Individual variability in esterase activity and CYP1A levels in Chinook salmon (Oncorhynchus tshawytscha) exposed to esfenvalerate and chlorpyrifos

Impacts of an organophosphate pesticide and water restriction on physiology and immunity in the passerine Zonotrichia capensis

Climate change, specifically rising temperatures and increased frequency of droughts will increase the level of exposure of organisms to chemical pollution. Notably, the impact of increased frequency and duration of drought events and subsequent dehydration on pesticide toxicity remains largely unknown. We evaluated the combined effects of exposure to the pesticide Chlorpyrifos (CPF) and water restriction (WR) on the enzymatic activities of three plasma esterases (acetylcholinesterase, butyrylcholinesterase and carboxylesterase), basal metabolic rate (BMR), leukocyte profile (proportion of heterophils to lymphocytes; H:L ratio), and bactericidal capacity of plasma in the rufous-collared sparrow (Zonotrichia capensis), a common passerine bird in Chile. The activity of the enzyme carboxylesterase decreased in birds exposed only to CPF and birds exposed to both the CPF and WR. In the group exposed to both stressors, the butyrylcholinesterase activity was also reduced. The BMR exhibited an increase in both groups exposed to CPF, with a higher rise observed in the group exposed to both CPF and WR, while the group subjected to WR showed no change. The bactericidal capacity of the plasma decreased significantly in birds exposed to CPF and in those exposed to both the pesticide and WR, while a marginal effect was observed in the group only subjected to WR. The H:L ratio increased in all groups, with the most pronounced effect in birds exposed to both stressors. These results suggest a shift in the energy budget of Z. capensis, favoring the detoxification of the pesticide through esterase activities, at the expense of reduced immunocompetence.

Methyl Parathion Exposure Induces Development Toxicity and Cardiotoxicity in Zebrafish Embryos

Methyl parathion (MP) has been widely used as an organophosphorus pesticide for food preservation and pest management, resulting in its accumulation in the aquatic environment. However, the early developmental toxicity of MP to non-target species, especially aquatic vertebrates, has not been thoroughly investigated. In this study, zebrafish embryos were treated with 2.5, 5, or 10 mg/L of MP solution until 72 h post-fertilization (hpf). The results showed that MP exposure reduced spontaneous movement, hatching, and survival rates of zebrafish embryos and induced developmental abnormalities such as shortened body length, yolk edema, and spinal curvature. Notably, MP was found to induce cardiac abnormalities, including pericardial edema and decreased heart rate. Exposure to MP resulted in the accumulation of reactive oxygen species (ROS), decreased superoxide dismutase (SOD) activity, increased catalase (CAT) activity, elevated malondialdehyde (MDA) levels, and caused cardiac apoptosis in zebrafish embryos. Moreover, MP affected the transcription of cardiac development-related genes (vmhc, sox9b, nppa, tnnt2, bmp2b, bmp4) and apoptosis-related genes (p53, bax, bcl2). Astaxanthin could rescue MP-induced heart development defects by down-regulating oxidative stress. These findings suggest that MP induces cardiac developmental toxicity and provides additional evidence of MP toxicity to aquatic organisms.

Joint toxic effects of phoxim and lambda-cyhalothrin on the small yellow croaker (Larimichthys polyactis)

Although pesticides commonly exist as combinations in real-life situations of the aquatic ecosystem, the impact of the toxicity of their mixtures has remained largely unclear. In this study, we investigated the combined effects of two neurotoxic pesticides, including one organophosphate insecticide phoxim (PHO) and one pyrethroid insecticide lambda-cyhalothrin (LCY), on the embryos of the small yellow croaker (Larimichthys polyactis), and their potential pathways. LCY exhibited higher toxicity relative to PHO, with a 72-h LC₅₀ value of 0.0074 mg a.i. L^-1, while the corresponding value for PHO was 0.12 mg a.i. L^-1. The mixture of PHO and LCY exerted a synergistic effect on the embryos of L. polyactis. The activities of antioxidant enzyme CAT and apoptotic enzyme caspase 3 were substantially changed in most single and combined exposure groups relative to the baseline value. Under both single and combined exposures, more significant changes were found in the mRNA expression of five genes, including the immunosuppression gene ngln2, the apoptosis gene P53, the endocrine system gene cyp19a1b, as well as neurodevelopment genes of ap and acp2, relative to the baseline value. Furthermore, the non-target metabolomic analysis demonstrated that hundreds of differential metabolites, including two bile acids (taurodeoxycholic acid and tauroursodeoxycholic acid), were significantly increased in the exposure groups. The bile acids were closely associated with the gut microbiota, and 16S rRNA sequencing results demonstrated dysfunction of the gut microbiota after exposure, especially in the combined exposure group. Our findings indicated that there might be a potential risk connected to the co-occurrence of these two pesticides in aquatic vertebrates. Consequently, future ecological risk assessments should incorporate synergistic mixtures because the current risk assessments do not consider them.

Chlorpyrifos stimulates ABCC-mediated transport in the intestine of the rainbow trout Oncorhynchus mykiss

The organophosphorus pesticide chlorpyrifos, detected in water and food worldwide, has also been found in the Río Negro and Neuquén Valley, North Patagonia, Argentina, where the rainbow trout, Oncorhynchus mykiss, is one of the most abundant fish species. We analyzed whether chlorpyrifos affects the transport activity of the ATP-binding cassette protein transporters from the subfamily C (ABCC), which are critical components of multixenobiotic resistance. We exposed ex vivo O. mykiss middle intestine strips (non-polarized) and segments (polarized) for one hour to 0 (solvent control), 3, 10, and 20 μg L^-1 and to 0, 10, and 20 μg L^-1 chlorpyrifos, respectively. We estimated the Abcc-mediated transport rate by measuring the transport rate of the specific Abcc substrate 2,4-dinitrophenyl-S-glutathione (DNP-SG). In addition, we measured the enzymatic activity of cholinesterase, carboxylesterase, glutathione-S-transferase, and 7-ethoxyresorufin-O-deethylase (EROD, indicative of the activity of cytochrome P450 monooxygenase 1A, CYP1A). We also measured lipid peroxidation using the thiobarbituric acid reactive substances method and the gene expression of Abcc2 and genes of the AhR pathway, AhR, ARNT, and cyp1a, by qRT-PCR. Chlorpyrifos induced the DNP-SG transport rate in middle intestine strips in a concentration-dependent manner (49-71%). In polarized preparations, the induction of the DNP-SG transport rate was observed only in everted segments exposed to 20 μg L^-1 chlorpyrifos (40%), indicating that CPF only stimulated the apical (luminal) transport flux. Exposure to chlorpyrifos increased GST activity by 42% in intestine strips and inhibited EROD activity (47.5%). In addition, chlorpyrifos exposure inhibited cholinesterase (34-55%) and carboxylesterase (33-42.5%) activities at all the concentrations assayed and increased TBARS levels in a concentration-dependent manner (71-123%). Exposure to 20 μgL^-1 chlorpyrifos did not affect the mRNA expression of the studied genes. The lack of inhibition of DNP-SG transport suggests that chlorpyrifos is not an Abcc substrate. Instead, CPF induces the activity of Abcc proteins in the apical membrane of enterocytes, likely through a post-translational pathway.

Synergistic effects of pesticides and environmental variables on earthworm standard metabolic rate

Endogeic earthworms such as Aporrectodea caliginosa play an essential role in the agroecosystems because of their continuous burrowing and feeding (geophagous) activity, which causes a profound impact on soil texture, organic matter decomposition, soil carbon storage, microbial activity, soil biodiversity, and nutrient cycling. Accordingly, endogeic earthworms are being proposed as suitable candidates for the ecotoxicity assessment of polluted soils. However, terrestrial ecotoxicology has little considered the interactive effects from pollutants and environmental variables (temperature, moisture). We acclimatized A. caliginosa for 90 days to two contrasting temperatures (10 °C and 20 °C) and moistures (25 % and 35 %, w/v) in soils contaminated with 20 mg kg^-1 of chlorpyrifos to examine how these two climate change drivers may modulate the pesticide toxicity. We measured the inhibition of cholinesterase (ChE) activities as indicators of organophosphorus exposure, the standard metabolic rate as an integrative physiological biomarker, and the lipid peroxidation (TBARS) and the total antioxidant capacity (TAC) both as indicators of oxidative stress. The main results were: i) chlorpyrifos strongly inhibited ChE activity (>75 % of controls), demonstrating earthworm bioavailability and acute toxicity at the test concentration; 2) a 50 % mortality and loss of body weight (49 %) were found in the earthworms exposed to the most severe environmental conditions (20 °C, 25 %, and pesticide); 3) this latter experimental group displayed a high SMR, which was concomitant with an increase of the oxidative balance index (TBARS/TAC). We postulated that earthworms acclimatized to stressing environmental conditions experienced a higher pesticide-induced metabolic cost and physiological challenges imposed by adverse environmental conditions.

Ecotoxicological Effects of Pesticides on Hematological Parameters and Oxidative Enzymes in Freshwater Catfish, Mystus keletius

Hematological parameters and changes in stress-induced functionalities of cellular enzymes have been recognized as valuable tools for monitoring fish health and determining the toxic effects of pesticides. The present study was conducted to evaluate the toxic effect of selected pesticides viz., Ekalux (EC-25%), Impala (EC-55%), and Neemstar (EC-15%) on freshwater catfish Mystus keletius. Fish were exposed to sub-lethal concentrations (mg/L) of the selected pesticide for a period of 7, 14, 21, and 28 days. Hematological parameters viz., total erythrocyte (RBC), hemoglobin (Hb), and hematocrit (Ht) packed cell volume values decreased with an increase in exposure time to pesticides, whereas the values for parameters viz., leucocytes (WBC), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) increased significantly. A decrease in packed cell volume (PCV) and hemoglobin values coupled with decreased and deformed erythrocytes as signs of anemia were also observed. The effect of pesticides on RBC content was 1.43 (million/mm3) on day 7 and reduced to 1.18 (million/mm3) on days 14 and 21. A similar trend was found for Impala on RBC, which had an initial value of 1.36 (million/mm3) on day 7 and reached a value of 1.10 (million/mm3) on day 28. In contrast, the value of Neemstar decreased from 1.59 (million/mm3) on day 7 in control to 1.02 (million/mm3) on day 28. Data indicates that the order of toxic effect of pesticides recorded a maximum for Impala followed by Ekalux and Neemstar in the selected fish model. Likewise, the overall pattern of pesticidal activity on cellular enzymes (GDH, MDH, and SDH) recorded a maximum toxic effect for Impala followed by Ekalux and Neemstar. Results indicate that Chlorpyrifos pesticide-Impala evoked maximum toxic effect on selected tissues compared to the other two pesticides tested. Statistical analysis of the summative data using two way ANOVA was statistically significant (p-value < 0.001). The differences in the hematological parameters analyzed are attributed to the physiological acclimatization of the fish to the local conditions, which influences the energy metabolism and consequently determines the health status of the fish. Overall, Impala exhibited the highest pesticidal activity on cellular enzyme, followed by Ekalux and Neemstar. Results suggest that natural pesticides may be preferable for rice field application in terms of environmental safety.

Biochemical and osmoregulatory responses of the African clawed frog experimentally exposed to salt and pesticide

Salinization and pollution are two main environmental stressors leading deterioration to water quality and degradation of aquatic ecosystems. Amphibians are a highly sensitive group of vertebrates to environmental disturbance of aquatic ecosystems. However, studies on the combined effect of salinization and pollution on the physiology of amphibians are limited. In this study, we measured the standard metabolic rate (SMR) and biochemical parameters of adult males of the invasive frog Xenopus laevis after 45 days of exposure to contrasting salinity environments (400 and 150 mOsm NaCl) with either 1.0 μg/L of the organophosphate pesticide chlorpyrifos (CPF) or pesticide-free medium. Our results revealed a decrease in SMR of animals exposed to the pesticide and in the ability to concentrate the plasma in animals exposed simultaneously to both stressors. The lack of ability to increase plasma concentration in animals exposed to both salt water and CPF, suggests that osmoregulatory response is decreased by pesticide exposure. In addition, we found an increase of liver citrate synthase activity in response to salt stress. Likewise, the liver acetylcholinesterase (AChE) activity decreased by 50% in frogs exposed to salt water and CPF and 40% in those exposed only to CPF, which suggest an additive effect of salinity on inhibition of AChE. Finally, oxidative stress increased as shown by the higher lipid peroxidation and concentration of aqueous peroxides found in the group exposed to salt water and pesticide. Thus, our results revealed that X. laevis physiology is compromised by salinization and pesticide exposure to both environmental stressors join.

The toxic effects of combined exposure of chlorpyrifos and p, p'-DDE to zebrafish (Danio rerio) and tissue bioaccumulation

Pesticides are widely used and frequently detected in the environment. The evaluation on the toxic effects of the co-exposure of two or more pesticides or related metabolites could reflect the real situation of the exposing risks. In this study, zebrafish was used as a model to investigate the potential toxic interactions of chlorpyrifos and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) on the survival rate, oxidative stress response and neurotoxicity, as well as their bioaccumulation and distribution in tissues. Co-exposure of chlorpyrifos and p,p'-DDE resulted in significant additive acute toxic effects on adult zebrafish with model deviation ratio (MDR) = 1.64. Both 7-day short-term at 1% LC₅₀ and 35-day long-term at 0.5% LC₅₀ co-exposure of chlorpyrifos with p,p'-DDE (50 and 100 µg/L) significantly reduced the survival rate of zebrafish colony to 75 and 82.5%. Co-exposure of chlorpyrifos and p,p'-DDE contributed to increased activity of antioxidant enzyme CAT, SOD and GST and excessive MDA generation, and decreased activity of CarE, CYP450 and AChE, compared with either single exposure of them. In co-exposure, the bioaccumulation of chlorpyrifos and p,p'-DDE was significantly different from the single exposure group. Overall, this study unraveled the potential toxic interaction of chlorpyrifos and p,p'-DDE on zebrafish and provided reference for environmental risk assessment of pesticide mixture.

Transient exposure to sublethal concentrations of a pesticide mixture (chlorpyrifos-difenoconazole) caused different responses in fish species from different trophic levels of the same community

The assessment of early effects caused in biota by sublethal exposure to pesticide mixtures should enhance the realism in the ecological risk assessment for agricultural landscapes. This study aimed to evaluate sub-individual responses in fish, which can be linked with outcomes at higher levels of biological organization and affect their trophic relationships. A multilevel biomarker approach was applied to assess the effects of a 48 h exposure of two freshwater mesoamerican fish species (Parachromis dovii and Poecilia gillii) to a mixture of sublethal concentrations of chlorpyrifos (5 μg/L) and difenoconazole (325 μg/L). Transcriptomic induction of cyp1A and the activities of 7-ethoxy-resorufin-O-distillase (EROD) and glutathione S-transferase (GST) were measured as biotransformation-related biomarkers; cholinesterase activity (ChE) was assessed as a neurotoxicity biomarker; resting metabolic rate (RMR) was measured as a physiological biomarker; and the movement of fish in a dark-light environment as a behavior biomarker. The exposure to the mixture had evident effects on P. gillii, with significant induction of cyp1A transcription, increased EROD activity, ChE inhibition in muscle, and increased permanence in the light side of the dark-light environment. Meanwhile, P. dovii only showed significant induction of cyp1A, without evidence of neurotoxicity or changes in behavior. This study demonstrates that the severity of the effects caused by the exposure to a mixture of pesticides can differ among species from the same trophic chain. The potential impairment of predator-prey relationships is a relevant effect that pesticide pollution can cause and it should be considered for the risk assessment of such contaminants.

Cellular level response of the bivalve Limecola balthica to seawater acidification due to potential CO2 leakage from a sub-seabed storage site in the southern Baltic Sea: TiTank experiment at representative hydrostatic pressure

Understanding of biological responses of marine fauna to seawater acidification due to potential CO₂ leakage from sub-seabed storage sites has improved recently, providing support to CCS environmental risk assessment. Physiological responses of benthic organisms to ambient hypercapnia have been previously investigated but rarely at the cellular level, particularly in areas of less common geochemical and ecological conditions such as brackish water and/or reduced oxygen levels. In this study, CO₂-related responses of oxygen-dependent, antioxidant and detoxification systems as well as markers of neurotoxicity and acid-base balance in the Baltic clam Limecola balthica from the Baltic Sea were quantified in 50-day experiments. Experimental conditions included CO₂ addition producing pH levels of 7.7, 7.0 and 6.3, respectively and hydrostatic pressure 900 kPa, simulating realistic seawater acidities following a CO₂ seepage accident at the potential CO₂-storage site in the Baltic. Reduced pH interfered with most biomarkers studied, and modifications to lactate dehydrogenase and malate dehydrogenase indicate that aerobiosis was a dominant energy production pathway. Hypercapnic stress was most evident in bivalves exposed to moderately acidic seawater environment (pH 7.0), showing a decrease of glutathione peroxidase activity, activation of catalase and suppression of glutathione S-transferase activity likely in response to enhanced free radical production. The clams subjected to pH 7.0 also demonstrated acetylcholinesterase activation that might be linked to prolonged impact of contaminants released from sediment. The most acidified conditions (pH 6.3) stimulated glutathione and malondialdehyde concentration in the bivalve tissue suggesting potential cell damage. Temporal variations of most biomarkers imply that after a 10-to-15-day initial phase of an acute disturbance, the metabolic and antioxidant defence systems recovered their capacities.

The insecticide chlorpyrifos modifies the expression of genes involved in the PXR and AhR pathways in the rainbow trout, Oncorhynchus mykiss

Chlorpyrifos (CPF) is an organophosphate pesticide, commonly detected in water and food. Despite CPF toxicity on aquatic species has been extensively studied, few studies analyze the effects of CPF on fish transcriptional pathways. The Pregnane X receptor (PXR) is a nuclear receptor that is activated by binding to a wide variety of ligands and regulates the transcription of enzymes involved in the metabolism and transport of many endogenous and exogenous compounds. We evaluated the mRNA expression of PXR-regulated-genes (PXR, CYP3A27, CYP2K1, ABCB1, UGT, and ABCC2) in intestine and liver of the rainbow trout, Oncorhynchus mykiss, exposed in vivo to an environmentally relevant CPF concentration. Our results demonstrate that the expression of PXR and PXR-regulated genes is increased in O. mykiss liver and intestine upon exposure to CPF. Additionally, we evaluated the impact of CPF on other cellular pathway involved in xenobiotic metabolism, the Aryl Hydrocarbon Receptor (AhR) pathway, and on the expression and activity of different biotransformation enzymes (CYP2M1, GST, FMO1, or cholinesterases (ChEs)). In contrast to PXR, the expression of AhR, and its target gene CYP1A, are reduced upon CPF exposure. Furthermore, ChE and CYP1A activities are significantly inhibited by CPF, in both the intestine and the liver. CPF activates the PXR pathway in O. mykiss in the intestine and liver, with a more profound effect in the intestine. Likewise, our results support regulatory crosstalk between PXR and AhR pathways, where the induction of PXR coincides with the downregulation of AhR-mediated CYP1A mRNA expression and activity in the intestine.

Cholinesterases of marine fish: characterization and sensitivity towards specific chemicals

Inhibition of cholinesterases has been frequently used as a biomarker for contamination of aquatic environments, because these enzymes are frequent targets for toxic effects of contaminants, such as insecticides derived from phosphoric and carbamic acids. However, this enzyme is also responsive to other contaminants, including metals. The use of cholinesterase inhibition as effect criterion in ecotoxicology studies requires the previous characterization of the specific enzymatic forms that can be present in the different tissues and/or organs of species. This work characterized the soluble ChEs present in the brain and dorsal muscle of three marine fish species, namely Scomber scombrus, Sardina pilchardus and Chelidonichthys lucerna. Pesticides (chlorpyrifos) and metals (copper sulphate) in vitro assays were conducted to quantify the effects of these contaminants on cholinesterases activity. The results of this study showed that acetylcholinesterase (AChE) was the predominant form present in the brain tissues of the three species and in the muscle tissue of one species (Sardina pilchardus). For Scomber scombrus and Chelidonichthys lucerna, the cholinesterase form present in the muscle tissue evidenced properties between the classic acetylcholinesterase and those of pseudocholinesterase forms. The results for the metal (copper) and pesticide (chlorpyrifos) showed that this species may be suitable for monitoring contaminations for these types of contaminants.

Toxicity of malathion during Senegalese sole, Solea senegalensis larval development and metamorphosis: Histopathological disorders and effects on type B esterases and CYP1A enzymatic systems

The toxicity of malathion to Solea senegalensis was studied in a static renewal bioassay during its first month of larval life (between 4 and 30 dph). Through the use of different biomarkers and biochemical, cellular and molecular approaches (inhibition of cholinesterases [ChEs], changes in cytochrome P450-1A [CYP1A] and the study of histopathological alterations), the effects of three concentrations of malathion (1.56, 3.12, and 6.25 μg/L) have been analyzed. In subacute exposure, malathion inhibited cholinesterase activities (AChE, BChE, CbE) in a dose- and time-dependent manner, ranging the inhibition percentage from 20% to 90%. However, the expression levels of CYP1A and AChE transcripts or proteins were not modified. Additionally, exposure to malathion provoked histopathological alterations in several organ systems of Senegalese sole in a time- and dose dependent way, namely disruption of parenchymal architecture in the liver, epithelial desquamation, pyknotic nuclei and steatosis in the intestine, disorganization of supporting cartilage, and sings of hyperplasia and hypertrophy in the gills and degeneration of the epithelial cells from the renal tubules. Malathion exposure also provoked strong disorganization of cardiac fibers from the heart. The findings provide evidence that exposure to sublethal concentrations of malathion that provoked serious injury to the fish S. senegalensis, were below the expected environmental concentrations reported in many other ecosystems and different fish species,revealing a higher sensitivity for Solea senegalensis to malathion exposure, thus reinforcing its use as sentinel species for environmental pollution in coastal and estuarine environments.

Modeling acetylcholine esterase inhibition resulting from exposure to a mixture of atrazine and chlorpyrifos using a physiologically-based kinetic model in fish

Aquatic organisms are exposed to mixtures of chemicals that may interact. Mixtures of atrazine (ATR) and chlorpyrifos (CPF) may elicit synergic effects on the permanent inhibition of acetylcholinesterase (AChE) in certain aquatic organisms, causing severe damage. Mechanistic mathematical models of toxicokinetics and toxicodynamics (TD) may be used to better characterize and understand the interactions of these two chemicals. In this study, a previously published generic physiologically-based toxicokinetic (PBTK) model for fish was adapted to ATR and CPF. A sub-model of the kinetics of one of the main metabolites of CPF, chlorpyrifos-oxon (CPF-oxon), was included, as well as a TD model. Inhibition of two esterases, AChE and carboxylesterase, by ATR, CPF and CPF-oxon, was modeled using TD modeling of quantities of total and inactive esterases. Specific attention was given to the parameterization and calibration of the model to accurately predict the concentration and effects observed in the fish using Bayesian inference and published data from fathead minnow (Pimephales promelas), zebrafish (Danio rerio) and common carp (Cyprinus carpio L.). A PBTK-TD for mixtures was used to predict dose-response relationships for comparison with available adult fish data. Synergistic effects of a joint exposure to ATR and CPF could not be demonstrated in adult fish.

Cypermethrin- and fipronil-based insecticides cause biochemical changes in Physalaemus gracilis tadpoles

Insecticides used for agricultural pest control, as cypermethrin-based insecticide (CBI) and fipronil-based insecticide (FBI), are constant threats to non-target aquatic organisms. This study aimed to investigate the effect of different concentrations of cypermethrin and fipronil on neurotoxicity and oxidative stress in Physalaemus gracilis. Physalaemus gracilis tadpoles were exposed to five insecticide concentrations and a control treatment, with six replicates. During the experimental period, the tadpole mortality rate was evaluated and after 168 h, the neurotoxic enzyme activity and metabolite quantification related to the antioxidant system were measured. Tadpoles reduced acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities when exposed to 20 μg L^-1 CBI and at all FBI concentrations, respectively. Glutathione S-transferase (GST) and superoxide dismutase (SOD) activities showed an increase from concentrations of 6 μg L^-1 and 20 μg L^-1 of CBI, respectively. After exposure of P. gracilis tadpoles to FBI, inhibitions of AChE and BChE were observed at the highest concentrations evaluated (500 and 1500 μg L^-1). SOD activity decreased from 50 μg L^-1 of FBI; however, catalase (CAT) and GST activities and carbonyl protein levels increased, regardless of the evaluated dose. We observed that both insecticides promoted oxidative stress and neurotoxic effects in P. gracilis tadpoles. These results suggest that biochemical biomarkers can be used for monitoring toxicity insecticides for the purpose of preservation of P. gracilis.

Evaluating Earthworms’ Potential for Remediating Soils Contaminated with Olive Mill Waste Sediments

The olive-oil industry generates large amounts of residues that, in the past, were accumulated in evaporating ponds in many Mediterranean countries. Currently, these open-air ponds pose a serious environmental hazard because of toxic chemicals that concentrate in their sediments. Bioremediation of olive mill waste (OMW) sediments has emerged as a viable option for managing this environmentally problematic residue. Here, we postulate that inoculation of an OMW-soil mixture with earthworms may be a complementary bioremediation strategy to that using native microorganisms only. A laboratory study assessed the ecotoxicity of OMW-amended soils (10%, 20%, 40% and 80% w/w) combining earthworm biomarker responses and soil enzyme activities. The doses of 40% and 80% were toxic to earthworms, as evidenced by the high mortality rate, loss of body weight and signs of oxidative stress after 30 d of soil incubation. Conversely, doses ≤ 20% w/w were compatible with earthworm activity, as indicated by the significant increase of soil enzyme activities. Total concentrations of phenolic compounds decreased by more than 70% respect to initial concentrations in 10% and 20% OMW treatments. These results suggest that OMW sediments intentionally mixed with soils in an up to 20% proportion is a workable bioremediation strategy, where earthworms can be inoculated to facilitate the OMW degradation.

Spirulina platensis Reduced Oxidative Damage Induced by Chlorpyrifos Toxicity in Nile Tilapia (Oreochromis niloticus)

Due to the numerous pharmacological impacts of Spirulina platensis (SP), the effects of SP on the oxidative status of Nile tilapia farmed under chlorpyrifos (CPF) ambient toxicity were considered in this study. Fish (60 ± 6.1 g) was randomly stocked in five groups where the SP free diet was fed to the control group while the second one was fed 1% SP without CPF exposure. Additionally, CPF (15 μg/L) was added in water and fish were fed with SP at 0, 0.5, and 1% (third, fourth, and fifth groups, respectively). Samples of blood and gills, kidneys, and liver tissues were assayed for biochemical measurements. Fish exposed to CPF exhibited significant (p ≤ 0.05) increments of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), cholesterol, urea, creatinine, and malondialdehyde (MDA), while significantly decreased total protein, albumin, and antioxidative enzyme activities (superoxide dismutase (SOD) and catalase (CAT) were observed in tilapia exposed to CPF (p ≤ 0.05). In contrast, SP feeding resulted in decreased levels of ALT, AST, ALP, cholesterol, urea, and creatinine as well as increased total protein, albumin, SOD, and CAT activities. Based on the obtained results, it can be suggested that SP is efficient in protecting Nile tilapia from CPF toxicity by increasing the antioxidative response.

Exposure to heavy metal-contaminated sediments disrupts gene expression, lipid profile, and life history traits in the midge Chironomus riparius

Despite the concern about anthropogenic heavy metal accumulation, there remain few multi-level ecotoxicological studies to evaluate their effects in fluvial ecosystems. The toxicity of field-collected sediments exhibiting a gradient of heavy metal contamination (Cd, Pb, and Zn) was assessed in Chironomus riparius. For this purpose, larvae were exposed throughout their entire life cycle to these sediments, and toxic effects were measured at different levels of biological organization, from the molecular (lipidomic analysis and transcriptional profile) to the whole organism response (respiration rate, shape markers, and emergence rate). Alterations in the activity of relevant genes, as well as an increase of storage lipids and decrease in membrane fluidity, were detected in larvae exposed to the most contaminated sediments. Moreover, reduced larval and adult mass, decrease of larval respiration rate, and delayed emergence were observed, along with increased mentum and mandible size in larvae and decreased wing loading in adults. This study points out the deleterious effects of heavy metal exposure at various levels of biological organization and provides some clues regarding the mode of toxic action. This integrative approach provides new insights into the multi-level effects on aquatic insects exposed to heavy metal mixtures in field sediments, providing useful tools for ecological risk assessment in freshwater ecosystems.

Presence of pharmaceutical compounds, levels of biochemical biomarkers in seafood tissues and risk assessment for human health: Results from a case study in North-Western Spain

This study assessed the presence of 27 pharmaceutically active compounds belonging to common therapeutic groups (cardiovascular, antiashmatic, psychoactive, diuretic, analgesic/anti-inflammatory, and antibiotic drugs) in the tissues of representative seafood species of bivalves, cephalopods, arthropods, and fish of high economic importance and consumption rates in North-Western Spain. Four pharmaceutical compounds, out of the 27 analyzed, were detected in the collected samples. The benzodiazepine citalopram was detected in the tissues of common octopus (14.1 ng g^-1 dry weight) and pod razor (9.4 ng g^-1 dw). The anxiolytic venlafaxine was detected in the tissues of common cockle (2.9 ng g^-1 dw). The veterinary antiparasitic ronidazole was found in pod razor (2.3 ng g^-1 dw) and, finally, the psychoactive compound alprazolam was also measured in common octopus (0.3 ng g^-1 dw). Hazard quotients were calculated to assess the hazard posed by the consumption of the sampled seafoods. Octopus and pod razor tissues containing citalopram and alprazolam exceeded our chosen hazard limits (HQ > 0.1) for toddlers who are high consumers of seafood (HQ values between 0.18 and 0.27). A battery of biochemical biomarkers of effects (acetylcholinesterase, glutathione S-transferase; catalase, glutathione peroxidase and glutathione reductase enzymes activities and reduced/oxidized glutathione and malondialdehyde levels) was applied to samples of the study species with the aim of characterizing their basal levels and evaluating their suitability as a tool in the monitoring chronic exposure to environmental contaminants such as those analyzed in this study. According to the measured biomarkers, pod razor and cockles have the potential to be good bioindicator species, based on the observed among-site differences detected on acetylcholinesterase, glutathione S-transferase, catalase, glutathione peroxidase activities; reduced/oxidized glutathione and malondialdehyde levels.

Effects of Agricultural Pesticides in Aquafeeds on Wild Fish Feeding on Leftover Pellets Near Fish Farms

Screening has revealed that modern-day feeds used in Atlantic salmon aquaculture might contain trace amounts of agricultural pesticides. To reach slaughter size, salmon are produced in open net pens in the sea. Uneaten feed pellets and undigested feces deposited beneath the net pens represent a source of contamination for marine organisms. To examine the impacts of long-term and continuous dietary exposure to an organophosphorus pesticide found in Atlantic salmon feed, we fed juvenile Atlantic cod (Gadus morhua), an abundant species around North Atlantic fish farms, three concentrations (0.5, 4.2, and 23.2 mg/kg) of chlorpyrifos-methyl (CPM) for 30 days. Endpoints included liver and bile bioaccumulation, liver transcriptomics and metabolomics, as well as plasma cholinesterase activity, cortisol, liver 7-ethoxyresor-ufin-O-deethylase activity, and hypoxia tolerance. The results show that Atlantic cod can accumulate relatively high levels of CPM in liver after continuous exposure, which is then metabolized and excreted via the bile. All three exposure concentrations lead to significant inhibition of plasma cholinesterase activity, the primary target of CPM. Transcriptomics profiling pointed to effects on cholesterol and steroid biosynthesis. Metabolite profiling revealed that CPM induced responses reflecting detoxification by glutathione-S-transferase, inhibition of monoacylglycerol lipase, potential inhibition of carboxylesterase, and increased demand for ATP, followed by secondary inflammatory responses. A gradual hypoxia challenge test showed that all groups of exposed fish were less tolerant to low oxygen saturation than the controls. In conclusion, this study suggests that wild fish continuously feeding on leftover pellets near fish farms over time may be vulnerable to organophosphorus pesticides.

An integrated approach in subtropical agro-ecosystems: Active biomonitoring, environmental contaminants, bioaccumulation, and multiple biomarkers in fish

Aquatic contamination in agricultural areas is a global problem, characterized by a complex mixture of organic and inorganic pollutants whose effects on biota are unpredictable and poorly investigated. In this context, in the present study, the Neotropical fish Prochilodus lineatus was confined in situ for 120 days in two sites with different levels of anthropic impact: 1) a fish hatchery station, within the State University of Londrina (reference site - REF) and 2) an agro-ecosystem area in one of the most productive regions of southern Brazil (experimental site - EXP). We evaluated multiple biomarkers at different levels of biological organization, such as biotransformation and antioxidant enzymes, oxidative damages, DNA damages and liver histopathology. We also evaluated the occurrence of 22 organochlorine pesticides (OCPs) and 6 trace metals in water and sediment; and 33 current-use pesticides (CUPs) in the water; besides the presence of OCPs in the liver and metals in different tissues of the confined fish. The chemical analysis confirmed that the two environments presented different levels of contamination. We verified a distribution gradient of data in the principal component analysis (PCA), separating the REF fish to one side and the fish at the agricultural area (EXP) to the other side. In general, the biomarker responses were more altered in fish from the EXP than fish from the hatchery station; and this fish presented a greater accumulation of endosulfan (an increase of 18× compared to basal value) and showed oxidative, genetic, and histological damage. Through the Biomarkers Response Index (BRI), we found that the EXP fish demonstrated a decrease in health status compared with the REF fish during the confinement time, due to their exposure to a higher concentration of contaminants. In conclusion, the use of multiple biomarkers at different response levels is an important tool for environmental monitoring.

Behavioral, molecular and physiological responses of embryo-larval zebrafish exposed to types I and II pyrethroids

Pyrethroids are potent neurotoxicants that may elicit multiple pathways of toxicity in non-target organisms. Comparative studies on the mechanistic and developmental effects of types I and II pyrethroids against non-target aquatic species are limited. This study assessed the effects of the two pyrethroid types against embryo-larval zebrafish (Danio rerio) at environmentally relevant and laboratory concentrations. Zebrafish embryos were exposed to type-I (permethrin, bifenthrin) and type-II (deltamethrin, λ-cyhalothrin, fenvalerate, esfenvalerate) pyrethroids at 1000, 10, 0.1, 0.01, 0.0 μg/L, starting at 5-h post-fertilization (hpf) through 5-d post-fertilization (dpf) under static exposure conditions. Swimming behavior (distance traveled and velocity) was assessed at 5-dpf. The relative expression of Nrf2a, GST, Casp-9 and p53 mRNA transcripts, carboxyl esterase (CES) activity and total reactive oxygen species (ROS) were measured. The stability of the pyrethroids across 5 days was analyzed. Bifenthrin-(10 μg/L) and esfenvalerate-(1000 μg/L) significantly (p < 0.05) reduced total distance traveled by larvae while 1000 μg/L deltamethrin and λ-cyhalothrin were lethal causing body axis curvature and pericardial edema. At environmentally relevant concentrations-(μg/L) compared to control, permethrin-(0.122) upregulated Nrf2a and Casp-9 expressions while λ-cyhalothrin-(0.053) downregulated Nrf2a and fenvalerate-0.037 downregulated GST. At laboratory concentrations-(μg/L), permethrin-(1000) upregulated Nrf2a, Casp-9 and p53 expressions, bifenthrin-(10) upregulated Casp-9 while fenvalerate-(0.1) and esfenvalerate-(1000) downregulated GST. There was concentration dependent increase in CES activity which correlated positively with total ROS. Pyrethroid concentrations decreased significantly by day 5. This study showed disparity in the mechanistic effects across the pyrethroids types and their instability in aqueous media may underestimate toxicity against non-target aquatic species when exposed in their natural environment.

A multi-biomarker approach to lambda-cyhalothrin effects on the freshwater teleost matrinxa Brycon amazonicus: single-pulse exposure and recovery

Effects of the pyrethroid lambda-cyhalothrin (LCH) were investigated in matrinxa Brycon amazonicus, a non-target freshwater teleost. The fish were submitted to a single-pulse exposure (10% of LC50; 96 h, 0.65 μg L^-1), followed by 7 days of recovery in clean water. Hematologic parameters indicated impairments in oxygen transport, which were not recovered. Plasma [Na⁺], [Cl^-], and protein were diminished, and only [Na⁺] remained low after recovery. Gill Na⁺/K⁺ATPase activity was increased and recovered to basal values. Brain acetylcholinesterase activity was not responsive to LCH. Liver ascorbic acid concentration was not altered, and reduced glutathione levels remained augmented even after recovery. LCH inhibited hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, while glutathione-S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH) activities were steady. After recovery, SOD remained low, and GPx was augmented. Liver depicted lipid peroxidation, which was not observed after recovery. Hepatic morphology was affected by LCH and was not completely recovered. These responses, combined with the persistence of changes even after recovery span, clearly show the feasibility of these biomarkers in evaluating LCH toxic potential to non-target organisms, highlighting the importance of pyrethroids' responsible use.

Exploring alternative biomarkers of pesticide pollution in clams

Acetylcholinesterase (AChE) is a reliable biomarker of pesticide exposure although in clams this activity is often very low or undetectable. Carboxylesterases (CEs) exhort several physiological roles, but also respond to pesticides. Searching for an AChE alternative, baseline CE activities were characterised in Ruditapes decussatus gills and digestive glands using five substrates suggestive of different isozymes. The long chain p-nitrophenyl butyrate and 1-naphthyl butyrate were the most sensitive. In the digestive gland, their kinetic parameters (V_max and K_m) and in vitro sensitivity to the organophosphorus metabolite chlorpyrifos oxon (CPX) were calculated. IC50 values, in the pM-nM range, suggest a high protection efficiency of CE-related enzymes towards CPX neurotoxicity. Other targeted enzymes were: activities of glutathione reductase, glutathione peroxidase, catalase, glutathione S-transferases (GSTs) and lactate dehydrogenase in gills and digestive glands. The high GSTs activity and CE/AChE ratio suggests that R. decussatus has a great capacity for enduring pesticide exposure.

Effects of sequential exposure to water accommodated fraction of crude oil and chlorpyrifos on molecular and biochemical biomarkers in rainbow trout

Fish can be simultaneously or sequentially exposed to various kinds of pollutants, resulting in combined effects. Polycyclic aromatic hydrocarbons induce cytochrome P450 monooxygenase 1A (CYP1A) expression, which catalyzes the conversion of the organophosphorus insecticide chlorpyrifos (CPF) into its most active derivative, CPF-oxon. CPF-oxon inhibits CYP1A and other enzymes, including carboxylesterases (CEs) and acetylcholinesterase (AChE). We studied the effects of an in vivo exposure to crude oil water accommodated fraction (WAF) followed by an ex vivo exposure of liver tissue to CPF on the expression of Cyp1a, AhR and ARNT mRNA, CYP1A protein and on the activity of biomarker enzymes in the rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were exposed to WAF (62 μg L^-1 TPH) for 48 h. Then, liver was dissected out, sliced and exposed to 20 μg L^-1 CPF ex vivo for 1 h. Liver tissue was analyzed for mRNA and protein expression and for CEs, AChE, glutathione S-transferase (GST) and CYP1A (EROD) activity. WAF induced Cyp1a mRNA and CYP1A protein expression by 10-fold and 2.5-8.3-fold, respectively, with no effect of CPF. WAF induced AhR expression significantly (4-fold) in control but not in CPF treated liver tissue. ARNT mRNA expression was significantly lowered (5-fold) by WAF. CPF significantly reduced liver EROD activity, independently of WAF pre-treatment. CEs activity was significantly inhibited in an additive manner following in vivo exposure to WAF (42%) and ex vivo exposure to CPF (19%). CPF exposure inhibited AChE activity (37%) and increased GST activity (42%).

Comparative evaluation of toxicological effects and recovery patterns in zebrafish (Danio rerio) after exposure to phosalone-based and cypermethrin-based pesticides

This study evaluated the toxic effects and recovery patterns in zebrafish (Danio rerio) after exposure to phosalone-based (PBP) and cypermethrin-based (CBP) pesticides. Initially, the 96 h LC₅₀ values of the pesticides were calculated as being 5.35 µg of active ingredient (AI) L^-1 for CBP and 217 µg AI L^-1 for PBP based on measured concentrations. Accordingly, experimental groups were exposed to three sublethal concentrations of pesticides for 96 h, separately, and then zebrafish were transferred to pesticide-free conditions for 10 and 20 days recovery periods. Biochemical markers were assessed including carboxylesterase (CaE), acetylcholinesterase (AChE), glutathione S-transferase (GST), lactate dehydrogenase, glutathione peroxidase, catalase, alanine and aspartate aminotransferase (ALT, AST) activities after the exposure and recovery periods. Also, the pesticide concentrations in test water were quantified by high-performance liquid chromatography (HPLC) analysis. Our results showed that AChE and CaE activities were significantly inhibited and GST was induced by both pesticides after 96 h exposure. For PBP exposure, the decreases for GST induction and CaE inhibition showed a partial recovery in pesticide-free conditions. However, the decreases in AChE activity for CBP exposure and insufficient increases in same enzyme activity for PBP exposure after 20 days in pesticide-free conditions indicated that the projected recovery period was not enough to the recovery of AChE activities and for the improvement of fish health.

The organophosphorus pesticide dimethoate decreases cell viability and induces changes in different biochemical parameters of rat pancreatic stellate cells

In the present study we employed cultured pancreatic stellate cells to study the effect of the organophosphorus insecticide dimethoate on pancreatic cell physiology. Esterase activity, cell viability, reactive oxygen species generation and Ca²⁺ mobilization were examined. Our results show that dimethoate (0.1, 1 and 10 μM) induced a concentration-dependent inhibition of cholinesterase enzymatic activity at all concentrations tested. A drop in carboxylesterase activity was noted in the presence of 10 μM dimethoate. In the presence of the pesticide a decrease in cell viability was detected. The clearer effect could be observed when the cells had been incubated during 96 h in the presence of dimethoate. The pesticide induced a slight but statistically significant increase in the production of reactive oxygen species in the mitochondria. Incubation of cells with dimethoate, in the presence of Ca²⁺ in the extracellular medium, led to a slow and progressive increase in [Ca²⁺]_c towards an elevated value over the prestimulation level. A similar behavior was observed in the absence of extracellular Ca²⁺, indicating that dimethoate releases Ca²⁺ from the intracellular stores. Our results suggest that dimethoate might alter intracellular pathways that are critical for pancreatic physiology, creating a situation potentially leading to dysfunction in the exocrine pancreas.

Response of digestive enzymes and esterases of ecotoxicological concern in earthworms exposed to chlorpyrifos-treated soils

Assessment of organophosphorus (OP) pesticide exposure in non-target organisms rarely involves non-neural molecular targets. Here we performed a 30-d microcosm experiment with Lumbricus terrestris to determine whether the activity of digestive enzymes (phosphatase, β-glucosidase, carboxylesterase and lipase) was sensitive to chlorpyrifos (5 mg kg^-1 wet soil). Likewise, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in the wall muscle and gastrointestinal tissues as indicators of OP exposure. Chlorpyrifos inhibited the acid phosphatase (34% of controls), carboxylesterase (25.6%) and lipase activities (31%) in the gastrointestinal content. However, in the gastrointestinal tissue, only the carboxylesterase and lipase activities were significantly depressed (42-67% carboxylesterase inhibition in the foregut and crop/gizzard, and 15% lipase inhibition in the foregut). Chlorpyrifos inhibited the activity of both cholinesterases in the gastrointestinal tissues, whereas the AChE activity was affected in the wall muscle. These results suggested chlorpyrifos was widely distributed throughout the earthworm body after 30 d of incubation. Interestingly, we found muscle carboxylesterase activity strongly inhibited (92% of control) compared with that detected in the gastrointestinal tissues of the same OP-exposed individuals. This finding was explained by the occurrence of pesticide-resistant esterases in the gastrointestinal tissues, which were evidenced by zymography. Our results suggest that digestive processes of L. terrestris may be altered by chlorpyrifos, as a consequence of the inhibitory action of the insecticide on some digestive enzymes.

Effect of selenium on Penaeus monodon and Perna viridis: Enzyme activities and histopathological responses

The study was carried out to evaluate enzyme activities and histopathological changes due to the effect of acute and chronic definitive toxicity of selenium (Se) on the post larvae (PL) of giant tiger shrimp (Penaeus monodon), and green mussel (Perna viridis). The 96-h Median Lethal concentration (LC₅₀) for the PL of shrimp was 3.36 mg L^-1 and the chronic value for the long-term survival endpoint in a 21-d exposure was 0.10 mg L^-1. The green mussel 96-h LC₅₀ was 28.41 mg L^-1 and the chronic value for the long-term survival endpoint in a 30-d exposure was 3.06 mg L^-1. Native polyacrylamide gel electrophoresis revealed altered diverse isoforms of esterase, superoxide dismutase and malate dehydrogenase activities in the PL of shrimp and green mussel exposed to sublethal concentration of Se. Cellular anomalies such as deformation and fusion of corneal cells, detachment of corneal cells from cornea facet and increased space between ommatidia were observed in the compound eye of PL of shrimp exposed to Se for 21-d. Shrinkage and clumping of mucous gland, degenerative changes in phenol gland, and ciliated epithelium were observed in the foot of green mussel exposed to Se for 30-d. This study shows that cellular anomalies in the compound eye of PL of P. monodon and foot tissues of P. viridis described would affect the vision of shrimp and byssus thread formation in green mussel.

Modification and quantification of in vivo EROD live-imaging with zebrafish (Danio rerio) embryos to detect both induction and inhibition of CYP1A

The visualization of specific activation of the aryl hydrocarbon receptor (AhR) directly in the zebrafish embryo (Danio rerio) via live-imaging is a reliable tool to investigate the presence of dioxin-like substances in environmental samples. The co-existence of inducers and inhibitors of cytochrome P450-dependent monooxygenases (CYP1A) is typical of complex environmental mixtures and requires modifications of the in vivo EROD assay: For this end, zebrafish embryos were used to evaluate the EROD-modifying potentials of common single-compound exposures as well as binary mixtures with the PAH-type Ah-receptor agonist β-naphthoflavone. For chemical testing, chlorpyrifos and Aroclor 1254 were selected; β-naphthoflavone served as maximum EROD induction control. Chlorpyrifos (≤EC₁₀) could be documented to be a strong CYP1A inhibitor causing characteristic edema-related toxicity. Aroclor 1254 resulted in inhibition of CYP1A catalytic activity in a concentration- and specific time-dependent manner. Next to a fast CYP1A induction, CYP1A inhibition could also be detected after 3h short-term exposure of zebrafish embryos to chlorpyrifos. This communication also describes techniques for the quantification of fluorescence signals via densitometry as a basis for subsequent statistical assessment. The co-exposure approach with zebrafish embryos accounts for the nature of potential interaction between CYP1A inducers and inhibitors and thus pays tribute to the complexity of environmental mixtures. The co-exposure EROD live-imaging assay thus facilitates a better understanding of mixture effects and allows a better assessment and interpretation of (embryo) toxic potentials.

Soil enzyme dynamics in chlorpyrifos-treated soils under the influence of earthworms

Earthworms contribute, directly and indirectly, to contaminant biodegradation. However, most of bioremediation studies using these annelids focus on pollutant dissipation, thus disregarding the health status of the organism implied in bioremediation as well as the recovery of indicators of soil quality. A microcosm study was performed using Lumbricus terrestris to determine whether earthworm density (2 or 4individuals/kg wet soil) and the time of exposure (1, 2, 6, 12, and 18wk) could affect chlorpyrifos persistence in soil initially treated with 20mg active ingredientkg^-1 wet soil. Additionally, selected earthworm biomarkers and soil enzyme activities were measured as indicators of earthworm health and soil quality, respectively. After an 18-wk incubation period, no earthworm was killed by the pesticide, but clear signs of severe intoxication were detected, i.e., 90% inhibition in muscle acetylcholinesterase and carboxylesterase (CbE) activities. Unexpectedly, the earthworm density had no significant impact on chlorpyrifos dissipation rate, for which the measured half-life ranged between 30.3d (control soils) and 44.5d (low earthworm density) or 36.7d (high earthworm density). The dynamic response of several soil enzymes to chlorpyrifos exposure was examined calculating the geometric mean and the treated-soil quality index, which are common enzyme-based indexes of microbial functional diversity. Both indexes showed a significant and linear increase of the global enzyme response after 6wk of chlorpyrifos treatment in the presence of earthworms. Examination of individual enzymes revealed that soil CbE activity could decrease chlorpyrifos-oxon impact upon the rest of enzyme activities. Although L. terrestris was found not to accelerate chlorpyrifos dissipation, a significant increase in the activity of soil enzyme activities was achieved compared with earthworm-free, chlorpyrifos-treated soils. Therefore, the inoculation of organophosphorus-contaminated soils with L. terrestris arises as a complementary bioremediation strategy in terms of recovery of soil biochemical performance and quality.

Reference intervals for B-esterases in gull, Larus michahellis (Nauman, 1840) from Northwest Spain: influence of age, gender, and tissue

Over the last years, cholinesterase (ChE) and carboxylesterase (CbE) activities have been increasingly used in environmental biomonitoring to detect the exposure to anticholinesterase insecticides such as organophosphorates (OPs) and carbamates (CBs). The aim of this study was to determine ChE and CbE enzymatic activities present in liver and muscle of yellow-legged gulls (Larus michahellis), a seabird species considered suitable to monitor environmental pollution. In order to provide reference data for further biomonitoring studies, the influence of different factors, such as gender, age, sampling mode, and tissue, was considered in the present study. Our data report a statistically significant difference in CbE enzymatic activity comparing liver and muscle samples (P < 0.05) along with an age-related CbE activity in liver samples (P < 0.05). Moreover, according to our results, capture method might influence CbE and ChE activity in both liver and muscle samples (P < 0.05). These findings underline the importance to assess basal levels of ChE and CbE activity considering, among other factors, gender-, age- and organ-related differences and confirm the suitability of Larus michahellis as a sentinel species especially within an urban environment.

Enzymatic activity and gene expression changes in zebrafish embryos and larvae exposed to pesticides diazinon and diuron

The zebrafish as a test organism enables the investigation of effects on a wide range of biological levels from molecular level to the whole-organism level. The use of fish embryos represents an attractive model for studies aimed at understanding toxic mechanisms and the environmental risk assessment of chemicals. In the present study, a zebrafish (Danio rerio) in vivo model was employed in order to assess the effects of two commonly used pesticides, the insecticide diazinon and the herbicide diuron, on zebrafish early life stages. Since it was previously established that diazinon and diuron cause effects at the whole-organism level, this study assessed the suborganismic responses to exposure to these pesticides and the enzymatic responses (biochemical level) and the gene expression changes (molecular level) were analyzed. Different exposure scenarios were employed and the following endpoints measured: acetylcholinesterase (AChE), carboxylesterase (CES), ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT) and glutathione peroxidase (GPx) activities; and gene expressions of the corresponding genes: acetylcholinesterase (ache), carboxylesterase (ces2), cytochrome P450 (cyp1a), glutathione-S-transferase (gstp1), catalase (cat), glutathione peroxidase (gpx1a) and additionally glutathione reductase (gsr). Significant changes at both the biochemical and the molecular level were detected. In addition, different sensitivities of different developmental stages of zebrafish were determined and partial recovery of the enzyme activity 48h after the end of the exposure was observed. The observed disparity between gene expression changes and alterations in enzyme activities points to the necessity of monitoring changes at different levels of biological organization. Different exposure scenarios, together with a comparison of the responses at the biochemical and molecular level, provide valuable data on the effects of diazinon and diuron on low organizational levels in zebrafish embryos and larvae.

Histopathological effects, responses of oxidative stress, inflammation, apoptosis biomarkers and alteration of gene expressions related to apoptosis, oxidative stress, and reproductive system in chlorpyrifos-exposed common carp (Cyprinus carpio L.)

In this study, we aimed to identify the toxic effects of chlorpyrifos exposure on the tissues of common carp. For this purpose, we evaluated histopathological changes in the brain, gills, liver, kidney, testis, and ovaries after 21 days of chlorpyrifos exposure. Activation of 8-OHdG, cleaved caspase-3, and iNOS were assesed by immunofluorescence assay in chlorpyrifos-exposed brain and liver tissue. Additionally, we measured the expression levels of caspase-3, caspase-8, iNOS, MT1, CYP1A, and CYP3A genes in chlorpyrifos-exposed brain tissue, as well as the expression levels of FSH and LH genes in chlorpyrifos-exposed ovaries, using qRT-PCR. We observed severe histopathological lesions, including inflammation, degeneration, necrosis, and hemorrhage, in the evaluated tissues of common carp after both high and low levels of exposure to chlorpyrifos. We detected strong and diffuse signs of immunofluorescence reaction for 8-OHdG, iNOS, and cleaved caspase-3 in the chlorpyrifos-exposed brain and liver tissues. Furthermore, we found that chlorpyrifos exposure significantly upregulated the expressions of caspase-3, caspase-8, iNOS, and MT1, and also moderately upregulated CYP1A and CYP3A in the brain tissue of exposed carp. We also noted downregulation of FSH and LH gene expressions in chlorpyrifos-exposed ovary tissues. Based on our results, chlorpyrifos toxication caused crucial histopathological lesions in vital organs, induced oxidative stress, inflammation, and apoptosis in liver and brain tissues, and triggered reproductive sterility in common carp. Therefore, we can propose that chlorpyrifos toxication is highly dangerous to the health of common carp. Moreover, chlorpyrifos pollution in the water could threaten the common carp population. Use of chlorpyrifos should be restricted, and aquatic systems should be monitored for chlorpyrifos pollution.

Tissue-specific bioconcentration and biotransformation of cypermethrin and chlorpyrifos in a native fish (Jenynsia multidentata) exposed to these insecticides singly and in mixtures

The aim of the present study was to evaluate the accumulation of cypermethrin and chlorpyrifos when the fish Jenynsia multidentata was exposed to these pesticides singly and in technical and commercial mixtures. Adult female fish were exposed over 96 h to 0.04 μg/L of cypermethrin; 0.4 μg/L of chlorpyrifos; 0.04 μg/L of cypermethrin + 0.4 μg/L of chlorpyrifos in a technical mixture; and 0.04 μg/L of cypermethrin + 0.4 μg/L of chlorpyrifos in a mixture of commercial products. Fish exposed to cypermethrin accumulated this compound only in muscle, probably because of the low biotransformation capacity of this organ and the induction of cytochrome P4501A1 (CYP1A1) expression in the liver. The accumulation of chlorpyrifos occurred in fish exposed to the insecticide (intestine > liver > gills) even when these fish had higher gluthatione-S-transferase (GST) activity in gills and P-glycoprotein (P-gp) expression in the liver, compared with the control. Fish exposed to the technical mixture showed cypermethrin accumulation (liver > intestine > gills) with higher levels than those measured in fish after only cypermethrin exposure. Higher expression levels of CYP1A1 in the liver were also observed compared with the Control. Fish exposed to the commercial mixture accumulated both insecticides (cypermethrin: intestine > gills and chlorpyrifos: liver > intestine > gills > muscle). In the organs where accumulation occurred, biotransformation enzymes were inhibited. Consequently, the commercial formulation exposure provoked the highest accumulation of cypermethrin and chlorpyrifos in J. multidentata, possibly associated with the biotransformation system inhibition. Environ Toxicol Chem 2017;36:1764-1774. © 2016 SETAC.

Toxicokinetic models and related tools in environmental risk assessment of chemicals

Environmental risk assessment of chemicals for the protection of ecosystems integrity is a key regulatory and scientific research field which is undergoing constant development in modelling approaches and harmonisation with human risk assessment. This review focuses on state-of-the-art toxicokinetic tools and models that have been applied to terrestrial and aquatic species relevant to environmental risk assessment of chemicals. Both empirical and mechanistic toxicokinetic models are discussed using the results of extensive literature searches together with tools and software for their calibration and an overview of applications in environmental risk assessment. These include simple tools such as one-compartment models, multi-compartment models to physiologically-based toxicokinetic (PBTK) models, mostly available for aquatic species such as fish species and a number of chemical classes including plant protection products, metals, persistent organic pollutants, nanoparticles. Data gaps and further research needs are highlighted.

Health Status of Sand Flathead (Platycephalus bassensis), Inhabiting an Industrialised and Urbanised Embayment, Port Phillip Bay, Victoria as Measured by Biomarkers of Exposure and Effects

Port Phillip Bay, Australia, is a large semi-closed bay with over four million people living in its catchment basin. The Bay receives waters from the Yarra River which drains the city of Melbourne, as well as receiving the discharges of sewage treatment plants and petrochemical and agricultural chemicals. A 1999 study demonstrated that fish inhabiting Port Phillip Bay showed signs of effects related to pollutant exposure despite pollution management practices having been implemented for over a decade. To assess the current health status of the fish inhabiting the Bay, a follow up survey was conducted in 2015. A suite of biomarkers of exposure and effects were measured to determine the health status of Port Phillip Bay sand flathead (Platycephalus bassensis), namely ethoxyresorufin-O-deethylase (EROD) activity, polycyclic aromatic hydrocarbons (PAH) biliary metabolites, carboxylesterase activity (CbE) and DNA damage (8-oxo-dG). The reduction in EROD activity in the present study suggests a decline in the presence of EROD activity-inducing chemicals within the Bay since the 1990s. Fish collected in the most industrialised/urbanised sites did not display higher PAH metabolite levels than those in less developed areas of the Bay. Ratios of PAH biliary metabolite types were used to indicate PAH contaminant origin. Ratios indicated fish collected at Corio Bay and Hobsons Bay were subjected to increased low molecular weight hydrocarbons of petrogenic origin, likely attributed to the close proximity of these sites to oil refineries, compared to PAH biliary metabolites in fish from Geelong Arm and Mordialloc. Quantification of DNA damage indicated a localised effect of exposure to pollutants, with a 10-fold higher DNA damage level in fish sampled from the industrial site of Corio Bay relative to the less developed site of Sorrento. Overall, integration of biomarkers by multivariate analysis indicated that the health of fish collected in industrialised areas was compromised, with biologically significant biomarkers of effects (LSI, CF and DNA damage) discriminating between individuals collected in industrialised areas from observations made in fish collected in less developed areas of the Bay.

Deltamethrin is toxic to the fish (crucian carp, Carassius carassius) heart

Pyrethroids are extensively used for the control of insect pests and disease vectors. Pyrethroids are regarded safe due to their selective toxicity: they are effective against insects but relatively harmless to mammals and birds. Unfortunately, pyrethroids are very toxic to fishes. The high toxicity of pyrethroids to fishes is only partly explained by slow metabolic elimination of pyrethroids, suggesting that some molecular targets in vital organs of the fish body are sensitive to pyrethroids. To this end we tested the effect of deltamethrin (DM) on fish (crucian carp, Carassius carassius) heart function in vitro. In sinoatrial preparations of the crucian carp heart DM (10 μM) caused irregularities in rate and rhythm of atrial beating and strong reductions in force of atrial contraction, thus indicating that DM is arrhythmogenic to the fish heart. Consistent with this, DM (10.0 μM) induced irregularities in electrical activity (surface electrocardiogram) of spontaneous beating hearts in vitro. In isolated ventricular myocytes, DM (0.1-30.0 μM) modified Na(+) current by slowing channel closing and shifting reversal potential and steady-state activation of the current to more negative voltages. Maximally about 48% of the cardiac Na(+) channels were affected by DM with a half-maximal effect occurring at the concentration of 1.3 μM. These findings indicate that DM can be cardiotoxic to the crucian carp and that these effects could be due to DM related changes in Na(+) channel function. These findings indicate that in addition to their neurotoxicity effects pyrethroid could also be cardiotoxic to fishes.

Integrated biomarkers induced by chlorpyrifos in two different life stages of zebrafish (Danio rerio) for environmental risk assessment

This study was performed to understand how chlorpyrifos (CHL) affects zebrafish (Danio rerio) embryos and adults, by exposing this model organism to various concentrations of the insecticide. The 96-h acute toxicity test to determine the effect of CHL on adult zebrafish yielded a LC50 of 709.43μg/L(-1). Small molecular weight proteins less than 25kDa and phospholipids were analyzed with MALDI-TOF MS/MS in order to compare expression patterns, revealing that some peaks were dramatically altered after CHL treatment. Whereas no acute toxicity was detected in the embryo toxicity test, malformation of zebrafish larvae was observed, with many individuals harboring curved spines. In an angiogenesis test on larvae of transgenic zebrafish, CHL did not have an inhibitory effect. Relative gene expression analyses using real-time polymerase chain reaction (RT-PCR) of DNA from zebrafish embryos revealed that different subtypes of cytochrome P450 (CYP450), such as CYP1A and CYP3A, were significantly up-regulated in response to CHL at a concentration of 400μg/L(-1) compared to the control. The expression level of NR1I2, a CYP gene transcriptional regulator, UGT1a1, and MDR1 were all up-regulated in the CHL-treated embryos. Finally, the expression level of acetylcholinesterase (AChE) and catalase (CAT) decreased, whereas that of superoxide dismutase (SOD) did not differ significantly. Our results suggest that the up-regulation of metabolic enzymes including CYP450 and MDR1 may be involved in CHL resistance in zebrafish.

Effects of the Pyrethroid Esfenvalerate on the Oligochaete, Lumbriculus variegatus

Esfenvalerate is a neurotoxic pyrethroid insecticide widely used for agricultural and residential purposes and is considered toxic to nontarget organisms such as fish and aquatic invertebrates. In this study, we evaluated the toxicity of esfenvalerate on the aquatic oligochaete Lumbriculus variegatus. In the acute test, organisms showed visible signs of stress but no LC50 value could be determined. In the 28-day chronic test, a significant decrease in reproduction was observed with a NOEC value of 0.25 µg/kg and a LOEC value of 2.34 µg/kg. As for biomass per worm, a significant decrease was also observed with a NOEC value of 2.34 µg/kg and a LOEC value of 36.36 µg/kg. Reproductive impairment and reductions in biomass of L. variegatus exposed to environmentally realistic concentrations of esfenvalerate observed in laboratory tests suggests potential deleterious effects of this pyrethroid on oligochaete natural populations.

Integrated assessment of biochemical markers in premetamorphic tadpoles of three amphibian species exposed to glyphosate- and methidathion-based pesticides in single and combination forms

In this study, we evaluated the toxic effects of a glyphosate-based herbicide (GBH) and a methidathion-based insecticide (MBI), individually and in combination, on premetamorphic tadpoles of three anuran species: Pelophylax ridibundus, Xenopus laevis, and Bufotes viridis. Based on the determined 96-h LC50 values of each species, the effects of a series of sublethal concentrations of single pesticides and their mixtures after 96-h exposure and also the time-related effects of a high sublethal concentration of each pesticide were evaluated, with determination of changes in selected biomarkers: glutathione S-transferase (GST), glutathione reductase (GR), acetylcholinesterase (AChE), carboxylesterase (CaE), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). Also, the integrated biomarker response (IBR) was used to assess biomarker responses and quantitatively evaluate toxicological effects. Isozyme differences in CaE inhibition were assessed using native page electrophoresis; results showed that GBH to cause structural changes in the enzyme but not CaE inhibition in P. ridibundus. In general, single MBI and pesticide mixture exposures increased GST activity, while single GBH exposures decreased GST activity in exposed tadpoles. The AChE and CaE activities were inhibited after exposure to all single MBI and pesticide mixtures. Also, higher IBR values and GST, GR, AST, and LDH activities were determined for pesticide mixtures compared with single-pesticide exposure. This situation may be indicative of a synergistic interaction between pesticides and a sign of a more stressful condition.

Chlorpyrifos-induced biomarkers in Japanese medaka (Oryzias latipes)

Chlorpyrifos (CHL) is an organophosphate compound that is widely used as an insecticide. Due to its repeated use and high environmental residual property, CHL is frequently passed into aquatic environments by runoff. Consequently, there may be an adverse effect on aquatic vertebrate animals, including fish. Therefore, in this study, we assessed how CHL affected Japanese medaka (Oryzias latipes). The acute toxicity of CHL in adult fish after 96 h of exposure was determined to be 212.50, 266.79, and 412.28 μg L(-1) (LC25, LC50, and LC95, respectively). Acetylcholinesterase (AChE), glutathione S-transferase (GST), and carboxylesterase (CE) activities were obtained from the livers of dead or surviving fish, and the results showed 4.8-fold lower, 4.5-fold higher, and 18.6-fold lower activities for the AChE, GST, and CE, respectively, for 64-h exposure at a concentration of 400 μg L(-1) of CHL. In the embryo toxicity test, curved spines were observed in embryos that were exposed to CHL for 48 h in a concentration-dependent manner. With identification of biomarkers for CHL in the fish, two protein peaks, 5550.86 and 5639.79 m/z, were found to be upregulated. These two proteins can be used as protein biomarkers for CHL contamination in aquatic systems. A phosphatidyl choline with an m/z ratio of 556.32 dramatically decreased after CHL exposure in the fish; thus, it may be considered as a lipid biomarker for CHL. It is assumed as the first report to identify a phospholipid biomarker using a lipidomics approach in fish toxicology. Taken together, these results demonstrated the adverse effects of CHL on Japanese medaka and reveal several candidate biomarkers that can be used as diagnostic tools for determining CHL.

An in vitro screening with emerging contaminants reveals inhibition of carboxylesterase activity in aquatic organisms

Pharmaceuticals and personal care products (PPCPs) form part of the new generation of pollutants present in many freshwater and marine ecosystems. Although environmental concentrations of these bioactive substances are low, they cause sublethal effects (e.g., enzyme inhibition) in non-target organisms. However, little is known on metabolism of PPCPs by non-mammal species. Herein, an in vitro enzyme trial was performed to explore sensitivity of carboxylesterase (CE) activity of aquatic organisms to fourteen PPCPs. The esterase activity was determined in the liver of Mediterranean freshwater fish (Barbus meridionalis and Squalius laietanus), coastal marine fish (Dicentrarchus labrax and Solea solea), middle-slope fish (Trachyrhynchus scabrus), deep-sea fish (Alepocephalus rostratus and Cataetix laticeps), and in the digestive gland of a decapod crustacean (Aristeus antennatus). Results showed that 100μM of the lipid regulators simvastatin and fenofibrate significantly inhibited (30-80% of controls) the CE activity of all target species. Among the personal care products, nonylphenol and triclosan were strong esterase inhibitors in most species (36-68% of controls). Comparison with literature data suggests that fish CE activity is as sensitive to inhibition by some PPCPs as that of mammals, although their basal activity levels are lower than in mammals. Pending further studies on the interaction between PPCPs and CE activity, we postulate that this enzyme may act as a molecular sink for certain PPCPs in a comparable way than that described for the organophosphorus pesticides.

Comparative intestinal esterases amongst passerine species: Assessing vulnerability to toxic chemicals in a phylogenetically explicit context

Inhibition of blood esterase activities by organophosphate (OP) pesticides has been used as a sensitive biomarker in birds. Furthermore, compared to mammalian vertebrates, less is known about the role of these enzyme activities in the digestive tracts of non-mammalian vertebrates, as well as the environmental and biological stressors that contribute to their natural variation. To fill this gap, we examined butyrylcholinesterase (BChE) and carboxylesterases (CbE) in the digestive tracts of sixteen passerine species from central Chile. Whole intestine enzyme activities were positively and significantly correlated with body mass. After correcting for body mass and phylogenetic effect, we found only a marginal effect of dietary category on BChE activity, but a positive and significant association between the percentage of dietary nitrogen and the mass-corrected lipase activity. Our results suggest that observed differences may be due to the dietary composition in the case of lipases and BChE, and also we predict that all model species belonging to the same order will probably respond differently to pesticide exposure, in light of differences in the activity levels of esterase activities.

A comparison of the sublethal and lethal toxicity of four pesticides in Hyalella azteca and Chironomus dilutus

Laboratory toxicity testing is the primary tool used for surface water environmental risk assessment; however, there are critical information gaps regarding the sublethal effects of pesticides. In 10-day exposures, we assessed the lethal and sublethal (motility and growth) toxicities of four commonly used pesticides, bifenthrin, permethrin, cyfluthrin, and chlorpyrifos, on two freshwater invertebrates, Chironomus dilutus and Hyalella azteca. Pyrethroids were more toxic than the organophosphate chlorpyrifos in both species. Bifenthrin was most toxic to H. azteca survival and growth. Cyfluthrin was most toxic to C. dilutus. However, cyfluthrin had the greatest effect on motility on both H. azteca and C. dilutus. The evaluated concentrations of chlorpyrifos did not affect C. dilutus motility or growth, but significantly impacted H. azteca growth. Motility served as the most sensitive endpoint in assessing sublethal effects at low concentrations for both species, while growth was a good indicator of toxicity for all four pesticides for H. azteca. The integration of sublethal endpoints in ambient water monitoring and pesticide regulation efforts could improve identification of low-level pesticide concentrations that may eventually cause negative effects on food webs and community structure in aquatic environments.