Actinomycetota, a central constituent microbe during long-term exposure to diazinon, an organophosphorus insecticide

Microbial biodegradation is a primary pesticide remediation pathway. Despite diazinon is one of the most frequently used organophosphate insecticides worldwide, its effect on soil microbial community remains obscure. We hypothesize that diazinon exposure reshapes microbial community, among them increased microbes may play a crucial role in diazinon degradation. To investigate this, we collected soil from an organic farming environment, introduced diazinon, cultivated it in a greenhouse, and then assessed its effects on soil microbiomes at three distinct time points: 20, 40, and 270 days after treatment (DAT). Results from HPLC showed that the level of diazinon was gradually degraded by 98.8% at 270 DAT when compared with day zero, whereas 16S rRNA gene analysis exhibited a significant reduction in the bacterial diversity, especially at the early two time points, indicating that diazinon may exert selection pressure to the bacteria community. Here, the relative abundance of phylum Actinomycetota increased at 20 and 40 DATs. In addition, the bacterial functional gene profile employing PICRUSt2 prediction also revealed that diazinon exposure induced the genomic function related to xenobiotics biodegradation and metabolism in soil, such as CYB5B, hpaC, acrR, and ppkA. To validate if bacterial function is caused by increased relative abundance in diazinon enriched soil, further bacteria isolation resulted in obtaining 25 diazinon degradation strains out of 103 isolates. Notably, more than 70% (18 out of 25) isolates are identified as phylum Actinomycetota, which empirically confirms and correlates microbiome and PICRUSt2 results. In conclusion, this study provides comprehensive information from microbiome analysis to obtaining several bacteria isolates responsible for diazinon degradation, revealing that the phylum Actinomycetota is as a key taxon that facilitates microbial biodegradation in diazinon spoiled soil. This finding may assist in developing a strategy for microbial detoxification of diazinon, such as using an Actinomycetota rich synthetic community (SynCom).

Sex-specific metabolic dysregulation in digestive glands of green mussels following exposure to triazophos

As a ubiquitous environmental pollutant in China, triazophos (TP) is known to have neurotoxicity, oxidative stress, and reproductive toxicity to mussels. To investigate the molecular mechanisms of TP toxicity, metabolic changes in the digestive glands of Perna viridis in different sexes were examined after treated with 35 μg/L TP. Notably, 158 significant different metabolites (SDMs) were detected in TP-treated mussels and more than half of the SDMs were lipids and lipid-like molecules, which suggested that TP disturbed the lipid metabolism of P. viridis. In addition, metabolites associated with neurotoxicity and reproductive disturbance were also detected in female and male mussels. Moreover, a larger number of SDMs were found in male mussels (120 SDMs) than females (99 SDMs), and 60 common metabolites exhibited consistent variation tendency and similar magnitude in both sexes. The metabolic alternations in female and male mussels displayed similar protective mechanisms and also sex-specific responses, male mussels were more sensitive to TP exposure. This research provided new data about the molecular mechanisms of TP toxicity and the gender specific changes in mussels after treated by chemicals.

Embryonic development, hatchling performance and metabolic profile after egg exposure to environmentally relevant levels of chlorpyrifos in an aquatic turtle

The extensive use of organophosphorus insecticides poses a threat to the survival of non-target organisms. Ecotoxicological outcomes of embryonic exposure to insecticides are rarely evaluated in various oviparous species. In this study, soft-shelled turtle (Pelodiscus sinensis) eggs were incubated in moist substrate containing different levels (0, 2, 20 and 200 μg/kg) of chlorpyrifos to investigate its toxic effects on embryonic development and survival, and hatchling physiological performance. Chlorpyrifos exposure had no significant impacts on embryonic development rate and egg survival in P. sinensis. Similarly, embryonic chlorpyrifos exposure neither obviously affected the size and locomotor performance of hatchlings, nor changed the activities of superoxide dismutase and catalase, and content of malondialdehyde in their erythrocytes. Based on liquid chromatography-mass spectrometry analysis, minor metabolic perturbations related to amino acid, lipid and energy metabolism in hatchlings after embryonic chlorpyrifos exposure were revealed by hepatic metabolite profiling. Overall, our results suggested that embryonic exposure to environmentally relevant levels of chlorpyrifos had only a limited impact on physiological performances of hatchlings, although it would result in a potential risk of hepatotoxicity in P. sinensis.

Multiple acetylcholinesterases in Pardosa pseudoannulata brain worked collaboratively to provide protection from organophosphorus insecticides

Acetylcholinesterase (AChE) is an essential neurotransmitter hydrolase in nervous systems of animals and its number varies among species. So far, five AChEs have been identified in the natural enemy Pardosa pseudoannulata. Here we found that Ppace1, Ppace2 and Ppace5 were highly expressed in the spider brain, among which the mRNA level of Ppace5, but not Ppace1 and Ppace2, could be up-regulated by organophosphorus insecticides at their sublethal concentrations. In spider brain, the treatment by organophosphorus insecticides at the sublethal concentrations could increase total AChE activity, although high concentrations inhibited the activity. The activity that increased from the sublethal concentration pretreatment could compensate for the activity inhibition due to subsequent application of organophosphorus insecticides at lethal concentrations, and consequently reduce the mortality of spiders. PpAChE1 and PpAChE2 were highly sensitive to organophosphorus insecticides, and their activities would be strongly inhibited by the insecticides. In contrast, PpAChE5 displayed relative insensitivity towards organophosphorus insecticides, but with the highest catalytic efficiency for ACh. That meant the up-regulation of Ppace5 under insecticide exposure was important for maintaining AChE activity in spider brain, when PpAChE1 and PpAChE2 were inhibited by organophosphorus insecticides. The study demonstrated that multiple AChEs in the spider brain worked collaboratively, with part members for maintaining AChE activity and other members responding to organophosphorus inhibition, to provide protection from organophosphorus insecticides. In fields, high concentration insecticides are often applied when ineffective controls of insect pests occur due to relative-low concentration of insecticides in last round application. This application pattern of organophosphorus insecticides provides more chances for P. pseudoannulata to survive and controlling insect pests as a natural enemy.

Estimation of chlorpyrifos distribution in forensic visceral samples and body fluids using LCMS method

The ingestion of the insecticide chlorpyrifos leads to fatal intoxication in suicidal cases, and its distribution can be assessed only after post-mortem. This study attempted to investigate the distribution of chlorpyrifos in forensic visceral tissue samples like stomach, liver, kidney, heart, brain, lung, spleen, muscle and body fluids like blood and urine by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with the liquid-liquid extraction method. An analysis time of 8.77 min with 1 μl as an injection volume was chosen. The results obtained are analysed using Labsolutions insight LCMS software, considering Multiple Reaction Monitoring (MRM) and Retention Time (RT). Our findings depict that the stomach tissue has very high concentrations of chlorpyrifos, which suggests the possibility of high distribution and aspiration in the stomach tissue. The concentration of chlorpyrifos in stomach tissue ranged from 816 to 901 μg/g in male cadavers and from 443 to 612 μg/g in female cadavers. Among all the tissues, the stomach tissue showed the highest concentration, while the lowest concentration was found in muscle. Metabolic distribution of chlorpyrifos from the stomach contents to the other surrounding organs may occur and hence the concentrations of CPF were also seen in other organs like the liver, lung, kidney, brain, and muscle. These toxicological results from autopsy findings, together with LC-MS/MS indicate that stomach tissue examination gives an accurate profile of insecticide poisoning in forensic samples with acute poisoning.

Lung injury caused by aspiration of organophosphorus insecticide and gastric contents in pigs

INTRODUCTION

Patients who require mechanical ventilation after self-poisoning with ingested organophosphorus (OP) insecticides often die. Aspiration of stomach contents may contribute to lung injury and lethality. This study was designed to assess the severity of direct and indirect pulmonary injury created by pulmonary instillation of mixtures of OP insecticide, solvent (Solv) and porcine gastric juice (GJ) compared to controls.

METHODS

Terminally anaesthetised minipigs (groups n = 5) were exposed to sham bronchoscopy or given mixtures (0.5 mL/kg) of: saline, GJ, OP insecticide and GJ (OP + GJ), or Solv and GJ (Solv + GJ), placed into the right lung, and monitored for 48 h. Lung injury was assessed through analysis of bronchoalveolar lavage fluid (BALF), computed tomography and histopathology.

RESULTS

OP + GJ created a direct lung injury consisting of neutrophil infiltration, oedema and haemorrhage, as well as indirect injury to the other lung. OP + GJ directly-injured lung parenchyma had increased concentrations of BALF protein, albumin, IL-6, IL-8 and C-reactive protein (CRP) at 24 h (p < 0.05), and BALF protein, albumin and CRP at 48 h (p < 0.05), when compared with controls. Aspiration of GJ produced similar direct effects to OP + GJ but less indirect lung injury. Lung injury was less severe after Solv + GJ, for combined lung histopathology scores (vs. OP + GJ, p < 0.05) and for the proportion of directly-injured lung that was poorly/non-aerated at 48 h.

CONCLUSION

Pulmonary instillation of OP + GJ created more lung damage than controls or Solv + GJ. In patients with severe OP insecticide poisoning and reduced consciousness, early airway protection is likely to reduce pulmonary damage.

Multi- and Trans-Generational Effects on Daphnia Magna of Chlorpyrifos Exposures

Chlorpyrifos, a broad-spectrum neurotoxic organophosphate insecticide, is subject to atmospheric and hydrolytic transport from application sites to aquatic ecosystems. Across the landscape, concentrations in surface water can vary spatially and temporally according to seasonal use practices. Standardized bioassays can provide a screening-level understanding of aquatic receptor acute and chronic toxicity. However, these bioassays do not address ecologically relevant exposure patterns that may impact fitness and survival within and across generations. The aim of the present study was to evaluate the utility of a second-tier, screening-level methodology employing Daphnia magna multi- and transgenerational bioassays spanning four generations to investigate the effect of variable chronic chlorpyrifos exposure. The multigenerational assay consisted of continuous chlorpyrifos exposure across four consecutive 21-day bioassays using progeny from the previous assay for each successive generation. In the transgenerational assay, only the parent (F0) generation was exposed. For both assays, survival and reproduction were assessed across treatments and generations. Results indicated that (1) following continuous chlorpyrifos exposure at ecologically relevant concentrations to four generations of D. magna, the highest treatment showed an apparent tolerance response for both survival and reproductive success in the F3 generation, and (2) chlorpyrifos exposure to the F0 generation did not result in treatment effects in the unexposed F1, F2, and F3 generations in the apical endpoints of survival and reproduction. Employing a suite of acute and chronic bioassays, including chronic exposures spanning multiple generations, allows for a more robust screening-level evaluation of the potential impact of chlorpyrifos on aquatic receptors for variable periods of exposure. Environ Toxicol Chem 2022;41:1054-1065. © 2021 SETAC.

Enantioselective degradation of the organophosphorus insecticide isocarbophos in Cupriavidus nantongensis X1T: Characteristics, enantioselective regulation, degradation pathways, and toxicity assessment

The chiral pesticide enantiomers often show selective efficacy and non-target toxicity. In this study, the enantioselective degradation characteristics of the chiral organophosphorus insecticide isocarbophos (ICP) by Cupriavidus nantongensis X1^T were investigated systematically. Strain X1^T preferentially degraded the ICP R isomer (R-ICP) over the S isomer (S-ICP). The degradation rate constant of R-ICP was 42-fold greater than S-ICP, while the former is less bioactive against pest insects but more toxic to humans than the latter. The concentration ratio of S-ICP to R-ICP determines whether S-ICP can be degraded by strain X1^T. S-ICP started to degrade only when the ratio (C_S-ICP/C_R-ICP) was greater than 62. Divalent metal cations could improve the degradation ability of strain X1^T. The detected metabolites that were identified suggested a novel hydrolysis pathway, while the hydrolytic metabolites were less toxic to fish and green algae than those from P-O bond breakage. The crude enzyme degraded both R-ICP and S-ICP in a similar rate, indicating that enantioselective degradation was due to the transportation of strain X1^T. The strain X1^T also enantioselectively degraded the chiral organophosphorus insecticides isofenphos-methyl and profenofos. The enantioselective degradation characteristics of strain X1^T make it suitable for remediation of chiral organophosphorus insecticide contaminated soil and water.

The impact of age-related sub-chronic exposure to chlorpyrifos on metabolic indexes in male rats

Chlorpyrifos (CPF), an organophosphorus pesticide (OP), has been implicated in metabolic diseases; however, the data are controversial. Rising age has been found as a main risk factor for metabolic diseases, and it has been proposed that advanced age increases susceptibility to the toxic effects of OPs. Therefore, this investigation aimed to evaluate the impact of CPF on hyperglycemia, hypercholesterolemia, and inflammation in animals with different ages. CPF (5 mg/kg) for 45 consecutive days was administered orally to male Wistar rats with different ages including 2-, 10-, and 20-month-old. The results indicated an increase in glucose and inflammatory indices, and also lipid profile was changed in the serum of aged animals in comparison with the 2-month-old animals. CPF administration amplified these parameters in the 20-month-old rats in comparison with that of aged-matched controls. The histopathological examination also indicated that CPF caused slight to moderate changes in the liver of 2-, 10-, and 20-month-old animals. Cholestasis was also observed in the CPF-administrated 20-month-old rats. In conclusion, aging may increase the susceptibility to CPF-induced metabolic disturbances in the animal models. It is proposed that advancing in age elevates the susceptibility to the metabolic effects of CPF.

Sensitivity of Boana pulchella (Anura: Hylidae) Tadpoles to Environmentally Relevant Concentrations of Chlorpyrifos: Effects at the Individual and Biochemical Levels

We report sublethal effects of environmentally relevant concentrations of chlorpyrifos at the individual (swimming alterations) and biochemical (esterase activities and antioxidant enzymes) levels in the Montevideo tree frog Boana pulchella larvae. The 50% lethal concentration at 96 h (LC50-96h) for chlorpyrifos in stage-29 B. pulchella tadpoles was 0.98 mg/L, which was close to the 65th percentile of published anuran species sensitivity. In B. pulchella, chlorpyrifos disrupted biochemical processes: tadpoles showed a significant inhibition of esterase activity and a significant induction of antioxidant enzymes, indicating a response to an environmental challenge causing oxidative stress. Using principal components analysis, we could associate chlorpyrifos reduction in esterase activity with swimming alterations at 0.5 mg/L of the toxicant. The biochemical biomarkers reported in the present study respond at levels 20 times lower than the LC50-96h and were associated with a biologically important response-swimming behavior. The link of responses across different levels of biological organization was demonstrated. The species is suitable as a model for ecotoxicological studies at different levels, including the individual and biochemical levels, and may be considered a good reference organism in environmental control programs. Environ Toxicol Chem 2020;39:834-841. © 2020 SETAC.

Metabolic mechanisms and acetylcholinesterase sensitivity involved in tolerance to chlorpyrifos-ethyl in the earwig Forficula auricularia

Apple orchards are highly treated crops, in which organophosphorus (OP) are among the most heavily sprayed insecticides. These pesticides are toxic to non-target arthropods and their repeated use increases the risk of resistance. We studied mechanisms involved in tolerance and resistance to OP insecticides in the earwig Forficula auricularia, an effective generalist predator in pomefruit orchards. Adult earwigs were sampled in three apple orchards managed under contrasting strategies: conventional, Integrated Pest Management, and organic. The threshold activities of enzyme families involved in pesticides tolerance: Glutathione-S-transferases (GSTs) and Carboxylesterases (CbEs) were measured in earwig extracts. Acetylcholinesterase (AChE) was monitored as a toxicological endpoint. Variations in these activities were assessed prior to and after exposure to chlorpyrifos-ethyl at the normal application rate. We observed that the mortality of earwigs exposed to chlorpyrifos-ethyl depended on the management strategy of orchards. Significantly lower mortality was seen in individuals sampled from conventional orchard. The basal activities of CbEs and GSTs of collected organisms were higher in conventional orchard. After in vivo exposure, AChE activity appeared to be inhibited in surviving males with no difference between orchards. However an in vitro inhibition trial with chlorpyrifos-oxon showed that AChE from earwigs collected in organic and IPM orchards were more sensitive than from conventional ones. These observations support the hypothesis of a molecular target modification in AChE and highlight the possible role of CbEs in effective protection of AChE. Our findings suggest that the earwigs with a high historic level of insecticide exposure could acquire resistance to chlorpyrifos-ethyl.

Evaluation of a robust engineered enzyme towards organophosphorus insecticide bioremediation using planarians as biosensors

Organophosphorus compounds (OPs) are neurotoxic molecules developed as insecticides and chemical warfare nerve agents (CWNAs). They are covalent inhibitors of acetylcholinesterase (AChE), a key enzyme in central and peripheral nervous systems and are responsible for numerous poisonings worldwide. Many animal models have been studied over the years but finding a suitable in vivo model to account for both acute toxicity and long-term exposure remains a topical issue. Recently, an emerging aquatic animal model harboring a mammalian-like cholinergic nervous system, the freshwater planarian from Platyhelminthes, has been used to investigate neurotoxicity and developmental disruption. Given the tremendous toxicity of OPs, various bioremediation strategies have been considered over the years to counter their poisonous effects. Among these, enzymes have been particularly highlighted as they can degrade OPs in a fast, non toxic and environmentally friendly manner. In this article we investigated the biotechnological potential for decontaminating OPs of the previously reported variant SsoPox-αsD6 from the hyperstable enzyme SsoPox, isolated from the archaea Sulfolobus solfataricus. The capacity to hydrolyze 4 new substrates (methyl-pirimiphos, quinalphos, triazophos and dibrom) was demonstrated and the degradation products generated by enzymatic hydrolysis were characterized. We further evaluated the capacity of SsoPox-αsD6 for in vivo protection of freshwater planarians Schmidtea mediterranea (Smed). The use of SsoPox-αsD6 drastically decreased mortality and enhanced mobility of planarians. Then, an enzyme-based filtration device was developed by immobilizing intact Escherichia coli cells expressing SsoPox-αsD6 into alginate beads. The efficacy of the device was demonstrated using planarians as biosensors.

Multiyear monitoring of bird communities in chlorpyrifos-treated orchards in Spain and the United Kingdom: Spatial and temporal trends in species composition, abundance, and site fidelity

The relationship between agricultural practices and the welfare of wild birds has gained increased attention over the last decades. To assess the potential effects of chlorpyrifos on the bird community, a multiyear, multisite monitoring program was carried out in treated cider orchards (in the United Kingdom) and treated citrus orchards (in Spain). Constant-effort mist netting was used over several consecutive years in the United Kingdom (2012-2014) and Spain (2010-2012). The general structure of the bird community and the presence of breeding species were analyzed. Twelve and 11 bird species (out of 81 and 45 trapped) in Spain and the United Kingdom, respectively, exceeded the 2% dominance value. For a selection of 6 species in citrus and 4 in cider orchards, N-mixture models were fitted to the number of trapped birds. The abundance of most species was strongly and significantly affected by seasonality. No species showed any indication of reduction in population size over the years. The results of this extensive field program support the indications that chlorpyrifos spray applications present a low risk to the bird community over the years. Environ Toxicol Chem 2019;38:616-629. © 2018 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.

Influence of sex on biomarkers of oxidative stress in the kidney, lungs, and liver of rabbits after exposure to diazinon

The present study evaluated the effect of two oral doses of the pesticide diazinon (25 and 125 mg/kg bw) on four biochemical parameters (malondialdehyde and glutathione levels, and catalase and glutathione S-transferase enzymatic activities) in the kidney, lungs, and liver of rabbit after 10 days of exposure. Malondialdehyde levels were significantly greater in exposed animals compared to controls, especially in the animals exposed to the higher dose of the pesticide. This result was reflected in the glutathione levels, which were significantly lower at that same higher dose. Catalase activity was also inhibited by the higher dose of the pesticide in all three organs analysed, whereas inhibition of glutathione S-transferase activity was only significant for the kidney and lungs. There were some slight differences between the sexes: taking the results for all three organs, the higher dose of diazinon resulted in a clearly significant inhibitory effect on the catalase activity and glutathione levels in males, and a significant enhancing effect on the malondialdehyde levels in females. These results help to confirm the interest of considering such endogenous factors in future ecotoxicological studies, and that the four biomarkers considered are suitable for reflecting the toxic effects of diazinon on rabbits, especially the effects related to oxidative stress. Graphical abstract.

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.

A supersensitive silver nanoprobe based aptasensor for low cost detection of malathion residues in water and food samples

In the present study, we report a highly sensitive, rapid and low cost colorimetric monitoring of malathion (an organophosphate insecticide) employing a basic hexapeptide, malathion specific aptamer (oligonucleotide) and silver nanoparticles (AgNPs) as a nanoprobe. AgNPs are made to interact with the aptamer and peptide to give different optical responses depending upon the presence or absence of malathion. The nanoparticles remain yellow in color in the absence of malathion owing to the binding of aptamer with peptide which otherwise tends to aggregate the particles because of charge based interactions. In the presence of malathion, the agglomeration of the particles occurs which turns the solution orange. Furthermore, the developed aptasensor was successfully applied to detect malathion in various water samples and apple. The detection offered high recoveries in the range of 89-120% with the relative standard deviation within 2.98-4.78%. The proposed methodology exhibited excellent selectivity and a very low limit of detection i.e. 0.5pM was achieved. The developed facile, rapid and low cost silver nanoprobe based on aptamer and peptide proved to be potentially applicable for highly selective and sensitive colorimetric sensing of trace levels of malathion in complex environmental samples.

Modulation of immune and antioxidant responses by azinphos-methyl in the freshwater mussel Diplodon chilensis challenged with Escherichia coli

The aim of the present study was to characterize the immune response-total hemocyte number, cell type proportion, hemocyte viability, lysosomal membrane stability, phagocytic activity, cellular acid and alkaline phosphatase activity, and humoral bacteriolytic and phenoloxidase activity--in Diplodon chilensis exposed to 0.2 mg/L of azinphos-methyl (AZM), using Escherichia coli as immunological and pro-oxidant challenges. In addition, glutathione-S-transferase and lipid peroxidation thiobarbituric acid reactive substances were analyzed in gill tissue. Mussels from an unpolluted site were treated for 3 d as follows: 1) experimental control; 2) solvent effects control (acetone 0.01%); 3) bacterial challenge effects control (E. coli, 5 cells/mL × 10⁴ cells/mL); 4) pesticide effects control (AZM in acetone); 5) control for combined effects of solvent and bacterial challenge; and 6) exposed to AZM, then challenged with E. coli. The results showed increased granulocyte proportion and phagocytic activity. Partial reversion of deleterious effects of E. coli on lysosomal membranes was observed in mussels exposed to AZM and then challenged with E. coli. Total hemocyte number and humoral bacteriolytic activity were increased only by E. coli challenge. Acid phosphatase activity was increased by both E. coli and AZM, whereas the stimulating effect of E. coli on alkaline phosphatase activity was negatively modulated by AZM. Azinphos-methyl inhibited phenoloxidase activity regardless of the E. coli challenge. Gill glutathione-S-transferase activity was increased by E. coli treatment either alone or pretreated with acetone or AZM and by AZM alone. Thiobarbituric acid reactive substance levels were reduced by AZM alone or combined with the E. coli challenge and by acetone followed by the E. coli challenge. Both acetone and AZM seem to be important modulators of immune and antioxidant responses in D. chilensis. Environ Toxicol Chem 2017;36:1785-1794. © 2016 SETAC.

Ecological risk assessment for Pacific salmon exposed to dimethoate in California

A probabilistic risk assessment of the potential direct and indirect effects of acute dimethoate exposure to salmon populations of concern was conducted for 3 evolutionarily significant units (ESUs) of Pacific salmon in California. These ESUs were the Sacramento River winter-run chinook, the California Central Valley spring-run chinook, and the California Central Valley steelhead. Refined acute exposures were estimated using the Soil and Water Assessment Tool, a river basin-scale model developed to quantify the impact of land-management practices in large, complex watersheds. Both direct effects (i.e., inhibition of brain acetylcholinesterase activity) and indirect effects (i.e., altered availability of aquatic invertebrate prey) were assessed. Risk to salmon and their aquatic invertebrate prey items was determined to be de minimis. Therefore, dimethoate is not expected to have direct or indirect adverse effects on Pacific salmon in these 3 ESUs. Environ Toxicol Chem 2017;36:532-543. © 2016 SETAC.

Adaptive response of rat pancreatic β-cells to insulin resistance induced by monocrotophos: Biochemical evidence

Our previous findings clearly suggested the role of duration of exposure to monocrotophos (MCP) in the development of insulin resistance. Rats exposed chronically to MCP developed insulin resistance with hyperinsulinemia without overt diabetes. In continuation of this vital observation, we sought to delineate the biochemical mechanisms that mediate heightened pancreatic β-cell response in the wake of MCP-induced insulin resistance in rats. Adult rats were orally administered (0.9 and 1.8mg/kgb.w/d) MCP for 180days. Terminally, MCP-treated rats exhibited glucose intolerance, hyperinsulinemia, and potentiation of glucose-induced insulin secretion along with elevated levels of circulating IGF1, free fatty acids, corticosterone, and paraoxonase activity. Biochemical analysis of islet extracts revealed increased levels of insulin, malate, pyruvate and ATP with a concomitant increase in activities of cytosolic and mitochondrial enzymes that are known to facilitate insulin secretion and enhanced shuttle activities. Interestingly, islets from MCP-treated rats exhibited increased insulin secretory potential ex vivo compared to those isolated from control rats. Further, MCP-induced islet hypertrophy was associated with increased insulin-positive cells. Our study demonstrates the impact of the biological interaction between MCP and components of metabolic homeostasis on pancreatic beta cell function/s. We speculate that the heightened pancreatic beta cell function evidenced may be mediated by increased IGF1 and paraoxonase activity, which effectively counters insulin resistance induced by chronic exposure to MCP. Our findings emphasize the need for focused research to understand the confounding environmental risk factors which may modulate heightened beta cell functions in the case of organophosphorus insecticide-induced insulin resistance. Such an approach may help us to explain the sharp increase in the prevalence of type II diabetes worldwide.

Effects of amphibian chytrid fungus exposure on American toads in the presence of an insecticide

Abiotic factors such as pesticides may alter the impact of a pathogen on hosts, which could have implications for host-pathogen interactions and may explain variation in disease outbreaks in nature. In the present laboratory experiment, American toad (Anaxyrus americanus) metamorphs were exposed to the amphibian chytrid fungal pathogen Batrachochytrium dendrobatidis (Bd) and environmentally relevant concentrations of the insecticide malathion to determine whether malathion altered the effects of Bd exposure on growth and survival of toad metamorphs. Exposure to Bd significantly decreased survival over the 51 d of the experiment, suggesting that Bd could reduce recruitment into the terrestrial life stage when exposure occurs at metamorphosis. Malathion did not impact survival, but a 12-h exposure at metamorphosis significantly reduced terrestrial growth. Toads that were exposed to both Bd and malathion showed a nonsignificant trend toward the smallest growth compared with other treatments. The present study suggests that Bd may pose a threat to American toads even though population declines have not been observed for this species; in addition, the presence of both the insecticide malathion and Bd could reduce terrestrial growth, which could have implications for lifetime fitness and suggests that environmental factors could play a role in pathogen impacts in nature.

Astrocytes protect against diazinon- and diazoxon-induced inhibition of neurite outgrowth by regulating neuronal glutathione

Evidence demonstrating that human exposure to various organophosphorus insecticides (OPs) is associated with neurobehavioral deficits in children continues to emerge. The present study focused on diazinon (DZ) and its active oxygen metabolite, diazoxon (DZO), and explored their ability to impair neurite outgrowth in rat primary hippocampal neurons as a mechanism of developmental neurotoxicity. Both DZ and DZO (0.5-10 μM) significantly inhibited neurite outgrowth in hippocampal neurons, at concentrations devoid of any cyototoxicity. These effects appeared to be mediated by oxidative stress, as they were prevented by antioxidants (melatonin, N-t-butyl-alpha-phenylnitrone, and glutathione ethyl ester). Inhibition of neurite outgrowth was observed at concentrations below those required to inhibit the catalytic activity of acetylcholinesterase. The presence of astrocytes in the culture was able to provide protection against inhibition of neurite outgrowth by DZ and DZO. Astrocytes increased neuronal glutathione (GSH) in neurons, to levels comparable to those of GSH ethyl ester. Astrocytes depleted of GSH by L-buthionine-(S,R)-sulfoximine no longer conferred protection against DZ- and DZO-induced inhibition of neurite outgrowth. The findings indicate that DZ and DZO inhibit neurite outgrowth in hippocampal neurons by mechanisms involving oxidative stress, and that these effects can be modulated by astrocytes and astrocyte-derived GSH. Oxidative stress from other chemical exposures, as well as genetic abnormalities that result in deficiencies in GSH synthesis and regulation, may render individuals more susceptible to these developmental neurotoxic effects of OPs.