Sublethal effects of the pyrethroid insecticide deltamethrin on oxidative stress parameters in green toad (Bufotes viridis L.)

Mechanism of deltamethrin biodegradation by Brevibacillus parabrevis BCP-09 with proteomic methods

Ester-containing deltamethrin pesticides are widely used in farmland and have inevitable side effects on the biosphere and human health. Microbia have been used for efficient degradation of deltamethrin, but the related mechanism and enzyme characteristics have not been elucidated. In this study, a species Brevibacillus parabrevis BCP-09 could degrade up to 75 mg L-1 deltamethrin with a degradation efficiency of 95.41%. Proteomic and genomic methods were used to explore its degradation mechanism. Enzymes belonged to hydrolases, oxidases and aromatic compound degrading enzymes were expressed enhanced and might participate in the deltamethrin degradtion. RT-PCR experiment and enzyme activity analysis verified the degradation of deltamethrin by bacterial protein. Additionally, the formation of endospores can help strain BCP-09 resist the toxicity of deltamethrin and enhance its degradation. This study supplies a scientific evidence for the application of Brevibacillus parabrevis BCP-09 in the bioremediation of environmental pollution and enriches the resources of deltamethrin-biodegradable proteins.

Biomarkers of oral subacute toxicity of deltamethrin in exposed male Albino rats

Deltamethrin is one of the most effective pyrethroid compounds, widely employed in veterinary medicine, public health, and farming. Deltamethrin-triggered oxidative stress largely causes serious harm to an organism. Acute toxicity of this compound was extensively investigated, while less information is available on its oral sub-acute effects. This study assessed, in the male Albino rats, the effects of oral gavage of either 0.874 mg/kg (0.01 LD50) or 8.740 mg/kg (0.10 LD50) of deltamethrin for successive 14 days to investigate its effects on biomarkers and to detect the tissue injury in rats following subacute deltamethrin treatment. It was found that levels of glutathione peroxidase, superoxide dismutase, and catalase in the brain, kidney, and liver, alkaline phosphatase (ALP), and uric acid in serum, hematocrit, mean corpuscular volume (MCV), white blood cells (WBC)s, eosinophils, and basophils were significantly reduced compared with untreated rats. However, when rats were treated with deltamethrin for successive 14 days, alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) activities in serum and the levels of thiobarbituric acid reactive substances (TBARs) in brain, kidney, and liver, red blood cell distribution width (RDW-CV), total protein, monocytes, and basophils and the ratios of neutrophils to lymphocytes, an aggregated marker of systemic inflammation and systemic immune inflammation indexes, significantly increased compared with the control group. Histologic lesions were observed in the liver, kidney, brain, testis, and epidemies in rats exposed to subacute deltamethrin for 14 days, and most tissues of rats treated with 0.10 LD50 of deltamethrin were more affected than those treated with 0.01 LD50. These findings strongly suggest that subacute exposure to deltamethrin caused significant systemic toxicity through oxidative stress resulting in biochemical and histological changes in the studied tissues. These findings highlight the potential harmful effects of deltamethrin and emphasize the importance of understanding the subacute effects of this compound, particularly in the context of veterinary medicine, public health, and farming.

Chronic exposure to low-dose deltamethrin can lead to colon tissue injury through PRDX1 inactivation-induced mitochondrial oxidative stress injury and gut microbial dysbiosis

OBJECTIVE

To date, it is unclear whether deltamethrin (DLM) intake causes damage to colon tissue. Hence, in this study, we aimed to clarify the effect of long-term exposure to low-dose DLM on colon tissues, and its potential mechanisms.

METHODS

Mice were treated with DLM (0.2 mg/kg/day) or DLM combined with N-acetyl-l-cysteine (NAC) (50 mg/kg/day) for 8 weeks. Human colon cancer cells (HCT-116) were treated with DLM (0, 25, 50, or 100 µM), NAC (2 mM), or overexpression plasmids targeting peroxiredoxin 1 (PRDX1) for 48 h. DLM was detected using a DLM rapid detection card. Colon injury was evaluated using haematoxylin and eosin staining and transmission electron microscopy. Apoptosis was determined using immunofluorescence staining (IF), western blotting (WB) and flow cytometry (FC) assays. MitoTracker, JC-1, and glutathione (GSH) detection were used to detect mitochondrial oxidative stress. Intestinal flora were identified by 16 S rDNA sequencing.

RESULTS

DLM accumulation was detected in the colon tissue and faeces of mice following long-term intragastric administration. Interestingly, our results showed that, even at a low dose, long-term intake of DLM resulted in severe weight loss and decreased the disease activity index scores and colon length. The results of IF, WB, and FC showed that DLM induced apoptosis in the colon tissue and cells. MitoTracker, JC-1, and GSH assays showed that DLM increased mitochondrial stress in colonic epithelial cells. Mechanistic studies have shown that increased mitochondrial stress and apoptosis are mediated by PRDX1 inhibition. Further experiments showed that PRDX1 overexpression significantly reduced DLM-induced oxidative stress injury and apoptosis. In addition, we observed that chronic exposure to DLM altered the composition of the intestinal flora in mice, including an increase in Odoribacter and Bacteroides and a decrease in Lactobacillus. The gut microbial richness decreased after DLM exposure in mice. Supplementation with NAC both in vivo and in vitro alleviated DLM-induced oxidative stress injury, colonic epithelial cell apoptosis, and gut microbial dysbiosis.

CONCLUSION

Chronic exposure to DLM, even at small doses, can cause damage to the colon tissue, which cannot be ignored. The production and use of pesticides such as DLM should be strictly regulated during agricultural production.

Chronic exposure to deltamethrin disrupts intestinal health and intestinal microbiota in juvenile crucian carp

The indiscriminate use of deltamethrin in agriculture and aquaculture can lead to residues increased in many regions, which poses negative impacts on intestinal health of aquatic organisms. Although the potential toxicity of deltamethrin have recently attracted attention, the comprehensive studies on intestinal injuries after chronic deltamethrin exposure remain poorly understood. Herein, in a 28-day chronic toxicity test, crucian carp expose to different concentrations of deltamethrin (0, 0.3, and 0.6 μg/L) were used as the research object. We found that the morphology changes and increased goblet cells in intestinal tissue, and the extent of tissue injury increased along with the increasing exposure dose of deltamethrin. Additionally, the genes expression of antioxidant activity (Cu/Zn superoxide dismutase (Cu-Zn SOD), glutathione peroxidase 1 (GPX1), and catalase (CAT)), inflammatory response (tumor necrosis factor alpha (TNFα), interferon gamma (IFNγ), and interleukin 1 beta (IL-1β)), and tight junctions (Claudin 12 (CLDN12), and tight junction protein 1 (ZO-1)) dramatically increased. Meanwhile, the apoptosis and autophagy process were triggered through caspase-9 cascade and autophagy related 5 (ATG5)- autophagy related 12 (ATG12) conjugate. Besides, chronic deltamethrin exposure increased the amount of Proteobacteria and Verrucomicrobiota, while decreased Fusobacteriota abundance, resulting in intestinal microbiota function disorders. In summary, our results highlight that chronic exposure to deltamethrin cause serious intestinal toxicity and results in physiological changes and intestinal flora disturbances.

What can we learn from commercial insecticides? Efficacy, toxicity, environmental impacts, and future developments

Worldwide pesticide usage was estimated in up to 3.5 million tons in 2020. The number of approved products varies among different countries, however, in Brazil, there are nearly 5000 of such products available. Among them, insecticides correspond to a group of mounting importance for controlling crop pests and disease-associated vectors in public health. Unfortunately, resistance to commercially approved insecticides is commonly observed, limiting the use of these products. Thus, the search for more effective and environmentally friendly products is both a challenge and a necessity since several insecticides are no longer allowed in many countries. In this review, we discuss the historical strategies used in the development of modern insecticides, including chemical structure alterations, mechanism of action and their impact on insecticidal activity. The environmental impact of each pesticide class is also discussed, with persistence data and activity on non-target organisms, along with the human toxicological effect. By tracing the historical route of discovery and development of blockbuster pesticides like DDT, pyrethroids and organophosphates, we also aim to categorize and relate the successful chemical alterations and novel pesticide development strategies that resulted in safer alternatives. A brief discussion on the Brazilian registration procedure and a perspective of insecticides currently approved in the country was also included.

Impact of desiccation pre-exposure on deltamethrin-induced oxidative stress in Bombina variegata juveniles

Global warming represents a severe threat to existing ecosystems, especially for anuran tadpoles who encounter significant fluctuations in their habitats. Decreasing water levels in permanent and temporary water bodies is a significant risk for larval survival or fitness. On the other hand, the natural environment of amphibians is extremely polluted by various xenobiotics. This study evaluated how pre-exposure of Bombina variegata tadpoles to chronic environmental stress (desiccation) modulates the biochemical response of juvenile individuals to following acute chemical stressor (pesticide deltamethrin). Our results demonstrated that individually applied pesticide changed the thiol and lipid status of the treated juveniles but animals subjected solely to desiccation pressure were more tolerant to free radicals and showed no induction of lipid peroxidation. Comparison of juveniles exposed to deltamethrin revealed that desiccation pretreatment during the larval stage of development modified cellular protection in the juveniles. Higher activities of CAT, GSH-Px and GR were recorded in the pre-exposed group, as well as a lower degree of lipid peroxidation relative to the group that was not pre-exposed to low water stress. Pre-desiccated groups displayed the greatest range of coordination of investigated antioxidant parameters, supported by Pearson's correlations. Activation of the GSH-redox system is a significant marker in juveniles against stress caused by desiccation and a chemical stressor. The stressful environment experienced during tadpole development produced an adaptive reaction to subsequent exposure to another stressor in juveniles. To develop relevant management and conservation strategies, more studies of the interactive effects of environmental and chemical stressors are necessary.

Histopathologic and genotoxic effects of deltamethrin on marsh frog, Pelophylax ridibundus (Anura: Ranidae)

It is known that amphibians inhabiting agricultural areas are constantly exposed to chemicals such as insecticides. Deltamethrin, a type II pyrethroid insecticide, is widely used in the world. The present study aimed to investigate the toxic effects of different concentrations (0.625, 1.25, and 2.50 mg/kg body wt) of orally applied deltamethrin to marsh frog (Pelophylax ridibundus) after 96 h of treatment. The histopathological abnormalities in liver, gastrointestinal tract, and kidney tissues were evaluated with quantitative analyses. In liver, increase of melanomacrophagic aggregates, non-homogeneous hepatocyte parenchyma, sinusoidal dilatations, infiltration, vascular epithelial degeneration, central vein degeneration, and congestion were determined in exposed frogs. In gastrointestinal tract, vacuolization, hypertrophy, congestion, infiltration, necrosis, and erosion of the epithelial layer, increasing goblet secretion, degeneration in villi, epithelial disorganization, and edema were observed in high-dose groups. In all experimental groups, glomerular shrinkage, hemorrhage, degeneration, infiltration, increase in Bowman distance, and eosinophilic-stained tubular lumens were detected in kidneys. Histopathological changes were more prominent in 1.25 and 2.50 mg/kg groups than the other groups. To determine the genotoxic effects of deltamethrin, the peripheral blood samples of the frogs were used. The erythrocytic nuclear abnormalities such as micro-nucleus, double-nucleus, kidney-shaped nucleus, notched nucleus, and bud nucleus were determined in the frogs, and the genotoxicity did not show a significant increase between control and low-dose groups, statistically. However, the genotoxic effects increased in medium- and especially high-dose groups. The results of this study showed that acute deltamethrin exposure can lead to histopathologic and genotoxic effects in P. ridibundus.

Nano-curcumin versus curcumin in amelioration of deltamethrin-induced hippocampal damage

We aimed to prove that oxidative stress is the main mechanism responsible for hippocampal neurotoxicity induced by deltamethrin (DLM). The protective role of curcumin (CMN) and nano-curcumin (NCMN) over this toxicity was studied. The rats were categorized into four groups: control, DLM, CMN and NCMN. The study continued for 30 days. Hippocampus was processed for histological, biochemical and immunohistochemical studies. Caspase-3, glial fibrillar acidic protein (GFAP), acetylcholinesterase (AChE), malondialdehyde (MDA), glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) were measured for DLM-induced oxidative stress (increased MDA by 354%/decreased GSH by 61%, SOD by 61%, CAT 57%). Oxidative stress induced apoptosis of hippocampal neurons through increasing Nrf2, gamma-glutamyl cysteine synthetase heavy subunit (GCS-HS) and light subunit (GCS-LS) and decreasing AChE. It increases the activity of astrocytes through increasing GFAP. Finally, oxidative stress has a bad impaction on cognitive function. Improvement of oxidative stress was observed with use of CMN and NCMN (decrease of MDA/increase of GSH, SOD, CAT). The level of Nrf2, GCS-HS and GCS-LS decreased, while AChE, GFAP increased. Improvement of cognitive function was observed in both groups. In conclusion, oxidative stress is the common mechanism responsible for DLM-induced hippocampal neurotoxicity. It exerts apoptosis of hippocampal neurons through increasing Nrf2, HS-GCS, LS-GCS and decreasing AChE. In addition, it activates astrocytes through increasing expression of GFAP. The protective role of CMN and CMMN is related to their potent antioxidant effect. Much improvement has been detected with NCMN as compared to CMN.

Biochemical parameters in skin and muscle of Pelophylax kl. esculentus frogs: Influence of a cyanobacterial bloom in situ

There is little information in scientific literature as to how conditions created by a microcystin (MC) producing cyanobacterial bloom affect the oxidant/antioxidant, biotransformation and neurotoxicity parameters in adult frogs in situ. We investigated biochemical parameters in the skin and muscle of Pelophylax kl. esculentus from Lake Ludaš (Serbia) by comparing frogs that live on the northern bloom side (BS) of the lake with those that inhabit the southern no-bloom side (NBS). A higher protein carbonylation level and lower antioxidant defense system capability in the skin of frogs living in conditions of the cyanobacterial bloom were observed. Inhibition of glutathione-dependent machinery was the major mechanism responsible for the induction of cyanobacterial bloom-mediated oxidative stress in frog skin. On the other hand, the detected higher ability of muscle to overcome bloom prooxidant toxicity was linked to a higher efficiency of the biotransformation system through glutathione-S-transferase activity and/or was the consequence of indirect exposure of the tissue to the bloom. Our results have also revealed that the cyanobacterial bloom conditions induced the cholinergic neurotransmitter system in both tissues. This study provides a better understanding of the ecotoxicological impact of the MC producing cyanobacterial bloom on frogs in situ. However, further investigations of the complex mechanism involved in cyanobacterial bloom toxicity in real environmental conditions are required.

Deltamethrin toxicity: A review of oxidative stress and metabolism

Deltamethrin is widely used worldwide due to its valuable insecticidal activity against pests and parasites. Increasing evidence has shown that deltamethrin causes varying degrees of toxicity. Moreover, oxidative stress and metabolism are highly correlated with toxicity. For the first time, this review systematically summarizes the deltamethrin toxicity mechanism from the perspective of oxidative stress, including deltamethrin-mediated oxidative damage, antioxidant status, oxidative signaling pathways and modulatory effects of antagonists, synergists and placebos on oxidative stress. Further, deltamethrin metabolism, including metabolites, metabolic enzymes and pathways and deltamethrin metabolite toxicity are discussed. This review will shed new light on deltamethrin toxicity mechanisms and provide effective strategies to ensure pest control and prevention of human and animal poisoning.

Influence of triazole pesticides on tillage soil microbial populations and metabolic changes

Pesticides are generally applied to agricultural soil to control crop diseases, with the critical goal of preventing yield loss and optimizing economic returns. However, the excessive utilization of pesticides in agriculture is a severe environmental and human health problem. In the present study, effect of triazole based fungicide, propiconazole on soil physicochemical properties, stimulatory impact of propiconazole residue on soil microbial communities and soil enzyme activities (phosphatise and urease) in contaminated red sandy loam and deep black soils of paddy (Oryza sativa L.) fields at different concentrations were evaluated. The liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis showed high levels of propiconazole residues of 434 and 426 ng g^-1 in red sandy loam and deep black soils, respectively. A total of 27 bacterial and 18 fungal strains were isolated from propiconazole-contaminated soils, identified by molecular markers and had their sequences deposited in the GenBank. We observed a pronounced increase in soil microbial growth, and urease and phosphatase activities at lower propiconazole concentrations up to 2 weeks post-treatment. On the contrary, the microbial growth and urease and phosphatase activities were relentlessly reduced at higher propiconazole concentrations and a long incubation period after 2 to 4 weeks of post-treatment. Overall, it was concluded that the concentration-dependency and incubation period of propiconazole would enhance the growth and activity of soil microbes and enzymes respectively and the higher application will be detrimental to the soil health.

Non-target toxicity of novel insecticides

Humans have used insecticides since ancient times. The spectrum and potency of available insecticidal substances has greatly expanded since the industrial revolution, resulting in widespread use and unforeseen levels of synthetic chemicals in the environment. Concerns about the toxic effects of these new chemicals on non-target species became public soon after their appearance, which eventually led to the restrictions of use. At the same time, new, more environmentally-friendly insecticides have been developed, based on naturally occurring chemicals, such as pyrethroids (derivatives of pyrethrin), neonicotinoids (derivatives of nicotine), and insecticides based on the neem tree vegetable oil (Azadirachta indica), predominantly azadirachtin. Although these new substances are more selective toward pest insects, they can still target other organisms. Neonicotinoids, for example, have been implicated in the decline of the bee population worldwide. This review summarises recent literature published on non-target toxicity of neonicotinoids, pyrethroids, and neem-based insecticidal substances, with a special emphasis on neonicotinoid toxicity in honeybees. We also touch upon the effects of pesticide combinations and documented human exposure to these substances.

Prooxidant effects of chronic exposure to deltamethrin in green toad Bufotes viridis

Pesticide-induced oxidative stress, as one of mechanism of toxicity, has been a focus of toxicological research. However, there is a lack of data for certain pesticides-oxidative stress effects especially on terrestrial amphibians. This study evaluates the prooxidative effects of orally administered insecticide deltamethrin (DM) in some tissues of the terrestrial toad Bufotes viridis. Toads were randomly divided and assigned to a control group and a test group that was orally exposed to the pesticide (5 mg/kg of body weight/daily) for 21 days. Animals were euthanized from each group on days 7, 14, and 21, and the liver, leg muscle, ventral skin, and gastrointestinal tissue (GIT) were dissected and used for analysis. From battery of investigated antioxidant components, superoxide dismutase (SOD) was the most differentiate parameter in all examined tissues. For the period of prolonged exposure to pesticide, antioxidative strategy of Bufotes viridis was based on SOD utilization in attempt to maintain the oxidative disbalance at acceptable level. The integrated biomarker response (IBR) as the measure of the overall biochemical response to DM exposure revealed that the group exposed for 21 days had the highest response. Our work has offered valuable data ensuring evidence that toads exposed to deltamethrin developed adaptive reactions that were tissue-specific and that DM-generated systemic toxicity was time-dependent. The present work showed that oxidative stress has significant role in pesticide-induced toxicity and contributes to better understanding of ecotoxicological risk in the terrestrial amphibians exposed to DM.