Dichlorvos exposure results in large scale disruption of energy metabolism in the liver of the zebrafish, Danio rerio

Seawater quality criteria derivation and ecological risk assessment for dichlorvos in China

Dichlorvos (DDVP) is a widely used organophosphorus pesticide (OPP) that has been frequently detected in the marine environment of China. Water quality criteria (WQC) is however not available for this emergent pollutant in the marine environment, which hinders its ecological risk assessment. This study, therefore, screened toxicity values of DDVP and conducted toxicity tests on six marine species to supplement toxicity data. The WQC for DDVP was derived with the species sensitivity distribution (SSD) methodology, based on which the ecological risk of DDVP in the seawater of China was assessed. The results showed that the recommended short-term (SWQC) and long-term water quality criteria (LWQC) for DDVP were 1.47 and 0.0521 μg/L, respectively. Most marine waters of China showed low or negligible risk (HQ < 1, ORP < 2 %), whereas some estuarine waters warrant further concern due to higher risk. This study provides the scientific basis for seawater quality standard formulation and ecological risk management for DDVP.

Pesticide-Induced Alterations in Locomotor Activity, Anxiety, and Depression-like Behavior Are Mediated through Oxidative Stress-Related Autophagy: A Persistent Developmental Study in Mice

Chlorpyrifos (CPF), dichlorvos (DDV), and cypermethrin (CP), as commonly used pesticides, have been implicated in inducing neuropsychiatric disorders, such as anxiety, depression-like behaviors, and locomotor activity impairment. However, the exact molecular mechanisms of these adverse effects, particularly in both sexes and their next-generation effects, remain unclear. In this study, we conducted behavioral analysis, along with cellular assays (monodansylcadaverine staining) and molecular investigations (qRT-PCR and western blotting of mTOR, P62, and Beclin-1) to clear the potential role of autophagy in pesticide-induced behavioral alterations. For this purpose, 42 adult female and 21 male inbred ICR mice (F0) were distributed into seven groups. Maternal mice (F0) and 112 F1 offspring were exposed to 0.5 and 1 ppm of CPF, DDV, and CP through drinking water. F1 male and female animals were studied to assess the sex-specific effects of pesticides on brain tissue. Our findings revealed pronounced anxiogenic effects and impaired locomotor activity in mice. F1 males exposed to CPF (1 ppm) exhibited significantly elevated depression-like behaviors compared to other groups. Moreover, pesticide exposure reduced mTOR and P62 levels, while enhancing the Beclin-1 gene and protein expression. These changes in autophagy signaling pathways, coupled with oxidative and neurogenic damage in the cerebral cortex and hippocampus, potentially contribute to heightened locomotor activity, anxiety, and depression-like behaviors following pesticide exposure. This study underscores the substantial impact of pesticides on both physiological and behavioral aspects, emphasizing the necessity for comprehensive assessments and regulatory considerations for pesticide use. Additionally, the identification of sex-specific responses presents a crucial dimension for pharmaceutical sciences, highlighting the need for tailored therapeutic interventions and further research in this field.

Cellular metabolism and health impacts of dichlorvos: Occurrence, detection, prevention, and remedial strategies-A review

Dichlorvos (2,2-Dichlorovinyl dimethyl phosphate, [DDVP]) belongs to the class of organophosphates and is widely used as an insecticide in agriculture farming and post-harvest storage units. Extensive research has been conducted to assess the factors responsible for the presence of DDVP in terrestrial and aquatic ecosystems, as well as the entire food chain. Numerous studies have demonstrated the presence of DDVP metabolites in the food chain and their toxicity to mammals. These studies emphasize that both immediate and chronic exposure to DDVP can disrupt the host's homeostasis, leading to multi-organ damage. Furthermore, as a potent carcinogen, DDVP can harm aquatic systems. Therefore, understanding the contamination of DDVP and its toxicological effects on both plants and mammals is vital for minimizing potential risks and enhancing safety in the future. This review aimed to comprehensively consolidate information about the distribution, ecological effects, and health impacts of DDVP, as well as its metabolism, detection, prevention, and remediation strategies. In summary, this study observes the distribution of DDVP contaminations in vegetables and fruits, resulting in significant toxicity to humans. Although several detection and bioremediation strategies are emerging, the improper application of DDVP and the alarming level of DDVP contamination in foods lead to human toxicity that requires attention.

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.

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).

Commercial pesticides for urban applications induced population growth and sub-cellular alterations in Raphidocelis subcapitata (Chlorophyceae) at concerning environmental concentrations

Information regarding the safety and environmental risks of pesticides intended for urban use remains limited. This study aimed to assess the effects of four common pesticides on the microalga Raphidocelis subcapitata: DIAZINON® 25% C. E., Roundup®, URBACIN® 20C. E., and VAPODEL® 20% C. E., which are commercial formulations of diazinon, glyphosate, dichlorvos, and cypermethrin, respectively. According to 96-h inhibition of population growth bioassays, the four pesticide toxicities exemplified the following order: DIAZINON® (diazinon) > Roundup® (glyphosate) > VAPODEL® (dichlorvos) > URBACIN® (cypermethrin). Increasing pesticide concentrations elicited alterations in the specific growth rates (µmax). The macromolecule contents and photosynthetic pigments increased in groups exposed to the highest concentrations of DIAZINON® 25%, Roundup®, and URBACIN® 20 compared to the control group, despite these treatments inducing lower population growth rates. VAPODEL® 20% induced higher growth rates and lower macromolecule content compared to the control. Since active ingredients were not quantified, certain comparisons may prove limiting, but it is important to assess the effects of the whole mixtures in the form that they enter the environment, especially for urban-intended applications or generic formulations with higher additive contents. Finally, this study demonstrated that commercial pesticide formulations designed for urban applications might pose a threat to freshwater microalgae due to their underestimated toxic potential, but further studies are required.

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.

Quercetin-3-O-β-D-Glucopyranoside-Rich Fraction from Spondias mombin Leaves Halted Responses from Oxidative Stress, Neuroinflammation, Apoptosis, and Lipid Peroxidation in the Brain of Dichlorvos-Treated Wistar Rats

Dichlorvos (2,3-dichlorovinyl dimethyl phosphate or DDVP), is a popular organophosphate (OP) with several domestic, industrial, and agricultural uses and applications in developing countries [...].

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

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

Getting more out of the zebrafish light dark transition test

In (eco-)toxicological studies the light/dark transition (LDT) test is one of the most frequently used behaviour assays with zebrafish eleutheroembryos. However, study results vary regarding data presentation and analysis and mostly focus on a limited amount of the recorded data. In this study, we investigated whether monitoring two behavioural outcomes (time and distance moved) together with analysing multiple parameters can improve test sensitivity and data interpretation. As a proof of principle 5-day old zebrafish (Danio rerio) eleutheroembryos exposed to either endocrine disruptors (EDs) or acetylcholine esterase (AChE) inhibitors were investigated. We analysed conventional parameters such as mean and sum and implemented additional endpoints such as minimum or maximum distance moved and new parameters assessing the bursting response of eleutheroembryos. Furthermore, changes in eleutheroembryonic behaviour during the moment of the light to dark transition were added. To improve data presentation control-normalised results were displayed in radar charts, enabling the simultaneous presentation of different parameters in relation to each other. This enabled us to identify parameters most relevant to a certain behavioural response. A cut off threshold using control data was applied to identify parameters that were altered in a biological relevant manner. Our approach was able to detect effects on different parameters that remained undetected when analysis was done using conventional bar graphs on - in most cases analysed - averaged, mean distance moved values. By combining the radar charts with additional parameters and by using control-based thresholds, we were able to increase the test sensitivity and promote a deeper understanding of the behaviour response of zebrafish eleutheroembryos in the LDT test and thereby increased its usability for behavioural toxicity studies.

Alterations in hematological parameters and the structure of peripheral erythrocytes in Nile tilapia (Oreochromis niloticus) exposed to profenofos

The burden of pesticide use from agricultural intensification lies in the fact that pesticides may end up in aquatic ecosystems and have pernicious effects on non-target organisms, including fish. Different blood biomarkers, including hemato-biochemical indices, erythrocytic nuclear abnormalities (ENA), and erythrocytic cellular abnormalities (ECA), were observed in Nile tilapia (Oreochromis niloticus) after exposure to varying sub-lethal concentrations (0%, 5%, 10%, 20%, and 40% of 96-h LC50) of profenofos at different time intervals (7, 14, 21, and 28 days). The results revealed that glucose and white blood cell (WBC) levels significantly increased, while hemoglobin, red blood cell (RBC), and packed cell volume (PCV) significantly decreased in a time- and concentration-dependent manner. Aberrant erythrocytic morphology-derived ENA, such as nuclear degeneration, micronuclear formation, binuclear development, nuclear budding, and karyopyknosis, significantly increased with time in profenofos-exposed groups compared to controls. Between the treatment and control groups, a significant execution was discerned for teardrop and fusion type ECA. For other cellular aberrations of erythrocytes, including elongated, twin, and spindle, a significant difference appeared only at the beginning of the experiment (day 7). This study concludes that the presence of widely used profenofos in aquatic systems has a pernicious effect on Nile tilapia.

Correlation between acute brain injury and brain metabonomics in dichlorvos-poisoned broilers

Dichlorvos (DDVP) is an insecticide with neurotoxicity that is widely used in agricultural production and life. However, the effects of acute DDVP poisoning on brain tissue remain underinvestigated. The purpose of this study was to evaluate the differences within 15 min-6 h in plasma biochemical indexes, brain histology and metabolites among three groups of commercial broilers orally administered different dosages of DDVP one time: (1) high-dose group (11.3 mg/kg), (2) low-dose group (2.48 mg/kg) and (3) control group (0 mg/kg). The results of biochemical indexes showed that acute DDVP poisoning could cause hyperglycemia and oxidative stress in poisoned broilers. Histological examination showed that DDVP could induce brain edema, abnormal expression of glial fibrillary acidic protein (GFAP) and neuronal mitochondrial damage in broilers. Whole-brain metabolism showed that DDVP could significantly change the secretion of neurotransmitters, energy metabolism, amino acid metabolism and nucleotide metabolism. Correlation analysis showed that metabolites such as hypoxanthine, acetylcarnitine and glucose 6-phosphate were significantly correlated with blood glucose, biomarkers of oxidative stress and brain injury pathology. The results of this study provide new insights into the molecular mechanism of brain tissue responses to acute DDVP exposure in broilers and deliver important information for clinical research on neurodegenerative diseases caused by acute DDVP poisoning.

Transcriptome-Based Identification of Genes Responding to the Organophosphate Pesticide Phosmet in Danio rerio

Organophosphate pesticides (OPPs) are one of the most widely used insecticides. OPPs exert their neurotoxic effects by inhibiting acetylcholine esterase (AChE). Most of the gross developmental abnormalities observed in OPP-treated fish, on the other hand, may not be explained solely by AChE inhibition. To understand the overall molecular mechanisms involved in OPP toxicity, we used the zebrafish (ZF) model. We exposed ZF embryos to an OPP, phosmet, for 96 h, and then analyzed developmental abnormalities and performed whole transcriptome analysis. Phenotypic abnormalities, such as bradycardia, spine curvature, and growth retardation, were observed in phosmet-treated ZF (PTZF). Whole transcriptome analysis revealed 2190 differentially expressed genes (DEGs), with 822 and 1368 significantly up-and downregulated genes, respectively. System process and sensory and visual perception were among the top biological pathways affected by phosmet toxicity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment of metabolic pathways, calcium signaling pathway, regulation of actin cytoskeleton, cardiac muscle contraction, drug metabolism-other enzymes, and phototransduction. Quantitative real-time PCR results of six DEGs agreed with the sequencing data expression profile trend. Our findings provide insights into the consequences of phosmet exposure in ZF, as well as an estimate of the potential risk of OPPs to off-target species.

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.

Emerging Technologies for Degradation of Dichlorvos: A Review

Dichlorvos (O,O-dimethyl O-(2,2-dichlorovinyl)phosphate, DDVP) is a widely acknowledged broad-spectrum organophosphorus insecticide and acaracide. This pesticide has been used for more than four decades and is still in strong demand in many developing countries. Extensive application of DDVP in agriculture has caused severe hazardous impacts on living systems. The International Agency for Research on Cancer of the World Health Organization considered DDVP among the list of 2B carcinogens, which means a certain extent of cancer risk. Hence, removing DDVP from the environment has attracted worldwide attention. Many studies have tested the removal of DDVP using different kinds of physicochemical methods including gas phase surface discharge plasma, physical adsorption, hydrodynamic cavitation, and nanoparticles. Compared to physicochemical methods, microbial degradation is regarded as an environmentally friendly approach to solve several environmental issues caused by pesticides. Till now, several DDVP-degrading microbes have been isolated and reported, including but not limited to Cunninghamella, Fusarium, Talaromyces, Aspergillus, Penicillium, Ochrobium, Pseudomonas, Bacillus, and Trichoderma. Moreover, the possible degradation pathways of DDVP and the transformation of several metabolites have been fully explored. In addition, there are a few studies on DDVP-degrading enzymes and the corresponding genes in microorganisms. However, further research relevant to molecular biology and genetics are still needed to explore the bioremediation of DDVP. This review summarizes the latest development in DDVP degradation and provides reasonable and scientific advice for pesticide removal in contaminated environments.

Cadmium induced skeletal underdevelopment, liver cell apoptosis and hepatic energy metabolism disorder in Bufo gargarizans larvae by disrupting thyroid hormone signaling

Cadmium (Cd) is hazardous to human health and it is also highly detrimental to amphibian life. In this study, Bufo gargarizans larvae were exposed to environmentally relevant Cd concentrations of 5, 100 and 200 μg L^-1 from Gosner stage (Gs) 26 to Gs 42 of metamorphic climax about 6 weeks. The results showed thyroid structural injuries and thyroid signaling disruption were induced by high Cd exposure (100 and 200 μg L^-1). Moreover, tadpole skeleton including whole body, vertebrata, forelimb and hindlimb was developmentally delayed by high Cd exposure through downregulating the mRNA expressions of genes involved with skeletal ossification and growth pathway. Moreover, liver histopathological injuries were caused by high Cd exposure featured by hepatocytes malformation, nuclear degeneration and increasing melanomacrophage centers. Meanwhile, liver apoptosis rate showed on the rise in a dose-dependent way and Cd stimulated liver apoptosis by upregulating mRNA expressions of genes related to extrinsic and intrinsic apoptosis pathways. Furthermore, high Cd caused hepatic glucometabolism disorder by decreasing the genetic expressions associated with glycolysis and mitochondrial oxidative phosphorylation. In addition, liver lipid metabolism was disrupted by high Cd exposure through downregulating mRNA levels of genes related to fatty oxidation and upregulating mRNA levels of genes related to fatty acid synthesis. We suggested that Cd did great harm to tadpole health by disturbing thyroid function, skeletal growth, liver cell apoptosis signaling and hepatic energy metabolism pathway.

Simulation of hemo- and biochemical toxicities associated with chronic inhalation exposure to 2,2-Dichlorovinyl dimethyl phosphate (DDVP) in Wistar rat

DDVP is a commonly used pesticide in Nigeria and those involved with DDVP manufacturing, packaging or utilizing facilities seldom use PPE to limit pesticide exposure. The study aim was to determine the impact of chronic exposure to DDVP by monitoring hematological and biochemical changes in Wistar rats. Male rats (n = 60; 150-180 g) were exposed to graded DDVP concentrations (0%, 20 %, 40 %, 60 %, 80 % and 100 %) via inhalation route for 60 days. Body weights were initially measured and then at 20-day intervals. Blood samples were collected for hematology and serum biochemistry on day 61. Results showed significant (p < 0.05) polycythemia, neutrophilia, thrombocytosis, hepatic and renal derangement in rats exposed to DDVP. Also, albumin, AST, ALP, creatinine, blood urea nitrogen, bilirubin levels and dyslipidemia significantly increased. Cholinergic signs and stunted growth were observed in higher concentrations. Study emphasized hazards of DDVP mishandling and risks of non-compliance with PPE use by workers in-contact with DDVP, as well as misuse/abuse in animals.

Mixed toxicity of chlorpyrifos and dichlorvos show antagonistic effects in the endangered fish species golden mahseer (Tor putitora)

Golden mahseer (Tor putitora) is an economically important but endangered fish species in many countries. Increasing pesticide application can possess a threat to this species but their sensitivity to pesticides, typically chlorpyrifos and dichlorvos, is unknown. We determined 96 h-LC₅₀ of chlorpyrifos and dichlorvos to be 0.753 mg/L and 12.964 mg/L, respectively, indicating higher toxicity of chlorpyrifos than dichlorvos. Despite the same mode of action, their joint effect was antagonistic, with an additive index value of - 0.58 at 96 h-LC₅₀. Moreover, to get insights in the temporal sub-lethal effects, fish were exposed to 10% and 50% of the 96 h-LC₅₀ values of the respective pesticides. Aerobic metabolism, opercular movements, and feeding behavior were examined for sub-lethal end-points following 24 h, 48 h, 72 h and 96 h exposure. Both chlorpyrifos and dichlorvos in single exposures induced a significant drop in oxygen consumption rate; while it was significantly elevated in the mixed pesticide exposure. Accelerated opercular movements were observed in all pesticide treatment groups but were more persistent in chlorpyrifos treatments. Reduced feeding attempts were more pronounced in chlorpyrifos and mixture treatments wherein feeding attempts dropped to zero. Overall, the acute toxicity data reported in the present study can be used to assess the maximum tolerance level of golden mahseer to chlorpyrifos and dichlorvos, and their mixture. Furthermore, the sub-lethal end point responses can be applied in monitoring the environmental risk posed by these waterborne pesticides either individually or in combination to the aquatic life.

Effects of sublethal phoxim exposure and lower food intake on nutrient metabolism in the midguts of Bombyx mori

Silkworm (Bombyx mori) is an economically important insect. However, the survival of silkworms has been significantly affected by the assault of chemical pesticides on mulberry trees through aerial application and water currents. Phoxim is a broad-spectrum organophosphorus insecticide widely used in China. Currently, very little is known about the non-neuronal effects of sublethal exposure to phoxim. The purpose of this study was to investigate the non-neuronal effects of sublethal phoxim exposure in the silkworm midgut, with a focus on nutrient metabolism. After phoxim treatment, lipase activity in the silkworm was shown to be up-regulated at 24 h before a decreasing trend was seen. Meanwhile, α-amylase activity showed the opposite trend. The expression levels of mitochondrial respiratory chain-related genes were all up-regulated at 24 h before falling continuously. To ensure that the effects of phoxim on nutrient metabolism were not simply a consequence of a decrease in mulberry consumption, the silkworms were treated with a reduced-food diet before the digestive enzyme activities and the transcription levels of mitochondrial respiratory chain-related genes were analyzed. Our results showed that the patterns in the reduced-diet and phoxim-exposed silkworm were markedly different, suggesting the alterations in the phoxim-exposed silkworm cannot readily be explained by nutrient deprivation.

Thiophanate-methyl induces severe hepatotoxicity in zebrafish

Thiophanate-methyl (TM) is widely used all over the world and is a typical example of pesticide residues, which can be detected in the soil, and even in vegetables and fruits. However, the molecular mechanisms underlying the hepatotoxicity of TM are not well understood. In this study, we utilized zebrafish to comprehensively evaluate the hepatotoxicity of TM and explore how the molecular mechanisms of hepatotoxicity are induced. The zebrafish larvae were exposed in 6.25, 12.5 and 25 mg/L TM from 72 to 144 hpf, while the adults were exposed in 2, 4 and 6 mg/L TM for 28 days. Here, we found that 12.5 and 25 mg/L TM induces specifically serious hepatotoxicity but not the toxicity of other organs in zebrafish larvae and adults. Moreover, it might triggered hepatotoxicity by activating the caspase-3 through apoptotic pathways and oxidative stress in zebrafish. Subsequently, this resulted in a metabolic imbalance in the zebrafish's liver. In conclusion, our results disclosed the fact that TM may induce severe hepatotoxicity by mediating activation of caspase-3 and oxidative stress in zebrafish.

Investigation of the effects of dichlorvos poisoning on AMPK signaling pathway in chicken brain tissues

Dichlorvos is a common crop insecticide widely used by people which causes extensive and serious environmental pollution. However, it has been shown that organophosphorus poisoning causes energy metabolism and neural disorders. The overall purpose of this study was to investigate the damage to brain tissue and the changes in AMPK signaling pathway-related gene expression after dichlorvos poisoning in chickens. White-feathered broiler chickens, as the research subjects of this experiment, were divided into three groups: control group, low-dose group (77.5% dichlorvos at 1.13 mg/kg dose) and high-dose group (77.5% dichlorvos at 10.2 mg/kg dose). Clinical symptoms were observed after modeling, and an integrative analysis was conducted using HE staining microscopy, immune-histochemical microscopy, electron microscopy and PCR arrays. The results showed that the high-dose group had more obvious dyspnea, salivation, convulsion and other neurological phenomena. Pathological sections showed that nuclear disintegration of neurons was most obvious in the low-dose group, and apoptosis of brain cells was most obvious in the high-dose group, and the mitochondrial structure was destroyed in the two poisoned group, i.e. low-dose group and high-dose group. PCR arrays showed that AMPK signaling pathway was inhibited and the expressions of genes involved in energy metabolism (ACACA and PRKAA1) were significantly changed. Furthermore, genes associated with protein synthesis (EIF4EBP1) were significantly upregulated. FASN and HMGCR expressions were significantly increased. There were significant changes in the expressions of cell cycle-related genes (STK11, TP53 and FOXO3). Organophosphate poisoning can cause a lot of nuclear disintegration of brain neurons, increases cell apoptosis, disrupts the energy metabolism of mitochondrial structure, and inhibits the AMPK signaling pathway. These results provide a certain idea and basis for studying the mechanism of AMPK signaling after organophosphorus poisoning and provide a research basis for the prevention and treatment of organophosphorus poisoning.

The detoxifying effect of Polygonum equisetiforme extracts against dichlorvos (DDVP)-induced oxidative stress and neurotoxicity in the commercial clam Ruditapes decussatus

Effects of Polygonum equisetiforme extracts against dichlorvos were investigated in the commercial clam Ruditapes decussatus. The toxicity of this pesticide was firstly tested in R. decussatus gill and digestive gland tissues using five doses varying from 0.05 to 1 mg/l during 2, 4, and 7 days. Results showed that 0.05 mg/l of DDVP induced oxidative stress and neurotoxicity in R. decussatus after 2 days of exposure. Investigations of the effects of P. equisetiforme extracts in R. decussatus exposed to 0.25 mg/l of DDVP were made in clams receiving three concentrations (0.009, 0.045, and 0.09 g/l) during 4 and 7 days. Antioxidant enzymes SOD and CAT as well as H₂O₂ content and AChE were quantified by colorimetric method. Four days of exposure to DDVP increased SOD and CAT activities and enhances H₂O₂ content. AChE levels decreased considerably following DDVP exposure, although a restoration in the enzyme activity was observed with P. equisetiforme extract (E3 = 0.09 g/l). Overall, P. equisetiforme extract at concentration (E1 = 0.009 g/l) prevents oxidative stress caused by DDVP, while 0.09 g/l of P. equisetiforme extract induced an effect similar to that obtained with DDVP alone. Nevertheless, this concentration was found effective for the restoration of the AChE activity.

Toxicity testing of pesticides in zebrafish-a systematic review on chemicals and associated toxicological endpoints

The use of zebrafish (Danio rerio) has arisen as a promising biological platform for toxicity testing of pesticides such as herbicides, insecticides, and fungicides. Therefore, it is relevant to assess the use of zebrafish in models of exposure to investigate the diversity of pesticide-associated toxicity endpoints which have been reported. Thus, this review aimed to assess the recent literature on the use of zebrafish in pesticide toxicity studies to capture data on the types of pesticide used, classes of pesticides, and zebrafish life stages associated with toxicity endpoints and phenotypic observations. A total of 352 articles published between September 2012 and May 2019 were curated. The results show an increased trend in the use of zebrafish for testing the toxicity of pesticides, with a great diversity of pesticides (203) and chemical classes (58) with different applications (41) being used. Furthermore, experimental outcomes could be clustered in 13 toxicity endpoints, mainly developmental toxicity, oxidative stress, and neurotoxicity. Organophosphorus, pyrethroid, azole, and triazine were the most studied classes of pesticides and associated with various toxicity endpoints. Studies frequently opted for early life stages (embryos and larvae). Although there is an evident lack of standardization of nomenclatures and phenotypic alterations, the information gathered here highlights associations between (classes of) pesticides and endpoints, which can be used to relate mechanisms of action specific to certain classes of chemicals.

The regulation of autophagy in the pesticide-induced toxicity: Angel or demon?

Pesticides have become an essential tool for pest kill, weed control and microbiome inhibition for both agricultural and domestic use. However, with the massive use, pesticides can exist in soil, air and water, and sometimes even accumulate in the human or other mammals through food chains. Lots of researches have proven that pesticides possess toxicity to mammals on endocrine, neural and immune systems. Autophagy, as a conservative intracellular process, which is activated by stress-related signals, plays a pivotal role, either "angle" or "demon", in regulation of cell fate and function. Recent evidences in researches elucidated a strong link between the autophagy and the toxicity of pesticides. In this review, we summarized the previous researches which focus on the autophagy regulation in the pesticides-induced toxicity, and hope that this work can help us to discover a potential strategy for the treatment of the disease caused by pesticides.

Analysis of tail coiling activity of zebrafish (Danio rerio) embryos allows for the differentiation of neurotoxicants with different modes of action

In (eco)toxicology, there is a critical need for efficient methods to evaluate the neurotoxic potential of environmental chemicals. Recent studies proposed analysis of early coiling activity in zebrafish embryos as a powerful tool for the identification of neurotoxic compounds. In order to demonstrate that the analysis of early tail movements of zebrafish embryos allows for the discrimination of neurotoxicants acting via different mechanisms, the present study investigated the effects of four different neurotoxicants on the embryogenesis (fish embryo toxicity test) and early tail coiling movements of zebrafish embryos. Cadmium predominantly increased the frequency of tail coiling at the late pharyngula stage. Dichlorvos delayed embryonic development and caused convulsive tail movements resulting in prolonged duration of tail coils. Embryos exposed to teratogenic concentrations of fluoxetine and citalopram displayed absence of spontaneous tail movements at 24 h post-fertilization. In contrast, a non-teratogenic test concentration of citalopram decreased coiling frequency at multiple time points. Results demonstrated that the analysis of tail coiling movements of zebrafish embryos has the potential to discriminate neurotoxic compounds with different primary modes of action. In addition, chemical-induced effects on coiling activity were shown to potentially overlap with effects on embryogenesis. Further studies are needed to clarify the interplay of unspecific developmental toxicity of neurotoxic chemicals and effects resulting from specific neurotoxic mechanisms.

Hepatotoxicity of tricyclazole in zebrafish (Danio rerio)

Tricyclazole is widely used in agriculture as a pesticide, but its toxicity in vertebrates is currently poorly evaluated. In this study, we used zebrafish to assess the toxicity of tricyclazole. We found that tricyclazole induces liver damage, or hepatotoxicity, in zebrafish, during both development and adulthood. In embryos, we found that tricyclazole affected the liver development rather than other endodermal tissues such as gut and pancreas. In both embryos and adult zebrafish livers, tricyclazole disrupted the relationship between oxidant and antioxidant system and resulted in reactive oxygen species (ROS) overload. Meanwhile, it triggered hepatocyte apoptosis and disturbed carbohydrate/lipid metabolism and energy demand systems. These results suggested that tricyclazole could cause severe consequences for vertebrate hepatic development and function.

Xenobiotic mediated diabetogenesis: Developmental exposure to dichlorvos or atrazine leads to type 1 or type 2 diabetes in Drosophila

The increased incidence of diabetes to the magnitude of a global epidemic is attributed to non-traditional risk factors, including exposure to environmental chemicals. However, the contribution of xenobiotic exposure during the development of an organism to the etiology of diabetes is not fully addressed. Developing stages are more susceptible to chemical insult, but knowledge on the consequence of the same to the onset of diabetes is residual. In this context, by using Drosophila melanogaster having conserved Insulin/Insulin growth factor-like signaling (IIS) as well as glucose homeostasis as a model, we evaluated the potential of developmental exposure to dichlorvos (DDVP, an organophosphorus pesticide) or atrazine (herbicide) to cause diabetes in exposed organisms. Flies exposed to DDVP during their development display insulin deficiency or type 1 diabetes (T1D) while those exposed to atrazine show insulin resistance or type 2 diabetes (T2D), suggesting that exposure to these xenobiotics during organismal development can result in diabetes and that different mechanisms underlie pesticide mediated diabetes. We show that oxidative stress-mediated c-Jun N-terminal kinase (JNK) signaling activation underlies insulin resistance in flies exposed to atrazine during their development while DDVP-mediated T1D involves activation of caspase-mediated cell death pathway. Mitigation of oxidative stress through over-expression of SOD2 in atrazine (20μg/ml) exposed flies, revealed significantly decreased oxidative stress levels and reduced phosphorylation of JNK. Moreover, glucose and Akt phosphorylation levels in SOD2 over-expression flies exposed to atrazine were comparable to those in controls, suggesting restoration in insulin sensitivity. Therefore, exposure to xenobiotics during development is a common risk factor for the development of type 1 or type 2 diabetes. Accordingly, the present study cautions against the use of such diabetogenic pesticides. Also, mitigation of oxidative stress or anti-oxidant supplementation could be a potential therapy for xenobiotic mediated type 2 diabetes.

MicroRNA-181a knockdown protects HepaRG cells from Dichlorvos-induced oxidative stress and apoptosis

The present study was designed to assess the molecular mechanism of Dichlorvos (DDVP)-induced hepatic cell toxicity in vitro using HepaRG cells. The cytotoxicity was determined by cell viability, apoptosis portion, and reactive oxygenspecies (ROS) generation. The results indicated that DDVP treatment significantly inhibited cell growth, induced cell apoptosis and promoted the production of ROS on HepaRG cells. Microarray analysis showed that miR-181a was significantly upregulated in HepaRG cells treated with DDVP. Furthermore, we found that miR-181a downregulation has a remedy effect on DDVP-induced cell toxicity, while miR-181a overexpression augments the DDVP-induced hepatic cell apoptosis and ROS production. Furthermore studies showed that miR-181a directly targeted Bcl-2, and Bcl-2 downregulation inhibited the remedy effect of miR-181a inhibitor on DDVP induced cell toxicity. It is, therefore, concluded that miR-181a knockdown could protect hepatic cells from DDVP induced oxidative stress and apoptosis by targeting bcl-2.

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

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Mixture toxicity emerged as greatest challenges in environmental toxicology.

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Combined (CMD) group shows maximum alterations (even at half dose).

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Individual exposure shows selected target organ toxicity.

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Combined exposure develops toxic manifestations in all three examined tissues.

The greatest challenge in environmental toxicology is to understand the effects of mixture toxicity as environmental pollutants co-exist and exhibit combined effects. Thus, it is necessary to evaluate the mixture toxicity associated with two or more co-existing compounds. Pesticides are widely used to control pest, they are ubiquitous in nature and present in all environmental components. Pesticide residue can be detected in almost all components of environment and food samples. Imidacloprid (IMD) (neonicotinoid), dichlorvos (DIC) (organophosphate) and atrazine (ATZ) are three widely used pesticides for commercial uses. Present work includes the assessment of effects of individual exposure of IMD (27.5 mg/L), DIC (15 mg/L), and ATZ (03 mg/L) and in combination of three (CMD) (13.75 + 7.5 + 1.5 mg/L IMD, DIC & ATZ, respectively) in terms of LPO, GSH content and antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxidase) in zebrafish (Danio rerio), exposed for 24 h. CMD group exhibits highest lipid peroxidation than other individually exposed groups. Similarly, the activities of antioxidant enzymes were highest in CMD group with reduced GSH content. Results indicate that exposure to mixture of pesticides develops synergistic effects which were more toxic in compare to individual exposure and also produce toxicity in all examined tissues rather than selective organ toxicity.