Applications of carboxylesterase activity in environmental monitoring and toxicity identification evaluations (TIEs)

Effects of Phenanthrene Exposure on the B-esterases Activities of Octopus maya (Voss and Solís Ramírez, 1996) Embryos

No ecotoxicological information exists on phenanthrene (Phe) exposure in cephalopods, animals of commercial and ecological importance. This study investigated the effect of Phe on two B-esterases, Acetylcholinesterase (AChE) and Carboxylesterases (CbE), in Octopus maya embryos. Octopus embryos were exposed to different treatments: control (seawater), solvent control (seawater and DMSO 0.01%), 10 and 100 µg/L of Phe. AChE and CbE activities were measured at different developmental stages (blastula, organogenesis, and growth). B-esterase activities increased in control and solvent control as the embryos developed, showing no statistically significant differences between them. On the other hand, the embryos exposed to Phe had significant differences from controls, and between the high and low concentrations. Our results indicate that B-esterases are sensitive biomarkers of exposure to Phe in O. maya. Still, complementary studies are needed to unravel the toxicodynamics of Phe and the implications of the found inhibitory effect in hatched organisms.

Using mesocosms to evaluate the impacts of pasture intensification and pasture-sugarcane conversion on tadpoles in Brazil

This study evaluated the effects of environmental contamination caused by pasture intensification and pasture-sugarcane conversion on oxidative stress, biotransformation, esterase enzymes, and development of Scinax fuscovarious and Physalaemus nattereri. Tadpoles were exposed in mesocosms allocated in three treatments: (1) untreated extensive pasture (EP); (2) intensive-pasture conversion (IP) (2,4-D herbicide + fertilizers); and (3) pasture-sugarcane conversion (SC) (fipronil + 2,4-D + fertilizers). After 7 days of exposure, IP reduced catalase (CAT) and increased malondialdehyde (MDA) levels in P. nattereri, while this treatment decreased glucose-6-phosphate dehydrogenase (G6PDH) and CAT activities in S. fuscovarious. SC decreased CAT, G6PDH, and glutathione S-transferase (GST) activities in P. nattereri. In S. fuscovarius, SC reduced G6PDH, acetylcholinesterase (AChE), and carboxylesterase (CbE) activities. MDA was raised in both tadpole species exposed to SC, evidencing oxidative stress. Integrated biomarker responses showed higher scores in both species exposed to SC. Our results warn that management practices currently applied to sugarcane cultivation in Brazil can negatively impact the functional responses of amphibians at natural systems.

Microbial elimination of pyrethroids: specific strains and involved enzymes

Pyrethroids, which are synthetic organic insecticides, are widely used in agriculture and households to resist pests and control disease transmission. However, pyrethroids have inevitably caused environmental pollution, leading to concerns for food safety and human health. Bioremediation has emerged as one of the most promising methods to eliminate pyrethroids compounds. Pyrethroid-degrading microorganisms and the relevant enzymes have shown an efficient ability in degrading pyrethroids by hydrolyzing the ester linkage. In this review, a wide variety of pyrethroid-degrading strains were presented and classified from different sources, such as wastewater, soils, and oceans. In addition, the recombinant expression, enzyme identification, and molecular modification of these microbial pyrethroid-degrading enzymes were also compared and discussed in detail. Moreover, the potential applications of pyrethroid-degrading enzymes, including immobilization and biodegradation towards a series of pyrethroids, were also presented. All of the positive results obtained from this review could be a good guideline for the other research in this field. KEY POINTS: • Distribution of pyrethroid-degrading strains in different sources was summarized. • Enzymatic properties including pH, temperature, and substrate specificity were compared. • Promising molecular modification and immobilization of hydrolases were present.

Environmental Occurrence, Toxicity Concerns, and Degradation of Diazinon Using a Microbial System

Diazinon is an organophosphorus pesticide widely used to control cabbage insects, cotton aphids and underground pests. The continuous application of diazinon in agricultural activities has caused both ecological risk and biological hazards in the environment. Diazinon can be degraded via physical and chemical methods such as photocatalysis, adsorption and advanced oxidation. The microbial degradation of diazinon is found to be more effective than physicochemical methods for its complete clean-up from contaminated soil and water environments. The microbial strains belonging to Ochrobactrum sp., Stenotrophomonas sp., Lactobacillus brevis, Serratia marcescens, Aspergillus niger, Rhodotorula glutinis, and Rhodotorula rubra were found to be very promising for the ecofriendly removal of diazinon. The degradation pathways of diazinon and the fate of several metabolites were investigated. In addition, a variety of diazinon-degrading enzymes, such as hydrolase, acid phosphatase, laccase, cytochrome P450, and flavin monooxygenase were also discovered to play a crucial role in the biodegradation of diazinon. However, many unanswered questions still exist regarding the environmental fate and degradation mechanisms of this pesticide. The catalytic mechanisms responsible for enzymatic degradation remain unexplained, and ecotechnological techniques need to be applied to gain a comprehensive understanding of these issues. Hence, this review article provides in-depth information about the impact and toxicity of diazinon in living systems and discusses the developed ecotechnological remedial methods used for the effective biodegradation of diazinon in a contaminated environment.

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.

Apatinib combined with Keytruda treatment induces apoptosis of gastric carcinoma cells through CES4/miR-616-5p/DUSP2 axis

Gastric carcinoma (GC) is a highly malignant and heterogeneous tumour. Long non-coding RNA CES4 is down-regulated in GC. However, whether CES4 can participate in GC remains unclear; we have carried out research on this topic. GC cells (HGC-27 and MKN-7) were treated with anti-tumour drugs: apatinib combined with Keytruda. Cell viability and apoptosis were detected by CCK-8 assay and flow cytometry. Gene and protein expression were examined by quantitative real-time PCR and western blot. Luciferase reporter assay was performed to verify the relationship among CES4, miR-616-5p and dual-specificity phosphatase-2 (DUSP2). CES4 was highly expressed in the apatinib combined with Keytruda-treated HGC-27 and MKN-7 cells. Apatinib combined with Keytruda treatment repressed cell viability and promoted apoptosis of HGC-27 and MKN-7 cells, which was abrogated by CES4 knockdown. Furthermore, CES4 promoted DUSP2 expression by sponging miR-616-5p in HGC-27 and MKN-7 cells. CES4 knockdown promoted cell viability and inhibited apoptosis of drug-treated HGC-27 and MKN-7 cells by regulating miR-616-5p/DUSP2 axis. In conclusion, these data demonstrate that apatinib combined with Keytruda treatment induces apoptosis of GC cells through CES4/miR-616-5p/DUSP2 axis. Thus, this work provides the experimental basis for the combination of apatinib and Keytruda as a treatment for GC.

Impact of dietary lipid level on esterase enzyme activities in the non-target freshwater shrimp Macrobrachium borellii exposed to chlorpyrifos

This study increases our understanding of how diet-driven phenotypic plasticity can help non-target aquatic invertebrates deal with chlorpyrifos (CPO) exposure. A bioassay was performed over 6 days with the freshwater shrimp Macrobrachium borellii. Experimental treatments included CPO-treated shrimps (10 μg L^-1) were fed with (i) a lipid-rich diet, (ii) a lipid-medium diet, or (iii) a lipid-poor diet. Control shrimps (no CPO exposure) received the same diets as detailed above. Cholinesterases and carboxylesterases were determined as an indicator of CPO exposure. Results showed that diets with a medium-to-high lipid content were important inducers of esterase activity, while shrimps exposed to CPO under a lipid-poor diet showed a significant enzymatic inhibition. This diet-dependent esterase induction suggests that the intake of fatty dietary items mitigates the esterase enzyme inhibition caused by CPO exposure.

What types of enzyme activities are useful biomarkers of bifenthrin exposure on Chironomus sp. (Diptera, Chironomidae) larvae under laboratory and field-based microcosm conditions?

Bifenthrin is a second generation synthetic pyrethroid insecticide that is widely used in Australia and worldwide. It is frequently found in urban freshwater sediments at concentrations likely to impact biota as it is highly toxic to fish and macroinvertebrates, such as chironomids. Our main goal was to evaluate if oxidative stress and hydrolase enzymes are useful biomarkers of effect of synthetic pyrethroids exposure under different scenarios. Chironomus tepperi larvae (5 days old) were exposed to sub-lethal sediment concentrations of bifenthrin for 5 days under controlled laboratory conditions. A field-based microcosm exposure with bifenthrin-spiked sediments (using the same concentrations as the laboratory exposure) was carried out at a clean field site for four weeks to allow for colonization and development of resident chironomid larvae. At the end of both experiments, Chironomus larvae (C. tepperi in the laboratory exposures and C. oppositus in the microcosm exposures) were collected and oxidative stress enzymes (Glutathione-s-Transferase, Glutathione Reductase and Glutathione Peroxidase) and hydrolase enzymes (Acetylcholinesterase and Carboxylesterase) were measured. Only the Glutathione Peroxidase activity was significantly impacted in larvae from the laboratory exposure. On the contrary, significant changes were observed in all the measured enzymes from the field-based microcosm exposure. This is likely because exposure was throughout the whole life cycle, from egg mass to fourth instar, showing a more realistic exposure scenario. Furthermore, this is the first time that changes in oxidative stress and hydrolase enzymes have been shown to occur in Australian non-biting midges exposed under field-based microcosm conditions. Thus, this study demonstrated the usefulness of these enzymes as biomarkers of effect following bifenthrin exposure in microcosms. It also highlights the importance of using a range of different biochemical endpoints to get a more holistic understanding of pesticide effects and the pathways involved.

Pyrethroid Carboxylesterase PytH from Sphingobium faniae JZ-2: Structure and Catalytic Mechanism

Carboxylesterase PytH, isolated from the pyrethroid-degrading bacterium Sphingobium faniae JZ-2, could rapidly hydrolyze the ester bond of a wide range of pyrethroid pesticides, including permethrin, fenpropathrin, cypermethrin, fenvalerate, deltamethrin, cyhalothrin, and bifenthrin. To elucidate the catalytic mechanism of PytH, we report here the crystal structures of PytH with bifenthrin (BIF) and phenylmethylsulfonyl fluoride (PMSF) and two PytH mutants. Though PytH shares low sequence identity with reported α/β-hydrolase fold proteins, the typical triad catalytic center with Ser-His-Asp triad (Ser78, His230, and Asp202) is present and vital for the hydrolase activity. However, no contact was found between Ser78 and His230 in the structures we solved, which may be due to the fact that the PytH structures we determined are in their inactive or low-activity forms. The structure of PytH is composed of a core domain and a lid domain; some hydrophobic amino acid residues surrounding the substrate from both domains form a deeper and wider hydrophobic pocket than its homologous structures. This indicates that the larger hydrophobic pocket makes PytH fit for its larger substrate binding; both lid and core domains are involved in substrate binding, and the lid domain-induced core domain movement may make the active center correctly positioned with substrates.IMPORTANCE Pyrethroid pesticides are widely applied in agriculture and household; however, extensive use of these pesticides also causes serious environmental and health problems. The hydrolysis of pyrethroids by carboxylesterases is the major pathway of microbial degradation of pyrethroids, but the structure of carboxylesterases and its catalytic mechanism are still unknown. Carboxylesterase PytH from Sphingobium faniae JZ-2 could effectively hydrolyze a wide range of pyrethroid pesticides. The crystal structures of PytH are solved in this study. This showed that PytH belongs to the α/β-hydrolase fold proteins with typical catalytic Ser-His-Asp triad, though PytH has a low sequence identity (about 20%) with them. The special large hydrophobic binding pocket enabled PytH to bind bigger pyrethroid family substrates. Our structures shed light on the substrate selectivity and the future application of PytH and deepen our understanding of α/β-hydrolase members.

Combined effects of goethite nanoparticles with metallic contaminants and an organophosphorus pesticide on Eisenia andrei

The effects of mixtures of nanoparticles (NPs) and other chemicals have been poorly studied in terrestrial invertebrates. In this study, we investigated the effects of binary mixtures of goethite (α-FeOOH) NPs and metallic (Cd and Pb) or organic (chlorpyrifos, CPF) contaminants in Eisenia andrei earthworms. We used the filter paper contact test to evaluate (i) the uptake of NPs in organisms exposed to the mixtures of NPs+Metals and NPs+CPF and (ii) the potential effects of the mixture of NPs+CPF on the CPF-induced inhibition of the biomarker enzymes acetylcholinesterase (AChE) and carboxylesterases (CES). We used the artificial soil test to deepen the study on joint effects of NPs+CPF. All compounds were applied separately and in binary mixtures. In the single exposure treatment, Fe levels decreased significantly in organisms exposed to NPs on filter paper, suggesting systemic effects aimed at eliminating Fe incorporated through NPs. Conversely, earthworms exposed to binary mixtures showed Fe levels similar (NPs+Metals) to or higher (NPs+CPF) than controls. The earthworms single exposed to NPs presented no changes in AChE and CES activities. In the artificial soil test, the only treatment that showed AChE inhibition after 72 h was single CPF exposure, while no significant changes were observed in CES activity. However, after 7-day exposure in artificial soil or 72-h exposure on filter paper, the mixture of NPs+CPF induced a similar degree of AChE and CES inhibition as single CPF exposure. All these suggested that NPs did not produce neurotoxic effects, and that the inhibition of the enzymes' activities in all cases was due to the presence of the pesticide. On the other hand, the differences in the pattern of Fe accumulation in the earthworms indicate that the presence of other contaminants in the exposure media can modify the uptake and/or the excretion of Fe and evidence the interactions that may be found in binary mixtures of metal oxide NPs and other pre-existing contaminants in the soil ecosystem.

Comparative Toxicity of Two Different Dimethoate Formulations in the Common Toad (Rhinella arenarum) Tadpoles

Dimethoate (D) are among the most commonly used organophosphates insecticides in the world. To evaluate the toxicity of two D formulations were selected as test organisms tadpoles of Rhinella arenarum. This toad species has an extensive neotropical distribution and is easy to handle and acclimate to laboratory conditions. The tadpoles were exposed in an acute assay for 48 h to D soluble concentrates (DSC) and emulsifiable concentrates (DEC). The 48 h-LC₅₀ (95% confidence limits) value of DSC was 57.46 mg L^-1 (40.52-81.43) and to DEC was 12.76 mg L^-1 (10.39-15.68). These differences in toxicity were statistically significant (p < 0.05). In both formulations, acetylcholinesterase), carboxylesterase, and glutathione-S-transferases enzyme activities varied significantly respect to those of control group (p < 0.05). The DEC formulation was the most toxic. These results would allow the assessment and characterization of potential ecological risks following the application of those formulations.

A multilevel response approach reveals the Asian clam Corbicula largillierti as a mirror of aquatic pollution

The endobenthic bivalves are widely used as a bioindicators since they inhabit the sediment-water interface and are able to accumulate a different kind of contaminants. In the present work, we evaluated wild Corbicula largillierti (Phillippi, 1844) as a bioindicator of water quality in the central region of Argentina. The responses at different levels of the biological organization were used. We measured organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) levels in water and clams tissues. The biomarkers selected were enzymatic activities (Glutathione S-Transferase, Catalase, Acetyl-, Butyryl-cholinesterase, and Carboxylesterase) morphometry of the digestive gland, condition index and morphology of valves. In order to integrate all the responses a multivariate analysis and integrated stress index were applied. Our results showed the presence of contaminants along the studied river and the ability of C. largillierti to bioaccumulate them. All the biomarkers selected varied according to the water quality gradient, although there was no specific correlation with OCPs and PCBs levels. At the most polluted sites, the detoxification and oxidative stress enzymes, the morphometric analysis of the digestive gland and the variation in the morphology of the valves indicated the water quality degradation. The multivariate analyses allowed to discriminate the sites according to the different biomarker responses. The IBR index also showed a variation pattern according to the environmental quality gradient along the basin. According to the responses shown by C. largillierti we suggest this species as an useful bioindicator of aquatic pollution.

Aspergillus terreus (Trichocomaceae): A Natural, Eco-Friendly Mycoinsecticide for Control of Malaria, Filariasis, Dengue Vectors and Its Toxicity Assessment Against an Aquatic Model Organism Artemia nauplii

Vector-borne diseases like malaria, filariasis, and dengue are transmitted by mosquitoes and they cause global mortality and morbidity due to an increased resistance against commercial insecticides. The present study was aimed to evaluate the neurobehavioral toxicity, knock-down effect, histopathology, ovicidal, adulticidal, and smoke toxicity effect of Aspergillus terreus extract against three mosquito species, namely Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti (Diptera: Culicidae). The isolated fungal strain was identified as A. terreus (GenBank accession no: KX694148.1) through morphological and molecular (phylogenetic) analysis. The morphological changes in the treated fourth instar larvae shown the demelanization of cuticle and shrinkage of the internal cuticle of anal papillae. The time duration of extract exposure against the larvae determines the level of toxicity. The extract treated larvae were displayed excitation, violent vertical and horizontal movements with aggressive anal biting behavior as the toxic effect on the neuromuscular system. The results of the biochemical analysis indicated that a decrease in the level of acetylcholinesterase, α-carboxylesterase, and β-carboxylesterase in extract treated fourth instar larvae of all tested mosquito species. The findings of histopathological investigation shown the disorganization of the abdominal region, mainly in mid, hindgut, and gastric caeca, loss of antenna, lateral hair, caudal hair, upper and lower head hairs in the mycelium extract treated An. stephensi, Cx. quinquefasciatus, and Ae. aegypti. The ovicidal bioassay test results showed the mosquito hatchability percentage was directly related to the concentrations of mycelium extract. Nil hatchability of mosquito eggs was noticed at 500 μg/ml concentration. The adulticidal activity of fungal mycelia ethyl acetate extract resulted in a dose-dependent activity (15 and 30 min recovery periods). The higher concentration of extract (1000 mg/L) acted as a repellent, the adult mosquitoes showed restless movement, uncontrolled/anesthetic flight at last died. The better adulticidal activity was observed in the ethyl acetate extract against An. stephensi, Cx. quinquefasciatus followed by Ae. aegypti with the best score of LD50 and LD90 values and nil mortality was found in the control. The results of smoke toxicity assay of the mycelia extract exhibited significant mortality rate against Ae. aegypti (91%), Cx. quinquefasciatus (89%), and An. stephensi (84%). In addition, the present investigation reported the stability and toxic effects of A. terreus mycelium ethyl acetate extract on Artemia nauplii. The swimming speed (0.88 mm s-1) of A. terreus was reduced with ethyl extract 24 h treatment whereas, the control A. nauplii showed the normal speed of 2.96 mm s-1. Altered behavior and swimming movement were observed in the 8 h A. terreus mycelium extract treated A. nauplii. A pale yellow color substance (metabolites) was found in the mid-gut region of the mycelial extract exposed A. nauplii. The outcome of the present study, suggest that the A. terreus metabolites might serve as an alternative, cost-effective, eco-friendly, and target specific mosquitocidal agent in the future.

Effects of azinphos-methyl on enzymatic activity and cellular immune response in the hemolymph of the freshwater snail Chilina gibbosa

The use of a battery of biomarkers, especially those more closely related to species integrity, is desired for more complete ecotoxicological assessments of the effects of pesticide contamination on aquatic organisms. The phosphorodithioate azinphos-methyl has been intensively used in agriculture worldwide and have been found in the habitat of Chilina gibbosa, a freshwater snail endemic to South America. This snail has been proposed as a good model organism for ecotoxicity bioassays on the basis of studies focused mainly on enzymatic responses in whole tissue homogenates. Our aim was to evaluate the effect of an acute 48 h exposure to an environmental concentration of azinphos-methyl on C. gibbosa hemolymph enzymatic activity and cellular immune response. Our results show that cholinesterase activity was strongly inhibited (94%) in hemolymph of exposed snails. Carboxylesterase activity measured with p-nitrophenyl butyrate and glutathione S-transferase activity were augmented 47% and 89% respectively after exposure. No differences were found for hemolymph carboxylesterase activity measured with p-nitrophenyl acetate. These results differ from those reported for whole tissue homogenates and reveal that tissue-specific responses of enzymatic biomarkers exist in this species. Regarding immune cell response, hemocytes were identified for the first time for C. gibbosa. Their viability and phagocytic activity decreased after azinphos-methyl exposure although total number of circulating cells did not differ between treatments. We conclude that concentrations of azinphos-methyl that can be found in the environment can compromise both hemolymph cholinesterase activity and the immune system of C. gibbosa. Furthermore, we propose that carboxylesterase and glutathione S-transferase activities measured in hemolymph and hemocyte viability and phagocytic activity could be incorporated as sensitive biomarkers to evaluate the effects of pesticide exposure on this and related species.

Blood biomarkers of common toad Rhinella arenarum following chlorpyrifos dermal exposure

Chlorpyrifos (CPF) is a broad spectrum pesticide commonly used for insect control, has great affinity for lipids and is thus a potential for bioaccumulation in aquatic organisms. The aim of this study was to evaluate the toxicity of CPF using the common toad Rhinella arenarum via dermal uptake in plastic bucket to simulate their natural exposition in ponds. R. arenarum toads were exposed individually to solutions containing a nominal concentration of a commercial formulation of CPF insecticide (5 and 10 mg/L). Different enzyme biomarkers (BChE: butyrylcholinesterase, CbE: carboxylesterase, and CAT: catalase) were measured in blood tissue after exposition. The capacity of pyridine-2-aldoxime methochloride (2-PAM) to reverse OP-inhibited plasma BChE and the ratio of heterophils and lymphocytes (H/L) as hematological indicators of stress were also determined. The normal values of plasma B-sterases (BChE and CbE) were highly inhibited (until ≈ 70%) in toads 48 h after exposure to CPF. The results indicate that 2-PAM produced BChE reactivation as well. The activity of CAT was also inducted for dermal exposure at more than double of that in the control toads (CPF; 5 mg/L). H/L ratios did not reveal a significantly increased stress. The study suggests that CPF via dermal uptake induced neurotoxicity and oxidative stress in the common toad R. areanum. Thus, some blood biomarkers employed in our study (i.e. BChE, CbE, 2-PAM, and CAT) might be used as predictors in health and ecological risk assessment of amphibian populations exposed to CPF.

The Development of Bacterial Carboxylesterase Biological Recognition Elements for Cocaine Detection

Enzyme recognition element-based biosensors are very attractive for biosensor application due to a variety of measurable reaction products arising from a catalytic process. In this study, biosensor recognition elements have been developed via engineer bacterial enzymes (carboxylesterases (CEs)) which will used for narcotic detection because of their role in narcotics metabolism. The modification (insertion of cys-tag) allows the enzyme to bind into a transducer surface of a biosensor which will translate the reaction product into the detection system. The results demonstrate the successful isolation, cloning, expression, and purification of recombinant (pnbA1 and pnbA2), and engineered (pnbA1-cys and pnbA2-cys) bacterial carboxylesterases. Enzyme capability to hydrolyse cocaine into benzoylecgonine and methanol was quantified using HPLC. Both enzymes showed broad maximal activity between pH (8.0, 8.5, and 9.0), PnbA1 temperature stability ranging between (25 and 45 °C); however, PnbA2 stability range was (25-40 °C). Insertion of cys-tag at the N-terminal of the enzyme did not limit entrance to the active site which is located at the base of a cavity with dimensions 20 by 13 by 18 Å, and did not prevent substrate hydrolysis. Bacterial carboxylesterases pnbA1 and pnbA2 mimic hCE1 and not hCE2 in its reaction pathways hydrolysing cocaine into benzoylecgonine and methanol rather than ecgonine methyl ester and benzoic acid. These results are the first experimental evidence confirming the capability of bacterial carboxylesterase to hydrolyse cocaine into its main metabolites, therefore opening up the possibility to use these enzymes in numerous biotechnological applications in addition to a cocaine biosensor.

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.

Oxidative stress of imidaclothiz on earthworm Eisenia fetida

Imidaclothiz, a kind of neonicotinoid insecticides, is developed as a commercial pesticide in China and used for the control of sucking and biting insects, including aphids, whiteflies, beetles and some Lepidoptera species as well. In recent years, more and more attention has been focused on the adverse effects of neonicotinoid insecticides on non-target organisms. In this study, inhibition effects of imidaclothiz and recovery capacity of molecular biomarkers (GST, CE, CAT, SOD and POD activity, and DNA damage) in earthworms were detected for the first time. Earthworms were exposed to imidaclothiz (0.3 and 1.0mgkg^-1) for 28days, and then transferred to the clean artificial soil for 28days. Regarding enzyme activities, GST, CE, CAT and POD were inhibited following exposure to imidaclothiz at one or more sample times, while SOD was not affected. After transferring to the clean artificial soil, POD continued to be significantly inhibited till sample time 35days at 0.3mg/kg^-1. For GST, CE, CAT and SOD, activities of them were significantly increased compared to those of the control during the recovery period. The olive tail moments (OTM) in comet assay, as an indication of DNA damage, were significantly increased compared to the control after treatment and then decreased during the recovery period. These results suggested that imidaclothiz induced oxidative damage on earthworms which caused damage to vital macromolecules including DNA. However, the recovery changes of all tested biomarkers following the transfer to clean soil suggested the tested earthworm recovery from imidaclothiz exposure.

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.

The use of juvenile Solea solea as sentinel in the marine platform of the Ebre Delta: in vitro interaction of emerging contaminants with the liver detoxification system

Juveniles of Solea solea were sampled during the spring season in three consecutive years at a marine site by the mouth of the Ebre river. The aim was to assess if the extractive works from the toxic load upstream the river could be reflected on the health status of the fish living at the immediate sea. The biomarkers selected for the in vivo field study are commonly used as indicators of chemical exposures. They include activities of energy metabolism: lactate dehydrogenase (LDH) and citrate synthase (CS); neurotoxicity: cholinesterases (ChE); xenobiotic metabolism: cytochrome P450 (CYP)-dependent: EROD and BFCOD, carboxylesterase (CbE), glutathione S-transferase (GST) and uridine diphosphate glucuronyltransferase (UDPGT); and oxidative stress parameters such as catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPX) as well as levels of lipid peroxidation (LPO). These biomarkers were mostly analysed in liver but also in gills and muscle depending on their particular tissue distribution and role. A complementary in vitro approach was also sought to see the capacity of common emerging contaminants (pharmaceuticals and personal care products; PPCPs) to interact with the liver microsomal detoxification system of the fish (EROD, BFCOD and CbE activities). The results indicated that in fish sampled in 2015 there was an enhancement in detoxification parameters (EROD, BFCOD and gill GR), muscular ChEs and gill CS, but a decrease in CbE activity and a marked oxidative stress situation (increased LPO and decreased CAT activity). Also, 4 out of the 10 PPCPs tested in vitro were able to interact with the CYP3A4 (BFCOD) enzymatic system while the lipid regulators simvastatin and fenofibrate inhibited CbE activity, as it occurs in higher vertebrates. The in vivo results support the use of a multibiomarker approach when assessing the disturbances due to chemical exposures, not only spatially but also over time, once the influence of other variables has been taken into consideration. The in vitro results highlight the importance of the CYP3A4 and CbE pathway in pharmaceutical metabolism, also in fish.

Vitellogenin, sex steroid levels and gonadal biomarkers in wild Solea solea and Solea senegalensis from NW Mediterranean fishing grounds

Specimens of Solea solea and Solea senegalenesis at different developmental stages were obtained from seven fishing grounds along the NW Mediterranean. Gonad development in males was classified into five stages, from early spermatogenesis to recovery, while four stages were considered in females, from growth to maturation. Vitellogenin (VTG) and sex steroid levels including an estrogen (estradiol, E2), two androgens (testosterone, T and 11-ketotestosterone, 11KT) and a progestin (17,20β-dihydroxy pregn-4-en-3-one, 17,20β-P or maturation inducing steroid, MIS) were analysed in plasma. Their levels were more clearly related to the developmental stage of the gonads than to the sampling site characteristics. In addition, enzyme activities in gonads, such as acetylcholinesterase (AChE) and carboxylesterase (CbE) were gender-dependent and higher in males than in females. Gonadal glutathione S-transferase (GST) activity was enhanced in the most anthropogenic impacted sites. VTG was absent in males and very low or undetectable in immature females, while mature females exhibited high VTG levels, clearly related to the gonado-somatic index. Sex steroid levels (ng/ml) varied in males and females regardless of the species. E2 levels in females ranged from 0.22 to 6.98 while in males ranged from 0.11 to 0.27. T varied from 0.12 to 0.93 in females and from 0.56 to 1.36 in males, while 11KT in females fluctuated from 0.03 to 0.57 and from 0.26 to 6.42 in males. Similarly, MIS in females ranged from 0.75 to 3.71 and from 1.12 to 5.61 in males. The lack of endocrine disturbances was confirmed by histological examination of the gonads. This study informs on basal sex hormone levels and enzyme activities during gonadal maturation of wild Solea spp. that can be useful in the identification and further remediation of possible pollution events.

Alteration of syncytiotrophoblast mitochondria function and endothelial nitric oxide synthase expression in the placenta of rural residents

The impact of environmental organophosphate (OP) pesticide exposure on respiratory complexes, enzymatic antioxidant defense activities, and oxidative damage markers in the syncytiotrophoblast and cytotrophoblast mitochondria was evaluated. Placental progesterone (PG) levels and endothelial nitric oxide synthase (eNOS) expression were studied. Samples from women non-exposed (control group-CG) and women living in a rural area (rural group-RG) were collected during pesticide spraying season (RG-SS) and non-spraying season (RG-NSS). In RG-SS, the exposure biomarker placental carboxylesterase decreased and syncytiotrophoblast cytochrome c oxidase activity increased, while 4-hydroxynonenal levels decreased. PG levels decreased in RG-SS and in the RG. Nitric oxide synthase expression decreased in RG, RG-SS and RG-NSS. No significant changes in mitochondrial antioxidant enzyme activities were found. These results suggest that the alteration of syncytiotrophoblast mitochondrial complex IV activity and steroidogenic function may be associated to pesticide exposure. Reduction in placental PG and eNOS expression may account for low newborn weight in RG.

B-esterase determination and organophosphate insecticide inhibitory effects in JEG-3 trophoblasts

The placenta and trophoblasts express several B-esterases. This family includes acethylcholinesterase (AChE), carboxylesterase (CES) and butyrylcholinesterase (BChE), which are important targets of organophosphate insecticide (OP) toxicity. To better understand OP effects on trophoblasts, B-esterase basal activity and kinetic behavior were studied in JEG-3 choriocarcinoma cell cultures. Effects of the OP azinphos-methyl (Am) and chlorpyrifos (Cp) on cellular enzyme activity were also evaluated. JEG-3 cells showed measurable activity levels of AChE and CES, while BChE was undetected. Recorded Km for AChE and CES were 0.33 and 0.26 mM respectively. Native gel electrophoresis and RT-PCR analysis demonstrated CES1 and CES2 isoform expression. Cells exposed for 4 and 24 h to the OP Am or Cp, showed a differential CES and AChE inhibition profiles. Am inhibited CES and AChE at 4 h treatment while Cp showed the highest inhibition profile at 24 h. Interestingly, both insecticides differentially affected CES1 and CES2 activities. Results demonstrated that JEG-3 trophoblasts express AChE, CES1 and CES2. B-esterase enzymes were inhibited by in vitro OP exposure, indicating that JEG-3 cells metabolization capabilities include phase I enzymes, able to bioactivate OP. In addition, since CES enzymes are important for medicinal drug activation/deactivation, OP exposure may interfere with trophoblast CES metabolization, probably being relevant in a co-exposure scenario during pregnancy.

Hepatic and branchial xenobiotic biomarker responses in Solea spp. from several NW Mediterranean fishing grounds

The common sole, Solea solea and the Senegalese sole, Solea senegalensis are two important commercial benthic species that coexist in the NW Mediterranean Sea. Several common biomarkers of chemical exposure were measured in two organs (liver and gills) involved in a different degree in biotransformation and detoxification processes. These parameters were: phase I cytochrome P450 CYP1A-dependent ethoxyresorufin O-deethylase and carboxylesterase activities, phase II glutathione S-transferase activity and the enzymatic antioxidants: catalase, glutathione reductase and glutathione peroxidase. Principal Component Analysis (PCA) considering biometric variables (size and weight) and all liver and gill biomarkers discriminated at a certain extent individuals of both species collected at the different fishing grounds. Esterase inhibition by the organophosphorus pesticides dichlorvos and diazinon was also compared in vitro in muscle, liver and gill of the two species revealing a differential sensitivity. The use of benthic sole in pollution monitoring of Southern Europe is discussed as local sentinel in respect to other benthic fish from more Northern latitudes.

Earthworm-induced carboxylesterase activity in soil: Assessing the potential for detoxification and monitoring organophosphorus pesticides

Soil enzyme activities are attracting widespread interest due to its potential use in contaminant breakdown, and as indicators of soil deterioration. However, given the multiple environmental and methodological factors affecting their activity levels, assessment of soil pollution using these biochemical endpoints is still complex. Taking advantage of the well-known stimulatory effect of earthworms on soil microbes, and their associated enzyme activities, we explored some toxicological features of carboxylesterases (CbEs) in soils inoculated with Lumbricus terrestris. A microplate-scale spectrophotometric assay using soil-water suspensions was first optimized, in which kinetic assay parameters (Km, Vmax, dilution of soil homogenate, and duration of soil homogenization) were established for further CbE determinations. Optimal conditions included a soil-to-water ratio of 1:50 (w/v), 30-min of shaking, and 2.5mM of substrate concentration. As expected, CbE activity increased significantly in soils treated with L. terrestris. This bioturbed soil was used for exploring the role of CbE activity as a bioscavenger for organophosphorus (OP) pesticides. Soil treated with two formulations of chlorpyrifos revealed that CbE activity was a significant molecular sink for this pesticide, reducing its impact on soil microbial activity as shown by the unchanged dehydrogenase activity. Dose-dependent curves were adjusted to an exponential kinetic model, and the median ecological dose (ED50) for both pesticide formulations was calculated. ED50 values decreased as the time of pesticide exposure increased (14 d-ED50s=20.4-26.7 mg kg(-1), and 28 d-ED50s=1.8-2.3 mg kg(-1)), which suggested that chlorpyrifos was progressively transformed into its highly toxic metabolite chlorpyrifos-oxon, but simultaneously was inactivated by CbEs. These results were confirmed by in vitro assays that showed chlorpyrifos-oxon was a more potent CbE inhibitor (IC50=35.5-4.67 nM) than chlorpyrifos (0.41-0.84 μM). The results showed that earthworm-induced CbE activity is an efficient bioscavengers for OP pesticides, acting as a soil safeguarding system. Moreover, the simple dose-response curves against OP exposure suggest that this enzyme--combined with other enzyme activities (e.g., dehydrogenase)--may be a suitable biomarker of pesticide exposure.

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.

Hepatic biotransformation and antioxidant enzyme activities in Mediterranean fish from different habitat depths

Marine fish are threatened by anthropogenic chemical discharges. However, knowledge on adverse effects on deep-sea fish or their detoxification capabilities is limited. Herein, we compared the basal activities of selected hepatic detoxification enzymes in several species (Solea solea, Dicentrarchus labrax, Trachyrhynchus scabrus, Mora moro, Cataetix laticeps and Alepocehalus rostratus) collected from the coast, middle and lower slopes of the Blanes Canyon region (Catalan continental margin, NW Mediterranean Sea). The xenobiotic-detoxifying enzymes analysed were the phase-I carboxylesterases (CbEs), and the phase-II conjugation activities uridine diphosphate glucuronyltransferase (UDPGT) and glutathione S-transferase (GST). Moreover, some antioxidant enzyme activities, i.e., catalase (CAT), glutathione peroxidase (GPX) and glutathione reductase (GR), were also included in this comparative study. Because CbE activity is represented by multiple isoforms, the substrates α-naphthyl acetate (αNA) and ρ-nitrophenyl acetate (ρNPA) were used in the enzyme assays, and in vitro inhibition kinetics with dichlorvos were performed to compare interspecific CbE sensitivity. Activity of xenobiotic detoxification enzymes varied among the species, following a trend with habitat depth and body size. Thus, UDPGT and some antioxidant enzyme activities decreased in fish inhabiting lower slopes of deep-sea, whereas UDPGT and αNA-CbE activities were negatively related to fish size. A trend between CbE activities and the IC50 values for dichlorvos suggested S. solea and M. moro as potentially more sensitive to anticholinesterasic pesticides, and T. scabrus as the most resistant one. A principal component analysis considering all enzyme activities clearly identified the species but this grouping was not related to habitat depth or phylogeny. Although these results can be taken as baseline levels of the main xenobiotic detoxification enzymes in Mediterranean fish, further research is needed to evaluate their response to environmental contaminant exposure.

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.

Comparative assessment of in vitro and in vivo toxicity of azinphos methyl and its commercial formulation

The toxic effects of Gusathion (GUS), which is a commercial organophosphate (OP) pesticide, and also its active ingredient, azinphos methyl (AzM), are evaluated comparatively with in vitro and in vivo studies. Initially, the 96-h LC50 values of AzM and GUS were estimated for two different life stages of Xenopus laevis, embryos, and tadpoles. The actual AzM concentrations in exposure media were monitored by high-performance liquid chromatography. Also, the sub-lethal effects of these compounds to tadpoles were determined 24 h later at exposure concentrations of 0.1 and 1 mg/L using selected biomarker enzymes such as acetylcholinesterase (AChE), carboxylesterase (CaE), glutathione S-transferase (GST), glutathione reductase, lactate dehydrogenase, and aspartate aminotrasferase. Differences in AChE inhibition capacities of AzM and GUS were evaluated under in vitro conditions between frogs and fish in the second part of this study. The AChE activities in a pure electrical eel AChE solution and in brain homogenates of adult Cyprinus carpio, Pelophylax ridibundus, and X. laevis were assayed after in vitro exposure to 0.05, 0.5, 5, and 50 mg/L concentrations of AzM and GUS. According to in vivo studies AChE, CaE and GST are important biomarkers of the effect of OP exposure while CaE may be more effective in short-term, low-concentration exposures. The results of in vitro studies showed that amphibian brain AChEs were relatively more resistant to OP exposure than fish AChEs. The resistance may be the cause of the lower toxicity/lethality of OP compounds to amphibians than to fish.

Impact of insecticide exposure on the predation activity of the European earwig Forficula auricularia

The European earwig Forficula auricularia is an effective predator in apple orchards. It is therefore crucial to study whether insecticides affect this natural pest control agent. Predation activity, i.e., the number of aphids eaten in 24 h, was determined under laboratory conditions after exposure of fourth-instar nymphs and adult earwigs to widely used insecticides (acetamiprid, chlorpyrifos-ethyl, deltamethrin, and spinosad), which were applied at the normal application rates. Inhibition of acetylcholinesterase and carboxylesterase activities were also measured as indicators of pesticide exposure. Predation activity decreased significantly in nymphs exposed to spinosad (62%) and chlorpyrifos-ethyl (98%) compared with controls. A similar response was found for both esterase activities. Spinosad had a stronger effect on AChE (-33%) whereas chlorpyrifos-ethyl affected CbE activity preferentially (-59%). Spinosad (20% of controls), acetamiprid (28%), and chlorpyrifos-ethyl (66%) also significantly decreased the predation behavior of adult male but not female (5 to 40%) earwigs. Adult AChE and CbE activities were also significantly reduced (28 to 67% of controls) in pesticide-exposed earwigs. Our results suggest that earwigs should be included in the environmental risk assessment framework for authorization of newly marketed plant protection products. Their predation behavior appears to be a sensitive and complementary biomarker.

Impact of wastewater on fish health: a case study at the Neckar River (Southern Germany) using biomarkers in caged brown trout as assessment tools

The present work describes a field survey aiming at assessing the impact of a sewage treatment plant (STP) effluent on fish health by means of biomarkers. Indigenous fish were absent downstream of the STP. To elucidate the reason behind this, brown trout (Salmo trutta f. fario) were exposed in floating steel cages up- and downstream of a STP located at the Neckar River near Tübingen (Southern Germany), for 10 and 30 days. A combination of biomarker methods (histopathological investigations, analysis of the stress protein Hsp70, micronucleus test, B-esterase assays) offered the possibility to investigate endocrine, geno-, proteo- and neurotoxic effects in fish organs. Biological results were complemented with chemical analyses on 20 accumulative substances in fish tissue. Even after short-term exposure, biomarkers revealed clear evidence of water contamination at both Neckar River sites; however, physiological responses of caged brown trout were more severe downstream of the STP. According to this, similar bioaccumulation levels (low μg/kg range) of DDE and 12 polycyclic aromatic hydrocarbons (PAHs) were detected at both sampling sites, while up to fourfold higher concentrations of four PAHs, methyl-triclosan and two synthetic musks occurred in the tissues of downstream-exposed fish. The results obtained in this study suggest a constitutive background pollution at both sites investigated at the Neckar River and provided evidence for the additional negative impact of the STP Tübingen on water quality and the health condition of fish.

Enlarging the substrate portfolio of the thermophilic esterase EST2 from Alicyclobacillus acidocaldarius

The enzymatic regioselective hydrolysis of (a) acetylated mono- to tetrasaccharides of different nature, (b) of acetylated aryl glycosides and (c) of different acetylated nucleosides was studied enlarging the portfolio of substrates that can be employed by the thermophilic esterase EST2 from Alicyclobacillus acidocaldarius. The reactions were optimised to the extent that the amount of enzyme needed was lowered of two orders of magnitude with respect to the previously reported reactions, namely from 4000 to 40 U of enzyme per reaction. New additional solvents were screened and dramatic changes in regioselectivity were observed depending on the amount and type of solvent used. For example, in the presence of 10 % DMF, only two α-D-glucose products 6-OH and 4,6-OH (in a 76:24 ratio) were detected, whereas with 25 % DMF, at least four products of similar amount were observed. This versatility adds specific value to the biocatalyst making possible the design of biocatalytic reactions with different hydrophobic ester substrates. As an additional remarkable example, EST2 catalysed with a good yield and high regioselectivity the hydrolysis of p-nitrophenyl β-D-xylopyranoside triacetate producing only the monoacetylated derivative with acetyl group in 3-O-position, in 2 min. The results with nucleosides as substrates are particularly interesting. The peracetates of 3',5'-di-O-acetylthymidine are converted almost quantitatively (95 %) to the monoacetylated derivative possessing free secondary OH; this regioselectivity is complementary to hydrolysis/alcoholysis reactions catalysed by CAL-B lipase or to other microbial hydrolytic biocatalysts, generally giving products with free primary OH groups. A docking analysis was undertaken with all analysed substrates suggesting a structural interpretation of the results. In most of cases, the best pose of the selected substrate was in line with the observed regioselectivity.

Inhibition and recovery of biomarkers of earthworm Eisenia fetida after exposure to thiacloprid

Thiacloprid, a neonicotinoid insecticide, has been used widely in agriculture worldwide. In recent years, the adverse effects of neonicotinoid insecticides on non-target organisms have attracted more and more attention. In the present study, effects of thiacloprid on molecular biomarkers (GST, CarE, CAT, SOD, POD, and DNA damage) of earthworm Eisenia fetida were investigated using the artificial OECD soil for the first time. Earthworms were exposed to thiacloprid (1 and 3 mg/kg) for 7, 14, and 28 days and then transferred to the clean OECD soil for 35, 42, and 56 days. Results showed that activities of GST, CarE, CAT, SOD, and POD are inhibited following the exposure to thiacloprid at one or more sample times and then increased during the recovery course compared with the control. Significant DNA damage to E. fetida was also observed by olive tail moments in comet assay. These results suggested that thiacloprid could have harmful effect on earthworms, and these studied biomarkers might be used in the assessment of the risk of thiacloprid to the soil ecosystem environment.

Investigation of insecticide-resistance status of Cydia pomonella in Chinese populations

The codling moth Cydia pomonella (L.) is an economically important fruit pest and it has been directly targeted by insecticides worldwide. Serious resistance to insecticides has been reported in many countries. As one of the most serious invasive pest, the codling moth has populated several areas in China. However, resistance to insecticides has not been reported in China. We investigated the insecticide-resistance status of four field populations from Northwestern China by applying bioassays, enzyme activities, and mutation detections. Diagnostic concentrations of lambda-cyhalothrin, chlorpyrifos-ethyl, carbaryl, and imidacloprid were determined and used in bioassays. Field populations were less susceptible to chlorpyrifos-ethyl and carbaryl than laboratory strain. Insensitive populations displayed an elevated glutathione S-transferases (GSTs) activity. Reduced carboxylesterase (CarE) activity was observed in some insecticide insensitive populations and reduced acetylcholinesterase activity was observed only in the Wuw population. The cytochrome P450 polysubstrate monooxygenases activities in four field populations were not found to be different from susceptible strains. Neither the known-resistance mutation F399V in the acetylcholinesterase (AChE) gene, ace1, nor mutations in CarE gene CpCE-1 were found in adult individuals from our field populations. Native-PAGE revealed that various CarE isozymes and AChE insensitivity were occurring among Chinese populations. Our results indicate that codling moth populations from Northwestern China were insensitivity to chlorpyrifos-ethyl and carbaryl. Increased GST activity was responsible for insecticides insensitivity. Decreased CarE activity, as well as the presence of CarE and AChE polymorphisms might also be involved in insecticides insensitivity. New management strategies for managing this pest are discussed.

Fructus Psoraleae contains natural compounds with potent inhibitory effects towards human carboxylesterase 2

Fructus Psoraleae (FP) is an edible Chinese herbal which is widely used in Asia for the treatment of various diseases including asthma, diarrhea, and osteoporosis. This study aimed to investigate the inhibitory effects of the crude ethanol extract from FP on human carboxylesterase 2 (hCE2), as well as to identity and characterize the naturally occurring inhibitors of hCE2 in FP. Our results demonstrated that the ethanol extract of FP displayed potent inhibitory effects towards hCE2, while five major bioactive constitutes in FP were efficiently identified by LC-DAD-ESI-MS/MS, with the aid of LC-based activity profiling. The identified bioactive compounds including neobavaisoflavone, isobavachalcone, bavachinin, corylifol A and bakuchiol were found to be naturally occurring potent inhibitors of hCE2, with low Ki values ranging from 0.62μM to 3.89μM. This is the first report of the chemical constitutes in FP as potent inhibitors of hCE2.

Resistance in cholinesterase activity after an acute and subchronic exposure to azinphos-methyl in the freshwater gastropod Biomphalaria straminea

Organophosphorous and carbamates insecticides are ones of the most popular classes of pesticides used in agriculture. Its success relies on their high acute toxicity and rapid environmental degradation. These insecticides inhibit cholinesterase and cause severe effects on aquatic non-target species, particularly in invertebrates. Since the properties of cholinesterases may differ between species, it is necessary to characterize them before their use as biomarkers. Also organophosphorous and carbamates inhibit carboxylesterases and the use of both enzymes for biomonitoring is suggested. Azinphos-methyl is an organophosphorous insecticide used in several parts of the word. In Argentina, it is the most applied insecticide in fruit production in the north Patagonian region. It was detected with the highest frequency in superficial and groundwater of the region. This work aims to evaluate the sensitivity of B. straminea cholinesterases and carboxylesterases to the OP azinphos-methyl including estimations of 48 h NOEC and IC50 of the pesticide and subchronic effects at environmentally relevant concentrations. These will allow us to evaluate the possibility of using cholinesterase and carboxylesterase of B. straminea as sensitive biomarkers. Previously a partial characterization of these enzymes will be performed. As in most invertebrates, acetylthiocholine was the preferred hydrolyzed substrate of B. straminea ChE, followed by propionylthiocholine and being butyrylthiocholine hydrolysis very low. Cholinesterase activity of B. straminea was significantly inhibited by the selective cholinesterases inhibitor (eserine) and by the selective inhibitor of mammalian acethylcholinesterase (BW284c51). In contrast, iso-OMPA, a specific inhibitor of butyrylcholinesterase, did not inhibit cholinesterase activity. These results suggest that cholinesterase activity in total soft tissue of B. straminea corresponds to acethylcholinesterase. Carboxylesterases activity was one order of magnitude higher than cholinesterase. A greater efficiency (Vmax/Km) was obtained using acetylthiocholine and p-nitrophenyl butyrate. Acute exposure to azinphos-methyl did not cause inhibition of cholinesterase activity until 10 mg L(-1) used. Carboxylesterases towards p-nitrophenyl butyrate was inhibited by azinphos-methyl being the IC502.20±0.75 mg L(-1) of azinphos-methyl. Subchronic exposure to environmental concentrations of azinphos-methyl (0.02 and 0.2 mg L(-1)) produced a decrease in survival, protein content and carboxylesterases activity despite no inhibition of cholinesterase activity was observed. B. straminea cholinesterase is not a sensible biomarker. On the contrary, carboxylesterases activity was inhibited by azinphos-methyl. Carboxylesterases could be protecting cholinesterase activity and therefore, protecting the organism from neurotoxicity. This work confirms the advantages of measuring cholinesterases and carboxylesterases jointly in aquatic biomonitoring of pesticide contamination. This becomes relevant in order to find more sensitive biomarkers and new strategies to protect non-target aquatic organisms from pesticide contamination.

Effects of selected xenobiotics on hepatic and plasmatic biomarkers in juveniles of Solea senegalensis

In recent years, Solea senegalensis has increasingly been used in pollution monitoring studies. In order to assess its response to some particular widespread pollutants, juveniles of S. senegalensis were administered an intraperitoneal injection of the model aryl hydrocarbon receptor agonist β-naphtoflavone (βNF) and chemicals of environmental concern, such as the fungicide ketoconazole (KETO), the lipid regulator gemfibrozil (GEM), the surfactant nonylphenol (NP) and the synthetic hormone ethinylestradiol (EE2). Two days after injection, the effect of these chemicals was followed up as alterations of hepatic microsomal activities of the cytochrome P450 (CYPs) and associated reductases, carboxylesterases (CbEs) and the conjugation enzyme uridine diphosphate glucuronyltransferase (UDPGT). In the cytosolic fraction of the liver, the effect on CbEs, glutathione S-transferase (GST) and antioxidant activities was also considered. Alterations on the endocrine reproductive system were evaluated by plasma levels of vitellogenin (VTG) and the sex steroids estradiol (E2), testosterone (T), 11-ketotestosterone (11KT) and the progestin 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P). Injection with the model compound βNF induced the hydrolysis rate of the seven CYP substrates assayed. The xenobiotic GEM induced three CYP-related activities (e.g. ECOD) and UDPGT, but depressed antioxidant defenses. EE2 induced four CYPs, more significantly ECOD and BFCOD activities. The xenoestrogens NP and EE2 altered the activities of CbE in microsomes and catalase, and were the only treatments that induced de novo VTG synthesis. In addition, the progestin 17,20β-P, was induced in NP-injected fish. None of the treatments caused statistically significant effects on steroid plasma levels. In conclusion, the CYP substrates assayed responded specifically to treatments and juveniles of S. senegalensis appear good candidates for assessing xenobiotics exposure.

Tissue distribution, characterization and in vitro inhibition of B-esterases in the earwig Forficula auricularia

Earwigs are important natural enemies of numerous pests in pome fruit orchards worldwide. Studying the effects of agricultural practices on these biological control agents is important for understanding its vulnerability in the field. The aim of this study was to characterize the B-esterase activities in the European earwig Forficula auricularia and to evaluate in vitro its sensitivity to organophosphate and carbamate pesticides. Acetylcholinesterase (AChE) activity was mainly measured with 1.5 mM acetylthiocholine as the substrate in the microsomal fraction of earwig heads (70% of total AChE activity). Carboxylesterase (CbE) activities were measured with three substrates [5 mM 4-nitrophenyl acetate (4-NPA), 1mM 4-nitrophenyl valerate (4-NPV), and 2 mM α-naphtyl acetate (α-NA)] to examine different isoenzymes, which were present mainly in the cytosolic fraction (about 70-88% of total activities) of all earwig tissues. CbE activity was higher than AChE activity, especially with α-NA, then 4-NPA and lastly 4-NPV. Chlorpyrifos-oxon an organophosphate, and carbaryl a carbamate pesticide, inhibited AChE and CbE activities in a concentration-dependent manner. Earwig CbE activities showed a stronger sensitivity to organophosphate than AChE, with the strongest effect for chlorpyrifos-oxon on male carboxylesterase activities. CbE and AChE showed about the same sensitivity to carbamate pesticides regardless of sex. These results suggest that B-type esterases in the European earwig F.auricularia are suitable biomarkers of pesticide exposure.

Neurologic dysfunction and genotoxicity induced by low levels of chlorpyrifos

Chlorpyrifos (CPF) is an organophosphorus cholinesterase inhibitor widely used as an insecticide. Neuro and genotoxicity of this agent were evaluated following daily subcutaneous injections at 0.1, 1 and 10mg/kg or its vehicle to laboratory rats during one week, at the end of which somatosensory evoked potentials (SEP) and power spectrum of the electroencephalogram (EEGp) were recorded under urethane anesthesia. In another group of conscious animals, auditory startle reflex (ASR) was evaluated followed, after euthanasia, with measurements of plasma B-esterases, and genotoxicity with the alkaline comet assay (ACA) at the same CPF doses. The results indicated a CPF dose related inhibition of B-esterases. Enhanced inhibition of the ASR by a subthreshold pre-pulse was observed at all doses and ACA showed a significant higher DNA damage than vehicle controls in animals exposed to 10mg/kg CPF. A trend to higher frequencies of EEGp and an increase in amplitude of the first negative wave of the SEP were found at all doses. The first positive wave of the SEP decreased at the CPF dose of 10mg/kg. In summary, a shift to higher EEG frequencies and alterations of somatosensory and auditory input to the central nervous system were sensitive manifestations of CPF toxicity, associated with depression of B-esterases. The changes in electrical activity of the cerebral cortex and DNA damage observed at doses that do not elicit overt toxicity may be useful in the detection of CPF exposure before clinical signs appear.

Integrated biomarker analysis of chlorpyrifos metabolism and toxicity in the earthworm Aporrectodea caliginosa

To increase our understanding about the mode of toxic action of organophosphorus pesticides in earthworms, a microcosm experiment was performed with Aporrectodea caliginosa exposed to chlorpyrifos-spiked soils (0.51 and 10 mg kg(-1) dry soil) for 3 and 21 d. Acetylcholinesterase (AChE), carboxylesterase (CbE), cytochrome P450-dependent monooxygenase (CYP450), and glutathione S-transferase (GST) activities were measured in the body wall of earthworms. With short-term exposure, chlorpyrifos inhibited CbE activity (51-89%) compared with controls in both treated groups, whereas AChE activity was depressed in the 10-mg kg(-1) group (87% inhibition). With long-term exposure, chlorpyrifos strongly inhibited all esterase activities (84-97%). Native electrophoresis revealed three AChE isozymes, two of which showed a decreased staining corresponding to the level of pesticide exposure. The impact of chlorpyrifos on CbE activity was also corroborated by zymography. CYP450 activity was low in unexposed earthworms, but it increased (1.5- to 2.4-fold compared to controls) in the earthworms exposed to both chlorpyrifos concentrations for 3d. Bioactivation of chlorpyrifos was determined by incubating the muscle homogenate in the presence of chlorpyrifos and NAD(H)2. The mean (±SD, n=40) bioactivation rate in the unexposed earthworms was 0.74±0.27 nmol NAD(H)2 oxidized min(-1) mg(-1) protein, and a significant induction was detected in the low/short-term exposure group. GST activity significantly increased (33-35% of controls) in earthworms short-term exposed to both chlorpyrifos concentrations. Current data showed that CYP450 and GST activities had a prominent role in the initial exposure to the organophosphorus. With short-term exposure, CbE activity was also a key enzyme in the non-catalytic detoxification of chlorpyrifos-oxon, thereby reducing its impact on AChE activity, before it became saturated at t=21 d. Results indicate that A. caliginosa detoxify efficiently chlorpyrifos, which would explain its tolerance to relatively high exposure levels to chlorpyrifos.

Placental oxidative status in rural residents environmentally exposed to organophosphates

The impact of environmental organophosphate pesticide exposure on the placenta oxidative status was assessed. Placental samples were collected from women residing in an agricultural area during pesticide pulverization period, non-pulverization period and from control group. Carboxylesterase activity was significantly decreased in pulverization period group. Enzymatic and non-enzymatic defense system, the oxidative stress biomarkers and the nuclear factor erythroid 2-related factor levels showed no differences among groups. However, in the pulverization period group, an inverse association between catalase activity and placental index, a useful metric for estimating placental inefficiency, was found. This result suggests that catalase may serve as a potential placental biomarker of susceptibility to pesticides. Further studies designed from a gene-environment perspective are needed.

Characterization of carboxylesterase in skin mucus of Cirrhinus mrigala and its assessment as biomarker of organophosphate exposure

Presence of carboxylesterase (CbE) activity in the skin mucus of Cirrhinus mrigala was investigated. CbE activity in skin mucus showed higher substrate preference for α-naphthyl acetate over p-nitrophenyl acetate. Four CbE isozymes-CbE-1, CbE-2, CbE-3, and CbE-4 were observed in skin mucus during zymography. The isozyme CbE-4 was characterized as typical serine esterase, whereas CbE-1, CbE-2, and CbE-3 were identified as sulphhydryl group-dependent serine esterases. In vitro treatment of skin mucus with the organophosphorus insecticide, Nuvan(®) showed strong inhibition of CbE activity. In vivo exposure of the fish to sublethal test concentrations (5 and 15 mg/l) of the insecticide also revealed significant inhibition of CbE activity in mucus. After the cessation of exposure, CbE activity recovered to its control level during the recovery periods. Thus, CbE activity in skin mucus could be considered a biomarker of the organophosphorus insecticide exposure to fish and a useful tool in monitoring environmental toxicity.

Esterases of Varroa destructor (Acari: Varroidae), parasitic mite of the honeybee

Varroa destructor is an ectoparasite that causes serious damage to the population of the honeybee. Increasing resistance of the parasite to acaricides is related, among others, to metabolic adaptations of its esterases to facilitate decomposition of the chemicals used. Esterases are a large heterogeneous group of enzymes that metabolize a number of endogenous and exogenous substrates with ester binding. The aim of the present study was to determine the activity of esterases in the body extracts (BE) and excretion/secretion products (E/SP) of the mite. The enzymes contained in the E/SP should originate mainly from the salivary glands and the alimentary system and they may play a particularly important role in the first line of defence of the mite against acaricides. Activity of cholinesterases (ChEs) [acetylcholinesterase (AChE) and butyrylcholinesterase], carboxylesterases (CEs) and phosphatases [alkaline phosphatase (AP) and acid phosphatase (AcP)] was investigated. The activity of all the enzymes except AChE was higher in the E/SP than in the BE. ChEs from the BE and from the E/SP reacted differently on eserine, a ChE inhibitor. Eserine inhibited both enzymes from the BE, increased decomposition of acetylcholine, but did not influence hydrolysis of butyrylcholine by the E/SP. Activity of the CEs from the BE in relation to the esters of carboxylic acids can be presented in the following series: C10 > C12 > C14 > C8 > C2 > C4 = C16, while activity of the CEs from the E/SP was: C4 > C8 > C2 > C14 > C10 > C12 > C16. The inhibitor of CEs, triphenyl phosphate, reduced the activity of esterases C2–C8 and C14–C16; however, it acted in the opposite way to CEs C10 and C12. The activity of both phosphatases was higher in the E/SP than in the BE (AcP about twofold and AP about 2.6-fold); the activities of AP and AcP in the same material were similar. Given the role of esterases in resistance to pesticides, further studies are necessary to obtain complete biochemical characteristics of the enzymes currently present in V. destructor.

Automated evaluation of pharmaceutically active ionic liquids' (eco)toxicity through the inhibition of human carboxylesterase and Vibrio fischeri

The toxicity of 16 pharmaceutical active ionic liquids (IL-APIs) was evaluated by automated approaches based on sequential injection analysis (SIA). The implemented bioassays were centered on the inhibition of human carboxylesterase 2 and Vibrio fischeri, in the presence of the tested compounds. The inhibitory effects were quantified by calculating the inhibitor concentration required to cause 50% of inhibition (EC50). The EC50 values demonstrated that the cetylpyridinium group was one of the most toxic cations and that the imidazolium group was the less toxic. The obtained results provide important information about the safety of the studied IL-APIs and their possible use as pharmaceutical drugs. The developed automated SIA methodologies are robust screening bioassays, and can be used as a generic tools to identify the (eco)toxicity of the structural elements of ILs, contributing to a sustainable development of drugs.

Cholinesterases and neurotoxicity as highly sensitive biomarkers for an organophosphate insecticide in a freshwater gastropod (Chilina gibbosa) with low sensitivity carboxylesterases

In the Upper Valley of Río Negro and Río Neuquén in Argentina, agriculture represents the second most important economic activity. Azinphos-methyl has been found in water from this region throughout the year at a maximum concentration of 22.48 μg L(-1) during the application period. Toxicological studies on local non-target species have been performed mostly on vertebrates, while mollusks, which could be more sensitive, have not been studied so far. This work aims to characterize cholinesterase (ChE) and carboxilesterase (CE) activities of Chilina gibbosa, a freshwater gastropod native to southern Argentina and Chile. These enzymes, together with neurotoxicity signals, are evaluated herein after as sensitive biomarkers of exposure to azinphos-methyl at environmentally relevant concentrations. Effects of azinphos-methyl on antioxidant defenses: glutathione (GSH), catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST) are also studied in order to complete a set of biomarkers with different sensitivity and specificity, to propose C. gibbosa as a sentinel species. The highest specific activity was obtained with acetylthiocholine as substrate, followed by propionylthiocholine (83% in comparison to acetylthiocholine) and butyrylthiocholine (19%).The lowest Km and the highest efficiency for ChE were obtained with acetylthiocholine. Regarding CEs activities, a higher efficiency was obtained with p-nitrophenyl butyrate than with p-nitrophenyl acetate. Eserine produced significant inhibition of ChE activity (81% with 0.001 mM and 98% with 1mM) while iso-OMPA did not produce any significant effect on ChE. Our results show that C. gibbosa ChE is very sensitive to azinphos-methyl (CI50 0.02 μg L(-1)) while CEs are inhibited at higher concentrations (CI50 1,000 μg L(-1)). CEs have been reported to be more sensitive to OPs than ChEs in most of the aquatic invertebrates protecting the organisms from neurotoxic effects. In contrast, C. gibbosa, has ChE which are much more sensitive to azinphos-methyl than CEs and shows marked signs of neurotoxicity. Regarding antioxidant defenses, GSH levels were significantly increased by 0.02 and 20 μg L(-1) azinphos-methyl (80 and 103%, respectively), CAT activity was increased 85% only at 0.02 μg L(-1) and SOD and GST did not show any significant response. Since ChE activity, neurotoxicity signs, GSH and CAT are sensitive biomarkers of acute exposure to azinphos-methyl at environmental concentrations C. gibbosa could be included as sentinel species in monitoring programs of pesticide hazard in regions of Argentina and Chile.

In vitro and in vivo inhibition of acetylcholinesterase and carboxylesterase by metals in zebrafish (Danio rerio)

Metals are natural components in ecosystems; however, if these elements are in excess, they can have adverse effects on living organisms. This study analyzes the interference of copper, lead, iron and cadmium in acetylcholinesterase (AChE) and carboxylesterase (CbE) activities in zebrafish. AChE was significantly inhibited in vitro by copper, iron, lead and cadmium at higher concentrations (10 and 20 mmol/L), whereas CbE was inhibited only at a concentration of 20 mmol/L. In vivo, only lead and cadmium were able to cause AChE inhibition at higher concentrations, while iron didn't cause any changes, and copper promoted an increase in AChE activity at a concentration of 0.06 mg/L. CbE activity did not change at any of the times (two and seven days) and concentrations tested, except in the case of copper exposure, which resulted in a decrease in CbE activity. Indeed, iodoacetamide treatment didn't changed AChE neither CbE activities, results which indicate that the metal inhibiting effect is probably not due to its biding to thiol groups close the active site of the enzyme. This outcome reveals that metals are important esterase inhibitors in zebrafish, and should be considered in environmental monitoring studies that use esterase inhibition as exposure biomarkers of organophosphate and carbamate pesticides.

Evaluation of biochemical markers in the golden mussel Limnoperna fortunei exposed to glyphosate acid in outdoor microcosms

In this study, the impact of technical grade glyphosate acid on Limnoperna fortunei was assessed employing outdoor microcosms treated with nominal glyphosate concentrations of 1, 3 and 6 mg L(-1). At the end of the experiment (26 days), catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST), acetylcholinesterase (AChE), carboxylesterases (CES) and alkaline phosphatase (ALP) activities, and lipid peroxidation levels were analyzed. GST and ALP activities and lipid peroxidation levels showed a significant increase with respect to controls in the mussels exposed to glyphosate (up to 90, 500 and 69 percent, respectively). CES and SOD activities showed a significant decrease in glyphosate exposed bivalves with respect to controls (up to 48 and 37 percent, respectively). CAT and AChE did not show differences between exposed and no exposed bivalves. The increase in lipid peroxidation levels and the decrease in SOD and CES activities observed in L. fortunei indicate that glyphosate had adverse effects on the metabolism of this bivalve. The results of the present study also indicate that a "multibiomarker approach" provides a more precise knowledge of the impact of glyphosate on L. fortunei.