DNA damage and effects on glutathione-S-transferase activity induced by atrazine exposure in zebrafish (Danio rerio)

Behavioral, metabolic, and biochemical alterations caused by an acute stress event in a zebrafish larvae model

Animal welfare is a growing concern in aquaculture practices. Stress induced by handling or transportation can lead to negative impacts on the sector. Zebrafish has raised as an important aquaculture model, but still with few focus on its stress response in early life stages. Therefore, the objective of this study was to improve the evaluation of different markers of the stress response after a stress event in a zebrafish larvae model. Zebrafish larvae (96 hpf) were vortex-stimulated for 1 min at 200 rpm for acute stress induction. After 10 min, 1- and 4-h behavioral larvae outcomes and larvae were sampled to the following quantification: levels of cortisol, lactate, glucose and biochemical biomarkers (reactive oxygen species, superoxide dismutase, catalase, glutathione peroxidase, lipidic oxidation level and protein carbonylation, glutathione s-transferase, acetylcholinesterase, lactate dehydrogenase and ATPase), and the metabolic rate. The cortisol, glucose, and lactate levels had no alterations. At the behavioral level, an increase in the distance swam and in the speed was observed and the metabolic rate also increased according to the behavioral outcomes. The ATPase and GST activity showed a decrease in their activity, probably through osmoregulation changes related to the hypothetic adrenocorticotropic hormone downregulation. Overall, the acute vortex stimulation at low speed induced an early stress response independent of the HPI-cortisol pathway. In addition, this study shows zebrafish early life stages as a sensitive model to acute vortex stimulation, identifying altered parameters which can be used in future work to assess the effect on animal welfare in similar acute situations.

Fine particulate matter‑induced cardiac developmental toxicity (Review)

Fine particulate matter (PM2.5) has become an important risk factor threatening human health. Epidemiological and toxicological investigations have revealed that PM2.5 not only leads to cardiovascular dysfunction, but it also gives rise to various adverse health effects on the human body, such as cardiovascular and cerebrovascular diseases, cancers, neurodevelopmental disorders, depression and autism. PM2.5 is able to penetrate both respiratory and placental barriers, thereby resulting in negative effects on fetal development. A large body of epidemiological evidences has suggested that gestational exposure to PM2.5 increases the incidence of congenital diseases in offspring, including congenital heart defects. In addition, animal model studies have revealed that gestational exposure to PM2.5 can disrupt normal heart development in offspring, although the potential molecular mechanisms have yet to be fully elucidated. The aim of the present review was to provide a brief overview of what is currently known regarding the molecular mechanisms underlying cardiac developmental toxicity in offspring induced by gestational exposure to PM2.5.

Stereoselective toxicity: Investigating the adverse effects of benzovindiflupyr on Xenopus laevis tadpoles

The novel chiral fungicide benzovindiflupyr exerts adverse effects on aquatic organisms; however, its toxic mechanism and stereoselectivity remain largely unknown. The current study aimed to investigate the enantioselective ecotoxicity mechanism of benzovindiflupyr in Xenopus laevis tadpoles using a 28-day exposure experiment. Results of the acute toxicity assessment indicated that (1S,4R)- and (1R,4S)-benzovindiflupyr exhibited high toxicity, with (1S,4R)- demonstrating approximately 75 times greater toxicity than (1R,4S)-. Compared to the latter, (1S,4R)-benzovindiflupyr significantly affected the growth, movement behavior, and oxidative stress of X. laevis tadpoles. The integration of metabolomics and transcriptomics data revealed that (1S,4R)-benzovindiflupyr disrupted the glycine, serine, and threonine metabolic pathways by modulating the activities of key enzymes. This dysregulation resulted in aberrant carbohydrate utilization, antioxidant pathways, and structural protein synthesis and degradation. Molecular docking confirmed that (1S,4R)-benzovindiflupyr exhibited superior docking activity with key enzymes, potentially contributing to its stereoselective toxicity. This study offers novel molecular perspectives on the enantioselective ecotoxicity mechanism of benzovindiflupyr toward aquatic organisms and highlights potential target proteins implicated in metabolic disorders.

A review on toxic effects of pesticides in Zebrafish, Danio rerio and common carp, Cyprinus carpio, emphasising Atrazine herbicide

The widespread use of pesticides has emerged as a pressing environmental concern nowadays. These chemical compounds pose a significant threat to aquatic organisms due to their toxic effects. Zebrafish and common carp are two common species used in pesticide toxicity studies. Atrazine, a widely used herbicide, is one of the most prevalent globally, detectable in nearly all surface waters. This article examines existing literature to provide a comprehensive review of the toxic effects of Atrazine on Zebrafish and common carp. The findings reveal that exposure to atrazine triggers a range of biochemical, physiological, behavioral, and genetic alterations in these fish species, even at concentrations deemed environmentally relevant. These changes could have severe consequences, including increased mortality rates, reproductive failures, and potentially leading to fish populations decline. It is, therefore, imperative to prioritize stringent regulatory measures to curb the usage of this herbicide and safeguard fish species as unintended victims of aquatic ecosystems.

Prolonged exposure to the synthetic glucocorticoid dexamethasone induces brain damage via oxidative stress and apoptotic response in adult Daniorerio

Due to its extensive use as a painkiller, anti-inflammatory, and immune modulatory agent, as well as its effectiveness in treating severe COVID-19, dexamethasone, a synthetic glucocorticoid, has gained attention not only for its impact on public health but also for its environmental implications. Various studies have reported its presence in aquatic environments, including urban waters, surface samples, sediments, drinking water, and wastewater effluents. However, limited information is available regarding its toxic effects on nontarget aquatic organisms. Therefore, this study aimed to investigate the mechanism of toxicity underlying dexamethasone-induced brain damage in the bioindicator Danio rerio following long-term exposure. Adult zebrafish were treated with environmentally relevant concentrations of dexamethasone (20, 40, and 60 ng L-1) for 28 days. To elucidate the possible mechanisms involved in the toxicity of the pharmaceutical compound, we conducted a behavioral test battery (Novel Tank and Light and Dark tests), oxidative stress biomarkers, acetylcholinesterase enzyme activity quantification, histopathological analysis, and gene expression analysis using qRT-PCR (p53, bcl-2, bax, caspase-3, nrf1, and nrf2).The results revealed that the pharmaceutical compound could produce anxiety-like symptoms, increase the oxidative-induced stress response, decrease the activity of acetylcholinesterase enzyme, and cause histopathological alterations, including perineuronal vacuolization, granular and molecular layers deterioration, cell swallowing and intracellular spaces. The expression of genes involved in the apoptotic process (p53, bax, and casp-3) and antioxidant defense (nrf1 and nrf2) was upregulated in response to oxidative damage, while the expression of the anti-apoptotic gene bcl-2 was down-regulated indicating that the environmental presence of dexamethasone may pose a threat to wildlife and human health.

Bioconcentration, oxidative stress and molecular mechanism of the toxic effect of acetamiprid exposure on Xenopus laevis tadpoles

Acetamiprid is a neonicotinoid commonly detected in aquatic ecosystems, with residual concentrations of up to 0.41 mg/L in surface water, posing a threat to the health of nontarget aquatic organisms. However, studies on the potential toxicity and underlying mechanisms of action of acetamiprid on nontarget aquatic organisms are limited. This study investigated the acute and short-term toxicity of acetamiprid to Xenopus laevis tadpoles. A 96-h acute toxicity test determined the LC50 of acetamiprid to be 32.1 mg/L. After 28 days of exposure to 1/10 and 1/100 LC50 concentrations, tadpole samples were collected for bioconcentration elimination analysis, biochemical analyses, transcriptomics, and metabolomics studies to comprehensively evaluate the toxic effects of acetamiprid and its underlying mechanisms. The results, indicating bioconcentration factors (BCFs) < 1, suggest that acetamiprid has a low bioconcentration in tadpoles. Additionally, oxidative stress was observed in treated Xenopus laevis tadpoles. Transcriptomic and nontargeted metabolomic analyses identified 979 differentially expressed genes (DEGs) and 95 differentially metabolites in the 0.321 mg/L group. The integrated analysis revealed that disruption of purine and amino acid metabolic pathways potentially accounts for acetamiprid-induced toxic effects in tadpoles. The disruptive effects of acetamiprid on valine, leucine and isoleucine biosynthesis; and aminoacyl-tRNA biosynthesis metabolic pathways in tadpoles were validated through targeted metabolomics analysis. These findings are crucial for assessing the risk of acetamiprid to nontarget aquatic organisms.

Enrichment and distribution of 3,6-dichlorocarbazole in red crucian carp (Carassius auratus) and its hepatotoxicity

Polyhalogenated carbazoles (PHCZs) are a class of organohalogen compounds where the hydrogen atom on the carbazole ring is replaced by a halogen atom. In recent years, PHCZs have drawn increasing concern due to their persistence, dioxin-like toxicity, bioaccumulation, potential ecological hazards and widespread occurrence in the environment. Current research on the enrichment and depuration of PHCZs in biological tissues and organs is insufficient, and the liver toxicity is unclear. Herein, to understand the enrichment and elimination of 3,6-DCCZ in fish tissues and organs as well as the hepatotoxicity, we exposed the red crucian carp to 20 and 100 μg/L of 3,6-DCCZ for 20 days followed by a depuration period of 10 days. The 3,6-DCCZ enrichment in each organ tissue was classified from high to low: brain > liver, intestine, gill > muscle. For depuration, 3,6-DCCZ was quickly excreted in the various organs of the red crucian carp; however, the liver depuration was slow, with the concentration of 3,6-DCCZ was maintained at 0.25-0.35 μg/g. 3,6-DCCZ exposure at both tested concentrations induced oxidative stress in red crucian carp, causing lipid peroxidation and DNA damage, as well as some histopathological changes in the liver, such as cell vacuolization, nucleus pyknosis, nucleus pleomorphism, no nucleus areas. Additionally, the 3,6-DCCZ exposure at higher concentration (100 μg/L) caused more serious damage and abnormal lipid metabolism in the red crucian carp liver.

Characterization of imidacloprid-induced hepatotoxicity and its mechanisms based on a metabolomic approach in Xenopus laevis

The toxic effects of imidacloprid are attracting increased concern because of its widespread use in agriculture and its persistence in the aquatic environment. Imidacloprid bioaccumulates and triggers various morphological and behavioral responses in amphibians, but the toxic effects and mechanism of imidacloprid in amphibians remain uncertain. In this study, the acute toxicity and chronic effects of imidacloprid on Xenopus laevis were studied. Acute toxicity for 96 h revealed that imidacloprid had an LC₅₀ value of 74.18 mg/L. After exposure for 28 d under 1/10 and 1/100 LC_50, liver samples from X. laevis were employed for biochemical analyses, pathological studies, and nontargeted metabolomics to systematically assess the toxic effects and mechanisms of imidacloprid. The results showed that oxidative stress and hepatic tissue morphology changes were observed in treated X. laevis liver. Twelve metabolites involved in metabolic pathway were altered between the control and high exposure groups and twenty-one metabolites were altered between the control and low exposure group. Eight metabolic pathways exposed to high levels and nine metabolic pathways exposed to low level of imidacloprid were disturbed. These pathways were primarily related to amino acid metabolism, lipid metabolism, and nucleotide metabolism. Our research provides essential information to evaluate the potential toxicity of imidacloprid to nontarget aquatic organisms.

Atrazine exposure induces necroptosis through the P450/ROS pathway and causes inflammation in the gill of common carp (Cyprinus carpioL.)

Atrazine (ATR) is used worldwide and has been confirmed be hazardous materials that harmful to the health of organisms. Since ATR was more persistent in the water, the specific damage caused by ATR to aquatic organisms should be concern. The role of P450/ROS has been proposed in many pathomechanisms. To explore whether P450/ROS mediated necroptosis and promote inflammatory response caused by ATR exposure, 120 common carp (Cyprinus carpio L.) were randomly divided into four groups which were exposed to 0 μg/L, 4 μg/L, 40 μg/L and 400 μg/L ATR respectively. The residual levels of ATR and its metabolites increased, signs of necrosis and inflammation were found in the gills of the ATR-treatment groups. The levels of ROS and cytochrome P450 content were increased, and P450 enzymes were activated. The expression levels of the core components of necroptosis (RIPK1, RIPK3 and MLKL) increased. Moreover, gene expression of inflammatory factors (TNF-α, NF-κB, iNOS, COX-2, IL-1β and PTGE) increased significantly in the ATR-spiked group. Our results suggested that ATR exposure triggered necroptosis through the P450/ROS pathway and causes inflammation of common carp gill. This study provides valuable clue about the mechanism by which ATR causes injury to common carp gill.

Environmentally relevant atrazine exposure leads to increases in DNA damage and changes in morphology in the hepatopancreas of crayfish (Faxonius virilis)

The herbicide atrazine is widely used for controlling broad leaf weeds and increasing crop yields in agricultural areas. Atrazine enters aquatic environments through runoff, ground water discharge and seepage where concentrations have been recorded above 300 ppb. Exposure to the herbicide atrazine at environmentally relevant concentrations has been shown to negatively impact aquatic organisms, including crayfish. Because xenobiotics are concentrated in the crayfish hepatopancreas (digestive gland), we examined changes in morphology and DNA damage in hepatopancreatic tissue structure and cells following a 10-day exposure to atrazine (0, 10, 40, 80, 100 and 300 ppb). We found that there were marked morphological changes, post-exposure, for all atrazine concentrations tested. Hepatopancreatic tissue exhibited degenerated tubule epithelium with necrosis of microvilli, tubule lumen dilation, changes in tubular epithelium height and vacuolization of the epithelium. Likewise, we also performed a terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick-end labeling (TUNEL) assay which showed the percentage of cells with DNA damage increased following atrazine exposure. Crayfish hepatopancreatic tissue displayed significant increases in TUNEL-positive cells following exposure to atrazine at 100 ppb and above. Overall, exposure to atrazine at environmentally relevant concentrations damages hepatopancreatic tissue. This impairment could lead to changes in biotransformation, detoxification, digestion and molting, subsequently reducing crayfish populations and negatively impacting the aquatic ecosystem.

Metsulfuron-methyl induced physiological, behavioural and biochemical changes in exotic (Eisenia fetida) and indigenous (Metaphire posthuma) earthworm species: Toxicity and molecular docking studies

In modern agricultural practices, Metsulfuron-methyl (sulfonylurea herbicide) is widely employed to inhibit the weeds and grasses. The current study revealed that Metaphire posthuma was more sensitive than Eisenia fetida against Metsulfuron-methyl (MSM). The LC₅₀ values for Eisenia fetida were 2884.08 mgkg^-1 and 1871.18 mgkg^-1after 7 and 14 days, respectively. Similarly, the LC₅₀ values for Metaphire posthuma were 2449.34 mgkg^-1 and 1673.10 mgkg^-1for 7 and 14 days, respectively. Reproduction parameters were significantly decreased at 400 (T3), 800 (T4) and 1600 (T5) mgkg^-1 MSM in E. fetida whereas at 200 (T2), 400 (T3), 800 (T4), 1600 (T5) mgkg^-1 MSM in M. posthuma. EC₅₀ of avoidance response for 20% MSM by E. fetida and M. posthuma was recorded 901.76 mgkg^-1and 544.21 mgkg^-1 respectively. Malondialdehyde (MDA) content along with guaiacol peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) activities were initially increased up to 21st day by MSM, inducing a slight oxidative stress in earthworms and recovered to control level on 28th day. The GST activities were continuously stimulated throughout the exposure period and enhance the detoxification effect thereby preventing the earthworms from toxins. Molecular docking studies indicated that hydrogen bonding and hydrophobic interactions are key forces in binding between MSM and SOD/CAT/POD/GST. As a result, this is the first study to be reported on physiological, behavioural and biochemical changes in two different earthworm species under the exposure of sulfonyl urea herbicide.

The toxicological effects of Eryngium foetidum extracts on zebrafish embryos and larvae depend on the type of extract, dose, and exposure time

Eryngium foetidum is a herbaceous plant found in tropical and subtropical regions. In vivo pharmacological parameters show that leaf extracts of this plant have antioxidant, anti-inflammatory, antidiabetic, and antimicrobial activities due to their bioactive compounds such as flavonoids and phenols. Despite the evidence for several bioactivities of E. foetidum, information on its safety and tolerability is limited. The objective of this study was to assess the effect and concentration of different extracts of E. foetidum on the development of zebrafish (Danio rerio) embryos. To study the impact of aqueous (AE), ethanolic (EE), and methanolic (ME) extracts, the embryos were exposed to 0.625, 1.25, 2.5, 5, and 10 mg mL-1 for up to 120-h postfertilization to assess embryonic developmental toxicity and then to 0.039, 0.078, 0.156, 0.312, and 0.625 mg mL-1 to assess the antioxidant responses of the enzymes superoxide dismutase catalase, glutathione S-transferase (GST), and cell apoptosis. The results showed that, depending on the extraction solvent, concentration used, and exposure time, E. foetidum extracts caused mortality, altered the hatching time, and promoted changes in enzymatic activities. Delays in development and increased GST activity were found in all treatments. Apoptosis was not observed in any of the treatments. In conclusion, AE, EE, and ME concentrations above 0.625 mg mL-1 can cause adverse effects on the early stages of zebrafish development.

Biochemical and cellular responses of the freshwater mussel, Hyriopsis bialata, to the herbicide atrazine

The present study aimed to evaluate biochemical and cellular responses of the freshwater mussel, Hyriopsis bialata, to the herbicide atrazine (ATZ). The mussels were exposed to environmentally-relevant concentrations of ATZ (0, 0.02 and 0.2 mg/L) and a high concentration (2 mg/L) for 0, 7, 14, 21 and 28 days. Tissues comprising male and female gonads, digestive glands and gills were collected and assessed for ethoxyresorufin-O-deethylase (EROD) activity, glutathione S-transferase (GST) activity, multixenobiotic resistance mechanism (MXR), histopathological responses, DNA fragmentation and bioaccumulation of ATZ and its transformation derivatives, desethylatrazine (DEA) and desisopropylatrazine (DIA). Additionally, circulating estradiol levels were determined. It appeared that ATZ did not cause significant changes in activities of EROD, GST and MXR. There were no apparent ATZ-mediated histopathological effects in the tissues, with the exception of the male gonads exhibiting aberrant aggregation of germ cells in the ATZ-treated mussels. Contrarily, ATZ caused significant DNA fragmentation in all tissues of the treated animals in dose- and time-dependent manners. In general, the circulating estradiol levels were higher in the females than in the males. However, ATZ-treated animals did not show significant alterations in the hormonal levels, as compared with those of the untreated animals. Herein, we showed for the first time differentially spatiotemporal distribution patterns of bioaccumulation of ATZ, DEA and DIA, with ATZ and DEA detectable in the gonads of both sexes, DEA and DIA in the digestive glands and only DEA in the gills. The differential distribution patterns of bioaccumulation of ATZ and its derivatives among the tissues point to different pathways and tissue capacity in transforming ATZ into its transformation products. Taken together, the freshwater mussel H. bialata was resistant to ATZ likely due to their effective detoxification. However, using DNA damage as a potential biomarker, H. bialata is a promising candidate for biomonitoring aquatic toxicity.

Toxicity evaluation of chlorpyrifos and its main metabolite 3,5,6-trichloro-2-pyridinol (TCP) to Eisenia fetida in different soils

The present study utilized a biomarker response method to evaluate the effect of 3,5,6-trichloro-2-pyridinol (TCP) in artificial and natural soils on Eisenia fetida after 7, 14, 28, 42 and 56 days exposure. Results indicated that TCP induced excessive reactive oxygen species, caused oxidative stress and DNA damage to Eisenia fetida. Biomarker responses were standardized to calculate the Integrated Biomarker Response (IBR) index. The IBR index of three enzymes (superoxide dismutase, catalase and glutathione S-transferase) activities showed that TCP induced the oxidative stress to E. fetida in red clay was stronger than in the other three soils. Specifically, chlorpyrifos exposure group showed a lower toxicity than TCP exposure group after 28 days exposure but a higher toxicity than TCP exposure group after 56 days exposure. Despite the deficiencies of this study, the above information is of great significance for assessing the risk of chlorpyrifos and its metabolite TCP pollution in soil ecosystems.

Synergistic protective effects of folic acid and resveratrol against fine particulate matter-induced heart malformations in zebrafish embryos

Ambient fine particulate matter (PM2.5) is a major environmental health problem worldwide, and recent studies indicate that maternal PM2.5 exposure is closely associated with congenital heart diseases (CHDs) in offspring. We previously found that supplementation with folic acid (FA) or Resveratrol (RSV) could protect against heart defects in zebrafish embryos exposed to extractable organic matter (EOM) from PM2.5 by targeting aryl hydrocarbon receptor (AHR) signaling and reactive oxygen species (ROS) production respectively. Thus, we hypothesized that FA combined with RSV may have a synergistic protective effect against PM2.5-induced heart defects. To test our hypothesis, we treated zebrafish embryos with EOM in the presence or absence of FA, RSV or a combination of both. We found that RSV and FA showed a clear synergistic protection against EOM-induced heart defects in zebrafish embryos. Further studies showed that FA and RSV suppressed EOM-induced AHR activity and ROS generation respectively. Although only RSV inhibited EOM-induced apoptosis, FA enhanced the inhibitory effect of RSV. Moreover, vitamin C (VC), a typical antioxidant, also exhibits a synergistic inhibitory effect with FA on EOM-induced apoptosis and heart defects. In conclusion, supplementation with FA and RSV have a synergistic protective effect against PM2.5-induced heart defects in zebrafish embryos by targeting AHR activity and ROS production respectively. Our results indicate that, in the presence of antioxidants, FA even at a low concentration level could protect against the high risk of CHDs caused by air pollution.

Bioavailability of citalopram to Daphnia magna in the presence of suspended sediments with various properties

The influence of suspended sediment (SPS) properties on the biological effects of antidepressant citalopram (CIT) was investigated in our study. For CIT exposure alone, the feeding behavior, energy available, glutathione-S-transferase (GST) activity of D. magna were vitally induced at 10 μg/L. In the presence of SPS, significant dose-dependent reduction in the ingestion and filtration rates were observed with the increase of SPS concentration, while SPS organic content (f_oc) of 1% exhibited the most serious aggravation. The protein was the main contributor to detoxification and cellular protection under the stress of CIT and SPS. Obvious disturbance effects on the malonaldehyde content, catalase and GST activities were observed for SPS of 0.1 g/L, 60-90 μm and f_oc of 2%. Overall, the important role of SPS properties on the biological effects of CIT should be taken into consideration for the accurate risk assessment of pollutants.

Biomarker responses and metabolism in Lumbricus terrestris exposed to drugs of environmental concern, an in vivo and in vitro approach

The earthworm Lumbricus terrestris is an anecic species living in natural soils but it is also a sentinel in pollution monitoring. Specimens of L.terrestris were exposed for 48 h though the filter paper contact test at 1 mg/mL of the chemicals: Lamotrigine (LMG), Cocaine (COC), Fipronil (FIP) and the pesticide bis-4-nitrophenyl phosphate (BNPP). After that period, the activities of Acetylcholinesterase, Glutathione S-transferase, Carboxylesterase (CE) using different substrates, and lipid peroxidation levels were evaluated in the exposed whole tissue earthworms. The results revealed differences only in CE activity, with 4-nitrophenyl butyrate (4NPB) and 1-naphthyl butyrate (1NB) the most responsive substrates to COC. The kinetic parameters of CE were characterized, for the first time, in whole tissue of this species. The chemical analysis by LC-MS/MS, confirmed the exposure to the parent compounds, identified metabolites and evidenced biotransformation pathways in earthworms. Metabolic reactions included oxidation (LMG and FIP), hydrolysis (COC and FIP) as well as glycosylation (LMG, COC and FIP). A hitherto unknown metabolite of LMG due to the conjugation with phenylalanine glutamine was formed. The in vivo results on CE activity with the specific inhibitor, BNPP, were confirmed in vitro. Moreover, in the in vitro approach, the inclusion of other contaminants of environmental concern supports the potential of CE as biomarker. This study identifies the main metabolites formed by earthworms for further in vivo exposures under more realistic conditions and the potential use of CE measures as biomarker of emerging contaminants.

Developmental toxicity induced by particulate matter (PM2.5) in zebrafish (Danio rerio) model

Contemporary research in epidemiology has found that being exposed to air pollution at an early stage of life has associations with both acute and chronic conditions of the multi-organs. Nevertheless, the reasons for this have yet to be fully explained. Because of this there is a need for a robust investigation into the damaging toxic influence of diesel particulate matter (PM2.5) on living organisms. This study is aimed to investigate the developmental toxicity of PM2.5 by using zebrafish (Danio rerio) embryo/larvae as a disease model and to understand the toxicity effects of PM2.5 on ecological environment more thoroughly. This research demonstrates that being exposed to PM2.5 leads to a significant increase in mortality, effective developmental morphology, reductions in hatching rates and lower heart rates in zebrafish. Additionally, it leads to increases in the length of string heart, area of pericardium, and apoptosis, reduces the number of normal intersegmental vessels (ISVs) and motor neurons in the trunk region and liver formation defects in zebrafish embryos. Investigation employing a scanning electron microscope demonstrates that being exposed to PM2.5 leads to damage in zebrafish larvae skin cell layers. Histological analysis demonstrates that when these larvae are treated with PM2.5 then abnormalities occur in the neurons, liver, heart, gills, brain, and eyes, and remarkable increase in in the cellular/subcellular levels of organelle dissolution. These findings are useful to help us understand the pathophysiological influence of being exposed to PM2.5 on the multi-organ defects of zebrafish. More research into which particular elements that make up diesel pollution contribute to this toxicity is needed so that the dangers to development can be further analysed.

Influence of suspended sediment on the bioavailability of benzophenone-3: Focus on accumulation and multi-biological effects in Daphnia magna

The UV-filter benzophenone-3 (BP3) tends to associate with suspended sediment (SPS) due to hydrophobicity, which could alter its toxicological effects on non-target aquatic organisms. In this study, the freshwater cladoceran Daphnia magna (D. magna) was selected as a model organism to investigate the impacts of the source and composition of SPS on the accumulation and multiple toxicological effects (from the molecular level to individual level) of BP3. Among the three components of SPS, amorphous organic carbon (AOC) and minerals promoted the body burden of BP3, while black carbon (BC) inhibited the bioaccumulation. The inhibition effects of BP3 on swimming and feeding behaviors of D. magna were also enhanced due to the presence of AOC and BC. Compared with BP3 exposure alone, higher oxidative stress and neurotoxicity were observed in the presence of SPS containing AOC, BC and minerals, corresponding to that superoxide dismutase, catalase and glutathione-S-transferase activities were further induced, and acetylcholinesterase activity was inhibited. Furthermore, BP3 induced mRNA expression levels of the endocrine system (ecdysone receptor, cytochrome P450 CYP314) and metabolic system (toxicant nuclear receptor HR96, P-glycoprotein), and the presence of SPS containing AOC, BC and minerals exhibited an enhanced effect. Combined with all endpoints, evident relationship was observed between the bioaccumulation level and the response of individual behavior and molecular biomarkers. The results demonstrated that the effects of SPS compositions on bioaccumulation and toxicological effects of organic UV-filters should be considered in aquatic environments.

Zebrafish (Danio rerio) using as model for genotoxicity and DNA repair assessments: Historical review, current status and trends

Genotoxic pollutants lead to both DNA damage and changes in cell repair mechanisms. Selecting suitable biomonitors is a fundamental step in genotoxicity studies. Thus, zebrafish have become a popular model used to assess the genotoxicity of different pollutants in recent years. They have orthologous genes with humans and hold almost all genes involved in different repair pathways. Therefore, the aim of the current study is to summarize the existing literature on zebrafish using as model system to assess the genotoxicity of different pollutants. Revised data have shown that comet assay is the main technique adopted in these studies. However, it is necessary standardizing the technique applied to zebrafish in order to enable better result interpretation and comparisons. Overall, pollutants lead to single-strand breaks (SSB), double-strand breaks (DSB), adduct formation, as well as to changes in the expression of genes involved in repair mechanisms. Although analyzing repair mechanisms is essential to better understand the genotoxic effects caused by pollutants, few studies have analyzed repair capacity. The current review reinforces the need of conducting further studies on the role played by repair pathways in zebrafish subjected to DNA damage. Revised data have shown that zebrafish are a suitable model to assess pollutant-induced genotoxicity.

Neonicotinoids caused oxidative stress and DNA damage in juvenile Chinese rare minnows (Gobiocypris rarus)

To assess the effects of neonicotinoid insecticides on fish, juvenile Chinese rare minnows (Gobiocypris rarus) were exposed to 0.1, 0.5, or 2.0 mg/L neonicotinoid insecticides (imidacloprid, nitenpyram, and dinotefuran) for 60 days. The endpoints, including oxidative stress and DNA damage, were determined. The results of oxidative stress assays showed that SOD activities were significantly increased in the 2.0 mg/L imidacloprid and 0.5 mg/L nitenpyram and dinotefuran treatments (p < 0.05). CAT activity was significantly increased with 0.1 mg/L nitenpyram (p < 0.05), whereas it was significantly decreased in the 0.1 and 2.0 mg/L dinotefuran treatment groups (p < 0.05). Moreover, MDA content was significantly decreased in all imidacloprid treatments and in the 0.5 and 2.0 mg/L dinotefuran treatments (p < 0.05); however, it was significantly increased in the 0.1 mg/L nitenpyram treatment (p < 0.05). GSH content was significantly increased at all treatments except for the 0.5 mg/L dinotefuran treatment (p < 0.05). The transcript expression results showed that gstm mRNA expression was significantly inhibited by 0.5 and 2.0 mg/L imidacloprid, and gstp1 mRNA expression was significantly inhibited by all nitenpyram treatments (p < 0.05). In addition, ugt1a mRNA expression was significantly inhibited in the 0.5 mg/L nitenpyram treatment (p < 0.05). The results of the DNA damage assay showed that tail moments were significantly increased by the 2.0 mg/L imidacloprid treatment (p < 0.01), while tail DNA was significantly increased by 0.5 and 2.0 mg/L imidacloprid, 2.0 mg/L nitenpyram and all dinotefuran treatments (p < 0.01). Moreover, olive tail moments were significantly increased by the 0.5 and 2.0 mg/L imidacloprid and 2.0 mg/L dinotefuran treatments (p < 0.01). Therefore, our oxidative stress and DNA damage findings demonstrated that imidacloprid and nitenpyram could cause adverse effects on juvenile rare minnows.

Evaluation of the acute toxic effect of azoxystrobin on non-target crayfish (Astacus leptodactylus Eschscholtz, 1823) by using oxidative stress enzymes, ATPases and cholinesterase as biomarkers

Azoxystrobin is a broad-spectrum fungicide used worldwide. Since azoxystrobin spreads to large areas, its toxic effects on non-target organisms have aroused interest. In this study, the acute toxicity (96 h) of azoxystrobin on the crayfish (Astacus leptodactylus) was examined by using various biomarkers. The 96 h-LC₅₀ dose (1656 mg L^-) and its three sub-doses (828, 414, 207 mg L^-1) were applied to crayfish. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were increased significantly compared to the control in hepatopancreas, gill and muscle tissues. The activities of acetylcholinesterase (AChE) and glutathione S-transferase (GST) increased, and glutathione reductase (GR) activity decreased significantly in hepatopancreas. Level of reduced glutathione (GSH) decreased significantly. The content of malondialdehyde (MDA) increased in a dose-dependent manner in all azoxystrobin treatments with the exception of the lowest dose (207 mg L^-1)treatment. ATPases (Na⁺/K⁺ -ATPase, Mg²⁺ -ATPase, Ca²⁺ -ATPase, total ATPase) were significantly inhibited in gill and muscle tissues. The results of the present study indicate that azoxystrobin induces oxidative stress, and has adverse effects on activities of AChE and ATPases in crayfish.

AHR-mediated ROS production contributes to the cardiac developmental toxicity of PM2.5 in zebrafish embryos

Recent studies have shown an association between maternal exposure to ambient fine particle matter (PM2.5) and congenital heart defects in the offspring, but the underlying molecular mechanisms are yet to be elucidated. Previously, we demonstrated that extractable organic matter (EOM) from PM2.5 induced heart defects in zebrafish embryos by activating the aromatic hydrocarbon receptor (AHR). Hence, we hypothesized that AHR mediates excessive reactive oxygen species (ROS) production, leading to the cardiac developmental toxicity of PM2.5. To test our hypothesis, we examined AHR activity and ROS levels in the heart of zebrafish embryos under a fluorescence microscope. mRNA expression levels were then quantified using qPCR whereas DNA damage and apoptosis were detected by immunofluorescence. Our results showed that the AHR inhibitor, CH223191 (CH) as well as the ROS scavenger, N-Acetyl-L-cysteine (NAC), significantly mitigated the PM2.5-induced cardiac malformations in zebrafish embryos. Furthermore, both CH and NAC diminished the EOM-elevated ROS generation, DNA damage and apoptosis in the test system. Incidentally, both CH and NAC attenuated the EOM-induced changes in the mRNA expression of genes involved in cardiac development (nkx2.5, sox9b), oxidative stress (nrf2a, nrf2b, gstp1, gstp2, sod2, ho1, cat) and apoptosis (p53, bax). We further confirmed that AHR activity is a necessary condition for EOM-induced ROS generation, DNA damage and apoptosis, through AHR knockdown. However, the ROS scavenger NAC did not counteract the EOM-induced AHR activity. In conclusion, our findings suggest that AHR mediates EOM-induced oxidative stress, resulting in DNA damage and apoptosis, thereby contributing to the cardiac developmental toxicity of PM2.5.

Biochemical responses and DNA damage induced by herbicide QYR301 in earthworm (Eisenia fetida)

QYR301, a novel herbicidal inhibitor of 4-hydroxyphenylpyruvate dioxygenase (HPPD), has great potential for resistant weed control in paddy fields, but massive use of pesticides may result in toxicity to soil non-target organisms. Thus, this study was designed to assess subchronic toxicity of different doses of QYR301 in artificial soil (0, 0.1, 1.0, 2.5, and 5.0 mg kg^-1) to earthworms (Eisenia fetida) on days 7, 14, 21, and 28 after exposure, using biomarkers of reactive oxygen species (ROS) and malondialdehyde (MDA) contents, activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and glutathione-S-transferase (GST), and DNA damage. The ROS content significantly increased for all treatments on 7 and 14 days then decreased, and recovered to control level for 0.1 and 1.0 mg kg^-1 treatment on day 28. Concerning enzymes activities, QYR301 increased POD, SOD, and GST activities, but inhibited CAT activity. Except for POD activity, SOD, CAT, and GST activities of 0.1 mg kg^-1 group recovered to control level on day 28. Also, the MDA content of 0.1 mg kg^-1 group reached control level on day 28. However, DNA damage was observed for all treatments throughout the experiment and it increased with increasing doses and time except for 5.0 mg kg^-1 treatment on day 28. These results suggested that QYR301 induced excessive ROS production leading to oxidative stress in earthworms, which caused lipid membrane peroxidation and DNA damage ultimately. The findings could provide a theoretical foundation for assessing ecological damage of QYR301 to soils and a guide for future QYR301 applications.

Evaluation of Tramadol Hydrochloride Toxicity to Juvenile Zebrafish—Morphological, Antioxidant and Histological Responses

The presence of pharmaceuticals in water bodies is associated with the increasing consumption of these substances and limited elimination from wastewater. Pharmaceutical residues and their metabolites may have an unfavorable impact on fish and other aquatic biota. As the purification of wastewater from tramadol is very limited and the knowledge on its effects on non-target organisms is low, we decided to assess the subchronic impact of tramadol hydrochloride on fish—on the mortality, growth and histopathology, together with the impact on selected indices of oxidative stress. The juvenile growth toxicity test was carried out on zebrafish (Danio rerio), in accordance with the Organisation for European Economic Cooperation Guidelines 215 (Fish, Juvenile Growth Test). The fish were exposed to a range of tramadol hydrochloride concentrations (0.2, 2, 20, 200 and 600 µg/L) for 28 days. The outcome of this study suggests that chosen concentrations of tramadol hydrochloride did not affect either mortality or growth (regarding weight, length and specific growth rate). However, the results of this study indicate that 28-day exposure can negatively influence selected indices of oxidative stress, which is a harmful imbalance between free radicals and antioxidants in an organism. A significant increase was observed in glutathione S-transferase activity in the experimental group exposed to 2 µg/L tramadol hydrochloride, compared to the control. Moreover, lipid peroxidation was observed in groups exposed to 20 and 200 µg/L, in comparison to the control.

Applying fungicide on earthworms: Biochemical effects of Eisenia fetida exposed to fluoxastrobin in three natural soils

Fluoxastrobin is one of the most widely used strobilurin fungicides, however, application of the fungicides may result in soil residues leading to environmental damage including oxidative stress and damage to sentinel organisms (i.e. earthworms). While this has been demonstrated in artificial soil, the biochemical response of Eisenia fetida exposed to fluoxastrobin in natural soils is unclear. This study utilized three typical natural soils (fluvo-aquic soils, red clay, and black soils) to evaluate the biochemical response of Eisenia fetida exposed to fluoxastrobin (0.1, 1.0, 2.5 mg/kg) including the production of reactive oxygen species, impact on three enzyme activities, lipid peroxidation, and 8-hydroxydeoxyguanosine after a 4-week exposure. The effects of fluoxastrobin on Eisenia fetida in different soils were assessed using an integrated biomarker response (IBR). The findings may be possible to state that the toxic effects of fluoxastrobin in artificial cannot exactly represent that in natural soils. Specifically, the fluoxastrobin subchronic toxicity was highest in red clay and lowest in black soil among the three natural soils. Furthermore, the 8-OHdG content was more sensitive to fluoxastrobin in all six environmental indicators of the present study.

Effects of sublethal and realistic concentrations of the commercial herbicide atrazine in Pacu (Piaractus mesopotamicus): Long-term exposure and recovery assays

Background and Aim:

The commercial formulations of the herbicide atrazine (cATZ) are widely employed in Brazilian agriculture, and, as a consequence, ATZ has been found at levels above that established by law in the river basins in Brazil. Although the toxicity of ATZ in fish is well documented, there are few studies on the recovery capacity after cATZ exposure. This work aimed to evaluate, using several biomarkers, the toxic effects of long-term exposure to the sublethal (3.57 mg/L) and nonlethal realistic (3.00 µg/L) cATZ concentrations followed by a recovery assay, in fingerlings of a Brazilian teleost, the Piaractus mesopotamicus (pacu).

Materials and Methods:

Pacu fingerlings were housed in glass tanks and divided into the following experimental groups (two tanks/group): Exposure control = EC, recovery control = RC, the sublethal groups exposed to 3.57 mg/L of cATZ, (sublethal exposure group = SLE and sublethal recovery group = SLR) and the nonlethal groups treated with 3.00 µg/L of cATZ (nonlethal exposure group = NLE and nonlethal recovery group = NLR). The exposure assay was semi-static with a duration of 30 days and the recovery assay (after cATZ withdrawal) lasted 14 days. Several biomarkers were evaluated in fingerlings from all groups: The swimming behavior, the body weight gain, the micronucleus formation and nuclear alterations in erythrocytes, and the hepatic and renal histopathology analyzed by qualitative and semi-quantitative morphological methods (using light and electron microscopy).

Results:

No significant difference in weight gain was observed among the groups after the exposure and recovery assays. The sublethal exposure induced impaired swimming movements, significant histopathological alterations, including necrosis in the liver and kidney, and a significant increase in the frequency of micronuclei in erythrocytes. The nonlethal exposure induced only subtle histopathological changes in the liver and kidney. After recovery assay, no genotoxic alteration was noted in pacu exposed to sublethal concentration, while the cATZ-induced kidney damage was partially reversed but not the hepatic injury.

Conclusion:

cATZ exhibits long-term toxic effects on pacu, even at relatively low concentrations, affecting mainly the liver and the kidney, and the effects of sublethal concentration are only partially reversed after cATZ withdrawal.

Environmentally relevant atrazine exposures cause DNA damage in cells of the lateral antennules of crayfish (Faxonius virilis)

The herbicide atrazine is heavily applied in agricultural areas in the Midwestern United States and can run-off and seep into surrounding aquatic habitats where concentrations can reach over 300 ppb. It is known that acute exposures to 80 ppb atrazine cause lasting deficiencies in the chemoreception of food and mate odors. Since atrazine impairs chemosensory responses, the goal of this study was to determine the effect of atrazine on cells, including olfactory sensory neurons, located in the lateral antennules of crayfish. In this experiment, we treated crayfish for 10 days with ecologically relevant concentrations of 0, 10, 40, 80, 100 and 300 ppb (μg L^-1) of atrazine. Following treatments, the distal portion of the lateral antennules was cryosectioned. We used a TdT mediated dUTP nick-end labeling (TUNEL) assay to determine if any cells had DNA damage and may be thus undergoing apoptosis. We found that as atrazine concentrations increase above 10 ppb, the number of TUNEL-positive cells, visualized in the lateral antennules, significantly increases. Our data show that atrazine exposure causes DNA damage in cells of the lateral antennules, including olfactory sensory neurons, thus leading to impairments in chemosensory abilities. Because crayfish rely heavily on chemoreception for survival, changes in their ability to perceive odors following atrazine exposure may have detrimental effects on population size.

Cytochrome P450 and Glutathione-S-Transferase Activity are Altered Following Environmentally Relevant Atrazine Exposures in Crayfish (Faxoniusvirilis)

The herbicide atrazine is heavily applied in the U.S. Midwest to control broadleaf weeds. It enters local streams and rivers through runoff and seepage, and exposure can affect non-target aquatic organisms, like crayfish. We examined sublethal effects of atrazine on the expression and activity of the detoxification enzymes cytochrome P450 (CYP450) and glutathione-S-transferase (GST) in crayfish. Crayfish were exposed to 0, 10, 40, 80, 100 and 300 ppb atrazine for 1, 2, 4, 7 and 10 days. Their hepatopancreas was collected and CYP450 expression and GST activity was analyzed. Atrazine exposure caused differential expression and activity of CYP450 and GST. CYP450 expression varied over exposure concentrations and time. Further, GST activity significantly increased following a 2 day, 10 ppb exposure to atrazine and a 300 ppb atrazine exposure for all days tested. We found that atrazine detoxification is a dynamic process that changes with the length and intensity of atrazine exposure.

Effects of atrazine on life parameters, oxidative stress, and ecdysteroid biosynthetic pathway in the marine copepod Tigriopus japonicus

Atrazine is a widely used pesticide which acts as an endocrine disruptor in various organisms. The aim of this study was to investigate adverse effects of atrazine on life parameters, oxidative stress, and ecdysteroid biosynthetic pathway in the marine copepod Tigriopus japonicus. In T. japonicus, no mortality was shown in response to atrazine up to 20 mg/L in acute toxicity assessment. In nauplii, retardation in the growth and prolonged molting and metamorphosis resulted under chronic exposure of atrazine at 20 mg/L. In addition, body sizes of T. japonicus nauplii were significantly decreased (P < 0.01 in length and P < 0.001 in width) in response to 20 mg/L of atrazine. Furthermore, atrazine induced oxidative stress by the generation of reactive oxygen species at all concentrations compared to the control in the nauplii. Also, significant increase in glutathione-S transferase activity was observed in adult T. japonicus at low concentration of atrazine. To understand effects of atrazine on ecdysteroid biosynthetic pathway-involved genes (e.g., neverland, CYP307E1, CYP306A1, CYP302A1, CYP3022A1 [CYP315A1], CYP314A1, and CYP18D1) were examined with mRNA expressions of ecdysone receptor (EcR) and ultraspiracle (USP) in response to 20 mg/L atrazine in nauplii and adults. In the nauplii, these genes were significantly downregulated (P < 0.05) in response to atrazine, compared to the control but not in the adult T. japonicus. These results suggest that atrazine can interfere in vivo life parameters by oxidative stress-induced retrogression and ecdysteroid biosynthetic pathway in this species.

Oxidative stress and genotoxic effects in earthworms induced by five imidazolium bromide ionic liquids with different alkyl chains

In this study, the acute and subchronic toxicity of 1-alkyl-3-methyl imidazole bromide ionic liquids (ILs) [C_nmim]Br (n = 2, 4, 6, 10, 12) was evaluated utilizing earthworms (Eisenia fetida) as a basis for their impact on terrestrial ecosystems. The filter paper tests and artificial soil tests were conducted as acute toxicity tests to investigate the LC₅₀ of ILs, while in subchronic toxicity tests, earthworms were exposed to ILs in artificial soil (5, 10, 20 and 40 mg kg^-1) for 28 d. Reactive oxygen species (ROS), antioxidant enzymes, detoxifying enzymes and oxidative damage were measured to determine subchronic effects of ILs on E. fetida. The results showed that when the earthworms were exposed to these five ILs in acute toxicity experiments, [C₂mim]Br had the lowest toxicity, as the alkyl length increased, the toxicity increased up to [C₁₀mim]Br: a "cut-off effect" (decreased toxicity) was observed at [C₁₂mim]Br. The results highlight the varying toxicity of ILs with different alkyl chains to E. fetida and provide valuable data for detailing the impact of ILs on ecological receptors.

Parental transfer of ethylhexyl methoxy cinnamate and induced biochemical responses in zebrafish

Ethylhexyl methoxy cinnamate (EHMC) is one of the major organic ultraviolet (UV) filter pollutants in the environment. The purpose of this study was to investigate the parental transfer of EHMC and induced biochemical responses in zebrafish (Danio rerio). Zebrafish embryos were exposed to EHMC solution (1, 10, and 100 μg/L) for 4 months until sexual maturation. Then male and female parents were paired to lay eggs. F1 generations were divided into 2 categories: with and without continued EHMC exposure. EHMC was detected in both F0 parents and F1 eggs, indicating that EHMC can accumulate in zebrafish and transfer to offspring through reproduction. The hatching rate decreased and malformation rate increased significantly among parents and progeny embryos in the high concentration exposure group. For 40 dpf (days post-fertilisation) F0 generations, estradiol hormone and vitellogenin (Vtg) contents, the expression levels of Vtg1, P450 aromatase (Cyp19a and Cyp19b), 17β-hydroxysteroid dehydrogenase (Hsd17b1, Hsd17b3), estrogen receptor-alpha and progesterone receptor in all concentration groups decreased significantly, while androgen receptor increased significantly in 10 and 100 μg/L exposure groups compared with the corresponding control group, showing anti-estrogen and androgen effects. For 120 dpf F0 generations, acetylcholinesterase activity was significantly decreased and glutathione and malondialdehyde levels, superoxide dismutase, catalase and glutathione reductase activities were significantly increased in all treatment groups compared with the corresponding control group. In addition, F1 offspring with or without continued exposure to EHMC suffered similar or stronger oxidative stress compared with their parents. DNA breakage and apoptosis also occurred in 120 dpf parental liver cells in all treatment groups as a result of oxidative damage. Results suggested that EHMC have transfer effects between parents and offspring, which may cause negative effects on growth and development of zebrafish and induce biochemical responses in both parents and offspring.

Evaluating subchronic toxicity of fluoxastrobin using earthworms (Eisenia fetida)

Potential toxicity to soil organisms by fluoxastrobin, a new strobilurin-type fungicide has drawn increasing attention. Thus, the present study investigated the subchronic toxicity induced by exposure to several concentrations (0, 0.1, 1.0, and 2.5 mg kg^-1) of fluoxastrobin to earthworms on days 7, 14, 21, and 28. Biochemical indicators (e.g., reactive oxygen species (ROS) content, activities of antioxidase and detoxifying enzymes (superoxide dismutase, catalase, and glutathione S-transferase), lipid peroxidation (malonaldehyde) and degree of DNA damage) were measured. No earthworm deaths were observed during the entire experimental period. For ROS and malonaldehyde, the bioassay values of the three doses reached a maximum on day 21 and then decreased. For superoxide dismutase and glutathione S-transferase, the values increased with the exposure doses of 0.1 and 1.0 mg kg^-1 and then decreased. In contrast, the values for catalase were lower on days 7, 14, and 28 and greater on day 21 compared to those of the controls. In addition, the comet assay was more sensitive than other biomarkers, and the degree of DNA damage was dose and time -dependent.

Responses of antioxidant and biotransformation enzymes in Carassius carassius exposed to hexabromocyclododecane

The ubiquitous existence of hexabromocyclododecane (HBCD) in environmental matrices has made it attractive to both field investigators as well as laboratory researchers. However, literature on the biological effects caused by HBCD on aquatic vertebrates seldom exist. This has inevitably increased the difficulty of toxicological assessment in the aquatic environment. Juvenile crucian carp (Carassius carassius) were exposed (flow-through) to different concentrations of technical HBCD (nominal 2, 20, 200 μg L^-1) for 7 days to determine the responses of antioxidant and biotransformation enzymes. HBCD was found to be increasingly bioconcentrated in the fish livers as time proceeds. Also, the contribution of α-HBCD exhibited an enhancement from 13% in the exposure solutions to 24% in crucian carp, still much lower than in wild fishes (ca. 80%). HBCD induced activities of antioxidant enzymes in most cases, as well as increased level of lipid peroxidation. In contrast to the weak response of 7-ethoxyresorufin-O-deethylase (EROD), 7-pentoxyresorufin-O-depentylase (PROD) activity was generally induced in a time-dependent manner with peaks at day 2. Phase II enzyme Glutathione-S-transferase (GST) showed a dose-dependent induction with maximums in the 20 μg L^-1 treatment at all the four timepoints of 1, 2, 4 and 7 days. Some enzymatic responses showed good associations, indicating coordinated functions. To sum up, tHBCD exposure in the present circumstance had produced an ecological stress to crucian carp. The low levels of biotransformation and slow rates of bioisomerization suggest a possible long-term toxic effect, especially around HBCD point sources.

Toxic effect of [Omim]BF4 and [Omim]Br on antioxidant stress and oxidative damage in earthworms (Eisenia fetida)

In this paper, model soil organism, earthworms (Eisenia fetida), were selected to examine the chronic toxic effect of two different ionic liquids (ILs) [Omim]BF₄ and [Omim]Br. Earthworms were put into different ILs concentrations (0, 5, 10, 20, 40 mg/kg) in artificial soil and random selected on days 7, 14, 21 and 28. Reactive oxygen species (ROS), antioxidant enzymes and detoxifying enzyme glutathione-S-transferase (GST) were researched for determination of antioxidant stress. Malondialdehyde (MDA) and olive tail moment (OTM) were researched to determine the oxidative damage. Both the pollutants had the same effect on earthworms: ILs led to accumulation of ROS, and then antioxidant enzymes and detoxification enzyme all changed to eliminate the effects of ROS, and the above process led to lipid peroxidation and DNA damage in earthworms. This paper shows that [Omim]BF₄ and [Omim]Br both caused toxicity to earthworms and had the similar toxicity levels.

Acute and chronic toxic effects of fluoxastrobin on zebrafish (Danio rerio)

Fluoxastrobin is a new strobilurin fungicide, similar to azoxystrobin and pyraclostrobin. Before the wide application of fluoxastrobin, the present study was performed to assay the acute and chronic toxicity of fluoxastrobin on zebrafish (Danio rerio). The 96-hour median lethal concentration (96h LC₅₀) after initiation of zebrafish exposure to fluoxastrobin was 0.51mg/L with a 95% confidence interval of 0.45 to 0.57mg/L, indicating that fluoxastrobin was highly toxic to zebrafish. As endpoints, we assayed the levels of reactive oxygen species (ROS), malondialdehyde (MDA), the activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and the degree of DNA damage at three different doses, 0.001, 0.01, and 0.1mg/L on days 7, 14, 21, and 28. The antioxidant enzymes partially ameliorated the ROS induced by fluoxastrobin t and were in turn inhibited by excess ROS, especially at 0.1mg/L. Lipid peroxidation and DNA damage were stimulated by ROS. The fluoxastrobin contents of the tested solutions were also determined; at the fluoxastrobin doses of 0.001, 0.01, and 0.1mg/L, the contents on day 28 were 3.9, 5.0, and 0.64% greater than those on day 0. Thus, fluoxastrobin was relatively stable in an aquatic environment. In addition, the present study provided more information regarding the toxic effects of fluoxastrobin and the scientific methods for selection and evaluation of fungicides in the future.

Acute and subchronic toxicity of pyraclostrobin in zebrafish (Danio rerio)

The aim of the present study was to assess the toxic effects of pyraclostrobin on DNA damage and antioxidant enzymatic activities in the zebrafish (Danio rerio) liver. Based on the 96-h median lethal concentration (96 h LC₅₀, 0.056 mg/L) of this chemical, fish were exposed to three doses (0.001, 0.01, and 0.02 mg/L) and sampled on days 7, 14, 21 and 28 after the initiation of a subchronic toxicity test. The levels of superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), glutathione S-transferase (GST), reactive oxygen species (ROS) and DNA damage were determined. The amount of pyraclostrobin residue in the water was also measured. The concentrations in the three treatment groups varied no more than 5% during the exposure periods, indicating that pyraclostrobin is relatively stable during this time in an aquatic environment. ROS and MDA levels significantly changed in a dose dependent manner during the experiment. Enzymatic activities were inhibited to a certain extent. DNA damage was significantly enhanced. These results collectively indicate that pyraclostrobin induces oxidative stress and DNA damage in zebrafish.

Acute toxicity, biochemical toxicity and genotoxicity caused by 1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium tetrafluoroborate in zebrafish (Danio rerio) livers

The present study examined the potential toxicity of 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and 1-butyl-3- methylimidazolium tetrafluoroborate ([Bmim]BF₄) in the liver cells of zebrafish (Danio rerio) with different doses (20-160mg/L) on 7 and 14days. The effects of [Bmim]Cl and [Bmim]BF₄ on acute toxicity, reactive oxygen species (ROS), antioxidant enzymes, glutathione S-transferase (GST), malondialdehyde (MDA), and DNA damage degree in livers of zebrafish were determined. The 50% lethal concentration (LC₅₀) values after a 96-h exposure to [Bmim]Cl and [Bmim]BF₄ were 632.8±67.4 and 604.6±56.2mg/L, respectively, which indicated that the substances were practically harmless. The minor discrepancy may be caused by the different anions. The ROS levels were dose-dependent, which may cause the inhibition of antioxidant enzyme activity, lipid peroxidation, DNA damage and the stimulation of detoxifying enzyme activity. The present study can also provide scientific support for the future selection and evaluation of ionic liquids (ILs).

Effects of oxidative stress reaction for the Eisenia fetida with exposure in Cd2

Earthworms are widely used in all kinds of pollutants as sensitive bio-indicator organisms because of their immediately oxidative stress response under the stress of heavy metal. However, there are a large number of indexes associated with the oxidative stress response. Finding out the key monitoring indexes in the stress process becomes a practical demand of the pollution monitoring and warning process. We studied two groups, the short-term test and the long-term test. The former one is for 10 days, taking out an earthworm every day. The latter test lasted 30 days, taking out an earthworm every 10 days. The Cd²⁺ concentration was set at 50, 100, 125, 250, and 500 mg kg^-1. Post-clitellum segments of earthworms were chosen to determine superoxide enzyme (SOD), peroxidase (POD), glutathione peroxidase (GSH-Px), glutathione-S transferase (GST), catalase (CAT), vitamin E (VE), malondialdehyde (MDA), and acetylcholinesterase (AChE). The results showed that the main bio-indicators associating with oxidative stress reaction in short-term group were CAT, SOD, and POD. MDA could be used as a bio-indicator in the early and mid-term. VE was only the bio-indicator in the mid-term stress. While with the long-term test, the main bio-indicators associated with oxidative stress reaction were GSH-Px and MDA. The AChE activity was only suitable for oxidative stress response caused by heavy metal stress more than 30 days.

Genotoxicity and oxidative stress induced by the fungicide azoxystrobin in zebrafish (Danio rerio) livers

Azoxystrobin is a frequently used fungicide in agriculture. Its toxicological effects on non-target organisms have aroused attention. In the present work, the toxic effects of azoxystrobin on zebrafish (Danio rerio) were investigated. Male and female zebrafish were separately exposed to a control solution and three azoxystrobin treatments (1, 10, and 100μg/L) and were sampled on days 7, 14, 21, and 28. Reactive oxygen species (ROS) were accumulated in excess in the zebrafish livers. Superoxide dismutase (SOD) activity was significantly inhibited in the male zebrafish. Moreover, a notable decrease was also observed after day 21 in the female zebrafish. Catalase (CAT) activity was induced by the azoxystrobin treatments with the exception of the 1μg/L treatment. A significant increase in glutathione-S-transferase (GST) activity was observed after day 21. Lipid peroxidation (LPO) was generated, and DNA damage was enhanced in a concentration-dependent manner. In conclusion, azoxystrobin induced oxidative stress and genotoxicity in zebrafish livers.

Study on the influential factors of Cd(2+) on the earthworm Eisenia fetida in oxidative stress based on factor analysis approach

When earthworms are exposed to pollutants, their antioxidant system will have responses immediately. Consequently earthworms are widely used to monitor various pollutants as a sensitive bio-indicator. However, there are a large number of indices associated with the oxidative stress response. Finding out the key monitoring indices in the stress process becomes a practical demand of the pollution monitoring and warning process. Factor analysis approach is a statistical method that uses a few factors to replace many original factors. This paper is aimed at analyzing and sorting factors related to Cd(2+) on the earthworm Eisenia fetida in oxidative stress. We studied two groups, the short-term test and the long-term test. The former test lasted for ten days, removing an earthworm every day for analysis; The latter test lasted for 30 days, taking out an earthworm every ten days. The Cd(2+) concentration was set at 0, 50, 100, 125, 250 and 500 mg kg(-1), post-clitellum segments of earthworms were chosen to determine SOD, POD, GPX, GST, CAT, VE, MDA and AChE. The results showed that in the short-term group, the main bioindicator associated with oxidative stress reaction was CAT at the exposure time of 1-3 days, at 4-5 days MDA, 6-7 days POD, and GST and GPX at 8th day, CAT at 9-10 days. While with the long-term test, the main bioindicator associated with oxidative stress reaction was GPX.

Biochemical responses and DNA damage in earthworms (Eisenia fetida) induced by ionic liquid [omim]PF6

Ionic liquids that are not that "green" to many organisms have recently been identified. This study examined the subchronic toxicity of the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([omim]PF6) to earthworms (Eisenia fetida). Earthworms were exposed for a 28-day period (sampled on days 7, 14, 21, and 28) at concentrations of 0, 5, 10, 20, and 40 mg/kg. The levels of reactive oxygen species (ROS), antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD)), detoxifying enzyme (glutathione S-transferase (GST)), lipid peroxidation, and DNA damage were measured. ROS significantly accumulated in all the treatment groups; the maximum ROS content was 51.9% higher than the control at 40 mg/kg [omim]PF6 on day 28. Increased SOD activities attenuated over the time of exposure, while the CAT activities of the treatment groups were similar to the controls, except on day 14. Furthermore, the activities of POD and GST were stimulated. Lipid peroxidation in earthworms was not apparent at 5 and 10 mg/kg [omim]PF6 but was quite obvious at 40 mg/kg [omim]PF6. In addition, DNA damage was dose- and time-dependent. In conclusion, [omim]PF6 caused oxidative stress and genotoxicity in earthworms.

Assessing toxic effects of [Omim]Cl and [Omim]BF4 in zebrafish adults using a biomarker approach

In the present study, the toxic effects of 1-octyl-3-methylimidazolium chloride ([Omim]Cl) and 1-octyl-3-methylimidazolium tetrafluoroborate ([Omim]BF4) on the zebrafish livers were studied at 0, 5, 10, 20, and 40 mg L(-1) on the 7th and 14th days. In addition, the concentrations of [Omim]Cl and [Omim]BF4 in the test water, the acute toxicity of the two ionic liquids (ILs), and the influence of anions on the toxicity of the ILs were evaluated. The acute toxicity test results showed 50 % lethal concentration (LC50) values of 152.3 ± 12.1 mg L(-1) for [Omim]Cl and 144.0 ± 11.4 mg L(-1) for [Omim]BF4. At the lowest concentration investigated (5 mg L(-1)), [Omim]Cl and [Omim]BF4 did not significantly affect zebrafish during the exposure period. However, the toxic effects of these substances were enhanced as dosing concentrations and exposure times were increased. Levels of reactive oxygen species (ROS) were significantly enhanced on the 7th day after 20 mg L(-1) and on the 14th day after 10 mg L(-1) of either substance was applied, resulting in oxidative damage, such as lipid peroxidation and DNA damage. The experimental results also indicated little effect of the anions on the toxicity of ILs and consistent toxic effects of [Omim]Cl and [Omim]BF4. Graphical Abstract The graphical abstract for the present study after exposure to [Omim]Cl and [Omim]BF4. The letter R represents the anions Cl(-) and BF4 (.)

Acute Atrazine Exposure has Lasting Effects on Chemosensory Responses to Food Odors in Crayfish (Orconectes virilis)

The herbicide atrazine is known to impact negatively olfactory-mediated behaviors in aquatic animals. We have shown that atrazine exposure has deleterious effects on olfactory-mediated behavioral responses to food odors in crayfish; however, recovery of chemosensory abilities post-atrazine exposure has not been investigated. We examined whether crayfish (Orconectes virilis) recovered chemosensory abilities after a 96-h exposure to sublethal, environmentally relevant concentrations of 80 ppb (µg/L) atrazine. Following treatment, we analyzed the ability of the crayfish to locate a food source using a Y-maze with one arm containing fish-flavored gelatin and the other containing unflavored gelatin. We compared the time spent in the food arm of the Y-maze, near the food source, as well as moving and walking speed of control and atrazine-treated crayfish. We also compared the number of crayfish that handled the food source and the amount of food consumed. Following 24-, 48-, and 72-h recovery periods in fresh water, behavioral trials were repeated to determine if there was any observable recovery of chemosensory-mediated behaviors. Atrazine-treated crayfish spent less time in the food arm, at the odor source, and were less successful at finding the food odor source than control crayfish for all times tested. Additionally, atrazine-treated crayfish consumed less fish-flavored than control crayfish; however, treatment did not affect locomotion. Overall, we found that crayfish are not able to recover chemosensory abilities 72 h post-atrazine exposure. Because crayfish rely heavily on their chemosensory abilities to acquire food, the negative impacts of atrazine exposure could affect population size in areas where atrazine is heavily applied.

Biochemical and genetic toxicity of the ionic liquid 1-octyl-3-methylimidazolium chloride on earthworms (Eisenia fetida)

Ionic liquids also known as "green solvents," are used in many fields. However, the dispersion of ionic liquids in soil systems is likely to cause damage to soil organisms. The objective of the present study was to investigate the toxicity of 1-octyl-3-methylimidazolium chloride ([C8 mim]Cl) on earthworms (Eisenia fetida). For this purpose, earthworms were exposed to different concentrations of [C8 mim]Cl (0 mg/kg, 5 mg/kg, 10 mg/kg, 20 mg/kg, and 40 mg/kg artificial soil) and sampled at 7 d, 14 d, 21 d, and 28 d. The results indicated that [C8 mim]Cl could cause an accumulation of reactive oxygen species (ROS) in earthworms, even at the lowest concentration (5 mg/kg). Compared with the controls, during the [C8 mim]Cl exposure period, the activities of superoxide dismutase (SOD) and catalase (CAT) decreased and then increased, whereas the activities of peroxidase (POD) and glutathione S-transferase (GST) increased. These changes in the activities of antioxidant enzymes and GST indicated that [C8 mim]Cl could induce oxidative damage in earthworms. The malondialdehyde content was increased by high levels of [C8 mim]Cl at 14 d and 28 d, indicating that [C8 mim]Cl could lead to lipid peroxidation in earthworms. In addition, the degree of DNA damage significantly increased with increasing [C8 mim]Cl concentrations and exposure time. The present study shows that [C8 mim]Cl caused biochemical and genetic toxicity in earthworms.

Transcriptional profiles of glutathione-S-Transferase isoforms, Cyp, and AOE genes in atrazine-exposed zebrafish embryos

Glutathione-S-transferase (GST) superfamily consists of multiple members involved in xenobiotic metabolism. Expressional pattern of the GST isoforms in adult fish has been used as a biomarker of exposure to environmental chemicals. However, GST transcriptional responses vary across organs, thus requiring a cross-tissue examination of multiple mRNAs for GST profiling in an animal after chemical exposure. Zebrafish embryos express all GST isoforms as adult fish and could therefore represent an alternative model for identification of biomarkers of exposure. To evaluate such a possibility, we studied a set of cytosolic and microsomal GST isoform-specific expression profiles in the zebrafish embryos after exposure to atrazine, a widely used herbicide. Expression of the GST isoforms was compared with that of CYP genes involved in the phase I of xenobiotic metabolism and antioxidant enzyme (AOE) genes. Using quantitative real-time PCR, we showed dynamic changes in the expressional pattern of twenty GST isoforms, cyp1a, cyp3a65, ahr2, and four AOEs in early development of zebrafish. Acute (48 and 72 h) exposure of 24 h-old embryos to atrazine, from environmentally relevant (0.005 mg/L) to high (40 mg/L) concentrations, caused a variety of transient, albeit minor changes (<2.5-fold) in the GST isoforms, ahr2 and AOE genes response. However, expression of cyp1a and cyp3a65 mRNA was markedly and consistently induced by high doses of atrazine (5 and 40 mg/L). In summary, an analysis of the response of multiple systems in the zebrafish embryos provided a comprehensive understanding of atrazine toxicity and its potential impact on biological processes.

Glutathione S-transferase activities in African catfish injected with β-naphthoflavone: effects of ploidy, gender, dose, and sampling time

Glutathione S-transferases (GST) are considered among the most controversial biomarkers of water pollutants in fish with little known about factors influencing their activities. The objective of this study was to investigate how gender, dose, ploidy, and sampling time alter hepatic GST activities in African catfish (Clarias gariepinus) following β-naphthoflavone (β-NF) injection. Newly matured male and female diploid and triploid fish were intraperitoneally (i.p.) injected with 0, 15, or 75 mg/kg of β-NF, and livers were excised 24, 48, and 72 h post-injection. Results showed that hepatic GST activities were significantly inhibited by both doses of β-NF. Inhibition was greater in females than males, but no significant differences were observed between diploid and triploid fish. Enzymatic activities differed over time with lowest levels 72 h post-injection. These results extend our understanding of GST activity in fish and highlight the necessity of considering confounding factors when comparing different studies.

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 Triggers DNA Damage Response and Induces DNA Double-Strand Breaks in MCF-10A Cells

Atrazine, a pre-emergent herbicide in the chloro-s-triazine family, has been widely used in crop lands and often detected in agriculture watersheds, which is considered as a potential threat to human health. Although atrazine and its metabolites showed an elevated incidence of mammary tumors in female Sprague–Dawley (SD) rats, no molecular evidence was found relevant to its carcinogenesis in humans. This study aims to determine whether atrazine could induce the expression of DNA damage response-related proteins in normal human breast epithelial cells (MCF-10A) and to examine the cytotoxicity of atrazine at a molecular level. Our results indicate that a short-term exposure of MCF-10A to an environmentally-detectable concentration of atrazine (0.1 µg/mL) significantly increased the expression of tumor necrosis factor receptor-1 (TNFR1) and phosphorylated Rad17 in the cells. Atrazine treatment increased H2AX phosphorylation (γH2AX) and the formation of γH2AX foci in the nuclei of MCF-10A cells. Atrazine also sequentially elevated DNA damage checkpoint proteins of ATM- and RAD3-related (ATR), ATRIP and phospho-Chk1, suggesting that atrazine could induce DNA double-strand breaks and trigger the DNA damage response ATR-Chk1 pathway in MCF-10A cells. Further investigations are needed to determine whether atrazine-triggered DNA double-strand breaks and DNA damage response ATR-Chk1 pathway occur in vivo.

Atrazine exposure affects the ability of crayfish (Orconectes rusticus) to localize a food odor source

Environmental pollutants, found in aquatic ecosystems, have been shown to have an effect on olfactory-mediated behaviors including feeding, mate attraction, and other important social behaviors. Crayfish are polytrophic, meaning that they feed on and become prey for all levels of the aquatic food web as well as are also important for the transfer of energy between benthic and terrestrial food webs. Because crayfish are a keystone species, it is important to investigate any factors that may affect their population size. Crayfish are active at night and rely heavily on their sensory appendages (e.g., antennulues, maxillipeds, and pereopods) to localize food sources. In this experiment, we investigated the effects of atrazine (ATR) exposure on the chemosensory responses of male and female crayfish to food odors. We exposed crayfish to environmentally relevant, sublethal levels of ATR [80 ppb (µg/L)] for 72 h and then examined the behavioral responses of both ATR-treated and control crayfish to food odor delivered from one end of a test arena. We used Noldus Ethovision XT software to measure odor localization and locomotory behaviors of crayfish in response to food (fish) odor. We found that control crayfish spent more time in the proximal region of the test arena and at the odor source compared with ATR-treated crayfish. Furthermore, there were no differences in the time spent moving and not moving, total distance travelled in the tank, and walking speed (cm/s) when control and ATR-treated crayfish were compared. Overall, this indicates that acute ATR exposure alters chemosensory abilities of crayfish, whereas overall motor function remains unchanged.