Daintree and Tully Rivers differ in upstream land uses, as well as sediment, nutrient, and pesticide loads, with the area of agricultural land use and contaminant loads lower in the Daintree. In fish collected from the Tully River, transcripts involved in fatty acid metabolism, amino acid metabolism, and citrate cycling were also more abundant, suggesting elevated circulating cortisol concentrations, whereas transcripts involved in immune responses were less abundant. Fish from the Tully also had an increased abundance of transcripts associated with xenobiotic metabolism. Previous laboratory-based studies observed similar patterns in fish and amphibians exposed to the agricultural herbicide atrazine. If these transcriptomic patterns are manifested at the whole organism level, the differences in water quality between the 2 rivers may alter fish growth and fitness. Environ Toxicol Chem 2017;36:103-112. © 2016 SETAC.

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

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

Altered levels of endocrine biomarkers in juvenile barramundi (Lates calcarifer; Bloch) following exposure to commercial herbicide and surfactant formulations

Agricultural pesticides that are known endocrine disrupting chemicals have been detected in waters in the Great Barrier Reef catchment and lagoon. Altered transcription levels of liver vitellogenin (vtg) have been documented in wild populations of 2 Great Barrier Reef fisheries species and were strongly associated with pesticide-containing runoff from sugarcane plantations. The present study examined endocrine and physiological biomarkers in juvenile barramundi (Lates calcarifer) exposed to environmentally relevant concentrations of commercial herbicide (ATRADEX(®) WG Herbicide, DIUREX(®) WG Herbicide) and surfactant (ACTIVATOR(®) 90) formulations commonly used on sugarcane in the Great Barrier Reef catchment. Estrogenic biomarkers (namely, liver vtg messenger RNA and plasma 17β-estradiol) increased following exposure to commercial mixtures but not to the analytical grade chemical, suggesting an estrogenic response to the additives. In contrast, brain aromatase (cyp19a1b) transcription levels, plasma testosterone and 11-ketotestosterone concentrations, and gill ventilation rates were not affected by any of the experimental exposures. These findings support the assertion that exposure to pesticide-containing runoff from sugarcane plantations is a potential causative agent of altered liver vtg transcription levels in wild barramundi. Whether exposure patterns in the Great Barrier Reef catchment and lagoon are sufficient to impair fish sexual and reproductive development and ultimately influence fish population dynamics remains to be determined. These findings highlight the need to consider both active and so-called inert ingredients in commercial pesticide formulations for environmental risk assessments.

Effects of atrazine in fish, amphibians, and reptiles: an analysis based on quantitative weight of evidence

A quantitative weight of evidence (WoE) approach was developed to evaluate studies used for regulatory purposes, as well as those in the open literature, that report the effects of the herbicide atrazine on fish, amphibians, and reptiles. The methodology for WoE analysis incorporated a detailed assessment of the relevance of the responses observed to apical endpoints directly related to survival, growth, development, and reproduction, as well as the strength and appropriateness of the experimental methods employed. Numerical scores were assigned for strength and relevance. The means of the scores for relevance and strength were then used to summarize and weigh the evidence for atrazine contributing to ecologically significant responses in the organisms of interest. The summary was presented graphically in a two-dimensional graph which showed the distributions of all the reports for a response. Over 1290 individual responses from studies in 31 species of fish, 32 amphibians, and 8 reptiles were evaluated. Overall, the WoE showed that atrazine might affect biomarker-type responses, such as expression of genes and/or associated proteins, concentrations of hormones, and biochemical processes (e.g. induction of detoxification responses), at concentrations sometimes found in the environment. However, these effects were not translated to adverse outcomes in terms of apical endpoints. The WoE approach provided a quantitative, transparent, reproducible, and robust framework that can be used to assist the decision-making process when assessing environmental chemicals. In addition, the process allowed easy identification of uncertainty and inconsistency in observations, and thus clearly identified areas where future investigations can be best directed.

Atrazine and its degradates have little effect on the corticosteroid stress response in the zebrafish

The present study examined the effects of atrazine on basal and forced swimming induced changes in whole body cortisol content in adult zebrafish. Zebrafish were exposed to graded concentrations of atrazine or the atrazine degradates deisopropylatrazine (DIA), deethylatrazine (DEA) and diamino-s-chlorotriazine (DACT) for up to 10 days. Some fish were sampled for the measurement of whole body cortisol levels under basal conditions while others were sampled after being subjected to a 20 min swimming challenge in order to quantify stress induced cortisol levels. In one experiment, zebrafish were subjected to two bouts of forced swimming 3h apart to test whether prior atrazine exposure affects the ability of the fish to respond appropriately to a repeated stressor. The results demonstrated that controls not exposed to atrazine and zebrafish exposed to atrazine or the atrazine degradates at nominal concentrations of up to 100 μg/L consistently exhibited increased whole body cortisol content in response to the swimming challenge. Separate analyses revealed few changes in basal or stress induced cortisol levels following atrazine exposure. Overall, these data suggest that atrazine and some of its degradates at the concentrations tested have minimal effects on the cortisol mediated stress response in the zebrafish.

Evaluating the treatment of a synthetic wastewater containing a pharmaceutical and personal care product chemical cocktail: compound removal efficiency and effects on juvenile rainbow trout

Pharmaceutical and personal care products (PPCPs) can evade degradation in sewage treatment plants (STPs) and can be chronically discharged into the environment, causing concern for aquatic organisms, wildlife, and humans that may be exposed to these bioactive chemicals. The ability of a common STP process, conventional activated sludge (CAS), to remove PPCPs (caffeine, di(2-ethylhexyl)phthalate, estrone, 17α-ethinylestradiol, ibuprofen, naproxen, 4-nonylphenol, tonalide, triclocarban and triclosan) from a synthetic wastewater was evaluated in the present study. The removal of individual PPCPs by the laboratory-scale CAS treatment plant ranged from 40 to 99.6%. While the efficiency of removal for some compounds was high, remaining quantities have the potential to affect aquatic organisms even at low concentrations. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to influent recreated model wastewater with methanol (IM, solvent control) or with PPCP cocktail (IC), or CAS-treated effluent wastewater with methanol (EM, treated control) or with PPCP cocktail (EC). Alterations in hepatic gene expression (evaluated using a quantitative nuclease protection plex assay) and plasma vitellogenin (VTG) protein concentrations occurred in exposed fish. Although there was partial PPCP removal by CAS treatment, the 20% lower VTG transcript levels and 83% lower plasma VTG protein concentration found in EC-exposed fish compared to IC-exposed fish were not statistically significant. Thus, estrogenic activity found in the influent was retained in the effluent even though typical percent removal levels were achieved raising the issue that greater reduction in contaminant load is required to address hormone active agents.

Early-life exposure to a herbicide has enduring effects on pathogen-induced mortality

Exposure to stressors at formative stages in the development of wildlife and humans can have enduring effects on health. Understanding which, when and how stressors cause enduring health effects is crucial because these stressors might then be avoided or mitigated during formative stages to prevent lasting increases in disease susceptibility. Nevertheless, the impact of early-life exposure to stressors on the ability of hosts to resist and tolerate infections has yet to be thoroughly investigated. Here, we show that early-life, 6-day exposure to the herbicide atrazine (mean ± s.e.: 65.9±3.48 µg l(-1)) increased frog mortality 46 days after atrazine exposure (post-metamorphosis), but only when frogs were challenged with a chytrid fungus implicated in global amphibian declines. Previous atrazine exposure did not affect resistance of infection (fungal load). Rather, early-life exposure to atrazine altered growth and development, which resulted in exposure to chytrid at more susceptible developmental stages and sizes, and reduced tolerance of infection, elevating mortality risk at an equivalent fungal burden to frogs unexposed to atrazine. Moreover, there was no evidence of recovery from atrazine exposure. Hence, reducing early-life exposure of amphibians to atrazine could reduce lasting increases in the risk of mortality from a disease associated with worldwide amphibian declines. More generally, these findings highlight that a better understanding of how stressors cause enduring effects on disease susceptibility could facilitate disease prevention in wildlife and humans, an approach that is often more cost-effective and efficient than reactive medicine.

Environmental concentration of nonylphenol alters the development of urogenital and visceral organs in avian model

Nonylphenol (NP) is an endocrine disruptor with harmful effects including feminization and carcinogenesis on various organisms. This substance is a degradation product of nonylphenol ethoxylates (NPEO) that is used in several industrial and agricultural processes. In this paper, we examined the assessment of NP exposure on chick embryo development, using a concentration consistent with the environmental concentrations of NP. With this aim, NP (between 0.1 and 50 μg/egg) was injected into the yolk of egg through a small needle hole in the shell. We report the effect of NP on chick reproductive system development although the effect we observed is lower than those observed by exposition to other endocrine disruptors. However, histological analysis highlighted a decrease of intraluminal seminiferous surface area in 64.12% of case (P=0.0086) and an heterogeneous organization of the renal tubules when 10 μg/egg were injected. Moreover, an impairment of liver development with an abnormal bile spillage was observed when higher concentration of NP was injected (50 μg/egg).

Effects of praziquantel and sanguinarine on expression of immune genes and susceptibility to Aeromonas hydrophila in goldfish (Carassius auratus) infected with Dactylogyrus intermedius

Praziquantel and sanguinarine have been demonstrated positive therapeutic effects on monogenean Dactylogyrus intermedius; however, few studies have considered the post impacts of these antiparasitic chemicals on host after repelling the parasites. The changes of expression of selected immune genes (CCL-1, CXCL-8, IL-1β-1, IL-1β-2, TNFα-1, TNFα-2 and TGF-β) in gill, kidney and spleen and bacterial loads of Aeromonas hydrophila in gill, kidney, spleen and liver following bath administration of these antiparasitic chemicals were evaluated. The results showed that praziquantel and sanguinarine up-regulated to varying degrees of CXCL-8, IL-1β-1, IL-1β-2, TNFα-1 and TNFα-2 in gill, kidney and spleen. They both decreased the CCL-1 expression in gill while increased it in kidney and spleen. However, in all the tested tissues, the expression of TGF-β decreased in praziquantel treated goldfish whereas that increased in sanguinarine treated goldfish. The A. hydrophila challenge test showed that the praziquantel treatment enhanced the susceptibility to A. hydrophila while sanguinarine treatment decreased the susceptibility, as compared with the non-treated group. Overall, the results indicate that bath administration of praziquantel and sanguinarine modulates the immune related genes in goldfish and these may, to some extent, affect their ability to resist bacterial pathogens.