Effect of single and combination of three triazine metabolites at environmental concentrations on early life stages of common carp (Cyprinus carpio L.)

Hesperidin alleviates terbuthylazine-induced ferroptosis via maintenance of mitochondria-associated endoplasmic reticulum membrane integrity in chicken hepatocytes

Terbuthylazine (TBA) is a common triazine herbicide used in agricultural production, which causes toxic damage in multiple tissues. Hesperidin (HSP) is a flavonoid derivative that has anti-inflammatory, antioxidant and cytoprotective effects, but its role in reducing toxic damage caused by pesticides is still unclear. In this study, we aimed to investigate the toxic effect of TBA exposure on chicken hepatocytes and the therapeutic effect of HSP on the TBA-induced hepatotoxicity. Our results demonstrated that HSP could alleviate TBA exposure-induced endoplasmic reticulum (ER) stress. Interestingly, TBA significantly disrupted the integrity of mitochondria-associated endoplasmic reticulum membrane (MAM), while HSP treatment showed the opposite tendency. In addition, TBA could significantly trigger ferroptosis in liver, and HSP treatment reversed ferroptosis under TBA exposure. These results suggested that HSP could inhibit ER stress and alleviate ferroptosis under TBA exposure via maintaining MAM integrity, which provided a novel strategy to take precautions against TBA toxicity.

Nitrogen fertiliser-domesticated microbes change the persistence and metabolic profile of atrazine in soil

Pesticides and fertilisers are frequently used and may co-exist on farmlands. The overfertilisation of soil may have a profound influence on pesticide residues, but the mechanism remains unclear. The effects of chemical fertilisers on the environmental behaviour of atrazine and their underlying mechanisms were investigated. The present outcomes indicated that the degradation of atrazine was inhibited and the half-life was prolonged 6.0 and 7.6 times by urea and compound fertilisers (NPK) at 1.0 mg/g (nitrogen content), respectively. This result, which was confirmed in both sterilised and transfected soils, was attributed to the inhibitory effect of nitrogen fertilisers on soil microorganisms. The abundance of soil bacteria was inhibited by nitrogen fertilisers, and five families of potential atrazine degraders (Micrococcaceae, Rhizobiaceae, Bryobacteraceae, Chitinophagaceae, and Sphingomonadaceae) were strongly and positively (R > 0.8, sig < 0.05) related to the decreased functional genes (atzA and trzN), which inhibited hydroxylation metabolism and ultimately increased the half-life of atrazine. In addition, nitrogen fertilisers decreased the sorption and vertical migration behaviour of atrazine in sandy loam might increase the in-situ residual and ecological risk. Our findings verified the weakened atrazine degradation with nitrogen fertilisers, providing new insights into the potential risks and mechanisms of atrazine in the context of overfertilisation.

ATR induces hepatic lipid metabolism disorder in rats by activating IRE1α/XBP1 signaling pathway

Atrazine (ATR) is a widely used herbicide and due to its persistence in environment and bioaccumulation, it can cause harmful impacts on human health. ATR exposure can lead to disorders of lipid metabolism in the liver, but its underlying mechanism is still unclear. 40 eight-week-old rats were given different doses of ATR (0, 0.5, 5 and 50 mg/kg/d) for 90 days. The liver tissue and serum were collected for histological observation and biochemical analysis. The levels of lipid and oxidative stress were assessed using colorimetry. Changes in MMP and ROS of liver cells were observed through flow cytometry. The expression of mRNA and protein was detected using Real-Time PCR and western blot. The results showed that TC and HDL-C levels in both the liver and serum were increased in the ATR-treated groups. The levels of MDA were accumulated, while the levels of SOD and GSH were depleted in the liver with ATR exposure. The expression of liver lipid metabolism related genes (SCD1, DGAT2, ACC1, PPARγ) was elevated. The liver ERS was activated and the gene expression of IRE1α/XBP1 signal pathway and GRP78, GRP94 in the liver was increased. There was a correlation between the levels of ERS and the levels of lipid metabolism. These results suggested that ATR can activate ERS and promote the expression of IRE1α/XBP1 signaling pathway, and further lead to lipid metabolism disorders in rat liver. This study can provide valuable insights as a reference for the prevention and control of hazards associated with agricultural residues.

Assessing the colonization by Daphnia magna of pesticide-disturbed habitats (chlorpyrifos, terbuthylazine and their mixtures) and the behavioral and neurotoxic effects

The spread of pesticides in water bodies integrated into agricultural landscapes may prevent some areas from being colonized. In this study, the effects on the colonization responses of D. magna exerted by gradients of realistic environmental concentrations of the pesticides chlorpyrifos, terbuthylazine and their mixtures were tested in a novel multicompartment non-forced exposure system. Furthermore, the effects of both pesticides and their mixtures on the swimming behavior and the neurotransmission activity of D. magna were analyzed using a traditional forced exposure system. The synthesis and concentration of the main environmental metabolites of terbuthylazine were also analyzed. Results confirmed that D. magna exposed to mixture gradients were able to detect the pollutants and their colonization dynamics were drastically inhibited. The swimming behavior increased in D. magna exposed to the highest concentration of the mixture treatment. AChE activity was only significantly inhibited in the D. magna exposed to the highest concentration of chlorpyrifos. Changes in swimming behavior could not be directly related to the effects on AChE. Furthermore, the synthesis of the metabolite terbuthylazine 2-hydroxy during the course of the experiments was confirmed. These results demonstrate the importance of integrating pesticide mixtures in both non-forced and forced exposure systems during ecotoxicological assays.

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

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

The effects of the herbicides terbuthylazine and metazachlor at environmental concentration on the burrowing behaviour of red swamp crayfish

Despite their low concentrations in many aquatic environments, evidence exists to suggest that herbicides do affect non-target organisms. Given that burrowing is a primary life-history trait in crayfish, herbicides could potentially have serious negative effects on these ecologically important freshwater macroinvertebrates. In this study, we exposed the red swamp crayfish Procambarus clarkii to terbuthylazine (a triazine) and metazachlor (a chloroacetanilide) at an environmental concentration of 2.0 μg/L for 28 days, and then observed their burrowing behaviour for two days. The metazachlor-exposed males excavated a greater number of burrows than the other tested groups, with comparable depths and volumes relative to individual specimen weight. The relative depth and volume of female burrows were identical in all groups. The natural habit of female crayfish of constructing deeper burrows than males was marginally significant in the control and META groups but was not significant for relative volume. The hypothesized adverse effects of chronic exposure to real environmental concentrations of herbicides were not documented in terms of either relative depth or volume. However, the increased number of burrows in metazachlor-exposed animals may mean that this invasive species will cause greater damage to embankments and river banks. The mechanisms behind these effects require closer study.

Embryotoxicity of atrazine and its degradation products to early life stages of zebrafish (Danio rerio)

Triazine herbicide atrazine is considered to be moderately toxic to various aquatic animals. The aim of our study was to evaluate the acute embryotoxicity of atrazine and its two degradation products, desisopropylatrazine and desethylatrazine, and their mixture to the early life stages of zebrafish (Danio rerio) by means of a modified method of the Fish Embryo Acute Toxicity (FET) Test - OECD guideline 236. Toxic effects were studied by the evaluation of lethal endpoints and development of disorders. Furthermore, sublethal endpoints such as hatching rate, formation of somites, development of eyes, spontaneous movement, heartbeat, blood circulation, pigmentation and occurrence of edema at 24, 48, 72 and 96 h post fertilization were assessed. Newly fertilized eggs were exposed to various concentrations of atrazine, desisopropylatrazine and desethylatrazine, and their combination 0.3, 30, 100, 300, 1000, 3,000 and 10,000 μg/l, which represent environmentally relevant levels of these pollutants in surface waters and multiples of these concentrations to find out if the toxic effect depends on dose. Single substances and their combination were not associated with a negative effect on mortality. Rare malformations were observed during these embryonal toxicity tests. Only pericardial edema was recorded during the monitored observation. A significant increase in the occurrence of pericardial edema between the control 0% and the experimental group 17.6 %) was found only in the group exposed to the highest concentration of a triazine herbicide combination (10,000 μg/l) at 72 and 96 h post fertilization. Obtained results indicate that especially higher not environmentally relevant concentrations of atrazine, its metabolites or their combination present a potencial risk of embryotoxicity for zebrafish.

Comprehensive fitness evaluation of common carp (Cyprinus carpio L.) after twelve weeks of atrazine exposure

Atrazine is frequently detected in surface waters and negatively affect physiological function in aquatic organisms. Even though numerous authors have intensively studied its toxicity, only limited information concerning the long-term fish exposure is available. The aim of this study was evaluation of chronic exposure in common carp. Fish were exposed to a range of atrazine concentrations (0.3 - environmentally relevant concentration; 300; 1000; and 3000 µg/l) for twelve weeks. The potential impact of atrazine exposure was studied using various markers (behaviour; biometrical characteristics; haematological, biochemical and oxidative stress indices and histopathological changes). Most alterations were recorded at the highest concentration (3000 µg/l) which is probably due to a combined effect of both the herbicide exposure and intensive parasite infection development during second week. This group was cancelled after three weeks due to adverse health status, which partly confirmed atrazine immunotoxicity. Chronic exposure resulted in long-term reduction in feed intake followed by a significant decrease in body weight and morphological changes in gill at 1000 µg/l. At the same concentration, significant alterations in haematological (e.g. increase in erythrocyte, leukocyte, lymphocytes and neutrophil counts as well as decrease in monocyte counts) and biochemical (e.g. changes in enzyme activities; increase in glucose; decrease in ammonia) indices were documented, especially during first three weeks. Similar trend, but not so intensive, was observed at 300 µg/l. Moreover, significant changes were observed in various indicators of oxidative stress. These alterations were highly variable with both increasing and decreasing trends depending on dose and analysed tissue. Significant changes, especially in white blood profile, enzyme activities and oxidative stress indices, were proven even at 0.3 µg/l. Obtained results indicate that chronic atrazine exposure of common carp can negatively influence many indicators of health status such as behaviour, immune response, haematological and biochemical profile, oxidative stress indices and organ histopathology.

Impacts of S-metolachlor and terbuthylazine in fatty acid and carbohydrate composition of the benthic clam Scrobicularia plana

S-metolachlor (SMOC) and terbuthylazine (TBA) are herbicides that commonly appear as active ingredients (a.i.) in the composition of plant protection products. In a previous work, experimental bioassays were performed using those chemicals to find suitable molecular biomarkers to assess its toxicity to the non-target species Scrobicularia plana. The results obtained showed that the pollutants produce mortality and biochemical changes at the species, namely in protein contents and enzymatic activity levels. Thus, for a better understanding of the total biochemical impacts of those pollutants in S. plana, the composition of fatty acids (FA) and carbohydrates (CH) of the survival organisms are investigated here. In addition, since this species is edible its biochemical profile is directly related to its nutritious quality, which is analysed in this study. Furthermore, the analyses were performed in two types of tissue - the muscle and visceral mass of each survival organism. The greatest changes in FA composition are observable in small size class, being the most sensitive size class both at the toxicological and biochemical level. FA contents are higher in small organisms, both at the field and under laboratory conditions, being the disparity between size classes higher in visceral masses than in muscles. Indeed, muscles adequately represent the FA profile since those molecules appear in higher content in this tissue compared to visceral masses, becoming the better indicator tissue of biochemical changes. Besides, using muscles, less amount of biomass is needed, so it turns out to be the most cost-effective tissue to be used as endpoint in future studies. FA profiles observed at SMOC and TBA exposure are different, organisms from TBA exposure presenting a lower nutritious quality, in terms of FA abundance and diversity, than the organisms exposed to SMOC. Still, SMOC produces reductions of HUFA, essential fatty acids that cannot be synthesized by the species. Moreover, HUFA (mostly EPA and DHA) occupied the greatest part of the FA composition of organisms exposed to the control treatments and to TBA; however, the decreases of HUFA caused by the SMOC exposure change the profiles and make SFA the most dominant group. These findings represent a risk of low occurrence of essential fatty acids in entire aquatic environments exposed to the chemicals studied. Regarding CH, glucose is the only monosaccharide found in S. plana which was expected since glycogen is the main polysaccharide in animal tissues. In general, the glucose content increases with a concentration of pollutants, whereas the glycogen concentration decreases, suggesting that the glucose is being released as a response to chemical stress. Thus, this work presents tools to assess biochemical impacts of S-metolachlor and terbuthylazine in aquatic systems and to goes deeper in the knowledge of these pollutants' toxicity to non-target species to predict its propagation through aquatic trophic webs.

Redox stress and signaling during vertebrate embryonic development: Regulation and responses

Vertebrate embryonic development requires specific signaling events that regulate cell proliferation and differentiation to occur at the correct place and the correct time in order to build a healthy embryo. Signaling pathways are sensitive to perturbations of the endogenous redox state, and are also susceptible to modulation by reactive species and antioxidant defenses, contributing to a spectrum of passive vs. active effects that can affect redox signaling and redox stress. Here we take a multi-level, integrative approach to discuss the importance of redox status for vertebrate developmental signaling pathways and cell fate decisions, with a focus on glutathione/glutathione disulfide, thioredoxin, and cysteine/cystine redox potentials and the implications for protein function in development. We present a tissue-specific example of the important role that reactive species play in pancreatic development and metabolic regulation. We discuss NFE2L2 (also known as NRF2) and related proteins, their roles in redox signaling, and their regulation of glutathione during development. Finally, we provide examples of xenobiotic compounds that disrupt redox signaling in the context of vertebrate embryonic development. Collectively, this review provides a systems-level perspective on the innate and inducible antioxidant defenses, as well as their roles in maintaining redox balance during chemical exposures that occur in critical windows of development.

Oxidative stress in triazine pesticide toxicity: a review of the main biomarker findings

This review article provides a summary of the studies relying on oxidative stress biomarkers (lipid peroxidation and antioxidant enzymes in particular) to investigate the effects of atrazine and terbuthylazine exposure in experimental animals and humans published since 2010. In general, experimental animals showed that atrazine and terbuthylazine exposure mostly affected their antioxidant defences and, to a lesser extent, lipid peroxidation, but the effects varied by the species, sex, age, herbicide concentration, and duration of exposure. Most of the studies involved aquatic organisms as useful and sensitive bio-indicators of environmental pollution and important part of the food chain. In laboratory mice and rats changes in oxidative stress markers were visible only with exposure to high doses of atrazine. Recently, our group reported that low-dose terbuthylazine could also induce oxidative stress in Wistar rats. It is evident that any experimental assessment of pesticide toxic effects should take into account a combination of several oxidative stress and antioxidant defence biomarkers in various tissues and cell compartments. The identified effects in experimental models should then be complemented and validated by epidemiological studies. This is important if we wish to understand the impact of pesticides on human health and to establish safe limits.

Effects of the chloro-s-triazine herbicide terbuthylazine on DNA integrity in human and mouse cells

Terbuthylazine belongs to the chloro-s-triazine group of herbicides and acts primarily as a photosynthesis inhibitor. The mechanisms of action related to its exposure, relevant both in animals and humans, are still insufficiently investigated. This comprehensive study focused on the outcomes of terbuthylazine exposure at cell level in vitro, and a mice model in vivo. Experiments in vitro were conducted on whole human peripheral blood, isolated lymphocytes, and HepG2 cells exposed for 4 h to terbuthylazine at 8.00, 0.80, and 0.58 ng/mL, which is comparable with current reference values set by the European Commission in 2011. Terbuthylazine cytotoxicity was evaluated using dual fluorescent staining with ethidium bromide and acridine orange on lymphocytes, and CCK-8 colorimetric assay on HepG2 cells. The levels of DNA damage were measured using alkaline and hOGG1-modified comet assays. The potency of terbuthlyazine regarding induction of oxidative stress in vitro was studied using a battery of standard oxidative stress biomarkers. The in vivo experiment was conducted on Swiss albino mice exposed to terbuthlyazine in the form of an active substance and its formulated commercial product Radazin TZ-50 at a daily dose of 0.0035 mg/kg bw for 14 days. Following exposure, the DNA damage levels in leukocytes, bone marrow, liver, and kidney cells of the treated mice were measured using an alkaline comet assay. In vitro results suggested low terbuthylazine cytotoxicity in non-target cells. The highest tested concentration (8.00 ng/mL) reduced lymphocyte viability by 15%, mostly due to apoptosis, while cytotoxic effects in HepG2 cells at the same concentration were negligible. Acute in vitro exposure of human lymphocytes and HepG2 cells to terbuthylazine resulted in low-level DNA instability, as detected by the alkaline comet assay. Further characterization of the mechanisms behind the DNA damage obtained using the hOGG1-modified comet assay indicated that oxidative DNA damage did not prevail in the overall damage. This was further confirmed by the measured levels of oxidative stress markers, which were mostly comparable to control. Results obtained in mice indicate that both the active substance and formulated commercial product of terbuthylazine produced DNA instability in all of the studied cell types. We found that DNA in liver and kidney cells was more prone to direct toxic effects of the parent compound and its metabolites than DNA in leukocytes and bone marrow cells. The overall findings suggest the formation of reactive terbuthylazine metabolites capable of inducing DNA cross-links, which hinder DNA migration. These effects were most pronounced in liver cells in vivo and HepG2 cells in vitro. To provide a more accurate explanation of the observed effects, additional research is needed. Nevertheless, the present study provides evidence that terbuthylazine at concentrations comparable with current reference values possesses toxicological risk because it caused low-level DNA instability, both at cellular and animal organism level, which should be further established in forthcoming studies.

Effect of thiacloprid on early life stages of common carp (Cyprinus carpio)

Toxicity of the neonicotinoid pesticide thiacloprid to embryos and larvae of common carp Cyprinus carpio was assessed under laboratory conditions. Carp embryos and larvae were exposed to thiacloprid at four concentrations: 4.5 (environmental concentration), 45, 225, and 450 μg/L for 35 days and compared to a non-treated control group. The effects on lipid peroxidation, antioxidant enzyme levels (superoxide dismutase, glutathione reductase, catalase, glutathione S-transferase, and reduced glutathione), mortality, growth, development, and histopathogenesis were assessed. Thiacloprid at tested concentrations were not associated with negative effects on hatching, behaviour, embryo viability, or Fulton's condition factor. Carp exposed to 45 μg/L thiacloprid showed lower weight and length compared to controls. Thiacloprid at 225 and 450 μg/L delayed development and led to lower weight and length of carp. Significantly lower superoxide dismutase and glutathione reductase activity was observed at all tested concentrations of thiacloprid compared with the control group. Chronic thiacloprid exposure of early-life stages of carp affected ontogeny and growth rate, and inhibited antioxidant capacity.