Effects of atrazine on hepatic metabolism and endocrine homeostasis in rainbow trout (Oncorhynchus mykiss)

Effects of low-dose ionizing radiation on the molecular pathways linking neurogenesis and autism spectrum disorders in zebrafish embryos

Prenatal exposure to environmental factors may play an important role in the aetiopathogenesis of autism spectrum disorder (ASD). We aim to investigate the potential effects of low-dose x-rays from dental diagnostic x-rays on neurodevelopment and molecular mechanisms associated with ASD in developing zebrafish embryos. Zebrafish embryos were divided into four groups and exposed using a dental x-ray unit: control, 0.08, 0.15 and 0.30 seconds, which are exemplary exposure settings for periapical imaging. These exposure times were measured as 7.17, 23.17 and 63.83 mSv using optical stimulated luminescence dosimeters. At the end of 72 hours post-fertilization, locomotor activity, oxidant-antioxidant status, and acetylcholine esterase (AChE) activity were analyzed. Expression of genes related to apoptosis (bax, bcl2a, p53), neurogenesis (α1-tubulin, syn2a, neurog1, elavl3) and ASD (eif4eb, adsl2a, shank3) was determined by RT-PCR. Even at reduced doses, developmental toxicity was observed in three groups as evidenced by pericardial edema, yolk sac edema and scoliosis. Deleterious effects of dental x-rays on neurogenesis through impaired locomotor activity, oxidative stress, apoptosis and alterations in genes associated with neurogenesis and ASD progression were more pronounced in the 0.30s exposure group. Based on these results we suggest that the associations between ASD and low-dose ionizing radiation need a closer look.

Non-microcystin extracellular metabolites of Microcystis aeruginosa impair viability and reproductive gene expression in rainbow trout cell lines

Microcystis aeruginosa is a ubiquitous freshwater cyanobacterium best known for producing hepatotoxic microcystins; however, this common bloom-forming species also produces myriad biologically active and potentially deleterious other metabolites. Our understanding of the effects of these non-microcystin metabolites on fish is limited. In this study, we evaluated cytotoxicity of extracellular metabolites harvested from both microcystin-producing (MC+) and non-producing (MC-) strains of M. aeruginosa on rainbow trout (Oncorhynchus mykiss) cell lines derived from tissues of the brain, pituitary, heart, gonads, gills, skin, liver, and milt. We also examined the influence of M. aeruginosa exudates (MaE) on the expression of critical reproduction-related genes using the same cell lines. We found that exudates of the MC- M. aeruginosa strain significantly reduced viability in RTBrain, RTgill-W1, and RT-milt5 cell lines and induced significant cellular stress and/or injury in six of the eight cell lines-highlighting potential target tissues of cyanobacterial cytotoxic effects. Observed sublethal consequences of Microcystis bloom exposure occurred with both MC+ and MC- strains' exudates and significantly altered expression of developmental and sex steroidogenic genes. Collectively, our results emphasize the contributions of non-MC metabolites to toxicity of Microcystis-dominated algal blooms and the need to integrate the full diversity of M. aeruginosa compounds-beyond microcystins-into ecotoxicological risk assessments.

Zinc Oxide Nanoparticles and Vitamin C Ameliorate Atrazine-Induced Hepatic Apoptosis in Rat via CYP450s/ROS Pathway and Immunomodulation

Atrazine, as an herbicide, is used widely worldwide. Because of its prolonged persistence in the environment and accumulation in the body, atrazine exposure is a potential threat to human health. The present study evaluated the possible protective effects of zinc oxide nanoparticles and vitamin C against atrazine-induced hepatotoxicity in rats. Atrazine administered to rats orally at a dose of 300 mg/kg for 21 days caused liver oxidative stress as it increased malondialdehyde (MDA) formation and decreased reduced glutathione (GSH) contents. Atrazine induced inflammation accompanied by apoptosis via upregulation of hepatic gene expression levels of NF-κB, TNF-α, BAX, and caspase-3 and downregulation of Bcl-2 gene expression levels. Additionally, it disturbed the metabolic activities of cytochrome P450 as it downregulated hepatic gene expression levels of CYP1A1, CYP1B1, CYP2E1. The liver function biomarkers were greatly affected upon atrazine administration, and the serum levels of AST and ALT were significantly increased, while BWG%, albumin, globulins, and total proteins levels were markedly decreased. As a result of the above-mentioned influences of atrazine, histopathological changes in liver tissue were recorded in our findings. The administration of zinc oxide nanoparticles or vitamin C orally at a dose of 10 mg/kg and 200 mg/kg, respectively, for 30 days prior and along with atrazine, could significantly ameliorate the oxidative stress, inflammation, and apoptosis induced by atrazine and regulated the hepatic cytochrome P450 activities. Furthermore, they improved liver function biomarkers and histopathology. In conclusion, our results revealed that zinc oxide nanoparticles and vitamin C supplementations could effectively protect against atrazine-induced hepatotoxicity.

Atrazine contaminated sites and bullfrog tadpoles: evasive trends and biochemical consequences

Atrazine (ATZ) is one of the most used active principles in agricultural systems. This pesticide has the ability to easily accumulate in terrestrial and aquatic environments, causing impacts with chronic adverse effects. Avoidance tests are tests that seek to assess the concentration from which a given organism escapes, that is, migrates to another habitat. They are being used as a modality of innovative and minimally invasive ecotoxicological tests. Our objective was to evaluate the sensitivity and possible toxic effects of ATZ in bullfrog tadpoles (Lithobates catesbeianus), through avoidance tests and oxidative stress analyses. We performed the behavioral avoidance test lasting 12 h, with observations every 60 min in a linear multi-compartment system with seven compartments. Each compartment corresponded to a concentration: negative control, 1, 2, 20, 200, 2000, 20,000 µg L^-1. After the selection of habitat, organisms were forcedly maintained in the chosen concentrations for 48 h and then, metabolic effects were measured assessing the blood plasma amino acid profile and liver protein degradation. We also determined the effective concentrations of ATZ tested at 0 h and 48 h. The results showed that there was an effect of the treatment on the distribution of tadpoles, but not on the hours or on the combined effect (interaction). The biochemical analyses also showed a concentration-dependent relationship which caused significant toxic effects even in a short period of time. In conclusion, these frogs were able to avoid places with high concentrations of ATZ in the first hours of exposure, which suggests that in the natural environment these animals can migrate or avoid areas contaminated by this herbicide; however, depending on the selected concentration, serious biochemical consequences can occur.

Embryotoxicity of atrazine and its degradation products to early life stages of zebrafish (Danio rerio)

Triazine herbicide atrazine is considered to be moderately toxic to various aquatic animals. The aim of our study was to evaluate the acute embryotoxicity of atrazine and its two degradation products, desisopropylatrazine and desethylatrazine, and their mixture to the early life stages of zebrafish (Danio rerio) by means of a modified method of the Fish Embryo Acute Toxicity (FET) Test - OECD guideline 236. Toxic effects were studied by the evaluation of lethal endpoints and development of disorders. Furthermore, sublethal endpoints such as hatching rate, formation of somites, development of eyes, spontaneous movement, heartbeat, blood circulation, pigmentation and occurrence of edema at 24, 48, 72 and 96 h post fertilization were assessed. Newly fertilized eggs were exposed to various concentrations of atrazine, desisopropylatrazine and desethylatrazine, and their combination 0.3, 30, 100, 300, 1000, 3,000 and 10,000 μg/l, which represent environmentally relevant levels of these pollutants in surface waters and multiples of these concentrations to find out if the toxic effect depends on dose. Single substances and their combination were not associated with a negative effect on mortality. Rare malformations were observed during these embryonal toxicity tests. Only pericardial edema was recorded during the monitored observation. A significant increase in the occurrence of pericardial edema between the control 0% and the experimental group 17.6 %) was found only in the group exposed to the highest concentration of a triazine herbicide combination (10,000 μg/l) at 72 and 96 h post fertilization. Obtained results indicate that especially higher not environmentally relevant concentrations of atrazine, its metabolites or their combination present a potencial risk of embryotoxicity for zebrafish.

Mesotrione herbicide does not cause genotoxicity, but modulates the genotoxic effects of Atrazine when assessed in mixture using a plant test system (Allium cepa)

Mesotrione (MES) is an herbicide from the triketone family and has been used as an alternative to Atrazine (ATZ), which was banned in some countries due to its toxicity to non-target organisms. Despite being considered an eco-friendly herbicide, data from the literature about the harmful effects of MES in its pure form and/or in combination with other herbicides is still scarce. Aimed at assessing the potential of MES to induce cell death and DNA damage, seeds of Allium cepa (higher plant, monocotyledon) were exposed to this herbicide, pure and in mixture with ATZ, and the number of dividing cells (cytotoxicity), chromosomal aberrations (CA, genotoxicity) and micronuclei (MN, mutagenicity) were then quantified. The pure MES (1.8 to 460 μg/L) did not show either cytotoxicity or genotoxicity/mutagenicity under the tested conditions. The genotoxicity of ATZ (1.5 to 400 μg/L), previous reported in the literature, was confirmed herein. The assessment of MES + ATZ mixtures (1.8 + 1.5; 7 + 6.25; 30 + 25 μg/L, respectively) showed that MES, at low concentrations, enhance the genotoxicity of ATZ (potentiation), since the significant frequencies of CA and MN were greater than the ones expected in additive effects. Taking together, MES in its pure form seems to be a safe alternative to ATZ regarding the capacity to damage (at cellular and DNA levels) non-target plants (Monocots); however, MES in combination with ATZ appeared to act as a co-mutagen at low concentrations.

Sub-lethal effects of herbicides penoxsulam, imazamox, fluridone and glyphosate on Delta Smelt (Hypomesus transpacificus)

Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone, and glyphosate) on an endangered fish species Delta Smelt (Hypomesus transpacificus). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox, and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt.

Acute toxicity of commercial atrazine in Piaractus mesopotamicus: Histopathological, ultrastructural, molecular, and genotoxic evaluation

Aim:

The aim of this work was to evaluate the sensitivity of Pacu fingerlings (Piaractus mesopotamicus) by measuring the effects of median lethal concentration (LC₅₀) of atrazine (ATZ - 28.58 mg/L) after acute exposure (up to 96 h).

Materials and Methods:

The fish were exposed to the LC₅₀ of ATZ for 96 h (28.58 mg/L) in a static system. During the experiment, the fingerlings were randomly distributed in four glass tanks (50 L) containing dechlorinated water. Four glass tanks were for the control group, and four were for the ATZ-exposed group (n=4 per glass tank), given a total number of 16 animals tested per group. The genotoxicity was evaluated by micronucleus (MN) test in erythrocytes from peripheral blood. Qualitative and semi-quantitative histopathological analyses, and also ultrastructural study, were applied in liver and kidney samples. Finally, the content of heat shock protein (Hsp70) in the liver was evaluated by the western blotting method.

Results:

The morphological alterations in the liver, which was associated with increased expression of Hsp70, included nuclear and cytoplasmic vacuolization, cytoplasmic hyaline inclusions, and necrosis. The kidney presented edema and tubular cell degeneration with cytoplasmic hyaline inclusion. The semi-quantitative histopathological analyses indicated that the liver was more sensitive than kidney to ATZ-induced damage. Ultrastructural analysis showed that ATZ caused membrane alterations in several organelles and increased the number of lysosomes in hepatocytes and kidney proximal tubular cells. Nevertheless, no significant difference was observed in MN frequency in erythrocytes comparing treated and control groups.,

Conclusion:

These results indicated that ATZ-induced damage to the kidney and liver function, ATZ at the concentration tested did not induce a significant difference in MN frequency in Pacu erythrocytes comparing treated and control groups, and also that Pacu fingerlings may be a good bioindicator for testing freshwater contamination.

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.

Activating nuclear xenobiotic receptors and triggering ER stress and hepatic cytochromes P450 systems in quails (Coturnix C. coturnix) during atrazine exposure

Atrazine (ATR) is one of the most widely detected contaminant in the ecosystem. Nuclear xenobiotic receptors are activated by herbicides and induce the transcription of CYP450 isoforms involved in xenobiotic metabolism and transport. However, little is known about hepatic nuclear xenobiotic receptors in birds are responsible for ATR-induced hepatotoxicity via regulating the cytochrome P450 enzyme systems (CYP450s). The objective of this study was to investigate the mechanism of ATR hepatotoxicity in quails. For this purpose, male quails were dosed by oral gavage from sexual immaturity to maturity with 0, 50, 250, and 500 mg/kg/day ATR for 45 days. The results showed that ATR exposure caused the hepatotoxicity damage and endoplasmic reticulum (ER) degeneration. It suggested that ER is a target organelle of ATR toxicity in hepatocytes. ATR exposure disrupted the hepatic CYP450s homeostasis. This study also demonstrated that ATR triggered the CYP450 isoforms transcription via activating the hepatic CAR/PXR pathway. The present study provides new insights regarding the mechanism of the ATR-induced hepatotoxicity through activating nuclear xenobiotic receptors and triggering ER stress and hepatic CYP450s in quails.

Effects of atrazine and chlorothalonil on the reproductive success, development, and growth of early life stage sockeye salmon (Oncorhynchus nerka)

The effects of 2 currently used commercial pesticide formulations on Pacific sockeye salmon (Oncorhynchus nerka), from fertilization to emergence, were evaluated in a gravel-bed flume incubator that simulated a natural streambed. Embryos were exposed to atrazine at 25 µg/L (low atrazine) or atrazine at 250 µg/L (high atrazine) active ingredient (a.i.), and chlorothalonil at 0.5 µg/L (low chlorothalonil) or chlorothalonil at 5 µg/L a.i. (high chlorothalonil) and examined for effects on developmental success and timing, as well as physical and biochemical growth parameters. Survival to hatch was reduced in the high chlorothalonil group (55% compared with 83% in controls), accompanied by a 24% increase in finfold deformity incidence. Reduced alevin condition factor (2.9-5.4%) at emergence and elevated triglyceride levels were seen in chlorothalonil-exposed fish. Atrazine exposure caused premature hatch (average high atrazine time to 50% hatch [H50] = 100 d postfertilization [dpf]), and chlorothalonil exposure caused delayed hatch (high chlorothalonil H50 = 108 dpf; controls H50 = 102 dpf). All treatments caused premature emergence (average time to 50% emergence [E50]: control E50 = 181 dpf, low chlorothalonil E50 = 175 dpf, high chlorothalonil E50 = 174 dpf, high atrazine E50 = 175 dpf, low atrazine E50 = 174 dpf), highlighting the importance of using a gravel-bed incubator to examine this subtle, but critical endpoint. These alterations indicate that atrazine and chlorothalonil could affect survival of early life stages of sockeye salmon in the wild. Environ Toxicol Chem 2017;36:1354-1364. © 2017 SETAC.

Immunotoxic effects of atrazine and its main metabolites at environmental relevant concentrations on larval zebrafish (Danio rerio)

Atrazine (ATZ) and its main metabolites, i.e., diaminochlorotriazine (DACT), deisopropylatrazine (DIP), and deethylatrazine (DE), have been widely detected in surface water around the world. In the present study, to determine their immunotoxic effects, zebrafish during the early developmental stage were exposed to ATZ and its main metabolites at environmental concentrations (30, 100, 300 μg L^-1). It was observed that ATZ, DACT, DIP and DE selectively induced the transcription of immunotoxic related genes including Tnfα, Il-1β, Il-6, Il-8, Cxcl-clc and Cc-chem in larval zebrafish. Pretreatment with ATZ and its metabolites also changed the immune response of larval zebrafish to LPS and E. coli challenge, which was indicated by the alternation in the mRNA levels of some cytokines. In addition, 300 μg L^-1 ATZ and DACT exposure could also increase the release of tryptase into water, indicating that they increased the anaphylactoid reaction in the larval zebrafish. According to these results, both of ATZ and its metabolites exposure could cause the immunotoxicity in larval zebrafish. Thus, we thought that the ecological risks of the metabolites of ATZ on aquatic organisms could not be ignored.

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.

ABC transporters and xenobiotic defense systems in early life stages of rainbow trout (Oncorhynchus mykiss)

Embryos of oviparous fish, in contrast to (ovo) viviparous species, develop in the aquatic environment, and therefore need solute transport systems at their body surfaces for maintaining internal homeostasis and defending against potentially harmful substances. We hypothesized that solute transporters undergo changes in tissue distribution from the embryo to the larval stage. We therefore studied the mRNA profiles of eight ABC transporters (abcb1a, abcb1b, abcc1, abcc2, abcc3, abcc4, abcc5, abcg2) and three solute carriers (oatp1d, putative oatp2 putative, mate1) in different body regions (head, yolk sac epithelium, abdominal viscera, skin/muscles) of developing rainbow trout. Additionally, we investigated mRNA levels of phase I (cyp1a, cyp3a) and phase II (gstp, putative ugt1, putative ugt2) biotransformation enzymes. The study covered the developmental period from the eleuthero-embryo stage to the first-feeding larval stage (1-20days post-hatch, dph). At 1dph, transcripts of abcc2, abcc4, abcg2, cyp3a, gstp, putative mate1, and putative oatp2 occurred primarily in the yolk sac epithelium, whereas at later stages expression of these genes was predominantly observed in the abdominal viscera. The functional activity of ABC transporters in fish early life stages was assessed by rhodamine B accumulation assays. Finally, we investigated the potential impact of xenobiotics (clotrimazole, clofibric acid) on the ABC and biotransformation systems of trout early life stages. While clofibric acid had no effect, clotrimazole lead to an increased rhodamine B accumulation. The results provide evidence that the transition from the eleuthero-embryo to the larval stage is accompanied by a major alteration in tissue expression of ABC transporters.

Atrazine and its main metabolites alter the locomotor activity of larval zebrafish (Danio rerio)

Atrazine (ATZ) and its main chlorometabolites, i.e., diaminochlorotriazine (DACT), deisopropylatrazine (DIP), and deethylatrazine (DE), have been widely detected in aquatic systems near agricultural fields. However, their possible effects on aquatic animals are still not fully understood. In this study, it was observed that several developmental endpoints such as the heart beat, hatchability, and morphological abnormalities were influenced by ATZ and its metabolites in different developmental stages. In addition, after 5 days of exposure to 30, 100, 300 μg L(-1) ATZ and its main chlorometabolites, the swimming behaviors of larval zebrafish were significantly disturbed, and the acetylcholinesterase (AChE) activities were consistently inhibited. Our results also demonstrate that ATZ and its main chlorometabolites are neuroendocrine disruptors that impact the expression of neurotoxicity-related genes such as Ache, Gap43, Gfap, Syn2a, Shha, Mbp, Elavl3, Nestin and Ngn1 in early developmental stages of zebrafish. According to our results, it is possible that not only ATZ but also its metabolites (DACT, DIP and DE) have the same or even more toxic effects on different endpoints of the early developmental stages of zebrafish.

Effect of 17α-methyltestosterone (MT) on oxidation stress in the liver of juvenile GIFT tilapia, Oreochromis niloticus

The normal dose of 17α-methyltestosterone (MT) used in fish farming was 60 mg/L, and now the analysis of residual androgens was carried out in waste water obtained from the Beijing area, which could be detected in levels ranging from 4.1 to 7.0 ng/L. For the purpose of aquatic early warning, the present study clearly demonstrated that chronic exposure by higher concentration of MT than environmental relevant concentrations could trigger oxidative stress response to juvenile tilapia by modulating hepatic antioxidant enzyme activities and gene transcription. Some antioxidative parameters (T-GSH, GSH/GSSG and MDA) were significant decreased under 0.5 mg/L MT exposure at 7 and 14 days. Some antioxidant enzymes (SOD, CAT and GST) and transcriptional changes (sod and cat) were revealed significant decreases for MT treated groups at 7 days. Total antioxidant capacity was significant increased only in 5 mg/L MT exposure groups, but GR activities were not affected all through the whole exposure period. Almost all of the antioxidant enzymatic genes detected in the present study were showed significant increments for MT exposure both at 14 and 21 days, and the genotoxicity profile of antioxidant enzymatic genes were revealed dose-dependent manner. This study presented evidence that MT could result in oxidative stress response in the early stages of GIFT tilapia.

Atrazine triggers developmental abnormality of ovary and oviduct in quails (Coturnix Coturnix coturnix) via disruption of hypothalamo-pituitary-ovarian axis

There has been a gradual increase in production and consumption of atrazine (ATR) in agriculture to meet the population rising demands. Female reproduction is necessary for growth and maintenance of population. However, ATR impact on females and particularly ovarian developmental toxicity is less clear. The aim of this study was to define the pathways by which ATR exerted toxic effects on ovarian development of ovary and hypothalamo-pituitary-ovarian (HPO) axis. Female quails were dosed by oral gavage from sexual immaturity to maturity with 0, 50, 250 and 500 mg ATR/kg/d for 45 days. ATR had no effect on mortality but depressed feed intake and growth and influenced the biochemical parameters. Notably, the arrested development of ovaries and oviducts were observed in ATR-exposed quails. The circulating concentrations of E2, P, LH and PRL were unregulated and FSH and T was downregulated in ATR-treated quails. The mRNA expression of GnRH in hypothalamo and LH in pituitary and FSH in ovary was downregulated significantly by ATR exposure and FSH and PRL in pituitary were upregulated. ATR exposure upregulated the level of P450scc, P450arom, 3β-HSD and 17β-HSD in ovary and downregulated ERβ expression in female quails. However, ATR did not change ERα expression in ovary. This study provides new insights regarding female productive toxicology of ATR exposure. Ovary and oviduct in sexually maturing females were target organs of ATR-induced developmental toxicity. We propose that ATR-induced developmental abnormality of ovary and oviduct is associated with disruption of gonadal hormone balance and HPO axis in female quails.

Atrazine-Mediated Disruption of Steroidogenesis in BLTK1 Murine Leydig Cells

Atrazine (ATR) is a broad-spectrum triazine herbicide that disrupts steroidogenesis resulting in reproductive and developmental toxicity at high doses. Mouse BLTK1 Leydig cells were used as a steroidogenic model to investigate the effects of ATR on testosterone (T) biosynthesis. Induction of steroidogenesis by 3 ng/ml recombinant human chorionic gonadotropin (rhCG) induced intracellular 3',5' cyclic adenosine monophosphate (cAMP) approximately 20-fold and T approximately 3-fold at 4 h. Co-treatment with 300 μM ATR super-induced cAMP levels 100-fold yet antagonized rhCG-mediated induction of T approximately 20% at 4 h. ATR inhibited cAMP-specific phosphodiesterase (cPDE) with an IC50 of ≥98 μM, suggesting cPDE inhibition contributes to the super-induction of cAMP. However, concentrations of up to 3 mM db-cAMP did not antagonize rhCG induction of T levels, suggesting cAMP super-induction alone does not decrease T biosynthesis. Western analysis of cAMP-activated protein kinase A (PKA) target proteins identified ATR-mediated concentration-dependent alterations in phosphorylation including phospho-CREB. These results suggest the cPDE inhibition by ATR and super-induction of cAMP are independent of effects on T levels, and that altered phosphorylation of key steroidogenic regulatory proteins may underlie ATR-mediated disruption of steroidogenesis.

Impact of Sediment on Agrichemical Fate and Bioavailability to Adult Female Fathead Minnows: A Field Study

Precipitation induced runoff is an important pathway for agrichemicals to enter surface water systems and expose aquatic organisms to endocrine-disrupting compounds such as pesticides and steroid hormones. The objectives of this study were to investigate the distribution of agrichemicals between dissolved and sediment-bound phases during spring pulses of agrichemicals and to evaluate the role of suspended sediment in agrichemical bioavailability to aquatic organisms. To accomplish these objectives, suspended sediment and water samples were collected every 3 days from a field site along the Elkhorn River, located at the downstream end of a heavily agricultural watershed, and were screened for 21 pesticides and 21 steroids. Adult female fathead minnows (Pimephales promelas) were exposed in field mesocosms to river water containing varying sediment loads. Changes in organism hepatic gene expression of two estrogen-responsive genes, vitellogenin (VTG) and estrogen receptor alpha (ERα), as well as the androgen receptor (AR) were analyzed during periods of both low and high river discharge. Trends in agrichemical concentrations of both the dissolved and sediment phases as a function of time show that, while sediment may act as both a source and a sink for agrichemicals following precipitation events, the overall driver for molecular defeminization in this system is direct exposure to the sediment-associated compounds. This study suggests that endocrine disrupting effects observed in organisms in turbid water could be attributed to direct exposure of contaminated sediment.

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 chlorpyrifos exposure induces liver autophagic response in common carp

Under normal conditions, autophagy occurs at basal levels but can be induced rapidly in response to stress conditions and extracellular signals. Increasing experimental evidence indicates that the expression of autophagy-related genes play very important roles in toxicology. Atrazine (ATR) and chlorpyrifos (CPF) are the most common agrochemical in the freshwater ecosystems of the world. This study assessed the effects of ATR, CPF and combined ATR/CPF exposure on the liver of common carp. Carp were sampled after a 40-d exposure to ATR and CPF, individually or in combination, followed by a 40-d recovery to measure the mRNA and protein levels of autophagy-related genes in the liver. In addition, we also investigated the change in ultrastructure in the liver. The results revealed that the mRNA and protein levels of microtubule-associated protein 1 light chain 3 B (LC3B) and dynein were significantly induced in the treated groups compared to the solvent control group. Transmission electron microscope assays indicated that autolysosomes were observed in the exposure and recovery groups. These results indicated that ATR and CPF could induce autophagy in carp liver. To the best of our knowledge, this is the first report to study the autophagy effects caused by sub-chronic exposure to ATR, CPF and the ATR/CPF combination in common carp. The information presented in the present study may provide new insights into the mechanisms used by fish to adapt to stressful environments.

Effects of atrazine exposure on male reproductive performance in Drosophila melanogaster

Atrazine is a commonly utilized herbicide to control broadleaf weeds in the agricultural setting. It can, however, have negative effects on male reproductive performance in a variety of vertebrate species. Much less is known, however, about the effects of atrazine on invertebrates. In this study, we investigated the effects of several different concentrations of larval atrazine exposure on measures of reproductive performance in adult male Drosophila melanogaster. Atrazine exposure had significant effects on a male's mating ability and the number of eggs his partner laid when he was successful at mating. Exposed males also sired a smaller proportion of the offspring under competitive conditions when they were the first male to mate to a doubly mated female. Atrazine exposure had no measurable effect on a male's ability to prevent a mated female from mating to another male or on the proportion of offspring sired when the exposed males were the second male to mate. Exposure upregulated expression of one male reproductive gene, ovulin, but had no effect on expression of another, sex peptide. Exposed males produced and transferred more sex peptide protein to the female during mating but ovulin protein levels were not affected. In general, we observed non-monotonic responses such that the intermediate exposure levels showed the largest reduction in male reproductive performance. This study suggests that atrazine exposure affects male reproductive performance in insects and future studies should aim to understand the molecular mechanisms underlying the fitness effects of exposure.

Melamine-cyanurate complexes and oxidative stress markers in trout kidney following melamine and cyanuric acid long-term co-exposure and withdrawal

In 2007, renal failure and death in pets were linked to pet food containing both melamine (MEL) and cyanuric acid (CYA). In mammals and fish, the co-administration of MEL and CYA causes renal crystal formation. Moreover, little is known about the process of crystal removal in fish. The aim of this study was to evaluate the formation of MEL-cyanurate crystals in kidney of rainbow trout (Oncorhynchus mykiss) fed combined MEL and CYA diets for 10 weeks at 250, 500 and 1,000 mg/kg in feed (equivalent to 2.5, 5, 10 mg/kg body weight of trout fed 1 % body weight per day). During the exposure trial and throughout a withdrawal period, prooxidant effects of MEL and CYA were evaluated on oxidative stress markers such as catalase, glutathione S-transferase and malondialdehyde. Crystal formation was dose and time dependent, and after six withdrawal weeks, crystals persisted in kidney of trout treated the highest triazine dose. Catalase and glutathione S-transferase activity in kidney of trout exposed to both triazines for 10 weeks indicated that MEL (with or without CYA) can exert a higher prooxidant effect than CYA dispensed singly. Although the enzymes activity increase appears to be reverted after two MEL withdrawal weeks, persistence of crystals may lead to severe damage in renal cells of fish.

Atrazine reduces reproduction in Japanese medaka (Oryzias latipes)

Atrazine is an effective broadleaf herbicide and the second most heavily used herbicide in the United States. Effects along the hypothalamus-pituitary-gonad axis in a number of vertebrate taxa have been demonstrated. Seasonally elevated concentrations of atrazine in surface waters may adversely affect fishes, but only a few studies have examined reproductive effects of this chemical. The present study was designed to evaluate a population endpoint (egg production) in conjunction with histological (reproductive stage, gonad pathology) and biochemical (aromatase activity, sex hormone production) phenotypes associated with atrazine exposure in Japanese medaka. Adult virgin breeding groups of one male and four females were exposed to nominal concentrations of 0, 0.5, 5.0, and 50 μg/L (0, 2.3, 23.2, 231 nM) of atrazine in a flow-through diluter for 14 or 38 days. Total egg production was lower (36-42%) in all atrazine-exposed groups as compared to the controls. The decreases in cumulative egg production of atrazine-treated fish were significant by exposure day 24. Reductions in total egg production in atrazine treatment groups were most attributable to a reduced number of eggs ovulated by females in atrazine-treated tanks. Additionally, males exposed to atrazine had a greater number of abnormal germ cells. There was no effect of atrazine on gonadosomatic index, aromatase protein, or whole body 17 β-estradiol or testosterone. Our results suggest that atrazine reduces egg production through alteration of final maturation of oocytes. The reduced egg production observed in this study was very similar to our previously reported results for fathead minnow. This study provides further information with which to evaluate atrazine's risk to fish populations.

Chlorotriazines do not activate the aryl hydrocarbon receptor, the oestrogen receptor or the thyroid receptor in in vitro assays

Atrazine, prometryn, propazine and simazine are chlorotriazines that are commonly employed as herbicides. However, their use is a major cause of concern, due to their reported endocrine disrupting effects in different taxa. Data from studies on the molecular and cellular processes underlying the hormonal action of these substances are contradictory. The ability of these chlorotriazines and the atrazine metabolites, desethyl-s-chlorotriazine and desisopropyl-s-chlorotriazine, to trigger responses mediated by the oestrogen receptor (ER), aryl hydrocarbon receptor (AhR) and thyroid receptor (TR), was studied by using in vitro approaches. Transcriptional activation assays were applied to observe the activation of ER and TR. The induction of ethoxyresorufin-O-deethylase (EROD) activity in the RTG-2 cell line served as an indicator of AhR activation. No responses were found in any of the assays, with any of the six chlorotriazines tested. Our observations indicate that the chlorotriazines tested are unlikely to cause their endocrine effects via these receptors.

Effects of atrazine and chlorpyrifos on cytochrome P450 in common carp liver

Atrazine (ATR) and chlorpyrifos (CPF), widely used in agriculture, have resulted in a series of toxicological and environmental problems. We investigated the activities of the biotransformation enzymes ethoxyresorufin-O-deethylase (EROD) and pentoxyresorufin-O-deethylase (PROD), total cytochrome P450 (CYP), CYP1A mRNA level and level of tissue ATR, CPF, and their metabolites in the liver of common carp (Cyprinus carpio L.) after a 40-d exposure to CPF and ATR, alone or in combination, and a 20-d recovery. In the present study, juvenile common carp was exposed to ATR (at concentrations of 4.28, 42.8 and 428 μg L(-1)), CPF (1.16, 11.6 and 116 μg L(-1)), and ATR/CPF mixture (at concentrations of 1.13, 11.3 and 113 μg L(-1)). A general increasing trend for the activity of the biotransformation enzymes (EROD and PROD), CYP and CYP1A mRNA level was observed in the liver of common carp exposed to ATR, CPF and the ATR/CPF mixture. In addition, ATR, CPF, and their metabolites demonstrated a high accumulation in the liver. These results demonstrated that the CYP system in fish could be used as a biomarkers in evaluating the impact of ATR and CPF exposure on the common carp.

Exposure of mice to atrazine and its metabolite diaminochlorotriazine elicits oxidative stress and endocrine disruption

Effects of atrazine (ATZ) and its metabolite diaminochlorotriazine (DACT) on the induction of oxidative stress and endocrine disruption were studied in mice. Body and liver weights decreased in all ATZ and DACT treated groups. Hepatic activities of superoxide dismutase (SOD) increased significantly after 1 week of intraperitoneal injection of 200 mg/kg ATZ, 100 and 200 mg/kg DACT. Hepatic activities of catalase (CAT) and glutathione S-transferase (GST) were also affected by the treatment with 200 mg/kg DACT. In serum, the glutathione peroxidase (GPX) and GST activities and glutathione (GSH) content decreased significantly in the 200 mg/kg DACT treated group. Moreover, the administration of ATZ and DACT decreased the transcription levels of key genes related to cholesterol transport and testosterone (T) synthesis including scavenger receptor class B type 1 (SR-B1), cytochrome P450 cholesterol side-chain cleavage enzyme (P450scc) and cytochrome P450 17α-hydroxysteroid dehydrogenase (P450 17α) in testes. Furthermore, the treatment with 200 mg/kg DACT significantly decreased the serum and testicular T levels, while the treatment with 200 mg/kg ATZ significantly decreased the testicular T levels. The results indicated that the acute exposure to ATZ and DACT induced oxidative stress and endocrine disruption in mice, and DACT showed much more toxic than ATZ did.

The effects of x-ray radiation on the eye development of zebrafish

The toxic effects of x-ray radiation on eye development was measured using zebrafish as a model organism. Zebrafish embryos at 8 h post-fertilization (hpf) were irradiated using X-rays at doses of 1, 2, 4, and 8 Gy. At 24 and 48 hpf, x-ray radiation induced a significant increase in reactive oxygen species (ROS) content and cell apoptotic signals. Both of these increases were dose dependent and there were significant positive relationships between them at 24 hpf. At 48 and 72 hpf, the increase of ROS concentration can be eliminated by increasing activities of superoxide dismutase and catalase. Although the ROS generated by x-ray radiation caused a significant increase in cell apoptosis at 24 and 48 hpf, the cellular layers of the retina and lens formation in the irradiated groups were not significantly disrupted at 144 hpf compared with the control group, with the exception of a heterogeneous distribution of the cells in inner nuclear cell layer and a significant decrease in the diameters of whole eyes after 8 Gy irradiation. X-Ray radiation at later stages of gastrulation may not cause distinct optic complications; however, there is still a risk of microophthalmia at high doses of irradiation.

Characterizing dose-responses of catalase to nitrofurazone exposure in model ciliated protozoan Euplotes vannus for ecotoxicity assessment: enzyme activity and mRNA expression

In environmental studies, some biological responses, known as biomarkers, have been used as a powerful bioassay tool for more than four decades. Disparity between enzyme activity and mRNA abundance leads to correlation equivocality, which makes the application of biomarkers for environmental risk assessment more complicated. This study investigates this disparity in the case of catalase when used as a biomarker for detecting ecotoxicity induced by antibiotics in aquatic ecosystems. In particular, dose-responses for catalase activity and mRNA expression abundance were investigated in Euplotes vannus which were exposed to graded doses of nitrofurazone for several discrete durations, and dose-response models were developed to characterize the dose-response dynamics. Significant differences were found in both catalase activity and mRNA expression abundance among the E. vannus treated with nitrofurazone. Catalase activity showed a hormetic-like effect in terms of dose-response, characterized by a biphasic relationship which was more clearly evident after a longer exposure period, while mRNA expression abundance increased linearly with the exposure duration. Additionally, the correlation between catalase activity and mRNA expression abundance reversed along with the duration of exposure to nitrofurazone. Taken together, our results demonstrate that catalase mRNA expression offers a more straightforward dose-response model than enzyme activity. Our findings suggest that both catalase enzyme activity and mRNA expression abundance can be used jointly as bioassay tools for detecting ecotoxicity induced by nitrofurazone in aquatic ecosystems.

Non-destructive multibiomarker approach in European quail (Coturnix coturnix coturnix) exposed to the herbicide atrazine

The effect of orally administered atrazine (25 or 100 mg/kg on days 0, 5, and 10 of the experiment) was studied in European quail (Coturnix coturnix coturnix) on four non-destructive biomarkers: fecal porphyrins, blood glutathione-S-transferase, glutathione reductase, reduced glutathione, and malondialdehyde (MDA). Uroporphyrin I (UPI) and coproporphyrins I and III (CPIII) were the main porphyrins detected in feces. The lowest dose of ATZ caused a significant (P < 0.05) increase in UPI and CPIII at day 5, and the highest dose of ATZ caused an induction of CPI and a significant (P < 0.05) decrease in MDA levels at day 30.

A comparative toxicogenomic investigation of oil sand water and processed water in rainbow trout hepatocytes

The purpose of this study was to compare the expression of gene transcripts involved in toxic stress in rainbow trout hepatocytes exposed to oil sand water (OSW), lixiviate (OSLW), and processed water (OSPW). We pose the hypothesis that the changes in gene expression responses in cells exposed to a simulated oil sand extraction procedure (OSPW) differ from the gene expression responses of OSLW and OS. Rainbow trout hepatocytes were exposed to increasing concentrations of OSW, OSLW, and OSPW for 48 h at 15 °C. Cell viability was assessed by measuring membrane permeability, total RNA levels, and gene expression using an array of 16 genes involved in xenobiotic biotransformation (GST, CYP1A1, CYP3A4, MDR), metal homeostasis and oxidative stress (MT, SOD, and CAT), estrogenicity (VTG, ERβ), DNA repair (LIG, APEX, UNG, and OGG), cell growth (GADD45 and PCNA), and glycolysis (GAPDH). The results showed that the toxicogenomic properties of OSPW differed from those of OSLW and OSW. Gene transcripts that were influenced by OSW and OSLW, and strongly expressed in OSPW, were MT, CAT, GST (induction), CYP1A1, VTG, UNG/OGG, and PCNA. These genes are therefore considered not entirely specific to OSPW but to water in contact with OS. We also found gene transcripts that responded only with OSPW: SOD, GST (inhibition), MDR (inhibition), CYP3A4, GAPDH, GADD45, and APEX. Of these gene transcripts, the ones strongly associated with toxicity (loss of cell viability and RNA levels) were CYP3A4, GST, and GAPDH. Genes involved in DNA repair were also strongly related to the loss of cell viability but responded to both OSLW and OSPW. The observed changes in cell toxicity and gene expression therefore support the hypothesis that OSPW has a distinct toxic fingerprint from OSLW and OSW.

Effect of atrazine and chlorpyrifos exposure on cytochrome P450 contents and enzyme activities in common carp gills

Chlorpyrifos (CPF) and atrazine (ATR) are the most widely used organophosphate insecticides and triazine herbicides, respectively, worldwide. This study aimed at investigating the effects of ATR, CPF and mixture on common carp gills following 40-d exposure and 40-d recovery experiments. Cytochrome P450 content, activities of aminopyrine N-demethylase (APND) and erythromycin N-demethylase (ERND) and the mRNA levels of the CYP1 family (CYP1A, CYP1B, and CYP1C) were determined. In total, 220 common carps were divided into eleven groups, and each group was treated with a specific concentration of ATR (4.28, 42.8 and 428 μg/L), CPF (1.16, 11.6 and 116 μg/L) or ATR-CPF mixture (1.13, 11.3 and 113 μg/L). The results showed that P450 content and activities of APND and ERND in fish exposed to ATR and mixture were significantly higher than those in the control group. After the 40-d recovery treatment (i.e., depuration), the P450 content and the activities of APND and ERND in fish decreased to the background levels. A similar tendency was also found in the mRNA levels of the CYP1 family (CYP1A, CYP1B, and CYP1C) in common carp gills. The CPF-treated fish showed no significant difference from the control groups, except for a significant CYP1C induction. These results indicated that CYP enzyme levels are induced by ATR but were only slightly affected by CPF in common carp gills. In addition, the ATR and CPF exposure showed an antagonistic effect on P450 enzymes in common carp gills.

Effects of (12)C(6+) ion radiation and ferulic acid on the zebrafish (Danio rerio) embryonic oxidative stress response and gene expression

The effects of carbon ion irradiation and ferulic acid (FA) on the induction of oxidative stress and alteration of gene expression were studied in zebrafish (Danio rerio) embryos. Zebrafish embryos at 8 hpf were divided into seven groups: the control group; the 1Gy, 3Gy and 7Gy irradiation groups; and three FA-pre-treated irradiation groups. In the irradiated groups, a significant increase in the teratogenesis of the zebrafish embryos and oxidative stress was accompanied by increased malondialdehyde (MDA) content, decreased glutathione (GSH) content and alterations in antioxidant enzyme activities (such as catalase [CAT] and superoxide dismutase [SOD]). Moreover, the mRNA levels for Cu/Zn-sod, Mn-sod, cat and gpx, the genes encoding these antioxidant proteins, were altered significantly. However, the mRNA expression patterns were not in accordance with those of the antioxidant enzymes and were more sensitive under low-dose irradiation. In addition, we detected the mRNA expression of ucp-2 and bcl-2, which are located at the mitochondrial inner membrane and related to reactive oxidative species (ROS) production. In the irradiated groups, the mRNA level of ucp-2 was significantly increased, whereas the mRNA level of bcl-2 was significantly decreased. Supplementation with FA, an antioxidant, was better able to reduce the irradiation-induced oxidative damage marked by changes in mortality, morphology, antioxidant enzyme activities and the MDA and GSH content, as well as in the mRNA expression levels. Overall, this study provided helpful information about the transcriptional effects of irradiation to better understand the mechanism of carbon ion-induced oxidative stress and FA-induced radioprotective effects.

Oral exposure to atrazine modulates hormone synthesis and the transcription of steroidogenic genes in male peripubertal mice

Atrazine (ATZ) is a widely used herbicide and is considered an endocrine disruptor of different organisms. However, the molecular interactions of ATZ with biological targets in mammalian endocrine systems are not understood fully. In the present study, we observed that ATZ administration (50, 100 and 200 mg/kg) for 3 weeks to peripubertal male ICR mice exerted adverse effects on several physiological features; these effects included a significant decrease in the body and liver weights and an increase in the relative testis weight. In addition, the serum testosterone (T) concentration was significantly decreased in all ATZ-treated mice, and the serum estradiol (E2) concentration and aromatase activity were significantly increased in mice exposed to 100 and 200 mg/kg ATZ. These results suggest that ATZ exposure affected hormone homeostasis in male mice. We also found that the transcript levels of the steroidogenic enzyme genes p450scc, p450 17α1 and 17β-HSD were significantly reduced in the testes of mice exposed to 100 and 200 mg/kg ATZ for 3weeks. Given the results of the present study and previous reports, it is possible that ATZ reduces the T concentration in peripubertal male mice by affecting the transcription of steroidogenic genes, such as p450scc, p450 17a1 and 17β-HSD. This study provides new insights into the mammalian toxicological mechanism of ATZ.

Antioxidant responses and renal crystal formation in rainbow trout treated with melamine administered individually or in combination with cyanuric acid

In 2007 and 2008, renal stone formation and kidney damage in human infants were linked to consumption of melamine (MEL)-contaminated infant formula, as well as renal failure and death in pets due to pet food containing both MEL and cyanuric acid (CYA). The aim of this study was to examine the effects of MEL and CYA administered individually or in combination on concentrations of certain metabolites and enzyme activities that serve as markers for oxidative stress in kidney and liver of rainbow trout. In addition, the levels of muscle MEL and renal crystal formation were determined. Trout were fed MEL and/or CYA for 8 wk at 250, 500, or 1000 mg of each compound/kg in feed. Fish muscle residues of MEL exhibited a dose-response relationship. Coexposure of trout to MEL and CYA at the highest dose led to lower MEL residue concentrations in muscle compared to exposure to MEL alone. Renal MEL-CYA complexes were found in kidneys of fish treated with combined MEL and CYA. A dose response was evident with respect to both (1) number of trout displaying renal crystals and (2) number of crystals per fish. Changes in concentration of antioxidant parameters, such as glutathione, superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase, were recorded in both tissues of MEL- and CYA-dosed trout. Lipid peroxidation was more pronounced in kidney than liver. Therefore, feed contaminated with both MEL and CYA could be problematic for fish, as MEL administered to trout, individually or in combination with CYA, may facilitate the onset of oxidative damage in trout.

Alterations in activity and mRNA expression of acetylcholinesterase in the liver, kidney and gill of common carp exposed to atrazine and chlorpyrifos

Insecticides and herbicides are widely used in modern agricultural production. The intensive use of insecticide chlorpyrifos (CPF) and herbicide atrazine (ATR) has resulted in serious environmental problems. Herein, we investigated alteration in activity and mRNA levels of AChE in the liver, kidney and gill from common carp after 40d exposure to CPF and ATR alone or in combination and 20d recovery treatment. Results indicated that activity and mRNA levels of AChE at all high-dose groups have been significantly decreased after CPF and ATR alone or ATR/CPF mixture exposure, and the changes were improved in the end of recovery tests in varying degrees, the activity and gene expression of AChE in the joint toxicity of ATR and CPF groups were significantly lower than that in the single toxicant group. Our study suggests that the decrease of AChE activity observed at all high-dose groups (CPF and ATR alone or in combination) may be directly related to a lower AChE expression, and the joint toxicity of ATR and CPF is higher than ATR and CPF alone.

Effects of atrazine and chlorpyrifos on the mRNA levels of HSP70 and HSC70 in the liver, brain, kidney and gill of common carp (Cyprinus carpio L.)

Although the chaperone role of heat shock proteins (HSPs) has been demonstrated in invertebrates, the function of HSPs in vertebrates, especially in fish, remains unclear. In this study, relative changes in the mRNA abundance of the HSP70 gene were examined by real-time PCR in the muscle, spleen, head kidney, heart, liver, brain, kidney and gill of common carp. Results indicated that the highest and lowest levels of HSP70 expression were found in the heart and muscle, respectively, and the highest and lowest levels of HSC70 expression were found in the spleen and muscle, respectively. In addition, we investigated differential HSP70 gene expression in common carp after a 40-d exposure to chlorpyrifos (CPF) and atrazine (ATR), alone or in combination, and after a 20-d recovery. Results indicated that the expression of carp HSP70 and 70-kDa heat shock cognate protein (HSC70) with ATR and CPF treatment alone or in combination was significantly upregulated. The present results provide new insights into the mechanisms used by fish to adapt to stressful environments.

Repeated exposure to the herbicide atrazine alters locomotor activity and the nigrostriatal dopaminergic system of the albino rat

Atrazine (ATR) is used as a pre- and post-emergent herbicide; although banned in several countries of the European Community, it is still used extensively around the world. A recent study in rats has shown that chronic, daily exposure to 10 mg ATR/kg BW causes hyperactivity, disrupts motor coordination and learning of behavioral tasks, and decreases dopamine levels in the brain. In order to evaluate the short-term effect of ATR exposure on locomotor activity, monoamine markers, and antioxidants, adult male Sprague-Dawley rats received six IP injections of 100 mg ATR/kg BW or vehicle over two weeks. After every ATR injection we found hypoactivity that lasted up to five days, and it was accompanied by reductions in levels of striatal DA, DOPAC, and HVA without any alteration in the striatal expression of the mRNAs for Mn-SOD, Trx-1, DAR-D(1), or DAR-D(2). In contrast, in the nucleus accumbens no changes in monoamine markers were observed, and a down-regulation of Trx-1 expression was detected shortly after the ATR treatment. Moreover, in the ventral midbrain, we found that ATR induced a down-regulation of mRNA for Th and DAT, but it increased VMAT2 mRNA expression. Decreases of monoamine levels and of locomotor activity disappeared three months after ATR treatment; however, an amphetamine challenge (1 mg/kg) given two months after the ATR treatment resulted in a significant stimulation in the exposed group, revealing hidden effects of ATR on dopaminergic systems. These results indicate that ATR exposure differentially modifies the dopaminergic systems, and these modifications may underlie the behavioral changes observed.

Endocrine disruption caused by oral administration of atrazine in European quail (Coturnix coturnix coturnix)

The widely used herbicide atrazine (ATZ) has been reported to exhibit reproductive toxicity in rats, fish and amphibians, with an avian LD(50) of 5000 mg/kg. In the present work, ATZ was administered as a single oral dose of 25 or 100 mg/kg to female European quail (Coturnix coturnix coturnix) at days 0, 5 and 10 of the experiment, being the animals sampled at days 15, 30 and 45. ATZ significantly increased the expression of hepatic estrogen receptor α (ERα) at both doses at day 30. An important increase was also observed in plasma 17β-estradiol (E2) concentrations. ATZ at 100 mg/kg increased the circulating concentration of vitellogenin (Vtg), but this effect was not related with an increase in hepatic Vtg mRNA levels. ATZ had no effect on the hepatic expression of both cytochrome P450 1A4 (CYP1A4) or the related biotransformation activity ethoxyresorufin-O-deethylase (EROD). These results led to the conclusion that ATZ provokes an estrogenic effect in sexually mature females of European quail. Further studies are necessary to establish the effect on sexual development or reproduction of female and male birds in the wild.

Atrazine promotes biochemical changes and DNA damage in a Neotropical fish species

The effects of Atrazine, an herbicide used worldwide and considered as a potential contaminant in aquatic environments, were assessed on the Neotropical fish Prochilodus lineatus acutely (24 and 48 h) exposed to 2 or 10 μg L(-1) of atrazine by using a set of biochemical and genetic biomarkers. The following parameters were measured in the liver: activity of the biotransformation enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione S transferase (GST), antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), content of reduced glutathione (GSH), generation of reactive oxygen species (ROS) and occurrence of lipid peroxidation (LPO); in brain and muscle the activity of acetylcholinesterase (AChE) and DNA damage (comet assay) on erythrocytes, gills and liver cells. A general decreasing trend on the biotransformation and antioxidant enzymes was observed in the liver of P. lineatus exposed to atrazine; except for GR, all the other antioxidant enzymes (SOD, CAT and GPx) and biotransformation enzymes (EROD and GST) showed inhibited activity. Changes in muscle or brain AChE were not detected. DNA damage was observed in the different cell types of fish exposed to the herbicide, and it was probably not from oxidative origin, since no increase in ROS generation and LPO was detected in the liver. These results show that atrazine behaves as enzyme inhibitor, impairing hepatic metabolism, and produces genotoxic damage to different cell types of P. lineatus.

Innate immune response of silver catfish (Rhamdia quelen) exposed to atrazine

The impact of agrichemicals on aquatic vertebrate species has been a matter of increasing concern to researchers and environmentalist. In the present study, we evaluated the effects of a sublethal concentration of atrazine (10% of the LC(50-96 h)), a world-wide used herbicide, on the innate immune system of silver catfish (Rhamdia quelen). A significant reduction on phagocytic index, bacteria agglutination and bactericidal activity of the serum, serum lysozyme and total serum peroxidase activity was observed in fish exposed to atrazine for 24 h. After 10 days exposure to atrazine, only bactericidal activity of the serum, bacteria agglutination and total serum peroxidase activity were significantly reduced. Atrazine had no effect on the natural complement hemolytic activity. Our results demonstrate that atrazine decreases the innate immune response of fingerlings, which might increase its susceptibility to opportunistic pathogens.

Oxidative stress response in atrazine-degrading bacteria exposed to atrazine

Rhodobacter sphaeroides W16 and Acinetobacter lwoffii DNS32 which were isolated from soil in cold area subjected to a long-term atrazine application in Heilongjiang Province (China) can degrade atrazine efficiently. The investigation of their antioxidant properties will be useful for bioremediation and engineering applications of atrazine-degrading bacteria. Superoxide dismutase (SOD) and catalase (CAT) from two atrazine-degrading bacteria and one non-atrazine-degrading bacterium were tested for response to the oxidative stress caused by atrazine. Atrazine produced a greater inhibition of growth in Bacillus subtilis B19. The three bacteria apparently produced two activity peaks of SOD and CAT. The results demonstrated all three bacteria possessed a mechanism for atrazine tolerance that may include controlling the cellular redox balance by producing reactive oxygen species (ROS) and the subsequent scavenging of the ROS, but such response was more rapid and at lower levels in the two atrazine-degrading bacteria, suggesting less oxidative damage in these cells upon atrazine exposure. Compared to B. subtilis B19, atrazine-degrading bacteria had relatively high tolerance to atrazine stress, especially R. sphaeroides W16. Therefore, R. sphaeroides W16 and A. lwoffii DNS32 have a good application prospect of bioremediation project for soil contaminated by atrazine in cold area in Heilongjiang Province.

Oxidative stress response in two representative bacteria exposed to atrazine

Bacteria are present extensively in the environment. Investigation of their antioxidant properties will be useful for further study on atrazine stress tolerance of bacteria and the defense mechanism of antioxidant enzymes against atrazine or other triazine herbicides. Superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and total antioxidant capacity (T-AOC) from one Gram-negative representative strain Escherichia coli K12 and one Gram-positive representative strain Bacillus subtilis B19, respectively, were tested for response to atrazine stress. The results indicated that SOD, CAT, GST and T-AOC were induced upon exposure to atrazine. The growth of two bacteria was better in the absence than in the presence of atrazine, indicating that atrazine can decrease bacterial growth. The changes of enzyme activities indicate the presence of oxidative stress. Oxidative stress induced by atrazine may be due to imbalance of redox potential in bacterial cells, which leads to bacterial metabolic disorder.

Differential changes in gene expression in rainbow trout hepatocytes exposed to extracts of oil sands process-affected water and the Athabasca River

The oil sands region of northern Alberta represents the world's largest reserves of bitumen, and the accelerated pace of industrial extraction activity has raised concern about the possible impacts on the Athabasca River and its tributaries. An ecotoxicogenomic study was undertaken on Oncorhynchus mykiss trout hepatocytes exposed to extracts of water samples near the oil sand development area, as well as to oil sands process-affected water (OSPW) extracts using the quantitative reverse transcriptase polymerase chain reaction technique. The expression of the following genes (mRNA) was monitored to track changes in xenobiotic biotransformation (CYP1A1, CYP3A4, glutathione S-transferase, multi-drug resistance transporter), estrogenicity (estrogen receptor and vitellogenin), oxidative stress (superoxide dismutase and metallothionein) and DNA repair activity (DNA ligase). The extent of DNA-aromatic hydrocarbon adducts was also determined in cells by immuno-staining. A comparative analysis of gene expression between the river/lake and OSPW samples revealed that CYP3A4, metallothioneins, DNA ligase and GST genes, were specifically expressed by OSPW. Cells exposed to OSPW, commercial naphthenic acids, and benzo(a)pyrene showed increased polyaromatic hydrocarbon DNA-adducts, as determined by cell immunofluorescence analysis. Other genes were induced by all types of water samples, although the induction potential was stronger in OSPW most of the time (e.g., VTG gene was expressed nearly 15-fold by surface waters from the lake and river samples but increased to a maximum of 31-fold in OSPW). A multivariate discriminant function analysis revealed that the lake and river water samples were well discriminated from the OSPW. The CYP3A4 gene was the most highly expressed gene in cells exposed to OSPW and responded less to the lake or river water in the Athabasca River area. This study identified a suite of gene targets that responded specifically to OSPW extracts, which could serve as toxicogenomic fingerprints of OSPW contamination.

Effects of atrazine and chlorpyrifos on activity and transcription of glutathione S-transferase in common carp (Cyprinus carpio L.)

Glutathione S-transferase isoenzymes (GSTs) play a critical role in detoxification pathways. Here we report the tissue distribution of four antioxidant GSTs gene in common carp, and their expression profiles. We also investigated the GSTs activity in different tissues after exposure to the agricultural chemicals atrazine (ATR), chlorpyrifos (CPF), and their mixture. Relative changes in the mRNA abundance of the GST isoforms were examined by real time PCR in liver, brain, kidney and gill of common carp. After exposure and recovery, we observed a statistically significant decrease in the GSTs activity in animals exposed to high concentrations of ATR (428 μg/L), CPF (116 μg/L), and their mixture (113 μg/L). At basal levels of tissue expression, four GSTs transcript were detected in liver, brain, kidney, and gill. High expression levels were found in all examined tissues. Transcription of some GST isoforms, GST kappa (GSTK), GST theta (GSTT) and GST rho (GSTR), decreased after exposure to CPF and ATR for the entire experimental period in both the kidney and gill. However, increased transcription of GST mu (GSTM) was observed in the kidney or gill 20 d after exposure to ATR or CPF, respectively. Transcription of both GSTT and GSTR was inhibited for the entire experimental period in the brain, kidney and gill of animals exposed to the ATR/CPF mixture, but transcription of GSTM was induced in the liver after 40 d of exposure. In summary, changes in the GSTs activity and their transcription varied within each organ and among organs of common carp after exposure to ATR, CPF, and their mixture.

Genotoxicity of diuron and glyphosate in oyster spermatozoa and embryos

We investigated the effects of genotoxicant exposure in gametes and embryos to find a possible link between genotoxicity and reproduction/developmental impairment, and explore the impact of chemical genotoxicity on population dynamics. Our study focused on the genotoxic effects of two herbicides on oyster gametes and embryos: glyphosate (both as an active substance and in the Roundup formulation) and diuron. France is Europe's leading consumer of agrochemical substances and as such, contamination of France's coastal waters by pesticides is a major concern. Glyphosate and diuron are among the most frequently detected herbicides in oyster production areas; as oyster is a specie with external reproduction, its gametes and embryos are in direct contact with the surrounding waters and are hence particularly exposed to these potentially dangerous substances. In the course of this study, differences in genotoxic and embryotoxic responses were observed in the various experiments, possibly due to differences in pollutant sensitivity between the tested genitor lots. Glyphosate and Roundup had no effect on oyster development at the concentrations tested, whereas diuron significantly affected embryo-larval development from the lowest tested concentration of 0.05 μg L⁻¹, i.e. an environmentally realistic concentration. Diuron may therefore have a significant impact on oyster recruitment rates in the natural environment. Our spermiotoxicity study revealed none of the tested herbicides to be cytotoxic for oyster spermatozoa. However, the alkaline comet assay showed diuron to have a significant genotoxic effect on oyster spermatozoa at concentrations of 0.05 μg L⁻¹ upwards. Conversely, no effects due to diuron exposure were observed on sperm mitochondrial function or acrosomal membrane integrity. Although our initial results showed no negative effect on sperm function, the possible impact on fertilization rate and the consequences of the transmission of damaged DNA for oyster development and physiological performances, requires further investigation. A likely hypothesis to explain the embryotoxic and genotoxic effects of diuron is that it may act via causing oxidative stress.

Proteomic analysis of hepatic tissue in adult female zebrafish (Danio rerio) exposed to atrazine

Atrazine (ATZ), the most common herbicide, is a frequently observed contaminant in freshwater ecosystems. In the present study, two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization tandem time-of-flight-mass spectrometry, combined with histopathological analysis, were used to detect the hepatic damage in adult female zebrafish (Danio rerio) exposed to ATZ. More than 600 hepatic protein spots were detected in each gel with silver staining, and most of the proteins ranged from 20 to 70 kD and pH 4-9. Through comparison and analysis, 7 proteins were found to be upregulated>2-fold, whereas 6 protein spots were downregulated>2-fold after 10 and 1000 μg/l ATZ exposures for 14 days, which had caused histological effects in zebrafish livers. We found that these changed proteins were associated with a variety of cellular biological processes, such as response to oxidative stress, oncogenesis, etc. The results demonstrated that ATZ comprehensively influenced a variety of cellular and biological processes in zebrafish. The information presented in this study will be helpful in fully understanding the mechanism of the potential effects induced by ATZ in fish.

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

This study was undertaken to investigate the protective effect of atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine) on the activity of glutathione-S-transferase (GST) and DNA damage in males and females of adult zebrafish (Danio rerio). Zebrafish were exposed to control and three treatments (0.01, 0.1, and 1 mg/L) of atrazine for 5, 10, 15, 20, and 25 days. The results indicated that, for males, the GST activity at lower atrazine concentrations (0.01 and 0.1 mg/L) was markedly higher than that of the controls throughout the duration of the experiment while there was a significant inhibition of the GST activity at 1 mg/L atrazine at days 5 and 20. For females, a significant increase was detected at 0.1 mg/L on the days 5 and 15 and at 0.01 mg/L on day 20. The DNA damage in zebrafish was evaluated using the comet assay; the olive tail moments obtained for hepatopancreas were enhanced after treatment with different concentrations of atrazine on days 5, 10, 15, 20, and 25. The DNA damage increased with increasing atrazine concentrations, indicating that genotoxicity of atrazine and significant differences was found compared to the controls. In conclusion, these findings provide further evidence of the effects of atrazine on aquatic ecosystems.