Oxidative effects of the acute exposure to a pesticide mixture of cypermethrin and chlorpyrifos on carp and zebrafish - A comparative study

Mixture toxic mechanism of phoxim and prochloraz in the hook snout carp Opsariichthysbidens

Pesticides are usually found as mixtures in surface water bodies, even though their regulation in aquatic ecosystems is usually approached individually. In this context, this work aimed to investigate the enzymatic- and transcriptional-level responses after the mixture exposure of phoxim (PHX) and prochloraz (PRC) in the livers of hook snout carp Opsariichthys bidens. These data exhibited that co-exposure to PHX and PRC induced an acute synergistic impact on O. bidens. The activities of catalase (CAT), superoxide dismutase (SOD), carboxylesterase (CarE), and caspase3 varied significantly in most of the individual and combined challenges relative to basal values, indicating the activation of oxidative stress, detoxification dysfunction, as well as cell apoptosis. Besides, the transcriptional levels of five genes (gst, erα, mn-sod, cxcl-c1c, and il-8) exhibited more pronounced changes when subjected to combined pesticide exposure in contrast to the corresponding individual compounds. The findings revealed the manifestation of endocrine dysfunction and immune disruption. These results underscored the potential biochemical and molecular toxicity posed by the combination of PHX and PRC to O. bidens, thereby contributing to a deeper comprehension of the ecological toxicity of pesticide mixtures on aquatic organisms. Importantly, the concurrent presence of PHX and PRC might exacerbate hepatocellular damage in hook snout carps, potentially attributable to their synergistic toxic interactions. This study underscored the toxicological potency inherent in the co-occurrence of PHX and PRC in influencing fish development, thereby offering valuable insights for the risk assessment of pesticide mixtures and the safeguarding of aquatic organisms.

The benefit of using in vitro bioassays to screen agricultural samples for oxidative stress: South Africa's case

Applied pesticides end up in non-target environments as complex mixtures. When bioavailable, these chemicals pose a threat to living organisms and can induce oxidative stress (OS). In this article, attention is paid to OS and the physiological role of the antioxidant defense system. South African and international literature was reviewed to provide extensive evidence of pesticide-induced OS in non-target organisms, in vivo and in vitro. Although in vitro approaches are used internationally, South African studies have only used in vivo methods. Considering ethical implications, the authors support the use of in vitro bioassays to screen environmental matrices for their OS potential. Since OS responses are initiated and measurable at lower cellular concentrations compared to other toxicity endpoints, in vitro OS bioassays could be used as an early warning sign for the presence of chemical mixtures in non-target environments. Areas of concern in the country could be identified and prioritized without using animal models. The authors conclude that it will be worthwhile for South Africa to include in vitro OS bioassays as part of a battery of tests to screen environmental matrices for biological effects. This will facilitate the development and implementation of biomonitoring programs to safeguard the South African environment.

Molecular and Biochemical Evidence of the Toxic Effects of Terbuthylazine and Malathion in Zebrafish

Our research sought to determine the molecular and biochemical effects of environmentally relevant exposure to commonly used chloro-s-triazine herbicide terbuthylazine and organophosphate insecticide malathion on zebrafish. To this aim, mature zebrafish were exposed to 2 and 30 µg L−1 terbuthylazine and 5 and 50 µg L−1 malathion alone and in combination for 14 days. Aside from the accumulation of TBARS and protein carbonyls, a decrease in antioxidants and succinate dehydrogenase activity, an increase in oxidized glutathione, and enhanced apoptosis via Caspase-3 and BAX overexpression were observed. Furthermore, terbuthylazine and malathion induced mitochondrial swelling (up to 210% after single exposure and up to 470% after co-exposure) and lactate dehydrogenase leakage (up to 268% after single exposure and up to 570% after co-exposure) in a concentration-dependent manner. Significant upregulation of ubiquitin expression and increased cathepsin D activity were characteristics that appeared only upon terbuthylazine exposure, whereas the induction of IgM was identified as the specific characteristic of malathion toxicity. Meanwhile, no alterations in the zebrafish hypothalamic-pituitary-thyroid axis was observed. Co-exposure increased the adverse effects of individual pesticides on zebrafish. This study should improve the understanding of the mechanisms of pesticide toxicity that lead to fish impairment and biodiversity decline.

Combined toxicities of cadmium and five agrochemicals to the larval zebrafish (Danio rerio)

Different pollutants usually co-exist in the natural environment, and the ecological and health risk assessment of agrochemicals needs to be carried out based on the combined toxicological effects of pollutants. To examine the combined toxicity to aquatic organisms, the effects of cadmium (Cd) and five pesticides (acetamiprid, carbendazim, azoxystrobin, chlorpyrifos, and bifenthrin) mixture on zebrafish (Danio rerio) larvae were assessed. The data from the 96-h toxicity test indicated that bifenthrin possessed the highest toxicity to D. rerio with the LC₅₀ value of 0.15 mg L^-1, followed by chlorpyrifos (0.36 mg L^-1) and azoxystrobin (0.63 mg L^-1). Cd (6.84 mg L^-1) and carbendazim (8.53 mg L^-1) induced the intermediate toxic responses, while acetamiprid (58.39 mg L^-1) presented the lowest toxicity to the organisms. Pesticide mixtures containing chlorpyrifos and bifenthrin or acetamiprid and carbendazim showed synergistic impacts on the zebrafish. Besides, two binary combinations of Cd-acetamiprid and Cd-chlorpyrifos also displayed a synergistic effect on D. rerio. Our results offered a better idea of the mixed ecological risk assessment of Cd and different agricultural chemicals to aquatic organisms. Our findings better interpreted how the interaction between Cd and various agrochemicals changed their toxicity to aquatic vertebrates and provided valuable insights into critical impacts on the ecological hazard of their combinations.

Pesticide Pollution: Detrimental Outcomes and Possible Mechanisms of Fish Exposure to Common Organophosphates and Triazines

Pesticides are well known for their high levels of persistence and ubiquity in the environment, and because of their capacity to bioaccumulate and disrupt the food chain, they pose a risk to animals and humans. With a focus on organophosphate and triazine pesticides, the present review aims to describe the current state of knowledge regarding spatial distribution, bioaccumulation, and mode of action of frequently used pesticides. We discuss the processes by which pesticides and their active residues are accumulated and bioconcentrated in fish, as well as the toxic mechanisms involved, including biological redox activity, immunotoxicity, neuroendocrine disorders, and cytotoxicity, which is manifested in oxidative stress, lysosomal and mitochondrial damage, inflammation, and apoptosis/autophagy. We also explore potential research strategies to close the gaps in our understanding of the toxicity and environmental risk assessment of organophosphate and triazine pesticides.

Toxic effects and mechanisms of common pesticides (Roundup and chlorpyrifos) and their mixtures in a zebrafish model (Danio rerio)

Agrochemicals can adversely affect biodiversity, environment and human health, and commonly occur in mixtures with poorly characterized toxic mechanisms and health hazards. Here, we evaluated the individual and mixture toxicities of Roundup and chlorpyrifos in environmentally relevant concentrations to zebrafish using molecular and biochemical indices. Studied pesticides alone and in combination caused depletion of total antioxidant capacity and cellular thiols, overproduction of ROS, accumulation of oxidative lesions and elevated DNA damage in zebrafish liver. Notably, low concentration of Roundup induced a hormesis-like effect by stimulating the protective cellular mechanisms. Chlorpyrifos showed stronger prooxidant effects than Roundup and additionally caused nitrosative and carbonyl stress in zebrafish. At the organismal level, studied pesticides and their mixtures induced hepato- and neurotoxicity. The effects of the studied pesticides on biomarkers of apoptosis, endocrine disruption and immune disorders were generally weak and inconsistent. The multibiomarker assessment showed that chlorpyrifos is considerably more toxic than Roundup to zebrafish. The toxic effects of the pesticide mixtures were mostly driven by chlorpyrifos, with minimal or mitigating effects of Roundup addition. These findings elucidate the toxic mechanisms of common pesticides in a model vertebrate and demonstrate that health hazards of pesticide mixtures cannot be predicted from the effects of single pesticides.

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

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

Transcriptomic and metabolomic investigation of metabolic disruption in Vigna unguiculata L. triggered by acetamiprid and cyromazine

A variety of pesticides are often used in agricultural management to control target pests but may trigger disruptions in the metabolism of nontarget organisms, ultimately affecting crop quality. Acetamiprid (ACE) and cyromazine (CYR) are two frequently used insecticides on cowpea, so it is critical to understand whether these two insecticides cause metabolic disorders in cowpea quality changes and the mechanism by which they do so. Here, we used metabolomic and transcriptomic methods to explore the mechanisms of the effects of ACE, CYR, and their mixture (MIX) on cowpea. In this study, ACE, CYR and MIX had no significant effects on plant biomass or growth status but decreased the contents of starch, soluble protein, and total flavonoids. All treatments reduced the total flavonoid content, but MIX showed the largest reduction of 10.02%. Metabolomic and transcriptomic analyses revealed that ACE markedly affected amino acid metabolism, and CYR and MIX affected sugar metabolism and flavonoid synthesis pathways. ACE and CYR reduced the levels of alanine, glutamic acid, isoleucine and phenylalanine and the expression of amino acid-related genes in cowpea, while MIX significantly increased the levels of most amino acids. All pesticide treatments reduced saccharide levels and related genes, with the most pronounced reduction in the MIX treatment. Exposure to ACE decreased the content of naringenin chalcone and quercetin and increased the content of anthocyanins in cowpeas, while MIX caused a significant decrease in the contents of quercetin and anthocyanins. According to the current study, single and mixed pesticides had different effects on the active ingredients of cowpea, with MIX causing the most significant decrease in the metabolite content of cowpea. These results provide important insights from a molecular perspective on how neonicotinoids and triazine insecticides affect cowpea metabolism.

Catechin from green tea had the potential to decrease the chlorpyrifos induced oxidative stress in larval zebrafish (Danio rerio)

Catechin is a biological compound in green tea (Camellia sinesis), which has anti-oxidant, anti-cancer, anti-apoptotic, anti-inflammatory, and attenuated effects in different experimental models. Chlorpyrifos (CPF), a broad-spectrum organophosphate insecticide, has resulted in oxidative stress, mitochondrial dysfunction, and apoptosis in zebrafish. The goal of this study is to assess whether catechin can alleviate CPF-induced oxidative damage and apoptosis in the early developmental stage of zebrafish. According to the results, we observed that 200 μg/L CPF exposure could induce oxidative stress, ROS production and changing the antioxidant-related enzymes and genes in larval zebrafish. Interestingly, catechin had the potential to reduce the oxidative damage and cell apoptosis caused by CPF exposure in larval zebrafish at different endpoints. Especially, catechin could promote the contents of GSH and activity of GST in zebrafish larvae injured by CPF, suggesting that catechin could repair oxidative damage at a certain degree by regulating the activities and gene transcription of some key enzymes related to GSH pathway in zebrafish. In addition, at transcriptional levels, a high concentration of catechin exposure reduced the expression genes of Mn-SOD, Cat, gst, and GPX induced by CPF in larval zebrafish. These genes mainly reflected the degree of oxidative damage of zebrafish, which was basically consistent with the enzyme activity. Catechin also could reduce the transcription of p53 and bax, which are tightly related to the apoptosis induced by CPF in zebrafish larvae. The expression of genes was consistent with ROS production, which proved that catechin could alleviate the apoptosis induced by CPF. This study discovered that catechin had some antioxidant effects in aquatic animals to reduce the toxicity caused by pesticides and offered the scientific basis for the utilization and development of catechin.

Vitamin C Mitigates Oxidative Stress and Behavioral Impairments Induced by Deltamethrin and Lead Toxicity in Zebrafish

Environmental contamination from toxic metals and pesticides is an issue of great concern due to their harmful effects to human health and the ecosystems. In this framework, we assessed the adverse effects when aquatic organisms are exposed to toxicants such as deltamethrin (DM) and lead (Pb), alone or in combination, using zebrafish as a model. Moreover, we likewise evaluated the possible protective effect of vitamin C (VC) supplementation against the combined acute toxic effects of the two toxicants. Juvenile zebrafish were exposed to DM (2 μg L^-1) and Pb (60 μg L^-1) alone and in combination with VC (100 μg L^-1) and responses were assessed by quantifying acetylcholinesterase (AChE) activity, lipid peroxidation (MDA), some antioxidant enzyme activities (SOD and GPx), three-dimension locomotion responses and changes of elements concentrations in the zebrafish body. Our results show that VC has mitigative effects against behavioral and biochemical alterations induced by a mixture of contaminants, demonstrating that it can be used as an effective antioxidant. Moreover, the observations in the study demonstrate zebrafish as a promising in vivo model for assessing the neuroprotective actions of bioactive compounds.

Heavy metal toxicity in Buriganga river alters the immunology of Nile tilapia (Oreochromis niloticus L)

The objective of the current study was to evaluate the biochemical and immunological responses of tilapia, Oreochromis niloticus due to heavy metals pollution. Histomorphological alterations in the liver and kidney suggested tissue damages due to this polluted water exposure. The brain acetylcholinesterase (AChE) as an indicator of neurotoxicity was significantly (P < 0.01) decreased after 10 days exposure of fish to heavy metal contained river water, while plasma glutamate oxalacetate transaminase and plasma glutamate pyruvate transaminase were significantly increased (P < 0.01). Moreover, superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase enzyme activities, as well as reduced glutathione and malondialdehyde levels were significantly increased in heavy metals contained river water treated fish compared to the control. Additionally, glucose level and blood serum Ca2+ concentrations were significantly (P < 0.01) decreased in fish exposed to heavy metal contained river water compared to the control. Hematological indices such as Hemoglobin, RBC, WBC, MCV etc. of polluted river water treated fish were significantly (P < 0.01) different in comparison to that of control fish. The cytokines i.e. IL-1β, IL-6, and TNF-α level were significantly (P < 0.01) increased in the fish exposed to heavy metals contained river water in comparison to that of control fish. The present findings explored the detrimental effects of heavy metal contained river water on fish at biochemical and immunological levels.

Is the Synthetic Fungicide Fosetyl-Al Safe for the Ecotoxicological Models Danio rerio and Enchytraeus crypticus?

Worldwide, pesticides have contaminated the environment, affecting non-target species. The aim of this work was to evaluate the effects of fosetyl-Al (FOS) on model organisms. Based on the 3 Rs for animal research and described guidelines, the OECD 236 and 220 were applied with some modifications. The FOS test concentrations were 0.02–0.2–2–20–200 mg/L for Danio rerio and 250–500–750–1000–1250 mg/kg for Enchytraeus crypticus. Besides the standard endpoints, additional endpoints were evaluated (D. rerio: behavior and biochemical responses; E. crypticus: extension of exposure duration (28 d (days) + 28 d) and organisms’ sizes). For D. rerio, after 96 h (h), hatching was inhibited (200 mg/L), proteins’ content increased (2 and 20 mg/L), lipids’ content decreased (2 mg/L), glutathione S-transferase activity increased (2 mg/L), and, after 120 h, larvae distance swam increased (20 mg/L). For E. crypticus, after 28 d, almost all the tested concentrations enlarged the organisms’ sizes and, after 56 d, 1250 mg/kg decreased the reproduction. In general, alterations in the organisms’ biochemical responses, behavior, and growth occurred at lower concentrations than the effects observed at the standard endpoints. This ecotoxicological assessment showed that FOS may not be considered safe for the tested species, only at higher concentrations than the predicted environmental concentrations (PECs). This research highlighted the importance of a multi-endpoint approach to assess the (eco)toxic effects of the contaminants.

Which Is More Toxic? Evaluation of the Short-Term Toxic Effects of Chlorpyrifos and Cypermethrin on Selected Biomarkers in Common Carp (Cyprinus carpio, Linnaeus 1758)

The general aim of this study was to investigate the negative short-term effects of different concentrations of chlorpyrifos (CPF) and cypermethrin (CYP), based on the EU legislation (MAC-EQS) in common carp (Cyprinus carpio Linnaeus, 1758) under laboratory conditions and to compare their toxicity. The fish were exposed to the pesticides for 96 h and then different histological and biochemical biomarkers were investigated in the gills and liver, and bioaccumulation analyses were conducted. The chemical studies showed increased pesticide concentrations in the gills as the first site for pollutants compared to the liver at the 96th hour. In addition, the histological analyses showed severe alterations in the gills and liver after exposure to both tested pesticides. In the gills, we found mainly intense proliferative and, to a lesser extent, degenerative changes and alterations in the circulatory system, such as necrosis and vasodilation. In the liver, regressive and progressive lesions, as well as circulatory disturbances and inflammation, were observed. The regressive lesions showed a higher degree of expression compared to the other changes. Furthermore, we found altered enzymatic activities—catalase, glutathione reductase, and glutathione peroxidase—in the liver, compared to the control. Overall, both tested pesticides impacted the studied biomarkers in common carp, even at concentrations lower than those permitted by law. However, the results of the comparative analysis showed a relatively higher toxicity of CYP compared to CPF in the fish. Still, questions persist as to whether the observed changes are adaptive or entirely destructive. To avoid any danger or risk, these pesticides must be applied cautiously, especially near water bodies.

The Toxic Effects of Glyphosate, Chlorpyrifos, Abamectin, and 2,4-D on Animal Models: A Systematic Review of Brazilian Studies

Brazil is a global agricultural commodity producer and the largest consumer of pesticides. Pesticide use in Brazil comprised 549 280 tons in 2018. In the country, soybean, corn, and sugar cane are extensively produced, which are the most pesticides demanding crops. In the last years, the records of new pesticides were the highest in the historical series. They can persist in soil or water, accumulate in organisms, and contaminate workers and the general population through the air, water, or food. This review aimed to gather toxicological data obtained by animal models exposed to 4 pesticides: glyphosate, chlorpyrifos, abamectin, and 2,4-D. An additional goal was to compose an overview of how this subject has been approached, surveying which research groups are working on this field, where they are located, and relations with pesticides used in those regions. We collected the papers from the platforms PubMed, Scopus, Scielo, and Web of Science, performed in Brazil from 2014 to 2019. After two-step blind selection using the software Rayyan QCRI by different authors, 67 studies were selected to extract data. We observed that research is more concentrated in the South region, followed by the Southeast and Midwest, with 43%, 32%, and 23% of the studies, respectively. The prevalent institutions are from the states of Rio Grande do Sul, São Paulo, and Goiás. The effects on a variety of biomarkers help predict the potential risks to humans and nontarget organisms. The prevalent animal model was fish (36%). Overall, the main toxic effects evaluated were mortality, abnormalities in the blood cells, developmental abnormalities, and behavior alterations. Integr Environ Assess Manag 2021;17:507-520. © 2020 SETAC.

Mixture toxicity of thiophanate-methyl and fenvalerate to embryonic zebrafish (Danio rerio) and its underlying mechanism

Though pesticide mixtures can reflect the real-life situation in the water ecosystem, the quantification of their toxicity is still not fully understood. Combined effects of thiophanate-methyl (THM) and fenvalerate (FEN) on embryonic zebrafish (Danio rerio) and underlying mechanism were conducted in this study. Results showed that the 96-h LC₅₀ values of THM to D. rerio at different growth periods ranged from 12.1 to 26.1 mg L^-1, which were lower in comparison with those of FVR ranging from 0.025 to 2.8 mg L^-1. Mixture of THM and FVR exhibited a synergetic response to zebrafish embryos. Activities of Cu/Zn-SOD, POD, caspase 3 and caspase 9 were significantly different in most of single and mixture administrations compared with the control group. In addition, five genes (P53, Cu/Zn-sod, crh, ERα and IL-8) associated with oxidative stress, cellular apoptosis, immune system and endocrine system showed greater variations of expressions when administrated to pesticide mixtures compared with single chemicals. Our experimental results exhibited that mixtures of thiophanate-methyl and fenvalerate produced higher toxicity towards aqueous vertebrates than when determined singly. Collectively, upcoming environmental risk assessments established according to single administrations might not be enough to protect the water ecosystem.

Ameliorative effect of Fennel (Foeniculum vulgare) essential oil on chlorpyrifos toxicity in Cyprinus carpio

Chlorpyrifos (CPF) is an organophosphate pesticide that is frequently and widely used to control both agricultural and domestic pests worldwide. In this study, the protective effect of Fennel (Foeniculum vulgare) essential oil (FEO) was investigated in carp (Cyprinus carpio) exposed to CPF. The fish were divided into six groups that one control group (no treatment) and five experimental groups (FEO (3ml/100g diet) group, CPF₁ (0.023 mg/l) group CPF₂ (0.046 mg/l) group, CPF₁ (0.023 mg/l) plus FEO (3ml/100g diet) group, CPF₂ (0.046 mg/l) plus FEO (3ml/100g diet) group). Blood and tissue (liver, kidney, gill, and brain) samples were taken from the fish at the end of 14 days of application. Hemoglobin (Hb) level, nitoblue tetrazolium (NBT) activity, and total immunoglobulin (TI) level were measured in blood samples of fish. Acetylcholinesterase (AChE) activity was determined in brain tissue while malondialdehyde (MDA) level, reduced glutathione (GSH) level, catalase (CAT), and glutathione peroxidase (GPx) activity were determined in liver, kidney, and gill tissues. The results showed that there was a significant decrease in Hb level, NBT activity, and TI levels in CPF-treated fish compared to the control group. In addition, increased in MDA levels and significant decreases in GSH level, AChE, CAT, and GPx activities were observed in CPF-treated groups. However, FEO-treated was showed a significant improvement in all parameters except AChE activity compared to CPF groups. These study findings showed that FEO could improve CPF-induced toxicity in C. carpio, except inhibition of AChE activity.

Effects of cypermethrin on the hepatic transcriptome and proteome of the red claw crayfish Cherax quadricarinatus

Cypermethrin (CYP) is a synthetic pyrethroid broadly used for pest control, however, it is extremely toxic to aquatic organisms. To assess the toxicity of CYP in red claw crayfish Cherax quadricarinatus, transcriptional and proteomic approaches combining two-dimensional polyacrylamide gel electrophoresis and tandem mass spectrometry were used to compare the hepatic expression profiles. A total of 41,349 unigenes and 8839 differentially expressed genes (DEGs) were obtained, which were enriched in the process. The category of 779 (0.625 ng L^-1 CYP vs Con), 1963 (1.25 vs Con), and 2066 (1.25 vs 0.625) DEGs were screened. All findings suggested that CYP can induce antioxidant and biotransformation modulation variations in C. quadricarinatus to resist immunotoxicity and oxidative damages. The category of 196 (0.625 ng L^-1 CYP vs Con) specific proteins were differentially expressed: 24 proteins were upregulated, and 20 proteins were downregulated relative to CYP. Protein identification indicated the KEGG pathways of the human immunodeficiency virus 1 infection, insulin signaling pathway, and influenza A enriched. From the differential expression of the selected nine proteins, the increased Loc113824800, Rps19, Atp2, Rps10, Hsp40, Brafldraft_124327, and the decreased Loc117331934, Loc113213835, and Loc106806551 revealed. While for the verification of the eight genes in transcriptome and the above nine genes in proteomic, specifically, gpx5, ggt, loc106458463, chelonianin decreased in the 0.625 ng L^-1 CYP group. The transcripts of loc113816050, akr1d1 and gst, chelonianin and loc108675455 decreased and increased in the 1.25 ng L^-1 CYP group, respectively. The present study reflects the overall change in cellular structure and metabolism related to the resistance of pyrethroid insecticides.

Synergistic effect of fenpropathrin and paclobutrazol on early life stages of zebrafish (Danio rerio)

Aquatic organisms are usually exposed to various co-existing pollutants. However, toxic effects of pesticide mixtures on aquatic organisms and its potential underlying mechanism still remain unclear. The joint effects of fenpropathrin (FEN) and paclobutrazol (PAC) on zebrafish (Danio rerio) using diverse toxicological endpoints were investigated in the current work. Our data exhibited that the 96-h LC₅₀ values of FEN to zebrafish at multiple life phases ranged from 0.0029 (0.0013-0.0042) to 0.16 (0.082-0.23) mg a.i. L^-1, which were lower by comparison to PAC ranging from 13.16 (8.564-21.03) to 23.43 (17.94-29.91) mg a.i. L^-1. Combination of FEN and PAC displayed synergistic effect on embryonic zebrafish. Activities of T-SOD, Cu/Zn-SOD and CYP450 were remarkably changed in the majority of single and mixture treatments by comparison to the untreated group. The mRNA levels of 17 genes related to oxidative stress, cellular apoptosis, immune system and endocrine system were assessed, and the data suggested that embryonic zebrafish were affected by both single pesticides and their mixtures. Five genes (P53, tsh, ERα, crh and cxcl-clc) showed greater alterations when exposed to pesticide mixtures by comparison to their individual chemicals. Therefore, it is urgently necessary to conduct more studies on mixture toxicities of different pesticides to explore the chemical mixtures with synergistic interactions.

Zebrafish as an Emerging Model System in the Global South: Two Decades of Research in Brazil

The zebrafish (Danio rerio) is an emerging model system in several research areas worldwide, especially in the Global South. In this context, the present study revised the historical use and trends of zebrafish as experimental models in Brazil. The data concerning the bibliometric parameters, research areas, geographic distribution, experimental design, zebrafish strain, and reporter lines, as well as recent advances were revised. In addition, the comparative trends of Brazilian and global research were discussed. Revised data showed the rapid growth of Brazilian scientific production using zebrafish as a model, especially in three main research areas (Neuroscience &and Behavior, Pharmacology and Toxicology, and Environment/Ecology). Studies were conducted in 19 Brazilian states (70.37%), confirming the wide geographic distribution and importance of zebrafish research. Results indicated that research related to toxicological approaches are widespread in Global South countries such as Brazil. Studies were performed mainly using in vivo tests (89.58%) with adult fish (59.75%) and embryos (30.67%). Moreover, significant research gaps and recommendations for future research are presented. The present study shows that the zebrafish is a suitable vertebrate model system in the Global South.

Polyps of the Jellyfish Aurelia aurita Are Unaffected by Chronic Exposure to a Combination of Pesticides

Pesticides are a major contaminant in coastal waters and can cause adverse effects in marine invertebrates such as jellyfish. Most studies have investigated short-term responses of organisms to unrealistically high concentrations of pesticides; however, chronic exposure to persistent low concentrations, which are more likely to occur in the environment, are rarely analyzed. We tested the response of polyps of the moon jellyfish Aurelia aurita to environmental concentrations of the herbicide atrazine and the insecticide chlorpyrifos, individually and in combination, over 9 wk. We hypothesized that exposure to individual pesticides would reduce rates of asexual reproduction and alter polyps' metabolite profiles, and that the results would be more severe when polyps were exposed to the combined pesticides. Polyps survived and reproduced (through budding) in all treatments, and no differences among treatments were observed. Proton nuclear magnetic resonance spectroscopy revealed no difference in profiles of polar metabolites of polyps exposed to the individual or combined pesticides. Our results suggest that A. aurita polyps are unaffected by chronic exposure to atrazine and chlorpyrifos at concentrations recommended as being protective by current Australian water quality guidelines. Environ Toxicol Chem 2020;39:1685-1692. © 2020 SETAC.

Multi-Biomarker Assessment in Common Carp (Cyprinus carpio, Linnaeus 1758) Liver after Acute Chlorpyrifos Exposure

The excessive use of pesticides at different stages of crop production can pose a great danger to the aquatic environment, and particularly to fish. The purpose of the present work was to assess the negative effects of chlorpyrifos (CPF) on the liver histological architecture and the activities of marker enzymes in common carp (Cyprinus carpio Linnaeus, 1758), by applying a multi-biomarker technique. The tested insecticide is categorized as a priority pollutant in surface waters in terms of Directive 2013/39/EU. The carps were exposed to different and environmentally relevant CPF concentrations for 72 h (a short-term acute experiment). The results showed that the tested insecticide alters the liver histological structure, causing degenerative lesions, such as granular and vacuolar degeneration; necrobiotic alterations and necrosis, as well as changes in the circulatory system. In addition, CPF induces changes in the enzymatic activity of lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), cholinesterase (ChE), glutathione peroxidase (GPx) and catalase (CAT). The results from such experimental set ups could be successfully used in the legislation related to the protection of water bodies from contamination, in areas with intensive application of plant protection products used in agricultural practices, and also in implementing the Water Frame Directive by using multi-biomarker approaches.

Assessment of River Water Quality in an Agricultural Region of Brazil Using Biomarkers in a Native Neotropical Fish, Astyanax spp. (Characidae)

Intensive agricultural and livestock activities demand high pesticide use and, consequently, contaminants reach aquatic ecosystems. In the lower Jacuí River, southern Brazil, there is a lack of knowledge about pesticide residues in water samples and the biochemical responses in native fish species. Thus, this study aimed to estimate the influence of pesticide residues and water parameters to biomarker responses in the native fish Astyanax spp. We performed seasonal biomonitoring in 2017 with water samples and fish collections. Biomarkers of oxidative stress, antioxidants, biotransformation, and neurotoxicity were analyzed in fish tissues. Fourteen pesticide residues were detected; they presented correlations with detoxification enzyme and oxidative stress biomarkers. These data indicate that most of variations can be related to the pesticide presence in water indicating high aquatic pollution in this place.

An influential meal: host plant dependent transcriptional variation in the beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae)

BACKGROUND

To understand the genetic mechanisms of insect herbivory, the transcriptional response of insects feeding on different host plant species has to be studied. Here, we generated gene expression data of the generalist herbivore Spodoptera exigua (Hübner) feeding on three selected host plant species and a control (artificial diet). The host plant species used in this study -cabbage (Brassica oleracea), maize (Zea mays) and tobacco (Nicotiana tabacum)- are members of different plant families that each employ specific defence mechanisms and toxins.

RESULTS

Spodoptera exigua larvae had a higher growth rate, indicator for herbivore success, when feeding on Z. mays compared to larvae feeding on B. oleracea or N. tabacum. Larvae feeding on the different host plant species showed divergent transcriptional responses. We identified shared and unique gene expression patterns dependent of the host plant species the larvae fed on. Unique gene expression patterns, containing uniquely upregulated transcripts including specific detoxification genes, were found for larvae feeding on either B. oleracea or N. tabacum. No diet-specific gene cluster was identified for larvae feeding on the host for which larvae showed optimal herbivore success, Z. mays, or artificial diet. In contrast, for larvae feeding on hosts for which they showed low herbivore success, specific diet-dependent gene clusters were identified. Functional annotation of these clusters indicates that S. exigua larvae deploy particular host plant-specific genes for digestion and detoxification.

CONCLUSIONS

The lack of a host plant-specific gene activity for larvae feeding on Z. mays and the artificial diet suggest a general and non-specific gene activity for host plants with optimal herbivore success. Whereas the finding of specific gene clusters containing particular digestion and detoxifying genes expressed in larvae feeding on B. oleracea and N. tabacum, with low herbivore success, imply a host plant-specific gene activity for larvae feeding on host plants with suboptimal herbivore success. This observation leads to the conclusion that a polyphagous herbivore is able to feed on a large variation of host plants due to the flexibility and diversity of genes involved in digestion and detoxification that are deployed in response to particular host plant species.

Nrf2 mediates the protective effect of edaravone after chlorpyrifos-induced nervous system toxicity

We aim to confirm the impairment of chlorpyrifos (CPF) in PC12 cells, evaluate the protective effect of edaravone on CPF-induced injury, and try to unravel its underlying mechanism perspective from Nrf2 signaling pathway. Viability of PC12 cells treated with CPF and edaravone (Ed) were evaluated by MTT assay. Cell apoptosis was observed by the Hoechst 33342 stain. The level of reactive oxygen species (ROS), the content of malondialdehyde (MDA), and the activity of superoxide dismutase (SOD) were detected to evaluate the oxidative stress injury. The expression of Nrf2 was detected by Western blot; profoundly, RNA interference was conducted to construct Nrf2 gene knockdown PC12 cells and to uncover its underlying mechanism. MTT results showed CPF injured PC12 cells in a concentration-dependent manner. Increased ROS and MDA content, decreased total SOD activity, or even apoptosis were occurred in PC12 cells when treated with CPF. Interestingly, CPF-induced cell injury was conspicuously reversed after Ed administration. Nrf2 signaling pathway was activated after Ed treatment and the neuroprotective effect of Ed was not significant in cells after Nrf2 gene knockdown. In conclusion, Ed exerts neuroprotective effect on CPF-induced oxidative stress injury and its mechanism was correlated with the Nrf2 signaling pathway.