Oxidative injury caused by individual and combined exposure of neonicotinoid, organophosphate and herbicide in zebrafish

Effects of 2,4,6-Trichloroanisole on the morphological development and motility of zebrafish

2,4,6-Trichloroanisole (2,4,6-TCA), a compound with a characteristic earthy odor, is a common source of odorous pollutants in drinking water and wine. However, research on its biological toxicity is limited. In this study, we used zebrafish as an indicator model to investigate the effects of 2,4,6-TCA exposure on morphological development, oxidative stress, apoptosis, heart rate, blood flow, and motility. We found that exposure to 2,4,6-TCA resulted in significant spinal, tail, and cardiac deformities in zebrafish larvae and promoted a pronounced oxidative stress response and extensive cell apoptosis, notably in the digestive tract, head, spine, and heart, ultimately leading to significant reductions in zebrafish heart rate, blood flow, and motility. Moreover, these effects became more pronounced with an increase in the concentration of 2,4,6-TCA to which the zebrafish were exposed. Furthermore, qPCR analysis revealed that exposure to 2,4,6-TCA promoted significant changes in the expression levels of genes associated with oxidative stress, apoptosis, cardiac development, and the nervous system, particularly key genes (p53, apaf1, casp9, and casp3) in the mitochondrial apoptotic pathway, which were significantly upregulated. Similarly, we detected significant upregulation of ache gene expression. These findings indicated that exposure to 2,4,6-TCA resulted in the accumulation of reactive oxygen species in zebrafish, induced strong oxidative stress responses, and triggered lipid peroxidation and extensive cell apoptosis. Cellular apoptosis, which mitochondrial signaling pathways may mediate, has been found to lead to malformations in zebrafish embryos, resulting in significant reductions in cardiac function and motility. To our knowledge, this is the first systematic assessment of the toxicity of 2,4,6-TCA, and our findings provide an important reference for risk assessment and early warning of 2,4,6-TCA exposure.

The Nrf2/ARE pathway as a potential target to ameliorate atrazine-induced endocrine disruption in granulosa cells

Atrazine (ATR) is widely used worldwide as a commercial herbicide, Diaminochlorotriazine (DACT) is the main metabolite of ATR in the organism. Both of them disrupt the production of steroids and induce abnormal reproductive development. The granulosa cells (GCs) are important for growth and reproduction of animals. However, the toxicity of ATR on the GCs of birds is not well clarified. To evaluate the effect of the environmental pollutant ATR on bird GCs. The quail GCs were allotted into 7 groups, C (The medium of M199), A20 (20 µM ATR), A100 (100 µM ATR), A250 (250 µM ATR), D20 (20 µM DACT), D100 (100 µM DACT) and D200 (200 µM DACT). The results demonstrated that ATR reduced the viability of GCs, disrupted mitochondrial structure (including mitochondrial cristae fragmentation and the mitochondrial morphology disappearance) and decreased mitochondrial membrane potential. Meanwhile, ATR interfered with the expression of key factors in the steroid synthesis pathway, inducing the secretion of the sex hormones E2 and P in GCs. which in turn induced apoptosis. Furthermore, the Nrf2/ARE pathway as a potential target to ameliorate ATR-induced endocrine disruption in GCs for proper reproductive functions. Our research provides a new perspective for understanding the effects of ATR on reproductive functions in birds.

Behavioral Effects of the Mixture and the Single Compounds Carbendazim, Fipronil, and Sulfentrazone on Zebrafish (Danio rerio) Larvae

Pesticides are often detected in freshwater, but their impact on the aquatic environment is commonly studied based on single compounds, underestimating the potential additive effects of these mixtures. Even at low concentrations, pesticides can negatively affect organisms, altering important behaviors that can have repercussions at the population level. This study used a multi-behavioral approach to evaluate the effects of zebrafish larvae exposure to carbendazim (C), fipronil (F), and sulfentrazone (S), individually and mixed. Five behavioral tests, thigmotaxis, touch sensitivity, optomotor response, bouncing ball test, and larval exploratory behavior, were performed to assess potential effects on anxiety, fear, and spatial and social interaction. Significant changes were observed in the performance of larvae exposed to all compounds and their mixtures. Among the single pesticides, exposure to S produced the most behavioral alterations, followed by F and C, respectively. A synergistic effect between the compounds was observed in the C + F group, which showed more behavioral effects than the groups exposed to pesticides individually. The use of behavioral tests to evaluate pesticide mixtures is important to standardize methods and associate behavioral changes with ecologically relevant events, thus creating a more realistic scenario for investigating the potential environmental impacts of these compounds.

Herbicides and pesticides synergistically interact at low concentrations in complex mixtures

Assessing a complex mixture of pesticides at the impacted sites has been challenging for risk assessors for 50 years. The default assumption is that at low concentrations, pesticides interact additively with one another; thus, the risk posed by each component of a complex mixture could be simply added up. The EPA interaction-based hazard index (HIInteraction) modifies this assumption using a binary weight-of-evidence (BINWOE). However, data gaps often preclude HIInteraction use at most sites. This study evaluated these assumptions using the BINWOE to estimate the hazard index (HI) of select pesticide mixtures. The lack of in vivo binary interaction data led us to use a cell line, SH-SY5Y, to obtain the data necessary for the BINWOE approach. In the risk assessment, we considered the most active exposure scenario inhaling a mixture of volatile pesticides from contaminated soil and groundwater. The potential interactions between pesticides in 15 binary mixtures were investigated using the MTT assay in SH-SY5Y cells. Our findings showed that 60% of the binary mixtures elicited synergism (in at least one concentration), 27% displayed antagonism, and 13% showed additive effects in SH-SY5Y cells. Combining human safety data with in vitro interaction data indicated that adults and toddlers were at the highest risk when considering industrial and commercial land use, respectively, compared to other subpopulations. Incorporating interaction data into the risk assessment either increased the risk by up to 20% or decreased the risk by 2%, depending on the mixture. Our results demonstrate the predominant synergistic interactions, even at low concentrations, altered risk characterization at the complex operating site. Most concerning, organochlorine pesticides with the same mechanism of action did not follow dose additivity when evaluated by SH-SY5Y cell lines. Based on our observations, we caution that current HI methods based on additivity assumptions may underestimate the risk of organochlorine mixtures.

Physiological responses of oxidative damage, genotoxicity and hematological parameters of the toxic effect of neonicotinoid-thiamethoxam in Oreochromis niloticus

The purpose of investigation assessed the impacts of neonicotinoid thiamethoxam (TMX) at sublethal concentrations in hematological profile and renal function of Oreochromis niloticus. In the experiment, fish were exposed to TMX in four groups (0, 50, 100 and 150 ppm) for 7 days. At the end of the experiment, biochemical analysis of blood samples showed that the parameters indicating renal function showed a significant increase in serum enzymes ALT, AST, ALP and metabolites (BUN, urea, uric acid, creatinine and cortisol) concentrations, while albumin concentration decreased in a dose-dependent manner compared to the control group. In parallel with the decrease in Na+, K+ and Ca+2 in blood ion levels, there was a significant decrease in the activity of Na+/K+ ATPase, Ca+2 ATPase and AChE enzyme, levels of GSH and HSP70 in kidney tissue in TMX groups compared to the control group. It was determined that the toxic effect of TMX caused a significant increase in TBARS, PC, 8-OHdG levels, respectively. In conclusion, our study shows that TMX causes dose-dependent toxic effects, with knock-on effects on physiological processes regarding the hematological profile and renal function of O. niloticus.

Antioxidant enzyme activity and pathophysiological consequences in the sludge worm Tubifex tubifex under acute and sub-lethal exposures to the fungicide Tilt ®

This study aimed to evaluate the effects of propiconazole on the tubificid segmented worm, Tubifex tubifex. The animals were exposed to various concentrations of propiconazole for 96 h to assess the acute effect of this fungicide and for subacute level animals were exposed for 14 days with 10% and 20% of the 96 h LC50 value (0.211 and 0.422 mg/l, respectively). The 96 h LC50 value was determined to be 2.110 mg/l, and sublethal propiconazole concentrations caused significant changes in the oxidative stress enzymes. When compared to control organisms, superoxide dismutase (SOD) and catalase (CAT) activity first decreases and then significantly increases on days 7 and 14. However, GST activity decreases and MDA concentration rises in a concentration- and time-dependent manner throughout the exposure period. In addition, the impacts of propiconazole on Tubifex tubifex were characterized and depicted using a correlation matrix and an integrated biomarker response (IBR) assessment. These findings suggest that exposure to this fungicide distorts the survivability and behavioral response in Tubifex tubifex at the acute level. In addition, it modulates changes in oxidative stress enzymes at the sublethal level. Furthermore, the species sensitivity distribution curve indicates that this tubificid worm has a high risk of survival in the presence of the fungicide propiconazole in aquatic ecosystems.

Biochemical and gene expression alterations due to individual exposure of atrazine, dichlorvos, and imidacloprid and their combination in zebrafish

In environmental toxicology, combined toxicity has emerged as an important concern. Atrazine (ATZ), dichlorvos (DIC), and imidacloprid (IMD) are the major pesticides, extensively used to control insect, flies, mosquitoes, and weed. Here, we investigate whether the exposure to three different types of pesticides individually and in combination for 24 h alters antioxidant enzyme responses in zebrafish (Danio rerio). Oxidative stress parameters (biochemical and mRNA expression), acetylcholinesterase (AChE) activity, and Metallothionein-II (MT-II) mRNA expression levels were measured. Present work includes toxicological assessment of individual and combined (CMD) exposure of ATZ (185.4 µM), DIC (181 µM), IMD (97.8 µ), and CMD (ATZ 92.7 µM + DIC 90.5 µM + IMD 48.9 µM), in the liver, kidney, and brain of adult zebrafish. Lipid peroxidation (LPO), glutathione (GSH) content, AChE, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity along with mRNA expression of SOD, CAT, GPx, and MT-II were evaluated. Briefly, LPO, GSH content, the activity of AChE, and all antioxidant enzymes enhanced significantly in individual exposure, which was further altered in the CMD group. The mRNA expression of SOD, CAT, GPx, and MT-II in the liver and kidney showed significant down-regulation in all exposed groups. In the brain, significant upregulation in mRNA expression of SOD, CAT, GPx, and MT-II was observed in DIC and IMD groups, while ATZ and CMD showed significant downregulation except for GPx. Findings postulate that the CMD group exhibits synergistic toxic manifestation. The present study provides the baseline data on the combined toxic effects of pesticides and suggests regulating the use of pesticides.

Impacts of neonicotinoids on biodiversity: a critical review

Neonicotinoids are the most widely used class of insecticides in the world, but they have raised numerous concerns regarding their effects on biodiversity. Thus, the objective of this work was to do a critical review of the contamination of the environment (soil, water, air, biota) by neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid, thiamethoxam) and of their impacts on terrestrial and aquatic biodiversity. Neonicotinoids are very frequently detected in soils and in freshwater, and they are also found in the air. They have only been recently monitored in coastal and marine environments, but some studies already reported the presence of imidacloprid and thiamethoxam in transitional or semi-enclosed ecosystems (lagoons, bays, and estuaries). The contamination of the environment leads to the exposure and to the contamination of non-target organisms and to negative effects on biodiversity. Direct impacts of neonicotinoids are mainly reported on terrestrial invertebrates (e.g., pollinators, natural enemies, earthworms) and vertebrates (e.g., birds) and on aquatic invertebrates (e.g., arthropods). Impacts on aquatic vertebrate populations and communities, as well as on microorganisms, are less documented. In addition to their toxicity to directly exposed organisms, neonicotinoid induce indirect effects via trophic cascades as demonstrated in several species (terrestrial and aquatic invertebrates). However, more data are needed to reach firmer conclusions and to get a clearer picture of such indirect effects. Finally, we identified specific knowledge gaps that need to be filled to better understand the effects of neonicotinoids on terrestrial, freshwater, and marine organisms, as well as on ecosystem services associated with these biotas.

Endocrine disruptive toxicity of cypermethrin in Labeo catla: Involvement of genes and proteins related to the HPG axis

Cypermethrin (CYP) is a synthetic pyrethroid abundantly used in agriculture and aquaculture. It is an established potent endocrine disruptor to fish, yet the molecular mechanism behind its reproductive toxicity remains unclear. In this study, fish Labeo catla (Catla) was exposed to environmentally relevant concentration of CYP (0.7 μg/L) and 0.14 μg/L for 30 days. The changes in circulating sex steroids, genes, and hormones linked to the hypothalamic-pituitary-gonadal (HPG) axis, stress response and associated histological alterations were studied. Significant decline (P < 0.05) in serum 17 beta (β) estradiol (E2), 11 ketotestosterone (11-KT), and brain (FSH and GnRH) were observed in 0.7 μg/L dose of CYP. These effects may be due to the down-regulated expression of the upstream genes of the HPG axis i.e. Kiss 1 and Kiss 2, which further downregulates the expression of the GnRH gene. The decreased level of E2 and 11-KT also affects the vitellogenin (Vtg) gene expression, reducing the production of Vtg, a crucial protein for ovarian development. Principal component analysis (PCA) revealed the relationship between CYP and the biosynthesis of sex steroids. The toxic effect of CYP was also visible in antioxidant enzyme assay and related histological alterations. Overall, the study elucidated that long-term exposure to CYP, even at an environmentally relevant dose, may affect reproductive potential and fish recruitment. The study provides important insights into molecular mechanisms underlying CYP-induced endocrine disruption in fish, and it also raises questions about CYP's potential toxicity at environmentally relevant concentration in terms of understanding ecological risk.

Co-exposure of avermectin and imidacloprid induces DNA damage, pyroptosis, and immune dysfunction in epithelioma papulosum cyprini cells via ROS-mediated Keap1/Nrf2/TXNIP axis

Pesticide mixtures can reduce pest resistance, however, their overuse severely threatens aquatic animal survival and public health. Avermectin (AVM) and imidacloprid (IMI) are potent insecticides often employed in agriculture. By inducing oxidative stress, these chemicals can induce cell death. Here, we evaluated the combined toxicity of AVM and IMI on EPC cells based on the concept of toxicity units (TU). We established EPC cell models exposed to AVM and IMI alone and in combination. The results showed that AVM and IMI had additive effects on the toxicity of EPC cells. Meanwhile, the co-exposure of AVM and IMI exacerbated oxidative stress and induced excessive production of reactive oxygen species (ROS), triggered Keap1/Nrf2/TXNIP axis, caused DNA damage and increased the expression of genes related to pyroptosis. In addition, co-exposure to AVM and IMI caused immunosuppression of EPC cells. The ROS inhibitor N-Acetyl-l-cysteine (NAC) can dramatically reverse these alterations brought on by AVM and IMI co-exposure. The findings above conclude that co-exposure to AVM and IMI causes DNA damage, pyroptosis, and immunosuppression in EPC cells through the ROS-mediated Keap1/Nrf2/TXNIP pathway. This study revealed the joint toxicity of AVM and IMI on EPC cells, and reminded people to consider its impact on aquatic animals when using pesticide mixtures.

Using proteomics, q-PCR and biochemical methods complementing as a multiapproach to elicit the crucial responses of zebrafish liver exposed to neonicotinoid pesticide

Pesticides enter the environment through runoff and leaching and this raises public concern about effects on non-target organisms. Imidacloprid (IMI) a synthetic pesticide, has an unstable half-life, metabolized in minutes to weeks in the water. To evaluate the effects of IMI on the zebrafish liver, we conducted proteomic, molecular and biochemical analysis in a multi-level approach, to highlight the complementary features regarding the results of each method. Adult zebrafish were exposed to 60 mg/L IMI for 48 h and were evaluated using nLC-MS/MS for proteins, q-PCR analysis for expression of cat, gpx, pxr, ache, along with CAT and AChE enzyme activities and GSH and MDA assays. Based on proteomics, the regulation of antioxidant and immune responses, as well as gene transcription were significant processes affected. Apoptosis and ER stress pathways were upregulated and there was a down-regulation of cat and gpx genes. There was also elevated CAT activity and GSH and decreased MDA. Additionally, elevated AChE activity and up regulation of ache expression was observed. The multi-approach results included regulators of antioxidant, xenobiotic response and neuro-protective related proteins (genes and enzymes), which overall reflected harmful effects of IMI. Consequently, this study highlights the effects of IMI on zebrafish liver and reveals new potential biomarkers. In this respect, evaluated outcomes reveal the complementary features emphasizing the importance of studying chemicals using several methods. Our study provides deeper insights for future work in ecotoxicological studies regarding IMI and contribute to existing toxicity literature.

Life-cycle assessment of a microalgae-based fungicide under a biorefinery approach

The aim of this work was to perform a life-cycle analysis of the production process of a fungicide based on amphidinols. Two scenarios were evaluated: (1) biorefinery process -biofungicide, fatty acids and carotenoids were considered as co-products-, and (2) biofungicide as only product. Inventory data were taken and scaled-up from previous work on pilot-scale reactors, as well as lab-scale downstream equipment. A yearly production of 22,000 L of fungicide, was selected as the production objective. Despite, photosynthetic biomass is a sink of anthropogenic CO2, harvesting and downstream processing have large carbon footprints that exceed the biomass fixed carbon. Producing the biofungicide resulted in 34.61 and 271.33 ton of CO2e (15 years) for the Scenarios 1 and 2, respectively. Different commercial agricultural fungicides were compared with the microalgal fungicide. A lower impact of the microalgal product for most of the indicators, including carbon footprint, was shown.

Prolonged darkness attenuates imidacloprid toxicity through the brain-gut-microbiome axis in zebrafish, Danio rerio

The present study investigated the toxic effects of IMI on brain and gut of zebrafish (Danio rerio) by a combination of transcriptome and microbiome analysis. In addition, the involvement of light/dark period was also evaluated. An acute toxic test was conducted on adult zebrafish weighing 0.45 ± 0.02 g with 4 experimental groups (n = 15): 1) IMI group (Light: Dark = 12: 12 h), 2) prolonged light group (Light: Dark = 20: 4 h), 3) prolonged darkness group (Light: Dark = 4: 20 h) which received 20 mg/L of IMI, and 4) control group, which was not treated with IMI (Light: Dark = 12: 12 h). The results showed that prolonged darkness improved the survival rate of zebrafish upon IMI exposure for 96 h. In the sub-chronic test, zebrafish were divided into the same 4 groups and exposed to IMI at 1 mg/L for 14 d (n = 30). The results showed that IMI induced oxidative stress in both IMI and prolonged light groups by inhibition of antioxidant activities and accumulation of oxidative products. Transcriptome analysis revealed a compromise of antioxidation and tryptophan metabolism pathways under IMI exposure. Several genes encoding rate-limiting enzymes in serotonin and melatonin synthesis were all inhibited in both IMI and LL groups. Meanwhile, significant decrease (P < 0.5) of serotonin and melatonin levels was observed. However, there's remarkable improvement of biochemical and transcriptional status in prolonged darkness group. In addition, microbiome analysis showed great alteration of gut bacterial community structure and inhibition of tryptophan metabolism pathway. Similarly, the gut microbiota dysbiosis induced by IMI was alleviated in prolonged darkness. In summary, sub-chronic IMI exposure induced neurotoxicity and gut toxicity in zebrafish by oxidative stress and impaired the brain-gut-axis through tryptophan metabolism perturbation. Prolonged darkness could effectively attenuate the IMI toxicity probably through maintaining a normal tryptophan metabolism.

Bifenthrin disrupts cytochrome c oxidase activity and reduces mitochondrial DNA copy number through oxidative damage in pool barb (Puntius sophore)

Bifenthrin (BF), a synthetic pyrethroid is used worldwide for both agricultural and non-agricultural purposes due to its high insecticidal activity and low toxicity in mammals. However, its improper usage implies a possible risk to aquatic life. The Study was aimed to correlate the association of BF toxicity with mitochondrial DNA copy number variation in edible fish Punitus sophore. The 96-h LC 50 of BF in P. sophore was 3.4 μg/L, fish was treated with sub-lethal doses (0.34 μg/L,0.68 μg/L) of BF for 15 days. The activity and expression level of cytochrome c oxidase (Mt-COI) were measured to assess mitochondrial dysfunction caused by BF. Results showed BF reduced the level of Mt-COI mRNA in treated groups, hindered complex IV activity and increased ROS generation leading to oxidative damage. mtDNAcn was decreased in the muscle, brain and liver after BF treatment. Furthermore, BF induced neurotoxicity in brain and muscle cells through the inhibition of AchE activity. The treated groups showed elevated level of malondialdehyde (MDA) and an imbalance of antioxidant enzymes activity. Molecular docking and simulation analysis also predicted that BF binds to the active sites of the enzyme and restricts the fluctuation of active sites' residues. Hence, outcome of the study suggests reduction of mtDNAcn could be a potential biomarker to assess Bifenthrin induced toxicity in aquatic ecosystem.

Effects of glyphosate, 2,4-D, chlorantraniliprole, and imidacloprid formulations, separately and in mixtures in Caiman latirostris hatchlings

The present study demonstrated the potential of glyphosate (GLY), 2,4-dichlorophenoxyacetic acid (2,4-D), imidacloprid (IMI) and chlorantraniliprole (CAP) separately and in mixtures to induce oxidative stress and DNA damage in Caiman latirostris hatchlings. Under controlled condition, an embryonic exposure to these pesticides was done at concentrations recommended for soybean crops. Treatments were: negative control, GLY, 2,4-D, IMI, CAP, mixture 1 (M1): GLY + 2,4-D, M2: IM I + CAP and M3: GLY + 2,4-D + IMI + CAP. At hatching, blood samples were taken for the evaluation of genotoxicity, oxidative damage to lipids and DNA, the enzymatic activity of Catalase (CAT) and Superoxide dismutase (SOD), and the expression level of their corresponding genes (catalase: cat and superoxide dismutase: sod). It has been shown that IMI, M2 and M3 induced a significant inhibition of CAT activity while no effect was observed on SOD. In turn, lipid peroxidation was significantly higher in individuals exposed to IMI, and to all the mixtures. Besides, genotoxicity and oxidative DNA damage were observed in all exposed groups. The results of mRNA expression showed no difference at transcription levels. In the same way, no alterations in growth parameters were recorded at hatching. Regarding to the mixtures, we observed a potentiating action of IMI on M3 in lipid peroxidation as well as independent action on oxidative DNA damage and genotoxicity parameters. Our results highlight the importance of investigating the effect of pesticides and their mixtures considering the potential consequences to caimans living in natural environments.

Single and mixed exposure to distinct groups of pesticides suggests endocrine disrupting properties of imidacloprid in zebrafish embryos

Due to their selective toxicity to insects, nicotinoid compounds have been widely used to control pests in crops and livestock around the world. However, despite the advantages presented, much has been discussed about their harmful effects on exposed organisms, either directly or indirectly, with regards to endocrine disruption. This study aimed to evaluate the lethal and sublethal effects of imidacloprid (IMD) and abamectin (ABA) formulations, separately and combined, on zebrafish (Danio rerio) embryos at different developmental stages. For this, Fish Embryo Toxicity (FET) tests were carried out, exposing two hours post-fertilization (hpf) zebrafish to 96 hours of treatments with five different concentrations of abamectin (0.5-11.7 mg L^-1), imidacloprid (0.0001-1.0 mg L^-1), and imidacloprid/abamectin mixtures (LC₅₀/2 - LC₅₀/1000). The results showed that IMD and ABA caused toxic effects in zebrafish embryos. Significant effects were observed regarding egg coagulation, pericardial edema, and lack of larvae hatching. However, unlike ABA, the IMD dose-response curve for mortality had a bell curve display, where medium doses caused more mortality than higher and lower doses. These data demonstrate the toxic influence of sublethal IMD and ABA concentrations on zebrafish, suggesting that these compounds should be listed for river and reservoir water-quality monitoring.

Organophosphate Insecticide Toxicity in Neural Development, Cognition, Behaviour and Degeneration: Insights from Zebrafish

Organophosphate (OP) insecticides are used to eliminate agricultural threats posed by insects, through inhibition of the neurotransmitter acetylcholinesterase (AChE). These potent neurotoxins are extremely efficacious in insect elimination, and as such, are the preferred agricultural insecticides worldwide. Despite their efficacy, however, estimates indicate that only 0.1% of organophosphates reach their desired target. Moreover, multiple studies have shown that OP exposure in both humans and animals can lead to aberrations in embryonic development, defects in childhood neurocognition, and substantial contribution to neurodegenerative diseases such as Alzheimer's and Motor Neurone Disease. Here, we review the current state of knowledge pertaining to organophosphate exposure on both embryonic development and/or subsequent neurological consequences on behaviour, paying particular attention to data gleaned using an excellent animal model, the zebrafish (Danio rerio).

Integrated biomarker approach strongly explaining in vivo sub-lethal acute toxicity of butachlor on Labeo rohita

Butachlor herbicide belongs to the family of chloroacetanilide group, widely used for control of grass and broadleaf weeds in paddy fields however, its repeated application may result in aquatic pollution. Butachlor residue has been detected in aquatic environments, which may produce toxic effects on non-target organisms including fish. Keeping this in mind, the present study was designed to estimate the LC₅₀ of butachlor (Shaktiman®), and to evaluate the sub-lethal toxicity at two concentrations (12.42 μg L^-1 and 62.10 μg L^-1) in Labeo rohita for a period of 24, 48, and 72 h. Fish exposed to butachlor reduced the counts of red blood cells (RBC), haemoglobin (HGB), hematocrit (HCT), and white blood cells (WBC). A significant (p < 0.05) increase in the antioxidant enzyme (superoxide dismutase-SOD, glutathione-s-transferase-GST), and hepatic enzyme (glutamate-oxaloacetate transaminase-GOT, glutamate-pyruvate transaminase-GPT) were noticed in butachlor exposed fish. Heat shock protein 70 (HSP70) and HSP90 in gill; cortisol, protein, albumin, globulin, and triglyceride in serum were increased upon exposure of butachlor. On the contrary, complement 3 (C3) and immunoglobulin (IgM) in serum was found to be decreased compared to control fish. The findings thus suggest that the fish upon exposure to butachlor disrupts the biomarkers which ultimately leads to growth retardation in fish.

Oxidative and osmoregulatory effects of imidacloprid, cadmium, and their combinations on Daphnia magna

Oxidative stress and osmoregulatory system damage-inducing potential of binary mixtures of neonicotinoid insecticide imidacloprid (IMI) and Cd²⁺ in Daphnia magna were evaluated. Animals were subjected to subchronic (7 days) and acute (48 h) of IMI and Cd²⁺ effects with single and binary mixtures. ATPase and antioxidant enzyme activities with lipid peroxidation were measured. Morphometric characteristics were also evaluated. Response patterns showed variability due to the duration, concentration, and toxicant type. While the enzyme activities mostly showed a decreasing trend upon the subchronic IMI effect, there was an increasing trend after the Cd²⁺. Declined enzyme activities were more pronounced with the acute higher IMI+Cd²⁺ exposure. Ca²⁺-ATPase and CAT were the most sensitive biomarkers in the toxicity response. IMI+Cd²⁺ exposures are appeared to increase their toxic effects due to their oxidative potential. ATPase inhibition and antioxidant enzyme alterations with a decrease in morphometric characteristics in Daphnia even at their low concentrations of IMI and Cd²⁺ show evidence of their toxicities on aquatic life. It was emphasized that investigating the combined effects of toxicants at their environmental level based on the multi-biomarker approach is essential in toxicity evaluation.

Genotoxicity of thiacloprid in zebrafish liver

Thiacloprid (TH), one of the most widely used pesticides in the world, might cause toxic effects like DNA damage in humans and animals due to their frequent use. Accordingly, this study investigated TH's potential DNA-damaging effects on zebrafish liver via alkaline comet assay. Two treatment groups of ten zebrafish each were exposed to TH at two different concentrations, 1.64 and 0.82 mg/L, for 21 days and compared with an untreated control group. After exposure, the fishes' liver tissues were excised, and an alkaline comet assay was performed. Two slides per sample and 50 cells per slide were assessed with a visual evaluation program. The average DNA Damage values of the control, 0.82 mg/L TH, and 1.64 mg/L TH groups were 4.37 ± 5.12, 8.51 ± 8.54, and 9.30 ± 9.99, respectively. Both TH treatment groups had statistically significantly more DNA damage than the control group (p < 0.001). When comparing the TH treatment groups alone, the 1.64 mg/L dose group featured greater damage than the 0.82 mg/L dose group (p < 0.05). TH therefore causes significant DNA damage to the liver in a dose-dependent manner, revealing it to be a genotoxic agent that should be further investigated.

Dinitroaniline herbicide pendimethalin affects development and induces biochemical and histological alterations in zebrafish early-life stages

Pendimethalin (PND) is a dinitroaniline preemergent herbicide widely used to control grasses and weeds. The present study aimed to evaluate the PND potential effects on the development of zebrafish early-life stages. The research focuses first on acute toxicity, followed by the integration of toxicity results through histopathology, oxidative status, and neurotoxicity evaluation of sublethal and environmentally relevant concentrations. Zebrafish larvae exposed to PND showed mortality and developed sublethal alterations including impaired fin development, lordosis, scoliosis, blood congestion, impaired blood flow, and reduced heartbeat. PND exposure (0.5 mg/L) affects musculoskeletal development leading to delayed and reduced ossification of the vertebral centra in the developing vertebral column and disruption of muscle morphology. Herbicide exposure (0.5 mg/L and 0.05 mg/L) led also to biochemical changes of antioxidant enzymes, increasing the activity of CAT, GR, and GPx, while no effects were observed on the activity of SOD and GST in zebrafish larvae. Lastly, AChE activity, a biochemical marker of neurotoxicity, was also increased in zebrafish larvae exposed to 0.5 mg/L of PND. These results confirm the developmental toxicity of PND in zebrafish early-life stages, pointing out the potential role of oxidative stress in the onset of sublethal alterations.

Combined effects of S-metolachlor and benoxacor on embryo development in zebrafish (Danio rerio)

It is necessary to study the combined toxicity of an herbicide and its safener because the two are often used in combination. S-metolachlor and its safener benoxacor have been detected in aquatic environments and can individually damage the oxidative stress system in zebrafish embryos (Danio rerio). However, only their separate toxicity in zebrafish (Danio rerio) embryo development has been reported. This study assessed the combined toxicity of benoxacor and S-metolachlor in zebrafish embryo development, including acute toxicity, developmental toxicity, oxidative damage, and cell apoptosis. The 96-h LC₅₀ values were higher in mixtures of benoxacor and S-metolachlor than in benoxacor alone. The treatments included S-metolachlor, Mix-1 (0.1 mg/L benoxacor + 0.1 mg/L S-metolachlor), Mix-2 (0.1 mg/L benoxacor + 0.3 mg/L S-metolachlor) and benoxacor alone. Embryos exposed to Mix-1 and Mix-2 had lower developmental toxicities, superoxide dismutase (SOD) activity, osx and cat expression levels than those exposed to benoxacor alone. Moreover, glutathione S-transferase (GST), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) activities, and the expressions of tbx16, nrf2, bcl2, and caspase9 were higher in the mixtures than in the benoxacor group. High-throughput RNA sequencing revealed that benoxacor had a greater effect on gene regulation than Mix-1 and Mix-2. The malformation rate, different enrichment gene numbers, and gene expression levels of hatched embryos were higher in Mix-1 than in Mix-2. The results indicate that a mixture of S-metolachlor and benoxacor has antagonistic effects in the early stage of embryo development. The mixtures can break the reactive oxygen species balance, causing abnormal cell apoptosis and developmental malformation in embryos. Besides investigating the combined toxicity of benoxacor and S-metolachlor in zebrafish embryo development, this study provides a risk assessment basis for a herbicide combined with its safener.

Thiacloprid-induced hepatotoxicity in zebrafish: Activation of the extrinsic and intrinsic apoptosis pathways regulated by p53 signaling pathway

Thiacloprid (THCP) is one of the major neonicotinoid insecticides, and its wide use has led to high detection in various media of aquatic environment, posing potential risks to aquatic organisms. This study was focused on the phenotypic responses and mechanisms of toxicity in zebrafish (Danio rerio) upon treatment with waterborne THCP (0.4, 4 and 40 μM) for 21 days in vivo or 412.9 μM for 24 h in vitro. In vivo, we found that THCP induced severe oxidative stress, hepatic abnormalities, leakage of alanine aminotransferase and aspartate aminotransferase and apoptosis. The analysis of RNA-sequencing suggested the activation of the p53 signaling pathway under THCP exposure. The following in vitro study showed that THCP intoxication activated reactive oxygen species (ROS)-dependent p53 signaling pathway and induced hepatotoxicity in the zebrafish liver cells. The addition of p53 inhibitor pifithrin-α (10 μM) exerted protection against of THCP-induced hepatotoxicity by reducing oxidative stress and inhibiting the p53 signaling pathway and apoptosis. Moreover, gene expression analyses indicated that both the extrinsic and intrinsic apoptosis pathways were involved in apoptosis induced by p53 activation. Overall, our results suggest that activation of the p53 signaling pathway is an important mechanism of THCP-induced hepatotoxicity.

Oxidative stress and metal homeostasis alterations in Danio rerio (zebrafish) under single and combined carbamazepine, acetamiprid and cadmium exposures

Contaminants of emerging concern (CEC) are routinely detected in aquatic environments, especially pharmaceuticals, such as carbamazepine (CBZ), and neonicotinoid pesticides, like acetamiprid (ACT). CECs can interact with each other and with other legislated contaminants like Cd, resulting in unknown effects. Most studies evaluate only the effects of single contaminant exposures on aquatic biota. Therefore, the aim of the present study was to assess the effects of both single and combined CBZ, ACT and Cd exposures on zebrafish brain and liver oxidative stress parameters and metal homeostasis. The biomarkers catalase (CAT), glutathione-S-transferase (GST), total thiols (TOT), metallothionein (MT) and malondialdehyde (MDA) and the essential elements Ca, Cu, K, Na, Mg, Mn and Zn were evaluated after 96-hour static exposures. CBZ, ACT and Cd single (brain and liver) and combined (liver) treatments resulted in oxidative effects in both fish organs, also leading to metal (Ca, Mg, K, Mn, Zn and Cu) homeostasis alterations. ACT exposure resulted in the greatest adverse effects in the brain, while CBZ was the cause of major element homeostasis and oxidative stress alterations in the liver. Lower LPO levels were observed in the combined treatments compared to single treatments, suggesting interactions and contaminant effect attenuation. This study is the first to evaluate the initial effects of combined CBZ, ACT and Cd exposures in zebrafish, paving the way for further investigations concerning other biomarkers during longer exposure times.

Assessment of the effect of sub-lethal acute toxicity of Emamectin benzoate in Labeo rohita using multiple biomarker approach

Emamectin benzoate (EMB) is a potent neurotoxin agent, widely used for ectoparasites control in aquaculture, but their detailed toxicological implications in Labeo rohita are unknown. Thus, this study was conceptualized to determine the LC₅₀ and to investigate the effects of two sub-lethal concentrations 1/50th of 96 h LC₅₀ (1.82 μgL^-1) and 1/10thof 96 h LC₅₀ (9.1 μgL^-1) on hemato-immunological and biochemical responses in L. rohita (mean weight 25.54 ± 2.3 g and length 10.35 ± 2.4 cm) for a period of 24 h, 48 h, and 72 h. LC₅₀ of EMB were 163 μgL^-1, 112 μgL^-1, 99 μgL^-1 and 91 μgL^-1 at 24 h, 48 h, 72 h, and 96 h respectively. The safe limit at 96 h LC₅₀ of EMB was 2.30 μgL^-1. In EMB treated fish, red blood cells, white blood cells, hemoglobin, and hematocrit counts were reduced (p < 0.05) significantly. Superoxide dismutase (SOD) activity in the liver and kidney declined (p < 0.05) at 72 h while in gill and muscle the activity increased significantly. Glutathione-s-transferase (GST) activity in the liver, gill, and kidney increased (p < 0.05) while muscle decreased significantly. Catalase (CAT) activity in liver, gill, and muscle decreased while in kidney increases. Glutamic-oxaloacetic acid transaminase (GOT) activity and Glutamate pyruvate transaminase (GPT) activity were increased in liver, kidney, and muscle tissue. The change in serum triglycerides, serum protein level was noticed. The level of cortisol, heat shock protein 70 (HSP70), and HSP90 increased (p < 0.05) while the immunological responses like immunoglobulin M (IgM) and complement 3(C3) activity decreased (p < 0.05) in EMB exposed fish. Thus, EMB exposure at two sub-lethal concentrations in L. rohita induces several hemato-immuno, and biochemical alterations in blood, serum, and different organs. The overall result of the present study indicated that EMB is toxic to fish even for a short-term exposure and low doses, and therefore utmost caution should be taken to prevent their drainage into water bodies.

The Neonicotinoid Thiacloprid Interferes with the Development, Brain Antioxidants, and Neurochemistry of Chicken Embryos and Alters the Hatchling Behavior: Modulatory Potential of Phytochemicals

Simple Summary

The present experiment was performed to investigate the toxic impact of thiacloprid (TH) on the brain of developing chicken embryos and also to measure its influence on the behavioral responses of hatchlings. The role of chicoric acid (CA) and rosmarinic acid (RA) in modulating the resulted effects was also investigated. TH resulted neurotoxic to chicken embryos and possibly neurotoxic to embryos of other vertebrates. Moreover, CA and RA exerted both an antioxidant and a neuroprotective effect on embryos.

Abstract

The present experiment was performed to investigate the toxic impact of thiacloprid (TH) on the brain of developing chicken embryos and also to measure its influence on the behavioral responses of hatchlings. The role of chicoric acid (CA) and rosmarinic acid (RA) in modulating the resulted effects was also investigated. The chicken eggs were in ovo inoculated with TH at different doses (0.1, 1, 10, and 100 ug/egg). TH increased the mortality and abnormality rates and altered the neurochemical parameters of exposed embryos dose-dependently. TH also decreased the brain level of monoamines and amino acid neurotransmitters and decreased the activities of acetylcholine esterase (AchE) and Na⁺/K⁺-ATPase. The brain activity of catalase (CAT) and superoxide dismutase (SOD) was diminished with downregulation of their mRNA expressions in the brain tissue. When TH was co-administered with CA and RA, the toxic impacts of the insecticide were markedly attenuated, and they showed a complementary effect when used in combination. Taken together, these findings suggested that TH is neurotoxic to chicken embryos and is possibly neurotoxic to embryos of other vertebrates. The findings also demonstrated the antioxidant and neuroprotective effects of CA and RA. Based on the present findings, the CA and RA can be used as invaluable ameliorative of TH-induced toxicity.

Effects of common environmental endocrine-disrupting chemicals on zebrafish behavior

Environmental endocrine-disrupting chemicals (EDCs), a type of exogenous organic pollutants, are ubiquitous in natural aquatic environments. Therefor, this review focused on the use of the zebrafish as a model to explore the effect of different EDCs on behavior, as well as the molecular mechanisms that drive these effects. Furthermore, our study summarizes the current knowledge on the neuromodulatory effects of different EDCs in zebrafish. This study also reviews the current state of zebrafish behavior research, in addition to the potential mechanisms of single and mixed pollutant-driven behavioral dysregulation at the molecular level, as well as the applications of zebrafish behavior experiments for neuroscience research. This review broadens our understanding of the influence of EDCs on zebrafish behavior and provides guidance for future research.

Exposure to the Insecticide Sulfoxaflor Affects Behaviour and Biomarkers Responses of Carcinus maenas (Crustacea: Decapoda)

Simple Summary

Sulfoxaflor is an insecticide for which there are few studies regarding its toxicity to non-target organisms. The present study aimed to investigate the acute and sub-lethal effects of sulfoxaflor on Carcinus maenas by addressing survival, behaviour, and biomarkers. Sulfoxaflor affected feed intake and motricity of C. maenas. From the integrated analysis of endpoints, with the increase in concentrations of sulfoxaflor, after seven days, one can notice a lower detoxification capacity, higher lipid peroxidation, and higher motricity effects and lower feed intake. This study aims to contribute to the understanding of the negative impacts of sulfoxaflor on green crabs and increase knowledge of this pesticide toxicity to non-target coastal invertebrates.

Abstract

Sulfoxaflor is an insecticide belonging to the recent sulfoximine class, acting as a nicotinic acetylcholine receptor (nAChRs) agonist. There are few studies regarding sulfoxaflor’s toxicity to non-target organisms. The present study aimed to investigate the acute and sub-lethal effects of sulfoxaflor on Carcinus maenas by addressing survival, behaviour (feed intake and motricity), and neuromuscular, detoxification and oxidative stress, and energy metabolism biomarkers. Adult male green crabs were exposed to sulfoxaflor for 96 h and an LC₅₀ of 2.88 mg L⁻¹ was estimated. All biomarker endpoints were sampled after three (T3) and seven (T7) days of exposure and behavioural endpoints were addressed at T3 and day six (T6). Sulfoxaflor affected the feed intake and motricity of C. maenas at T6. From the integrated analysis of endpoints, with the increase in concentrations of sulfoxaflor, after seven days, one can notice a lower detoxification capacity (lower GST), higher LPO levels and effects on behaviour (higher motricity effects and lower feed intake). This integrated approach proved to be valuable in understanding the negative impacts of sulfoxaflor on green crabs, while contributing to the knowledge of this pesticide toxicity to non-target coastal invertebrates.

In vivo assessment of dichlorvos induced histological and biochemical impairments coupled with expression of p53 responsive apoptotic genes in the liver and kidney of fish, Channa punctatus (Bloch, 1793)

Sub-lethal exposure of dichlorvos induces oxidative stress, consequent genetic instability and apoptosis coupled with impairments in biochemical, histopathological and transcription of genes in Channa punctatus. Exposure of 5% (0.041 mg/L; E2) and 10% (0.082 mg/L; E3) of 96 h-LC₅₀ of dichlorvos significantly (p < 0.05) elevated the reactive oxygen species (ROS) generation and activities of SOD and CAT, as compared to control (E1) after 30 d. The maximum reduction in reduced glutathione (GSH) was recorded in the liver (18.53 ± 0.81 μg/mg of protein) and kidney (19.32 ± 0.97 μg/mg of protein); while the total protein contents were also found reduced, 278.38 ± 8.40 μg/mL (liver) and 248.44 ± 7.28 μg/mL (kidney), after 30 days in E3, in comparison to respective controls. Further, significant (p < 0.05) induction in micronuclei (MN) and apoptotic cells (AC), in a dose- and exposure-based manner were also recorded. Moreover, a significant (p < 0.05) up-regulation of p53 (2.51-fold in liver), bax (2.03-fold in liver; 1.99-fold in kidney) and casp3a (2.26-fold in liver; 2.10-fold in kidney) together with an elevated expression of cat (1.73-fold in liver; 1.12-fold in kidney), p53 (1.27-fold in kidney) and apaf-1 (1.72-fold in liver) in fish exposed to higher dose of dichlorvos for 30 d evidently reflects geno-toxicological potential of referenced pesticide. Disturbed biochemical and molecular parameters evince that the fish experienced oxidative stress as is further supported by prominent pathological observations in liver and kidney. Findings are, thus, helpful in organ-specific molecular scanning against aquatic toxicants like dichlorvos.

Pro-oxidant potency of clothianidin in rainbow trout

Clothianidin is a systemic neonicotinoid insecticide interfering with the central nervous system by acting as a nicotinic acetylcholine receptor agonist. Although previous studies on fish report low toxicity, its proven toxic potential for aquatic invertebrates and lack of data on its effect on juvenile fish have prompted us to investigate its adverse effects in environmentally relevant concentrations of 3, 15 and 30 μg/L for 7, 14 and 21 days on heart and spleen tissues of 10-month-old rainbow trout (Oncorhynchus mykiss). We detected a conspicuous increase in protein carbonyl and malondialdehyde (MDA) levels, which triggered antioxidant response of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), resulting in increased levels of glutathione (GSH). Clothianidin inhibited the activity of acetylcholinesterase (AChE) and lowered tissue protein levels. Heart tissue weight increased, while that of spleen decreased significantly. The effects were time- and concentration-dependent. What raises particular concern is the inhibition of AChE in the trout, even though clothianidin is claimed to be selective for insect receptors. Increased antioxidant activity in response to oxidative stress was clearly insufficient to keep MDA and protein carbonyl at normal levels, which evidences the pro-oxidant potency of the insecticide. All this calls for further investigation into potential adverse effects on biological pathways in different fish species.

Chronic effects of a binary insecticide Acer 35 EC on Nile tilapia Oreochromis niloticus through a multi-biomarker approach

Acer 35 EC is a widely used insecticide (a binary mixture of lambda-cyhalothrin and acetamiprid) in pest control in many West African countries, particularly in the cotton culture in north Benin. The aim of this study was to investigate the chronic effects of Acer 35 EC on Nile tilapia Oreochromis niloticus juveniles using a multi-biomarker approach under laboratory conditions. For this purpose, fish were exposed to sublethal concentrations of Acer 35 EC (0, 1 and 10% of LC₅₀- 96 h value). After 28 and 56 days of exposure, several biomarkers were measured in males and females including enzymatic activities related to detoxification and oxidative stress, neurotoxicity and immune responses, sex steroid hormones (testosterone, 17β-estradiol and 11-keto-testosterone) and histological alterations of liver, kidney and gonads. An Integrated Biomarker Response (IBR) was then calculated. The results showed a reduction of cholinesterase activity in muscles, and intercellular superoxide anion production in both sexes. Female steroidogenesis and gametogenesis were affected, especially testosterone levels and oocyte growth. More alterations were observed in liver after exposure to Acer 35 EC. In both sexes, IBR values were higher after 56 days than after 28 days of exposure. In conclusion, based on a large set of biomarkers and IBR values, the chronic exposure to low doses of insecticide Acer 35 EC seems to impair different physiological functions in Nile tilapia juveniles on a time-dependent manner, with a stronger impact on females than on males.

Environmentally relevant pesticides induce biochemical changes in Nile tilapia (Oreochromis niloticus)

The high demand for food consequently increases the entry of agricultural residues into water resources, and this phenomenon can affect non-target organisms in different ways. Environmentally relevant pesticide effects (per se or in combinations) are scarce in the scientific literature. Therefore, the aim of this study was to investigate: (1) the presence of pesticide residues in an important Brazilian source of water supply and power generation (Jacuí river), during 1 year of monitoring. (2) in a laboratory study verify the effects of the most frequently, herbicide, fungicide, and insecticide found in Jacuí river (individualized or in a mixture) on biochemical parameters in different tissues of Oreochromis niloticus. Twenty pesticide residues were detected in superficial water samples, and two of them are banned in Brazilian territory. Atrazine (0.56 µg L^-1), azoxystrobin (0.024 µg L^-1), and imidacloprid (0.11 µg L^-1) were the most frequently herbicide, fungicide, and insecticide, respectively, found in the river and were used in the laboratory assay. O. niloticus exposed to the pesticide mixture exhibited more biochemical effects than individualized exposure groups. This response can be a result of the combined pesticide effects, culminating in an additive or synergistic effect, depending on the biomarker. In individual exposure groups, atrazine presented the most pronounced alterations, followed by azoxystrobin and imidacloprid. Overall, pesticide exposure increased levels of oxidative stress parameters, reduced antioxidant enzyme activities, and induced acetylcholinesterase activity. These findings highlight the threat to aquatic organisms which may be exposed to a miscellaneous of toxic compounds in the environment.

Acute toxicity and sublethal effects of sodium laureth sulfate on oxidative stress enzymes in benthic oligochaete worm, Tubifex tubifex

The present study was performed to determine the acute toxicity of sodium laureth sulfate (SLES) and its sublethal effects on oxidative stress enzymes in benthic oligochaete worm Tubifex tubifex. The results showed that 96 h median lethal concentration (LC₅₀) value of SLES for Tubifex tubifex is 21.68 mg/l. Moreover exposed worms showed abnormal behaviours including incremented erratic movement, mucus secretion, and decreased clumping tendency at acute level. Percentage of autotomy additionally increased significantly (P < 0.05) with the increasing dose of toxicant at 96 h exposure. Sublethal concentrations of SLES (10% and 30% of 96 h LC₅₀ value) caused paramount alterations in the oxidative stress enzymes. Superoxide dismutase (SOD), reduced glutathione (GSH), glutathione S-transferase (GST), and glutathione peroxidase (GPx) exhibited a striking initiatory increment followed by a resulting descending pattern. Moreover, during exposure times, catalase (CAT) activity and malondialdehyde (MDA) level increased markedly with incrementing concentrations of SLES. However, the effects of sodium laureth sulfate on Tubifex tubifex were characterized and portrayed by the development of a correlation matrix and an integrated biomarker response (IBR) assessment. These results indicate that exposure to this anionic surfactant alters the survivability and behavioral response at acute level and modifies changes in oxidative stress enzymes at sublethal level in Tubifex tubifex.

Low concentrations of imidacloprid exposure induced gut toxicity in adult zebrafish (Danio rerio)

Neonicotinoid insecticide imidacloprid (IMI) is widely used in agriculture, and its repeated application may result in environmental pollution. Recently, the toxicity of IMI to non-target animals has received increasing attention. In the current study, adult zebrafish were exposed to low concentrations of IMI (100 and 1000 μg/L) for 21 days. The results showed that IMI exposure induced intestinal histological injury and oxidative stress in the gut of zebrafish, and the levels of superoxide dismutase (SOD), catalase (CAT) were noticeably increased. Furthermore, IMI exposure also resulted in higher intestinal LPS levels and significant increases in the expression of inflammatory factors. Simultaneously, IMI exposure also slightly induced gut microbiota dysbiosis and specific bacteria alterations. These findings indicated that low concentrations of IMI could induce gut toxicity in adult zebrafish, which could provide new insights into the potential risks of IMI to aquatic animals.

Oxidative stress in benthic oligochaete worm, Tubifex tubifex induced by sublethal exposure to a cationic surfactant cetylpyridinium chloride and an anionic surfactant sodium dodecyl sulfate

The present study was assessed to determine the in vivo toxic effects of a cationic surfactant, cetylpyridinium chloride (CPC), and an anionic surfactant, sodium dodecyl sulfate (SDS) in terms of oxidative stress biomarkers in benthic oligochaete worm Tubifex tubifex for 14 days. The investigation demonstrated that sublethal concentrations of CPC (0.0213, and 0.0639 mg L^-1) and SDS (1.094 and 3.092 mg L^-1)induced paramount alterations in the oxidative stress enzymes in Tubifex tubifex. Superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH), and glutathione peroxidase (GPx) exhibited an initial notable increase in their activities in the surfactants exposed worms at 1d and 7d of exposure period followed by consequential reduction at 14d exposure period with respect to control, while catalase (CAT) and malondialdehyde (MDA) activities markedly incremented gradually throughout the exposure periods. Through the construction of the correlation matrix and integrated biomarker response (IBR), the effects of CPC and SDS on Tubifex tubifex were distinguished. These results indicate that exposure to these cationic and anionic surfactants modulates the levels of oxidative stress enzymes in Tubifex tubifex.

Toxic effects of fenitrothion on freshwater microcosms in Bangladesh

The organophosphate pesticide fenitrothion is widely used as an agricultural pesticide to control tiger bug in larval rearing for aquaculture. The objectives of the present study were to assess the effects of fenitrothion on certain structural (phytoplankton, zooplankton, macro-invertebrates and periphyton) and functional (organic matter decomposition) endpoints of freshwater microcosms. Fenitrothion 50 EC was applied in 12 microcosms (PVC tanks having 400 L of dechlorinated tap water) providing concentrations of 0, 25, 50 and 100 μg/L at a 4-day interval over a period of 4 weeks. Each of the experimental treatment was executed in three replicates. The results indicated the consistent significant effects for most of the species composition of zooplankton and macro-invertebrates. Univariate analysis showed a significant decrease in abundance (p < 0.05) of all identified insects (i.e. Notonecta sp., Gerris sp., Ranatra linearis and Chironomid larvae), when compared to control in all sampling days throughout the treatment period (no observed effect concentration; NOEC = < 25 μg/L). No consistent significant effects were observed for most of the phytoplankton taxa and organic matter decomposition and water quality variables (dissolved oxygen, free CO₂, pH, nitrate etc.). However, several taxa of different endpoints were found sensitive to even the lowest concentration of fenitrothion (25 μg/L). Further studies with acute and chronic conditions are recommended involving more local species exposed to < 25 μg/L of fenitrothion.

Effect of Occupational Exposure to Herbicides on Oxidative Stress in Sprayers

Background

Herbicides such as glyphosate, paraquat, and 2,4-dichlorophenoxyacetic acid have been reported to cause adverse side effects through production of reactive oxygen species. However, there were no data representing the adverse effects of a mixture herbicide usage in farmers, especially the changes in oxidative marker and antioxidant defense. This study aimed to determine the urinary malondialdehyde (MDA) and glutathione (GSH) level in farmers using mixed herbicides.

Methods

Ninety-three farmers were recruited, and two spot urine samples (before and after work) were collected. The urinary MDA level was evaluated by thiobarbituric acid reactive substance assay, and the urinary GSH level was determined using the enzymatic recycling method.

Results

Sixty-two percent of the participants were men, and 59% of the participants worked in a farm for 20–40 years. The common combinations of herbicide usage were glyphosate with 2,4-dichlorophenoxyacetic acid (36.5%). There was no significant difference between pre- and post-work urinary MDA and GSH levels among the 3 groups of herbicides. However, the urinary MDA levels in farmers using the combination of glyphosate and paraquat were significantly higher than those found in farmers using glyphosate alone. The associated factors with changes in MDA levels found that the exposure intensity index (B = 0.154), the cumulative exposure intensity index (B = 0.023), and wearing gloves while working (B = −2.347) were found to be significantly associated with MDA level.

Conclusion

The results suggest that the combined use of glyphosate and paraquat caused a significant increase in urinary MDA levels. Moreover, intensity of exposure to herbicide and wearing gloves were associated with the level of MDA.

Toxicities of Neonicotinoid-Containing Pesticide Mixtures on Nontarget Organisms

Neonicotinoids are a widely used class of pesticides. Co-exposure to neonicotinoids and other classes of pesticides can exert potentiating or synergistic effects, and these mixtures have been detected in human bodily fluids. The present review summarizes studies into the effects of neonicotinoid-containing pesticide mixtures on humans and other nontarget organisms. Exposure to these mixtures has been reported to result in reproductive and hormonal toxicity, genotoxicity, neurotoxicity, hepatotoxicity, and immunotoxicity in vertebrates. Mortality of pollinators and toxicity in other organisms has also been reported. The underlying mechanism of pesticide mixture toxicity may be associated with impairment of cytochrome 450 enzymes, which are involved in metabolizing pesticides. However, a comprehensive explanation of the adverse effects of neonicotinoid-containing pesticide mixtures is still required so that effective prevention and control measures can be formulated. Environ Toxicol Chem 2020;39:1884-1893. © 2020 SETAC.

Stereoselective uptake and metabolism of prothioconazole caused oxidative stress in zebrafish (Danio rerio)

Prothioconazole (PTA) is a novel, broad-spectrum, chiral triazole fungicide that is mainly used to prevent and control the disease of cereal crops. However, the adverse effects of PTA and its major metabolite on nontarget organisms have aroused wide concern. In the present work, the acute toxic of the metabolite prothioconazole-desthio (PTA-desthio), with an LC₅₀ of 1.31 mg L^-1, was 3.5-fold more toxic than the parent compound, indicating that the metabolism of PTA in zebrafish was toxic. The stereoselective uptake and metabolism of PTA and PTA-desthio in zebrafish was firstly investigated using LC-MS/MS. Remarkable enantioselectivity was observed: S-PTA and S-PTA-desthio were preferentially uptake with the uptake rate constants of 8.22 and 8.15 d^-1 at exposure concentration of 0.5 mg L^-1, respectively, and the R-PTA-desthio were preferentially metabolized. PTA-desthio was rapidly formed during the uptake processes. The antioxidant enzyme activities in the zebrafish changed significantly, and these effects were reversible. A metabolic pathway including 13 phase I metabolites and 2 phase II metabolites was firstly proposed. A glucuronic acid conjugate and sulfate conjugate were observed in zebrafish. The results of this work provide information that highlights and can help mitigate the potential toxicity of PTA to the ecological environment and humans health.

Insights into the Toxicity and Degradation Mechanisms of Imidacloprid Via Physicochemical and Microbial Approaches

Imidacloprid is a neonicotinoid insecticide that has been widely used to control insect pests in agricultural fields for decades. It shows insecticidal activity mainly by blocking the normal conduction of the central nervous system in insects. However, in recent years, imidacloprid has been reported to be an emerging contaminant in all parts of the world, and has different toxic effects on a variety of non-target organisms, including human beings, due to its large-scale use. Hence, the removal of imidacloprid from the ecosystem has received widespread attention. Different remediation approaches have been studied to eliminate imidacloprid residues from the environment, such as oxidation, hydrolysis, adsorption, ultrasound, illumination, and biodegradation. In nature, microbial degradation is one of the most important processes controlling the fate of and transformation from imidacloprid use, and from an environmental point of view, it is the most promising means, as it is the most effective, least hazardous, and most environmentally friendly. To date, several imidacloprid-degrading microbes, including Bacillus, Pseudoxanthomonas, Mycobacterium, Rhizobium, Rhodococcus, and Stenotrophomonas, have been characterized for biodegradation. In addition, previous studies have found that many insects and microorganisms have developed resistance genes to and degradation enzymes of imidacloprid. Furthermore, the metabolites and degradation pathways of imidacloprid have been reported. However, reviews of the toxicity and degradation mechanisms of imidacloprid are rare. In this review, the toxicity and degradation mechanisms of imidacloprid are summarized in order to provide a theoretical and practical basis for the remediation of imidacloprid-contaminated environments.

Differential responses of larval zebrafish to the fungicide propamocarb: Endpoints at development, locomotor behavior and oxidative stress

The fungicide propamocarb (PM) is widely used to protect cucumbers, tomatoes and other plants from pathogens. According to previous studies, PM could be detected in the aquatic system in some area. However, the toxic effects of PM on zebrafish received very limited attention. In this study, we examined the toxic effects of various concentration of PM on the endpoints of development, locomotor behavior and oxidative stress in larval zebrafish. It was observed that PM exposure delayed embryonic development, inhibited hatchability at 60 and 72 h postfertilization and increased heart rate. After PM exposure, the larval zebrafish showed abnormal free swimming behavior and the swimming behavior in response to light-dark transition, indicating that PM had the potential to induce neurotoxicity. Moreover, PM exposure also affected the enzymatic activity of acetylcholinesterase and dopamine and the transcriptional level of genes related to neurotoxicity. In addition, PM exposure not only affects catalase (CAT), glutathione peroxidase (GPX), and glutathione S-transferase (GST) activity but also affects the transcription level of various genes. We believed that PM induced oxidative stress was also a possible reason to cause neurotoxicity in larval zebrafish. In summary, our results suggested that PM could disturb the endpoints at development, locomotor behavior and oxidative stress in larval zebrafish.

Urinary organophosphate metabolites and oxidative stress in children living in agricultural and urban communities

Exposure to organophosphate (OP) pesticides in children may increase oxidative stress, resulting in the development of chronic diseases. This study aims to compare urinary OP metabolites and oxidative stress between children in agricultural and urban communities. The study also investigated the factors associated with urinary OP metabolites among children. Urine samples were collected from children for measuring levels of OP metabolites, glutathione (GSH), and malondialdehyde (MDA). The remarkable findings were that total dialkylphosphate (DAP) levels detected among children in this agricultural community were significantly higher than those from the urban community (P = 0.001). Multiple linear regression showed that total diethylphosphate (DEP) levels among children in the agricultural community were negatively associated with distances from children's residence to the agricultural fields (β ± SE. = - 1.535 ± 0.334, 95%CI = - 2.202, - 0.863) and positively associated with playing on farms (β ± SE. = 0.720 ± 0.342, 95%CI = 0.036, 1.405). In addition, total dimethylphosphate (DMP) levels were positively associated with children working on farms (β ± SE. = 0.619 ± 0.264, 95%CI = 0.091, 1.147). Importantly, GSH levels among children in the agricultural community were significantly lower than those in the urban community (P < 0.001), but MDA levels did not differ. These results therefore suggest that children can be exposed to OPs both outdoors and indoors. Our results also provide supporting evidence that OP exposure can cause oxidative stress in children. As oxidative stress contributes to several chronic diseases, a good proposed strategy for the future would include measurement of oxidative stress biomarkers among children exposed to OPs as an early warning of chronic diseases.

The association between PON1 and GSTM1 genetic variation with methylation of p16 gene promoter among Javanese farmers exposed to pesticides at Magelang Regency, Central Java, Indonesia

Occupational exposure to pesticides leads to the development of cancer. Aberrant DNA methylation plays a crucial role in cancer. The manifestation of the carcinogenic effect of pesticides could be determined by the variation of genes encoding enzyme, including PON1 Q192R and GSTM1. The goal of this study was to find out polymorphism of PON1 Q192R and methylation of p16 gene promoter, and their correlation on Javanese farmers in the agricultural area of Ngablak Subdistrict, Magelang Regency, Central Java. Seventy-eight pesticide-exposed farmers enrolled in the study. Polymorphism of PON Q192R was determined using PCR-RFLP and variation of GSTM1 was examined using conventional PCR. The methylation of the p16 gene promoter was determined using methylation-specific PCR. The result revealed 94.9% polymorphism of PON1 Q192R, which was higher in the R/R (Arg/Arg) genotypes than Q/R (Gln/Arg) and lowest in Q/Q (Gln/Gln) genotypes. We also found 82.1% GSTM1 null genotype among the farmers enrolled in the study. As many as 26.9% methylations of p16 gene promoter were found among farmers. Genetic variation of PON1 Q192R and GSTM1 were not found to be correlated to the methylation status of p16 gene promoter in the Javanese population.

Neonicotinoid insecticides exposure cause amino acid metabolism disorders, lipid accumulation and oxidative stress in ICR mice

Neonicotinoids are increasingly being used for pest control, and their potential health risks are now receiving attention. In this study, the toxic effects of three neonicotinoids (dinotefuran, nitenpyram and acetamiprid) were evaluated in ICR mice. After 30 days of exposure to neonicotinoids (1/200 LD50), oxidative stress levels, biochemical parameters, free fatty acids contents, and ¹H NMR-based hepatic metabolomics were tested. All treatment groups showed signs of amino acid metabolism disorders especially elevated branched chain amino acids and phenylalanine. Furthermore, animals exposed to neonicotinoids had elevated lipid levels, which induced oxidative stress. Overall, we found that oxidative stress is a common toxic effect of exposure to neonicotinoids. In addition, lipid accumulation induced by amino acid metabolism disorder may be the cause of oxidative stress. Our results further our understanding of the toxicological effects of neonicotinoids on mammals.

Toxicity of the organophosphate insecticide sumithion to embryo and larvae of zebrafish

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The 24 h LC₅₀ value of sumithion for embryo was 0.235 mg L⁻¹.

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Several malformations were observed in embryos exposed to different concentrations of sumithion.

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The 24, 48 and 72 h LC₅₀ values of sumithion for larvae were 0.620, 0.475 and 0.341 mg L⁻¹, respectively.

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Different deformities were evident in the sumithion exposed larvae.

Sumithion, a synthetic organophosphate, is widely used as an agricultural insecticide and for control of tiger bug (Cicindela spp.) in larval rearing for aquaculture. An experiment was conducted to examine the effects of sumithion on embryological and larval development of zebrafish Danio rerio. Fertilized egg (n = 100) and larvae (n = 100) were exposed to six concentrations of sumithion (0, 0.1, 0.2, 0.4, 0.8 and 1.6 mg L⁻¹) in three replicates. LC₅₀ values for embryos and larvae were calculated by probit analysis. The 24 h LC₅₀ value of sumithion for embryo was 0.235 (0.079-0.428) mgL⁻¹. Increasing sumithion concentrations decreased hatching success and increased embryonic mortality. In embryos, sumithion induced several malformations including immature yolk sac, dark yolk sac, yolk sac bud, broken eggshell and notochord, unhatched eggs. Larval LC₅₀ values at 24, 48 and 72 h of various doses of sumithion exposure were 0.620 (0.436-0.963), 0.475 (0.302-0.801) and 0.341 (0.177-0.617) mgL⁻¹, respectively. Various physical deformities, including edema, notochord deformity, yolk sac damage, body arcuation, lordosis and black pigmentation on the yolk sac were evident in response to different concentrations of sumithion. The results of the current study indicate that sumithion exerts developmental toxicity to zebrafish embryos and larvae. It is expected that current findings will increase sensitivity about the toxic effect of sumithion in early development, as well the possibility of similar actions induced by other insecticides and pesticides.

Assessing the effects of neonicotinoid insecticide on the bivalve mollusc Mytilus galloprovincialis

In the present work, the marine invertebrate Mytilus galloprovincialis was used as model organism to evaluate the toxic effects of the neonicotinoid Calypso 480 SC (CAL) following 20 days of exposure to sub-lethal concentrations of 7.77 mg L^-1 (0.1% 96 h-LC50) and 77.70 mg L^-1 (1% 96 h-LC50), and a recovery period of 10 days in uncontaminated seawater. Results revealed that exposure to both concentrations of CAL increased significantly mortality rate in the cells of haemolymph and digestive gland, while digestive gland cells were no longer able to regulate cell volume. Exposure significantly reduced haemolymph parameters (Cl^-, Na⁺), affected the enzymatic activities of superoxide dismutase of digestive gland and catalase of gill, and caused also histopathological alterations in digestive gland and gills. Main histological damages detected in mussels were lipofuscin accumulation, focal points of necrosis, mucous overproduction and infiltrative inflammations. Interestingly, alterations persisted after the recovery period in CAL-free water, especially for haemocyte parameters (K⁺, Na⁺, Ca²⁺, lactate dehydrogenase, glucose). A slight recovery of histological conditions was detected. These findings suggested that sub-chronic exposure to the neonicotinoid insecticide caused significant alterations in both cell and tissue parameters of M. galloprovincialis. Considering the ecologically and commercially important role of mussels in coastal waters, a potential risk posed by neonicotinoids to this essential aquatic resource can be highlighted.