Glutathione and its dependent enzymes' modulatory responses to neonicotinoid insecticide sulfoxaflor induced oxidative damage in zebrafish in vivo

The toxicity effects of imidacloprid and chlorpyrifos on oxidative stress and blood biochemistry in Cyprinus carpio

This study aimed to assess the toxicity effects of chlorpyrifos and imidacloprid, alone and in combination, on oxidative biomarkers and blood biochemistry of Cyprinus carpio. A total of 324 common carp (Cyprinus carpio) were distributed among 27 tanks and exposed to concentrations of 0.0, 100, and 200 μg L-1 of chlorpyrifos and 0.0, 10.0, and 20.0 μg L-1 of imidacloprid for 28 days. Changes in enzyme activities in the plasma of fish exposed to chlorpyrifos depended on the dose. In contrast, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatine phosphokinase (CPK), gamma-glutamyl transferase (GGT) activities were significantly increased in fish exposed to imidacloprid, alone and in combination with chlorpyrifos. However, the activity of butyrylcholinesterase (BChE) was significantly decreased. Exposure to imidacloprid and chlorpyrifos, alone and in combination, increased glucose, urea, cholesterol, triglycerides, and creatinine levels, whereas total protein and albumin levels were significantly decreased. The activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and catalase (CAT) was significantly increased, while glutathione reductase (GR) was significantly decreased. Additionally, although the total antioxidant capacity (TAN) was significantly decreased, malondialdehyde (MDA) levels increased after exposure to imidacloprid and chlorpyrifos, alone and in combination. In conclusion, exposure to imidacloprid and chlorpyrifos, alone and in combination, induced oxidative stress and altered blood biochemistry in carp fish. Moreover, imidacloprid and chlorpyrifos had synergistic effects on some oxidative and biochemical biomarkers.

Co-administration of thymol and sulfoxaflor impedes the expression of reproductive toxicity in male rats

This study investigated the capability of a co-delivery system of thymol (THY) and sulfoxaflor that can serve to minimize the development of epididymal and testicular injury arise from SFX exposures alone. Forty-eight adult male rats were orally treated by gavage for 28 consecutive days. The rats were divided into six groups comprising control, THY alone (30 mg/kg), low SFX alone (79.4 mg/kg), high SFX alone (205 mg/kg) and co-exposure groups. After euthanasia, the rats epididymal and testicular damage and antioxidant status markers, myeloperoxidase (MPO) activity, levels of nitric oxide, total antioxidant capacity (TAC), total oxidative stress (TOS) and lipid peroxidation (LPO) were analyzed. Levels of tumor necrosis factor alpha (TNF-α), interleukin-1 b (IL-1β) and caspase-3 activity were assessed using ELISA kits. The results revealed that SFX exposure caused a significant (p < 0.05) decrease in the body weight, sperm functional parameters, serum testosterone level with widespread histological abnormalities in a dose-dependent manner. Increased relative organ weights, serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were observed in low SFX-treated rats. Similarly, the epididymal and testicular myeloperoxidase activity, malondialdehyde (MDA), reactive oxygen species (RONS), tumor necrosis-α, interleukin-1β levels and caspase-3 activity were significant (p < 0.05) increased and a significant (p < 0.05) reduction in antioxidant enzyme activities and reduced glutathione (GSH) were revealed in SFX-treated rats. However, co-treatment of THY with SFX prevented SFX-induced epididymal and testicular toxicities. Thus, thymol protected against potential epididymis and testes alterations elicited by oxido-inflammatory mediators and up regulated antioxidant status.

Residues of sulfoxaflor and its metabolites in floral and extrafloral nectar from Hibiscus rosa-sinensis L. (Malvaceae) with or without co-application of tebuconazole

Systemic pesticide exposure through nectar is a growing global concern linked to loss of insect diversity, especially pollinators. The insecticide sulfoxaflor and the fungicide tebuconazole are currently widely used systemic pesticides which are toxic to certain pollinators. However, their metabolisms in floral or extrafloral nectar under different application methods have not yet been well studied. Hibiscus rosa-sinensis was exposed to sulfoxaflor and tebuconazole via soil drenching and foliar spraying. Sulfoxaflor, tebuconazole, and their main metabolites in floral and extrafloral nectar, soil, and leaves were identified and quantified using liquid chromatography coupled with triple quadrupole mass spectrometry (LC-QqQ MS). The chemical compositions of unexposed and contaminated H. rosa-sinensis floral nectar or extrafloral nectar were compared using regular biochemical methods. The activities of two pesticide detoxifying enzymes, glutathione-s-transferase and nitrile hydratase, in H. rosa-sinensis nectar were examined using LC-MS and spectrophotometry. The floral nectar proteome of H. rosa-sinensis was analysed using high-resolution orbitrap-based MS/MS analysis to screen for sulfoxaflor and tebuconazole detoxifying enzymes. H. rosa-sinensis can absorb sulfoxaflor and tebuconazole through its roots or leaf surfaces and secrete them into floral nectar and extrafloral nectar. Both sulfoxaflor and tebuconazole and their major metabolites were present at higher concentrations in extrafloral nectar than in floral nectar. X11719474 was the dominant metabolite of sulfoxaflor in the nectars we studied. Compared with soil application, more sulfoxaflor and tebuconazole remained in their original forms in floral nectar and extrafloral nectar after foliar application. Sulfoxaflor and tebuconazole exposure did not modify the chemical composition of floral or extrafloral nectar. No active components, including proteins in the nectar, were detected to be able to detoxify sulfoxaflor.

Sulfoxaflor induces immunotoxicity in zebrafish (Danio rerio) by activating TLR4/NF-κB signaling pathway

Sulfoxaflor is an insecticide that is widely used and affects the nervous system of sucking pests. However, studies on the molecular mechanism of the toxicity of sulfoxaflor to non-target species are limited. Zebrafish (Danio rerio) was used as an experimental subject in this study. Zebrafish embryos were exposed to 20, 25, and 30 mg/L sulfoxaflor solution to detect hatchability, mortality, heart rate, neutrophil count, oxidative stress, and expression of genes related to apoptosis and immune inflammation. The results showed that zebrafish embryos exposed to sulfoxaflor solution increased mortality and growth retardation, and the number of innate immune cells decreased significantly. In addition, the expression levels of apoptotic and proapoptotic genes increased significantly, and oxidative stress-related indexes changed significantly. Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway was further studied, and the interleukin 6 (IL-6), interleukin 1 beta (IL-1β), cyclooxygenase-2 (COX2), tumor necrosis factor-alpha (TNF-α), TLR4, and myeloid differentiation primary response 88 (MYD88) gene expression levels were significantly up-regulated. We used small molecule inhibitor QNZ for the rescue experiment and detected the expression of relevant target proteins in the QNZ signaling pathway. QNZ reduced the expression of TLR4/NF-κB signaling pathway-related protein NF-κB p65 in the cytoplasm and nucleus and rescued the number of innate immune cells. In summary, sulfoxaflor may induce developmental toxicity and immunotoxicity in zebrafish by activating the TLR4/NF-κB signaling pathway, which provides a basis for further studies on the molecular mechanism of sulfoxaflor action in the aquatic ecosystem and the development and utilization of QNZ.

Toxic effects of bisphenol AF on the embryonic development of marine medaka (Oryzias melastigma)

Bisphenol AF (BPAF), an emerging environmental endocrine disruptor, has been detected in surface waters worldwide and has adverse effects on aquatic organisms. The accumulation of BPAF in oceans and its potential toxic effect on marine organisms are important concerns. In this study, the effects of BPAF (10, 100, 1, and 5 mg/L) on marine medaka (Oryzias melastigma) were evaluated, including effects on the survival rate, heart rate, hatchability, morphology, and gene expression in embryos. The survival rate of marine medaka embryos was significantly lower after treatment with 5 mg/L BPAF than in the solvent control group. Exposure to 1 mg/L and 5 mg/L BPAF significantly reduced hatchability. Low-dose BPAF (10 μg/L) significantly accelerated the heart rate of embryos, while high-dose BPAF (5 mg/L) significantly decreased the heart rate. BPAF exposure also resulted in notochord curvature, pericardial edema, yolk sac cysts, cardiovascular bleeding, and caudal curvature in marine medaka. At the molecular level, BPAF exposure affected the transcript levels of genes involved in the thyroid system (dio1, dio3a, trhr2, tg, and thra), cardiovascular system (gata4, atp2a1, and cacna1da), nervous system (elavl3 and gap43), and antioxidant and inflammatory systems (sod, pparβ, and il-8) in embryos. These results indicate that BPAF exposure can alter the expression of functional genes, induce abnormal development, and reduce the hatching and survival rates in marine medaka embryos. Overall, BPAF can adversely affect the survival and development of marine medaka embryos, and BPAF may not be an ideal substitute for BPA.

Pesticides and tremor: An overview of association, mechanisms and confounders

Pesticides are a heterogeneous class of chemicals mainly used for the protection of crops from pests. Because of their very widespread use, acute or/and chronic exposure to these chemicals can lead to a plethora of sequelae inflicting diseases, many of which involve the nervous system. Tremor has been associated with pesticide exposure in human and animal studies. This review is aimed at assessing the studies currently available on the association between the various types of pesticides/insecticides and tremor, while also accounting for potential confounding factors. To our knowledge, this is the first coherent review on the subject. After appraising the available evidence, we call for more intensive research on this topic, as well as intonate the need of implementing future preventive measures to protect the exposed populations and to reduce potential disabilities and social drawbacks.

Bromuconazole exposure induces cardiotoxicity and lipid transport disorder in larval zebrafish

Bromuconazole (BRO), as one of the typical triazole fungicides, has not been reported on its effects on aquatic organisms. In this study, zebrafish embryos were used as experimental objects to evaluate the toxicity of BRO. In the acute embryo toxicity test, it was observed that the heart rate and growing development were affected by BRO in a concentration-dependent manner, and the half-lethal concentration (LC50) of BRO at 96 h post-fertilization (hpf) was about 11.83 mg/L. Then, low concentrations of BRO (50 ng/L, 0.075 mg/L, 0.3 mg/L, 1.2 mg/L), which were set according to the LC50 and environmental related concentrations, were used to analyze the toxic effects on the different endpoints in larval zebrafish. Interestingly, the transcriptomic analysis found that most different expressed genes (DEGs) could be focused on the pathways of lipid metabolism, myocardial function, glycometabolism, indicating that heart function and lipid metabolism in larval zebrafish were disrupted by BRO. For supporting this idea, we re-exposed the transgenic zebrafish and WT zebrafish embryos, proved that BRO caused damage to heart development and lipid transport on morphological and genetic level, which was consistent with transcriptomic results. In addition, BRO exposure caused oxidative damage in the larvae. Taken together, BRO exposure could affect the myocardial contraction function and lipid transport in larval zebrafish, accompanied by disturbances in the level of oxidative stress, which was of great significance for improving the biotoxicological information of BRO.

Identification and quantitation of the novel insecticide sulfoxaflor and its metabolites in floral nectar from Salvia splendens Ker Gawl. (Lamiaceae)

Sulfoxaflor is a new systemic insecticide developed as a replacement for older neonicotinoids which are known to be toxic to pollinators. However, its metabolism in nectar and effect on nectar biosynthesis have not been investigated. After soil and foliar application, sulfoxaflor and its main metabolites in soil, leaf and Salvia splendens nectar, were measured by liquid chromatography coupled with triple quadrupole mass spectrometer (LC-MS/MS). The chemical composition between the clean and sulfoxaflor spiked nectar were also compared. The activities of two possible sulfoxaflor detoxifying enzymes in S. splendens nectar, nitrile hydratase and glutathione-s-transferase, were measured by LC-MS and spectrophotometry. S. splendens nectar proteome was investigated by high-resolution orbitrap-based MS/MS to screen for sulfoxaflor detoxifying relevant proteins. S. splendens could absorb sulfoxaflor through root or leaf surface and secrete a proportion of sulfoxaflor along with its metabolites into the nectar. After soil application, sulfoxaflor's low toxic metabolite X11719474 was dominant in the nectar and reached an average concentration of 8905 ppb. However, after foliar application, sulfoxaflor was dominant over its metabolites in the nectar. S. splendens nectar has no nitrile hydratase and glutathione-s-transferase activity and none of the 106 proteins identified in the nectar were predicted to function in detoxifying sulfoxaflor. Soil and foliar sulfoxaflor application can result in different profiles of sulfoxaflor and its metabolites presented in the nectar. However, sulfoxaflor had no effects on S. splendens nectar secretion and chemical composition and cannot be directly detoxified by components in the nectar.

Reproductive effects of sulfoxaflor in male Sprague Dawley rats

The study objective was to evaluate the potential reproductive toxicity of sulfoxaflor (SFX) insecticide in male Sprague Dawley rats. To attain these objectives, forty male Sprague Dawley rats of 10-12 weeks old were randomly divided into four equal groups; the 1st group was used as a control group; the other three groups were exposed to 25, 100, and 500 mg/kg body weight SFX by oral gavage for 4 weeks. Relative testicular weight, testosterone, FSH, LH, MDA, and GPx levels, sperm viability, sperm morphology, sperm DNA damage, and histopathological changes in testes, epididymis, and seminal vesical of these rats were investigated after 4 weeks. The results showed that SFX exposure resulted in a significant increase in FSH, LH, MDA, and GPx levels as well as the percentage of dead and abnormal sperms and DNA damage in rat sperms. Histopathological examination of testes established testicular degeneration with coagulative necrosis as well as the proliferation of interstitial connective tissue infiltrated with inflammatory cells with congestion of intertubular blood vessels in epididymis and degeneration of lining epithelium of seminal vesicles.

Neonicotinoids: mechanisms of systemic toxicity based on oxidative stress-mitochondrial damage

Neonicotinoids are the most widely used pesticides in the world. However, research studies have shown that it can affect the cognitive abilities and health of non-target bees and other wild pollinators by inducing DNA damage, apoptosis and mitochondrial damage, injure to its central nervous system, and it is even developmentally neurotoxic to mammals and humans, with mitochondria being an important target of neonicotinoids. Therefore, this article reviews the role of mitochondrial morphology, calcium ions (Ca²⁺) homeostasis, respiratory function, apoptosis, and DNA damage in neonicotinoids-induced systemic toxicity. Additionally, it evaluates the protective effects of various active substances including vitamin C, N-acetylcysteine (NAC), curcumin (CUR), glutathione reduced (GSH), caffeic acid phenethyl ester (CAPE), resveratrol, and thymoquinone (TQ) on neonicotinoids-induced toxicity. This review manuscript found that mitochondria are important targets to neonicotinoids. Neonicotinoids can cause DNA damage, apoptosis, protein oxidation, and lipid peroxidation in non-target organisms by altering mitochondrial Ca²⁺ homeostasis, inhibiting mitochondrial respiration, and inducing reactive oxygen species (ROS) production. Several active substances (vitamin C, NAC, CUR, GSH, resveratrol, CAPE, and TQ) play a protective role against neonicotinoid-induced systemic toxicity by inhibiting ROS signaling pathways, apoptosis, and lipid peroxidation. This review manuscript emphasizes the importance and urgency of the development of neonicotinoid antidotes, emphasizes the prospect of the application of targeted mitochondrial antidotes, and prospects the development of neonicotinoid antidotes in order to provide some strategies for the prevention of neonicotinoid toxicity.

Fucoidan Protects against Acute Sulfoxaflor-Induced Hematological/Biochemical Alterations and Oxidative Stress in Male Mice

Fucoidan is a sulfated polysaccharide which can be found among a number of macroalgea species. It has a broad spectrum of biological activities including anti-oxidant, anti-tumor, immunoregulation, anti-viral and anti-coagulant. The current study was performed to investigate possible protective effects of fucoidan for sulfoxaflor-induced hematological/biochemical alterations and oxidative stress in the blood of male Swiss albino mice. For this purpose, sulfoxaflor was administered at a dose of 15 mg/kg/day (1/50 oral LD₅₀), and fucoidan was administered at a dose of 50 mg/kg/day by oral gavage alone and combined for 24 h and 7 days. Hematological parameters (RBC, HGB, HCT, MCV, MCH, MCHC, Plt, WBC, Neu, Lym and Mon), serum biochemical parameters (AST, ALT, GGT, LDH, BUN, Cre and TBil), and serum oxidative stress/antioxidant markers (8-OHdG, MDA, POC and GSH) were analyzed. The results indicated that sulfoxaflor altered hematological and biochemical parameters and caused oxidative stress in mice; fucoidan ameliorated some hematological and biochemical parameters and exhibited a protective role as an antioxidant against sulfoxaflor-induced oxidative stress.

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.