Sulfone Metabolite of Fipronil Blocks γ-Aminobutyric Acid- and Glutamate-Activated Chloride Channels in Mammalian and Insect Neurons

Facial synthesis of fluorine-engineered magnetic covalent organic framework for selective and ultrasensitive determination of fipronil, its metabolites and analogs in food samples

To improve the adsorption affinity and selectivity of fipronils (FPNs), including fipronil, its metabolites and analogs, a magnetic covalent organic framework (Fe3O4@COF-F) with copious fluorine affinity sites was innovatively designed as an adsorbent of magnetic solid-phase extraction (MSPE). The enhanced surface area, pore size, crystallinity of Fe3O4@COF-F and its exponential adsorption capacities (187.3-231.5 mg g-1) towards fipronils were investigated. Combining MSPE with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), an analytical method was established for the selective determination of fipronils in milk and milk powder samples. This method achieved high sensitivity (LODs: 0.004-0.075 ng g-1), satisfactory repeatability and accuracy with spiked recoveries ranging from 89.9% to 100.3% (RSDs≤5.1%). Overall, the constructed Fe3O4@COF-F displayed great potential for the selective enrichment of fipronils, which could be ascribed to fluorine‑fluorine interaction. This method proposed a feasible and promising strategy for the development of functionalized COF and broadened its application in fluorine containing hazards detection.

Insights into the biodegradation of fipronil through soil microcosm-omics analyses of Pseudomonas sp. FIP_ A4

Fipronil, a phenylpyrazole insecticide, is used to kill insects resistant to conventional insecticides. Though its regular and widespread use has substantially reduced agricultural losses, it has also caused its accumulation in various environmental niches. The biodegradation is an effective natural process that helps in reducing the amount of residual insecticides. This study deals with an in-depth investigation of fipronil degradation kinetics and pathways in Pseudomonas sp. FIP_A4 using multi-omics approaches. Soil-microcosm results revealed ∼87% degradation within 40 days. The whole genome of strain FIP_A4 comprises 4.09 Mbp with 64.6% GC content. Cytochrome P450 monooxygenase and enoyl-CoA hydratase-related protein, having 30% identity with dehalogenase detected in the genome, can mediate the initial degradation process. Proteome analysis revealed differential enzyme expression of dioxygenases, decarboxylase, and hydratase responsible for subsequent degradation. Metabolome analysis displayed fipronil metabolites in the presence of the bacterium, supporting the proposed degradation pathway. Molecular docking and dynamic simulation of each identified enzyme in complex with the specific metabolite disclosed adequate binding and high stability in the enzyme-metabolite complex. This study provides in-depth insight into genes and their encoded enzymes involved in the fipronil degradation and formation of different metabolites during pollutant degradation. The outcome of this study can contribute immensely to developing efficient technologies for the bioremediation of fipronil-contaminated soils.

Using an internal body residue approach to assess acute pesticide toxicity in juvenile Chinook salmon (Oncorhynchus tshawytscha)

The use of internal body residues has the potential to improve toxicological assessments of hydrophobic pesticides. The acute toxicity of three classes of pesticides were assessed in juvenile Chinook salmon using internal body residues. Chinook salmon were exposed to two current-use pesticides bifenthrin and fipronil, and 4,4'- dichlorodiphenyldichloroethylene (DDE), which is a degradation product of the legacy pesticide dichlorodiphenyltrichloroethane (DDT). After 96-h of aqueous exposure to each pesticide, the pesticide content in whole-body Chinook salmon homogenates was measured using gas chromatography/mass spectrometry with methane negative chemical ionization. The wet-weight (ww) normalized lethal residue at 50% mortality (LR50) was lowest for bifenthrin (0.654 nmol/g ww), followed by fipronil (7.17 nmol/g ww) and the sum of fipronil and its sulfone, sulfide, and desulfinyl degradation products (8.72 nmol/g ww). No lethality was observed for DDE, even at the highest body residue (>116 nmol/g ww). LR50 estimates were also normalized to dry weight and lipid content and compared to field-caught fish to assess risk. The use of a risk quotient approach indicated that bifenthrin imparts the highest risk of acute toxicity in juvenile Chinook salmon among the three pesticides tested. In comparison to external dose metrics, the use of internal body residues has the potential to improve risk assessment by providing a more direct link between pesticide concentration at the receptor site and toxicological effects.

Immunoassays and Emerging Analytical Techniques of Fipronil and its Metabolites for Food Safety: A Review

Fipronil, classified as a phenylpyrazole insecticide, is utilized to control agricultural, public health, and veterinary pests. Notably, its unique ecological fate involves degradation to toxic metabolites, which poses the risk of contamination in water and foodstuffs and potential human exposure through the food chain. In response to these concerns, there is a pressing need to develop analytical methodologies for detecting fipronil and its metabolites. This review provides a concise overview of the mode of action, metabolism, and toxicology of fipronil. Additionally, various detection strategies, encompassing antibody-based immunoassays and emerging analytical techniques, such as fluorescence assays based on aptamer/molecularly imprinted polymer/fluorescent probes, electrochemical sensors, and Raman spectroscopy, are thoroughly reviewed and discussed. The focus extends to detecting fipronil and its metabolites in crops, fruits, vegetables, animal-derived foods, water, and bodily fluids. This comprehensive exploration contributes valuable insights into the field, aiming to foster the development and innovation of more sensitive, rapid, and applicable analytical methods.

Effect of Fipronil Exposure on Hematological Aspects of Rhesus Monkeys (Macaca mulatta): Risk and Toxicity Assessment in Agro-Workers

Background

Fipronil (FPN) is a broad-spectrum phenylpyrazole insecticide, widely used in agriculture and veterinary medicine. Published research on FPN toxicity has established the fact that its inhalation or dermal exposure may lead to very serious clinical outcomes in non-target animals. In line to its exposure and toxicity related damage, FPN has been investigated in many invertebrates, however, its exposure-related noxiousness is less reported in higher animals.

Objective

To assess the FPN-induced effects to agro-workers in the field, in the present study, we used physiological human surrogates, adult rhesus monkeys as models.

Method

We exposed well habituated, chair restraint adult rhesus monkeys with a field spray concentration of FPN (0.3 mg/1 mL distilled water) through an inhalation route in the closed system. Animals were divided into control and treatment groups, each containing three animals. Inflammatory and hematological effects were determined by evaluating the kidney and liver biomarker enzymes; serum creatinine and alanine transaminase (ALT), aspartate transaminase (AST) levels respectively.

Results

Our findings reveal that FPN treated monkeys show significantly increased levels of ALT (p = 0.000461), AST (p = 0.0681) and creatinine (p = 0.00656) as compared to the control group. Furthermore, significant differences of red blood cells (RBCs) (p = 0.0139) and white blood cells (WBCs) (p = 0.00642) were also observed in the treated and control group monkeys which reflect strong toxic effects on the blood cells.

Conclusion

Our findings demonstrate that FPN exposure is very toxic to higher animals and causes severe damage to the liver and kidneys along with other clinical problems. The study highlights the effect and impact of passive inhalation of insecticides in intentionally carefree agro-workers and raises the concern of public awareness toward pesticides use.

Soy, Rice and Oat Drinks: Investigating Chemical and Biological Safety in Plant-Based Milk Alternatives

During the last decades, plant-based milk has become very appreciated by consumers, becoming a staple ingredient, especially for alternative breakfasts. Milk contains lactose, which is a sugar hydrolysed by the lactase enzyme. Lactose intolerance and lactose malabsorption are very common food intolerances among individuals. However, a lot of consumers consider themselves as lactose intolerant on the basis of self-reported intolerance and start to avoid dairy products, ignoring that plant-based milk alternatives are not nutritionally comparable to animal milk, especially in terms of protein intake. The aim of this study is to grow folder knowledge of the security of plant-based drinks, helping competent authorities to issue a risk assessment and to apply national plans about consumer safety. Results show that proper sanitary practices, such as pasteurization, are necessary in plant-based milk alternatives as well as in dairy milk. Chemical analysis has highlighted that there are no pesticide risks for consumers.

Putative target sites in synganglion for novel ixodid tick control strategies

Acaricide resistance is a global problem that has impacts worldwide. Tick populations with broad resistance to all commercially available acaricides have been reported. Since resistance selection in ticks and their role in pathogen transmission to animals and humans result in important economic and public health burden, it is essential to develop new strategies for their control (i.e., novel chemical compounds, vaccines, biological control). The synganglion is the tick central nervous system and it is responsible for synthesizing and releasing signaling molecules with different physiological functions. Synganglion proteins are the targets of the majority of available acaricides. In this review we provide an overview of the mode-of-action and resistance mechanisms against neurotoxic acaricides in ticks, as well as putative target sites in synganglion, as a supporting tool to identify new target proteins and to develop new strategies for tick control.

Toxicological effects of fipronil on laying hens and its residue elimination in eggs

Eighty 24-week-old laying hens were divided into eight groups, seven given a single oral dose per chicken with 7 dosing levels from 13.6 to 137 mg/kg body weight (bw) and one serving as sham control. The hens were observed for 28 days for clinical abnormalities, egg yield, and body weight. Egg samples from groups of low-to-medium doses were analyzed for residues of fipronil and its metabolites by LC-MS/MS. Blood and organ samples from hens of the group receiving 63.3 mg/kg bw were collected for hematochemical and histopathological analysis. We found that the median lethal dose (LD₅₀) of fipronil was 74 mg/kg bw for laying hens. No death occurred, and there were no obvious changes in body weight and egg production in the hens receiving doses at or below 20 mg/kg bw. In the hens that survived exposure to the dose at 63.3 mg/kg bw, there was significant reduction in body weight and egg yield; histopathological changes in the liver and kidney; and increased levels of creatine, urea, glutamate oxaloacetate transferase, and glutamate pyruvic transaminase. Fipronil-sulfone was the residual marker in eggs with significantly higher concentrations and longer withdrawal periods than its maternal compound. We conclude that fipronil is efficiently transformed into fipronil-sulfone in the body with subsequent excretion into eggs. More attention should be paid to the potential food safety risk of fipronil-sulfone because of its persistence in eggs.

Garlic and allopurinol alleviate the apoptotic pathway in rats' brain following exposure to fipronil insecticide

Fipronil can cause oxidative tissue damage and apoptosis. Our goal is to evaluate the antiapoptotic impact of garlic or allopurinol against fipronil neurotoxicity. Thirty-six mature male albino rats were separated into control, garlic aqueous extract (500 mg/kg), allopurinol (150 mg/L in their drinking water), fipronil (13.277 mg/kg), garlic+fipronil, and allopurinol+fipronil. Our results revealed that fipronil induced a significant increase in brain malondialdehyde, protein carbonyl levels as well as enzymatic antioxidant activities (superoxide dismutase, catalase, glutathione peroxidase, and xanthine oxidase), but glutathione-S-transferase recorded a significant decrease as compared to the control. In addition, fipronil significantly up-regulated the brain pro-apoptotic (Bax) and caspase -3 mRNA gene expression and induced DNA fragmentation but caused down-regulation in anti-apoptotic (Bcl-2) mRNA genes expression. Interestingly, co-administration with garlic or allopurinol improved the lipid peroxidation, antioxidant disturbance, and apoptosis induced by fipronil in the brain tissues. In conclusion, garlic or allopurinol reduced fipronil-induced apoptosis and reduced oxidative tissue damage, most likely through enhancing the tissue antioxidant defense system.

Determination of fipronil and its metabolites in environmental water samples by meltblown nonwoven fabric based solid-phase extraction combined with gas chromatography-electron capture detection

In this study, a new method for determination of fipronil and its three metabolites in environmental water samples was developed based on meltblown nonwoven fabric solid-phase extraction combining with gas chromatography-electron capture detection. As the core material of medical mask, meltblown nonwoven fabric is made of polypropylene superfine fibers which are randomly distributed and bonded together with a relatively large specific surface area and good permeability. Polypropylene as a high molecular hydrocarbon-based polymer, has the characteristics of good hydrophobicity and lipophilicity, which can be applied for separation and enrichment of hydrophobic substances in food, environment and biology samples. The meltblown nonwoven fabric is soft and can fill the solid-phase extraction cartridge tightly. This aspect also makes it suitable to be used as an ideal solid-phase extraction sorbent. A series of parameters influencing the extraction efficiency were investigated, and under the optimized conditions, fipronil and its three metabolites had good linear relationship in the range of 0.2-100 μg/L with correlation coefficient R² more than 0.999. The recoveries at three spiked concentrations were in the range of 99.2-107.3% with the relative standard deviations less than 9.8% (intra-day) and 8.1% (inter-day). The limit of detection for the four target analytes were in the range of 0.02-0.06 μg/L. Finally, this method was successfully applied in the analysis of fipronil and its three metabolites in various types of environmental water samples. This article is protected by copyright. All rights reserved.

Oxidative stress, apoptosis and histopathological alterations in brain stem and diencephalon induced by subacute exposure to fipronil in albino rats

Fipronil (FIP) is a highly effective insecticide that has been used in agriculture and veterinary medicine. Its neurotoxic effect to insects and to non-target organisms, after nonintentional exposure, was reported. Many studies were conducted to evaluate FIP effects on mammals. However, slight is known about its effect on the brain stem and diencephalon. The current study was designed to investigate the ability of FIP to induce oxidative stress as a molecular mechanism of FIP neurotoxicity that resulted in apoptosis and neural tissue reactivity in these regions. Ten adult male rats received 10 mg/kg of FIP technical grade by oral gavage, daily for 45 days. Brain stem and diencephalon were processed to examine oxidative stress-induced macromolecular alteration (MDA, PCC and DNA fragmentation). Also, the histopathological assessment and immunoreactivity for caspase-3 (active form), iNOS and GFAP were performed on the thalamus, hypothalamus and medulla oblongata. Our results revealed that FIP significantly raised MDA, PCC and DNA fragmentation (p ≤ 0.05). In addition, significantly increased immunoreactivity to GFAP, iNOS and caspase-3 (active form) in the FIP-treated group was noticed (p ≤ 0.05). Moreover, alterations in the histoarchitecture of the neural tissue of these regions were observed. We conclude that FIP can induce oxidative stress, leading to apoptosis and tissue reaction in brain stem and diencephalon.

Differential microbial responses to antibiotic treatments by insecticide-resistant and susceptible cockroach strains (Blattella germanica L.)

The German cockroach (Blattella germanica L.) is a major urban pest worldwide and is known for its ability to resist insecticides. Past research has shown that gut bacteria in other insects can metabolize xenobiotics, allowing the host to develop resistance. The research presented here determined differences in gut microbial composition between insecticide-resistant and susceptible German cockroaches and compared microbiome changes with antibiotic treatment. Cockroaches received either control diet or diet plus kanamycin (KAN) to quantify shifts in microbial composition. Additionally, both resistant and susceptible strains were challenged with diets containing the insecticides abamectin and fipronil in the presence and absence of antibiotic. In both strains, KAN treatment reduced feeding, leading to higher doses of abamectin and fipronil being tolerated. However, LC50 resistance ratios between resistant and susceptible strains decreased by half with KAN treatment, suggesting gut bacteria mediate resistance. Next, whole guts were isolated, bacterial DNA extracted, and 16S MiSeq was performed. Unlike most bacterial taxa, Stenotrophomonas increased in abundance in only the kanamycin-treated resistant strain and was the most indicative genus in classifying between control and kanamycin-treated cockroach guts. These findings provide unique insights into how the gut microbiome responds to stress and disturbance, and important new insights into microbiome-mediated insecticide resistance.

Strategic control of cattle co-parasitized by tick, fly and gastrointestinal nematodes: Is it better to use ecto + endoparasiticide or just endectocide formulations?

Ticks, flies, and gastrointestinal helminths (GINs) significantly affect cattle productivity; thus, ectoparasiticide, endoparasiticide, and endectocide drugs have commonly been used for their control. The study aimed to compare the technical (parasites counts), productive, and financial effects of a treatment protocol comprising ecto- + endoparasiticides formulations (T01: fluazuron 2.5 mg/kg + fipronil 1.25 mg/kg and fenbendazole 5 mg/kg; n = 15) to a treatment with one formulation of endectocide (T02: ivermectin 450 μg/kg + abamectin 250 μg/kg; n = 15) over 308 days under field conditions in crossbred cattle co-parasitized by Rhipicephalus microplus, Haematobia irritans, and GINs. Bovine weight gain and return on investment (ROI) were also evaluated. Bovines from T01 received four treatments against the cattle tick and two against two GINs. For T02, four treatments were performed. Animals from T01 gained 15.4 kg more than T02 and provided a comparative ROI of 15.8. In cattle co-parasitized with R. microplus, H. irritans, and GINs, the treatment protocol used in this study with ecto- + endoparasiticidal action formulations showed better technical results regarding parasite counts and productive and financial data than the strategic treatment protocol using only an endectocide formulation.

Synergistic effects of sitagliptin and losartan against fipronil-induced hepatotoxicity in rats

Background and Aim

Fipronil (FPN) is a potent pesticide that is heavily used around the world in agriculture. However, its irrational use could potentially have deleterious effects on animals and humans. The present study aimed to investigate the ability of sitagliptin (Sit) and losartan (LOS), when used both individually or concurrently, to guard rat liver against the acute hepatotoxicity caused by FPN.

Materials and Methods

Forty-two adult male Wistar rats were equally divided into seven groups (6/group). Group I (control) received normal saline (0.5 mL/rat, vehicle for all treatments) by gavage once daily for 10 days. Group II received oral Sit (10 mg/kg body weight [BW]) daily for 10 days and Group III received oral LOS (5 mg/kg BW) daily for 10 days. Group IV received oral FPN (19.4 mg/kg BW; 1/5 of the oral LD₅₀) for the past 5 days of the study. Groups V and VI received oral Sit (10 mg/kg BW) and LOS (5 mg/kg BW) daily, respectively, 5 days prior and 5 days during FPN administration (19.4 mg/kg BW). Group VII received oral Sit (10 mg/kg BW) and LOS (5 mg/kg BW) for 10 days with daily FPN during the past 5 days. After the end of the treatment period, the rats were humanely sacrificed and blood and liver tissue samples were collected for biochemical analysis and histopathological and immunohistochemical investigations.

Results

FPN administration resulted in elevated alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase serum concentrations as well as increased malondialdehyde levels and reduced catalase, superoxide dismutase, glutathione peroxidase, and glutathione activity. The histopathological investigation showed disorganization of the hepatic cords and focal necrosis of the hepatocytes in FPN-intoxicated rats. Furthermore, the immunohistochemical examination showed that hepatic caspase-3 was overexpressed in the FPN-treated rats. The administration of Sit and LOS before and alongside FPN markedly mitigated the alterations caused by FPN and the hepatoprotective effects were more prominent in the combination group.

Conclusion

Sit and LOS, both individually or in combination, confers considerable hepatoprotection against FPN-induced hepatotoxicity.

A natural deep eutectic solvent as a novel dispersive solvent in dispersive liquid-liquid microextraction based on solidification of floating organic droplet for the determination of pesticide residues

Current trends in analytical chemistry encourage the use of innocuous solvents to develop modern methods aligned with green chemistry. In this sense, natural deep eutectic solvents (NADESs) have emerged as a novel generation of green solvents which can be employed in sample treatments as an alternative to the toxic organic solvents commonly used so far. In this work, a new extraction method employs dispersive liquid-liquid microextraction based on a solid floating organic droplet (DLLME-SFO), by using a mixture composed of a less dense than water extraction solvent, 1-dodecanol, and a novel dispersive solvent, NADES. The methodology was proposed to extract and preconcentrate some pesticide residues (fipronil, fipronil-sulfide, fipronil-sulfone, and boscalid) from environmental water and white wine samples before analysis by liquid-chromatography coupled to ultraviolet detection (HPLC-UV). Limits of quantification (LOQs) lower than 4.5 μg L^-1, recoveries above 80%, and precision, expressed as RSD, below 15% were achieved in both samples showing that the proposed method is a powerful, efficient, and green alternative for the determination of these compounds and, therefore, demonstrating a new application for NADES in sample preparation. In addition, the DLLME-SFOD-HPLC-UV method was evaluated and compared with other reported approaches using the Analytical GREEnness metric approach, which highlighted the greenness of the proposed method.

Association of CYP4G19 Expression With Gel Bait Performance in Pyrethroid-Resistant German Cockroaches (Blattodea: Ectobiidae) From Taiwan

Overexpression of a cytochrome P450 gene, CYP4G19, is known to associate with pyrethroid resistance in the German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae). In this study, we investigated the CYP4G19 expression level in 20 field-collected strains of B. germanica in Taiwan. We also examined the level of adult male susceptibility to imidacloprid, fipronil, indoxacarb, and hydramethylnon using single-diagnostic dose bioassays and their susceptibility to corresponding gel baits to determine how the CYP4G19 expression level influences the cockroach gel bait performance. Results showed that the CYP4G19 gene expression level among the field-collected German cockroach was 1.8- to 9.7-fold higher than that of the susceptible strain. It was negatively correlated (P < 0.05) with the % mortality after treatments with imidacloprid and fipronil diagnostic doses. However, no correlation was found between CYP4G19 gene expression with the % mortality after treatment with indoxacarb and hydramethylnon diagnostic doses. Indoxacarb and hydramethylnon baits showed high efficacy against the field strains with a mean mortality of 97.58 ± 1.35% and 90.95 ±1.65%, respectively. This study provided the first evidence of cross-resistance to imidacloprid and fipronil in pyrethroid-resistant German cockroaches due to overexpression of CYP4G19.

A comprehensive review of environmental fate and degradation of fipronil and its toxic metabolites

The use of pesticides to increase crop production has become one of the inevitable components of modern agriculture. Fipronil, a phenylpyrazoles insecticide, is one of the most widely used, systemic, broad-spectrum insecticides. Owing to its unique mode of action and selective toxicity, it was once regarded as safer alternatives to more toxic and persistent organochlorine insecticides. However, with the increased use, many studies have reported the toxicity of fipronil and its metabolites in various non-target organisms during the last two decades. Currently, it is regarded as one of the most persistent and lipophilic insecticides in the market. In the environment, fipronil can undergo oxidation, reduction, hydrolysis, or photolysis to form fipronil sulfone, fipronil sulfide, fipronil amide, or fipronil desulfinyl respectively. These metabolites except fipronil amide are more or less toxic and persistent than fipronil and have been reported from diverse environmental samples. Recently many studies have focused on the degradation and removal of fipronil residues from the environment. However, a comprehensive review summarizing and combining these recent findings is lacking. In the present review, we evaluate, summarize, and combine important findings from recent degradation studies of fipronil and its metabolites. An attempt has been made to elucidate the possible mechanism and pathways of degradation of fipronil and its toxic metabolites.

The potential of pro-insecticides for resistance management

Pro-insecticides have been a significant part of the insecticide market for decades. Bioactivation of such compounds is generally an enzyme-controlled process, in which the target insect metabolizes the pro-form into an active compound. This approach has several potential advantages, including improved bio-kinetic properties and safety profiles of the pro-insecticide relative to the active form. A less common advantage of pro-insecticides is increased activity on metabolically resistant strains. Specific cases in which a pro-insecticide demonstrates negative cross-resistance (NCR) on a metabolically resistant strain due to increased bioactivation of the pro-insecticide have been noted sporadically over the past 50+ years but have not been reviewed before. The purpose of this mini-review is to catalog the cases in which a pro-insecticide demonstrated improved activity on an insect strain resistant to a second insecticide via a metabolic mechanism. Cases are relatively rare, but where it does occur the mechanism of NCR is generally recognized as being due to the increased metabolic activity of the resistant strain. These observations can provide learnings with potential application for resistance management if the correct pro-insecticide is selected for a resistant strain which is better able to bioactivate it. A better understanding of the bioactivation of pro-insecticides by resistant insects could also aid in insecticide discovery, potentially leading to improved pro-insecticide design. © 2021 Society of Chemical Industry.

Neurotoxic Effect of Fipronil in Male Wistar Rats: Ameliorative Effect of L-Arginine and L-Carnitine

Simple Summary

Insecticides are widely used in agricultural and household environments. They induce wide range of deleterious effects. Fipronil is one of the most widely used phenylpyrazoles insecticides. The neurotoxic effect of such insecticide was tested in the present study with special emphasis on cognitive deficit as well as testing the possible ameliorative impacts of L-arginine and L-carnitine. The study proposed fipronil-induced cognitive deficit as a reflection to oxidative stress and neuro-inflammation. Moreover, L-arginine and L-carnitine exerted ameliorative influence on fipronil induced oxidative stress and neuro-inflammation. Therefore, L-arginine and L-carnitine can be considered as prospective candidates for mitigation of pesticide induced neurotoxicity especially in people with high-risk exposure to pesticide.

Abstract

The ameliorative effect of L-arginine (LA) and L-carnitine (LC) against fipronil (FPN)-induced neurotoxicity was explored. In this case, 36 adult male rats were randomly divided into six groups: group I received distilled water, group II received 500 mg/kg LA, group III received 100 mg/kg LC, group IV received 4.85 mg/kg FPN, group V received 4.85 mg/kg FPN and 500 mg/kg LA and group VI received 4.85 mg/kg FPN and 100 mg/kg LC for 6 weeks. Cognitive performance was assessed using Barnes maze (BM). Serum corticosterone, brain total antioxidant capacity (TAC), malondialdehyde (MDA) and dopamine were measured. Histopathology and immunohistochemistry of ionized calcium-binding adaptor (Iba-1), doublecortin (DCX) and serotonin (S-2A) receptors were performed. Fipronil induced noticeable deterioration in spatial learning and memory performance. In addition, FPN significantly (p < 0.05) diminished brain antioxidant defense system and dopamine coincide with elevated serum corticosterone level. Histopathological examination revealed degenerative and necrotic changes. Furthermore, Iba-1 and DCX were significantly expressed in cortex and hippocampus whereas S-2A receptors were significantly lowered in FPN group. However, administration of LA or LC alleviated FPN-induced deteriorations. In conclusion, LA and LC could be prospective candidates for mitigation of FPN-induced neurotoxicity via their antioxidant, anti-inflammatory and neuropotentiating effects.

The effects of fipronil on emotional and cognitive behaviors in mammals

Fipronil is a phenylpyrazole insecticide that is widely used as a pesticide and a veterinary drug, although studies suggest that it could be toxic to mammals. The objectives of this study were to examine the pharmacokinetic profile of fipronil in mice, dogs, and cats, and to evaluate its effects on emotional and cognitive behaviors of dogs and cats using the data obtained from mice. The assessment of in vivo kinetics of fipronil was conducted in mice and dogs. We also performed behavioral tests (elevated plus-maze and Y-maze) and measured the levels of neurotransmitters in mice exposed to fipronil. In addition, the in vitro metabolism of fipronil were evaluated using liver microsomes of rats, mice, dogs, and cats. The results revealed that fipronil is distributed throughout the body (blood, brain, adipose tissue, and liver) of mice after dermal application. It was metabolized to fipronil sulfone primarily in the liver. The data on kinetics show that both fipronil and fipronil sulfone have a longer half-life in dogs and cats than in mice. The behavioral tests indicated that fipronil and fipronil sulfone could affect emotional and cognitive behaviors and alter the levels of neurotransmitters (dopamine in the striatum and serotonin in the hippocampus) in mice. Furthermore, we found that dogs and cats have a low ability to metabolize fipronil than mice and rats. However, further comprehensive studies are needed to determine whether fipronil affects the emotional and cognitive behaviors when administered to dogs and cats. To the best of our knowledge, this is the first study to examine the pharmacokinetic data and verify the effects of fipronil on emotional and cognitive behaviors of dogs and cats using the data obtained from mice.

Residual molecular and behavioral effects of the phenylpyrazole pesticide fipronil in larval zebrafish (Danio rerio) following a pulse embryonic exposure

Pesticides are typically applied to crops as acute applications, and residual effects of such intermittent exposures are not often characterized in developing fish. Fipronil is an agricultural pesticide that inhibits γ-amino-butyric acid (GABA) gated chloride channels. In this study, zebrafish (Danio rerio) embryos were exposed for 48 h (starting at ~3 h post fertilization, hpf) to various concentrations of fipronil (0.02 μg/L up to 4000 μg/L). Following this acute exposure, a subset of fish was transferred to clean water for a 7-day depuration phase. We hypothesized that a pulse exposure to fipronil during critical periods of central nervous system development would adversely affect fish later in life. After a 48 hour pulse exposure, survival was reduced in embryos exposed to 2 μg fipronil/L or greater. However, there was no further mortality during the depuration phase, nor were there changes in body length nor notochord length in larvae 9 dpf (days post-fertilization) compared to controls. Additional experiments were carried out at higher concentrations over 96 h (up to 4 dpf) to also elucidate developmental effects and teratogenicity of fipronil (43.7 μg/L up to 4370 μg/L). Fipronil at these higher concentrations significantly impacted the development of zebrafish, and the following morphometric and teratogenic effects were observed in 4 dpf fish; reduced body length, yolk sac and pericardial edema, reduced midbrain length, reduced optic and otic diameter, and truncation of the lower jaw. In depurated fish, we hypothesized that there would exist residual effects of exposure at the molecular level. Transcriptome profiling was therefore conducted on 9 dpf depurated larvae exposed initially for 48 h to one dose of either 0.2 μg/L, 200 μg/L or 2000 μg/L fipronil. The expression of gene networks associated with glycogen and omega-3-fatty acid metabolism were decreased in larvae exposed to each of the three concentrations of fipronil, suggesting metabolic disruption. Moreover, transcriptomics revealed that fipronil suppressed gene networks related to light-dark adaptation, photoperiod sensing, and circadian rhythm. Based on these data, we tested fish for altered behavioral responses in a Light-Dark preference test. Larvae exposed to >200 μg fipronil/L as embryos showed fewer number of visits (20-30% less) to the dark zone compared to controls. Larvae also spent a lower amount of time in the dark zone compared to controls, suggesting that fipronil strengthened dark avoidance behavior which is indicative of anxiety. This study demonstrates that a short pulse exposure to fipronil can affect transcriptome networks for metabolism, circadian rhythm, and response to light in fish after depuration, and these molecular responses are hypothesized to be related to aberrant behavioral effects observed in the light-dark preference test.

Preclinical Transplacental Transfer and Pharmacokinetics of Fipronil in Rats

Fipronil, a widely used insecticide and pesticide, with its toxic metabolite fipronil sulfone was detected in fipronil-contaminated eggs as a result of inappropriate use. However, little is known about whether fipronil and fipronil sulfone transfer into fetus through the blood-placenta barrier. Our objectives were to investigate the transplacental transfer and the pharmacokinetics of fipronil and fipronil sulfone in rats. Male and female (with 13 days of gestation) Sprague-Dawley rats were used in pharmacokinetics and transplacental transfer experiments, respectively. Biologic samples were collected at each time point after fipronil intravenous or oral administration. To monitor fipronil and fipronil sulfone in the plasma, placenta, amniotic fluid, and fetus, a validated liquid chromatography tandem mass spectrometry method was developed. After fipronil administration in male rats, the oral bioavailability decreased, whereas the biotransformation increased as the dose increased, revealing an enhancement of first-pass effect and a fast metabolism in vivo. The results of fipronil transplacental transfer in pregnant rats demonstrated that the concentration of fipronil and fipronil sulfone varied in the following order, respectively: placenta > plasma > fetus > amniotic fluid and plasma > placenta > fetus > amniotic fluid. This is the first direct evidence that fipronil and fipronil sulfone cross the blood placental barriers and enter the fetus. The amount of fipronil distributed to the fetus was greater than that of fipronil sulfone in the short term, but by contrast, pharmacokinetic data showed that the latter stayed longer in the body. These findings provide constructive information for public health alarm. SIGNIFICANCE STATEMENT: Fipronil and fipronil sulfone interfere with the GABAergic system. Fipronil can cause thyroid dysfunction, which may affect brain growth and nerve development. Although we knew that fipronil and fipronil sulfone could enter eggs, there was no direct evidence that they would enter fetuses. This research provided evidence on the pharmacokinetics and transplacental transfer of fipronil and fipronil sulfone, confirming our hypothesis.

Long-Term Fipronil Treatment Induces Hyperactivity in Female Mice

Fipronil is an insecticide widely used for veterinary and agricultural purposes. While its insecticidal properties mostly rely on its high affinity antagonistic activity on insect γ aminobutyric acid (GABA) receptors, fipronil and its main metabolite fipronil sulfone nevertheless display non-negligible affinity for mammalian GABAA receptor. As several environmental toxicants have been shown to raise the risk of developing various neurodegenerative disorders, the aim of this study was to evaluate whether long-term low dose administration of fipronil could lead to cognitive deficiencies. Our results indicate that long-term fipronil treatment leads to behavioral perturbations in mice, indicating an accumulative effect of sustained exposure to low dose of fipronil. Although no memory impairment was observed during the course of our study, we noticed a significant hyperlocomotion behavior after 43 weeks of weekly fipronil administration, which is consistent with its direct effect on the GABAergic system.

Synergistic antioxidant effects of resveratrol and curcumin against fipronil-triggered oxidative damage in male albino rats

Fipronil (FPN), a phenylpyrazole insecticide, has been receiving increased attention owing to its toxicity, which is largely mediated through its effects on antioxidant systems. The present study was undertaken to assess the effects of resveratrol (RSV) and curcumin (CUR) on oxidative damage induced by FPN. Forty mature male Wistar rats were randomized into five groups (n = 8 per group): the first group was the control; the second was administered FPN (10 mg/kg); and the third, fourth, and fifth were co-treated with RSV (10 mg/kg), CUR (200 mg/kg), and their combination, respectively, 2 h prior to FPN administration. All animals were dosed via oral gavage for 4 weeks. FPN significantly (p < 0.05) elevated the sera of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), γ-glutamyl transferase (GGT), urea, creatinine, and cholesterol levels, whereas serum total protein, albumin, and triglyceride levels were significantly (p < 0.05) decreased, compared to those of the control group. Reduced glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were decreased (p < 0.05) in the FPN-treated group compared to those in the control group; however, malondialdehyde (MDA) and nitric oxide (NO) levels were markedly increased (p < 0.05) in the hepatic, renal, and brain tissues. Co-treatment with RSV or CUR alleviated (p ˂ 0.05) the increased lipid peroxidation and changes in enzymatic/nonenzymatic antioxidants induced by FPN; all these variables mostly returned to normal levels with the combined of RSV and CUR treatment. In conclusion, RSV and/or CUR relieved and synergistically reversed the FPN-induced tissue oxidative injury, probably by improving the antioxidant defenses via their free radical scavenging and antioxidant characteristics.

Multibiomarker approach to fipronil exposure in the fish Dicentrarchus labrax under two temperature regimes

Fipronil is a phenylpyrazole insecticide widely used to control pests in agriculture even though evidence of harmful side effects in non-target species has been reported. A comprehensive study on the effects of dietary administration of Regent®800WG (80 % fipronil) in European sea bass juveniles was carried out under two temperature regimes: a) natural conditions, and b) 3 °C above the natural temperature (an increase predicted for the NW Mediterranean by the end of this century). Fipronil was added to the fish food (10 mg fipronil /Kg feed) and the effects were studied at several time points including right before administration, 7 and 14 days after daily fipronil feed and one-week after the insecticide withdrawal from the diet (depuration period). A wide array of physiological and metabolic biomarkers including feeding rate, general condition indices, plasma and epidermal mucus metabolites, immune response, osmoregulation, detoxification and oxidative-stress markers and digestive enzymes were assessed. General linear models and principal component analyses indicated that regardless of water temperature, fipronil resulted in a significant alteration of several of the above listed biomarkers. Among them, glucose and lactate levels increased in plasma and decreased in epidermal mucus as indicators of a stress response. Similarly, a depletion in catalase activity and higher lipid peroxidation in liver of fipronil-exposed fish were also indicative of an oxidative-stress condition. Fipronil induced a time dependent inhibition of Cytochrome P450-related activities and an increase of phase II glutathione-S-transferase. Moreover, fipronil administration was able to reduce the hypo-osmoregulatory capability as shown by the increase of plasmatic osmolality and altered several digestive enzymes including trypsin, lipase, alpha amylase and maltase. Finally, analyses in bile and muscle confirmed the rapid clearance of fipronil but the persistence of the metabolite fipronil-sulfone in bile even after the 7-day depuration period. Altogether, the results reveal a notable impact of this compound on the physiological condition of the European sea bass. The results should be considered in future environmental risk assessment studies since fipronil could be hazardous to fish species, particularly those inhabiting estuarine ecosystems exposed to the discharge of agriculture runoffs where this pesticide is mainly used.

A first approach using micellar electrokinetic capillary chromatography for the determination of fipronil and fipronil-sulfone in eggs

Fipronil is an insecticide that is not approved in the European Union in food. In 2017, fipronil was involved in a European health alert due to its presence in fresh hen eggs because of an illicit use in poultry farms, so reliable methods are needed to determine fipronil and its main metabolites in these matrixes. In this work, we report the first approach to the study of fipronil and two metabolites, fipronil-sulfone and fipronil-sulfide by CE. MEKC mode was employed using a solution of 50 mM ammonium perfluorooctanoate pH 9.0 with 10% (v/v) methanol as background electrolyte. The proposed method was combined with a simple sample treatment based on salting-out assisted LLE (SALLE) using acetonitrile as extraction solvent and ammonium sulfate as salt. The SALLE-MEKC-UV method allowed the simultaneous quantification of fipronil and fipronil-sulfone. Validation parameters yielded satisfactory results, with precision, expressed as relative SD, below 14% and recoveries higher than 83%. Limits of detection were 90 µg/kg for fipronil and 150 µg/kg for fipronil-sulfone, so in terms of sensitivity further studies of sample treatments allowing extra preconcentration or the use of more sensitive detection, such as MS, would be needed.

Garlic and allopurinol attenuate hepatic apoptosis induced by fipronil in male albino rats

Fipronil (FPN) can induce oxidative tissue damage and may be contemplated as an apoptosis inducer. Our aim is to investigate the possible hepatoprotective roles of garlic or allopurinol (ALP) against fipronil subacute toxicity. Thirty-six mature male albino rats were randomly divided into six groups; the first group was saved as control (C), the 2nd (G) was orally intubated with 500 mg/kg aqueous garlic extract, and the 3rd (A) received 150 mg/L allopurinol in their drinking water. The 4th group (F) was administered 13.277 mg/kg fipronil by gavage, while the 5th (G + F) and 6th (A + F) groups received the same doses of garlic and allopurinol, respectively two hours before fipronil intoxication. Our results revealed that FPN significantly increased the hepatic malondialdehyde, protein carbonyl levels, and the enzymatic activities of superoxide dismutase, catalase, glutathione peroxidase, and xanthine oxidase, but it decreased glutathione-S-transferase compared to the control group. Moreover, FPN exhibited significant up-regulation in the hepatic pro-apoptotic (Bax) and caspase-3 genes expression, down-regulation in the anti-apoptotic (Bcl-2) mRNA gene expression and induced DNA fragmentation. Surprisingly, garlic or allopurinol co-treatment ameliorated the hepatic lipid peroxidation, antioxidants disruption, and apoptosis induced by FPN. In conclusion, garlic and allopurinol relieved the oxidative injury and reduced the fipronil-induced apoptosis probably by improving the tissue antioxidant defense system.

Induction of Amyloid-β42 Production by Fipronil and Other Pyrazole Insecticides

Generation of amyloid-β peptides (Aβs) by proteolytic cleavage of the amyloid-β protein precursor (AβPP), especially increased production of Aβ42/Aβ43 over Aβ40, and their aggregation as oligomers and plaques, represent a characteristic feature of Alzheimer's disease (AD). In familial AD (FAD), altered Aβ production originates from specific mutations of AβPP or presenilins 1/2 (PS1/PS2), the catalytic subunits of γ-secretase. In sporadic AD, the origin of altered production of Aβs remains unknown. We hypothesize that the 'human chemical exposome' contains products able to favor the production of Aβ42/Aβ43 over Aβ40 and shorter Aβs. To detect such products, we screened a library of 3500 + compounds in a cell-based assay for enhanced Aβ42/Aβ43 production. Nine pyrazole insecticides were found to induce a β- and γ-secretase-dependent, 3-10-fold increase in the production of extracellular Aβ42 in various cell lines and neurons differentiated from induced pluripotent stem cells derived from healthy and FAD patients. Immunoprecipitation/mass spectrometry analyses showed increased production of Aβs cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and shorter. Strongly supporting a direct effect on γ-secretase activity, pyrazoles shifted the cleavage pattern of another γ-secretase substrate, alcadeinα, and shifted the cleavage of AβPP by highly purified γ-secretase toward Aβ42/Aβ43. Focusing on fipronil, we showed that some of its metabolites, in particular the persistent fipronil sulfone, also favor the production of Aβ42/Aβ43 in both cell-based and cell-free systems. Fipronil administered orally to mice and rats is known to be metabolized rapidly, mostly to fipronil sulfone, which stably accumulates in adipose tissue and brain. In conclusion, several widely used pyrazole insecticides enhance the production of toxic, aggregation prone Aβ42/Aβ43 peptides, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in sporadic AD.

Fluxametamide: A novel isoxazoline insecticide that acts via distinctive antagonism of insect ligand-gated chloride channels

Fluxametamide is a novel wide-spectrum insecticide that was discovered and synthesized by Nissan Chemical Industries, Ltd. To identify the mode of action of fluxametamide, we first performed [³H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB) binding assays. Fluxametamide potently inhibited the specific binding of [³H]EBOB to housefly-head membranes, suggesting that fluxametamide affects insect γ-aminobutyric acid (GABA)-gated chloride channels (GABACls). Next, the antagonism of housefly GABACls and glutamate-gated chloride channels (GluCls) was examined using the two-electrode voltage clamp (TEVC) method. Fluxametamide inhibited agonist responses in both ion channels expressed in Xenopus oocytes in the nanomolar range, indicating that this insecticide is a ligand-gated chloride channel (LGCC) antagonist. The insecticidal and LGCC antagonist potencies of fluxametamide against fipronil-susceptible and fipronil-resistant strains of small brown planthoppers and two-spotted spider mites, which are insensitive to fipronil, were evaluated. Fluxametamide exhibited similar levels of both activities in these fipronil-susceptible and fipronil-resistant arthropod pests. These data indicate that fluxametamide exerts distinctive antagonism of arthropod GABACls by binding to a site different from those for existing antagonists. In contrast to its profound actions on the arthropod LGCCs, the antagonistic activity of fluxametamide against rat GABACls and human glycine-gated chloride channels was nearly insignificant, suggesting that fluxametamide has high target-site selectivity for arthropods over mammals. Overall, fluxametamide is a new type of LGCC antagonist insecticide with excellent safety for mammals at the target-site level.

Effects of short-term, sublethal fipronil and its metabolite on dragonfly feeding activity

Dragonflies, Sympetrum spp., are indispensable to agriculture and are a central element of culture in Japan. However, S. frequens populations in rice paddy fields have declined in recent decades. Dragonfly larvae are predatory aquatic insects that feed on other organisms found in habitats with slow-moving or standing water. The increasing use of fipronil and neonicotinoid insecticides in agriculture is also increasing exposure to Sympetrum spp. in larval stages through paddy soil and water. The role of fipronil insecticides in the decline of dragonflies is of concern, and we here examine the sublethal effects of this insecticide on the feeding behaviors of two Sympetrum spp. Based on the quantity of prey items consumed and the time to capture prey items, feeding inhibition was determined to be a potential mechanism of the decline of Sympetrum spp. following 48-h exposure to fipronil and fipronil sulfone. Prey consumption by S. infuscatum was significantly reduced for fipronil sulfone at all concentrations (0.01-1000 μg/L). S. frequens exposed to 1, 10, 100 and 1000 μg/L fipronil sulfone had significantly longer prey capture times. Fipronil sulfone was 2.8, 9.7 and 10.5 times more toxic to S. infuscatum than fipronil in terms of acute toxicity, feeding inhibition and delayed toxicity, respectively. In addition, fipronil sulfone was 6.6, 2.9 and 9.1 times more toxic, respectively, to S. frequens than fipronil. Our findings suggest that sublethal effects on feeding inhibition lead to severe mortality at realistic paddy soil and water concentrations. Our results provide the first demonstration that short-term exposure to fipronil and fipronil sulfone can consequently cause significant harm to dragonfly larvae survival due to feeding inhibition. These findings have implications for current pesticide risk assessment and dragonfly protection.

Capture and Reductive Transformation of Halogenated Pesticides by an Activated Carbon-Based Electrolysis System for Treatment of Runoff

This study evaluates an electrochemical system to treat the halogenated pesticides, fipronil, permethrin, and bifenthrin, in urban runoff. Compared to the poor sorption capacity of metal-based electrodes, granular activated carbon (GAC)-based electrodes could sorb halogenated pesticides, permitting electrochemical degradation to occur over longer timescales than reactor hydraulic residence times. In a dual-cell configuration, a cathode constructed of loose GAC containing sorbed pesticides was separated from the anode by an ion-exchange membrane to prevent chloride transport and oxidation to chlorine at the anode. When -1 V was applied to the cathode, fipronil concentrations declined by 92% over 15 h, releasing molar equivalents of chloride (2) and fluoride (6), suggesting complete dehalogenation of fipronil. An electrode constructed of crushed GAC particles attached to a carbon cloth current distributor achieved >90% degradation of fipronil, permethrin, and bifenthrin within 2 h under the same conditions. To evaluate a simpler single-cell configuration suitable for scale-up, two of the carbon cloth-based electrodes were placed in parallel without an ion-exchange membrane. For -1 V applied to the cathode, fipronil degradation was >95% over 2 h, and energy consumption declined with closer electrode spacing. However, chloride oxidation at the anode produced chlorine, and the anode degraded. Application of an alternating potential (-1 to +1 V at 0.0125 Hz) to the parallel-plate electrodes achieved >90% degradation of fipronil, bifenthrin, and permethrin over 4 h, releasing chloride at 50-70% of that expected for complete dechlorination. No loss of performance or formation of chlorine or halogenated byproducts was observed over 5 cycles of treating fipronil-spiked surface water.

Chance and design in proinsecticide discovery

Many insecticides are inactive on their target sites in the form that is sold and applied, needing first to be bioactivated. This proinsecticide strategy has often been achieved by design, through systematic derivatization of intrinsically active molecules with protecting groups that mask their toxic effects until their selective removal in target insects by metabolic enzymes generates the toxiphore. Proinsecticides can be designed to gain selectivity between target and non-target organisms, or to improve bioavailability by enhancing plant or insect uptake. In most cases, however, chance trumps design in proinsecticide discovery: most first-in-class products that we now know to be proinsecticides were only discovered a posteriori to be such, often after having been on the market for years. Knowing the active form of an insecticide is essential to mode of action identification, and early mode of action studies on novel chemotypes should take into account the possibility that the compounds might be proinsecticides. This paper reviews examples of proinsecticides in the marketplace, strategies for making proinsecticides and techniques for unmasking proinsecticides in mode of action studies. Our analysis of global agrochemical sales data shows that 34% of the dollar value of crop insecticides used in 2015 were proinsecticides. © 2016 Society of Chemical Industry.

Toxicity of four veterinary pharmaceuticals on the survival and reproduction of Folsomia candida in tropical soils

This study aimed to evaluate the effect of veterinary pharmaceuticals (VPs) used to control endo- and ectoparasites in ruminants, on the survival and reproduction of the collembolan species Folsomia candida. Standard ecotoxicological tests were conducted in Tropical Artificial Soil and the treatments consisted of increasing dosages of four commercial products with different active ingredients: ivermectin, fipronil, fluazuron and closantel. Ecotoxicological effects were related to the class and mode of action of the different compounds. Fipronil and ivermectin were the most toxic compounds causing a significant reduction in the number of juveniles at the lowest doses tested (LOEC_reprod values of 0.3 and 0.2 mg kg^-1 of dry soil, respectively) and similar low EC₅₀ values (fipronil: 0.19 mg kg^-1 dry soil, CL_95% 0.16-0.22; ivermectin: 0.43 mg kg^-1 dry soil, CL_95% 0.09-0.77), although the effects observed in the former compound were possibly related to a low adult survival (LC₅₀ of 0.62 mg kg^-1 dry soil; CL_95%: 0.25-1.06). For the latter compound no significant lethal effects were observed. Fluazuron caused an intermediate toxicity (EC₅₀ of 3.07 mg kg^-1 dry soil, CL_95%: 2.26-3.87), and also here a decrease in adult survival could explain the effects observed at reproduction. Closantel, despite showing a significant reduction on the number of juveniles produced, no dose-response relationship nor effects higher than 50% were observed. Overall, all tested compounds, especially ivermectin, when present in soil even at sub-lethal concentrations, can impair the reproduction of collembolans and possibly other arthropods. However, the actual risk to arthropod communities should be further investigated performing tests under a more realistic exposure (e.g., by testing the dung itself as the contaminated matrix) and by deriving ecotoxicologically relevant exposure concentration in soil derived from the presence of cattle dung.

Assessment of the mutagenic, recombinogenic and carcinogenic potential of fipronil insecticide in somatic cells of Drosophila melanogaster

Fipronil (FP) is an insecticide that belongs to the phenylpyrazole chemical family and is used to control pests by blocking GABA receptor at the entrance channel of the chlorine neurons. The aim of this study was to evaluate the mutagenic, recombinogenic and carcinogenic potential of FP. The mutagenic and recombinogenic effects were evaluated using the somatic mutation and recombination test (SMART) on wing cells of Drosophila melanogaster. Third instar larvae from standard (ST) and high bioactivation (HB) crosses were treated with different concentrations of FP (0.3, 0.7, 1.5 or 3.0 × 10^-5 mM). The results showed mutagenic effects at all concentrations tested in the HB cross; and all concentrations tested in the ST cross, except at concentration of 0.7 × 10^-5 mM. The carcinogenic effect of FP was assayed through the test for detection of epithelial tumor (warts) in D. melanogaster. Third instar larvae from wts/TM3 virgin females mated to mwh/mwh males were treated with different concentrations of FP (0.3, 0.7, 1.5 or 3.0 × 10^-5 mM). All these concentrations induced a statistically significant increase in tumor frequency. In conclusion, FP proved to be mutagenic, recombinogenic and carcinogenic in somatic cells of D. melanogaster.

Fipronil and two of its transformation products in water and European eel from the river Elbe

Fipronil is an insecticide which, based on its mode of action, is intended to be predominantly toxic towards insects. Fipronil bioaccumulates and some of its transformation products were reported to be similar or even more stable in the environment and to show an enhanced toxicity against non-target organisms compared to the parent compound. The current study investigated the occurrence of Fipronil and two of its transformation products, Fipronil-desulfinyl and Fipronil-sulfone, in water as well as muscle and liver samples of eels from the river Elbe (Germany). In water samples total concentrations of FIP, FIP-d and FIP-s ranged between 0.5-1.6ngL(-1) with FIP being the main component in all water samples followed by FIP-s and FIP-d. In contrast, FIP-s was the main component in muscle and liver tissues of eels with concentrations of 4.05±3.73ngg(-1) ww and 19.91±9.96ngg(-1) ww, respectively. Using a physiologically based toxicokinetic (PBTK) model for moderately hydrophobic organic chemicals, the different distributions of FIP, FIP-d and FIP-s in water and related tissue samples could be attributed to metabolic processes of eels. The measured concentrations in water of all analytes and their fractional distribution did not reflect the assumed seasonal application of FIP and it seems that the water was constantly contaminated with FIP, FIP-d and FIP-s.

Fipronil sulfone induced higher cytotoxicity than fipronil in SH-SY5Y cells: Protection by antioxidants

Fipronil is a broad spectrum insecticide from the phenyl pyrazole family, which targets GABA receptor. Limited information is available about the metabolite fipronil sulfone cytotoxic actions. This study examined in vitro neurotoxicity of fipronil and fipronil sulfone and evaluated Trolox (vitamin E analog) (0.3, 1μM), N-acetyl-cysteine (0.5, 1mM), melatonin (0.1, 1μM) and Tempol (superoxide dismutase analog) (0.3, 0.5mM) protective role in SH-SY5Y cells. MTT and LDH assays were carried out to assess the cytotoxicity of fipronil and fipronil sulfone at 3-100μM concentrations. Fipronil sulfone was more toxic than fipronil. Tempol showed the best neuroprotectant profile against fipronil (50 and 150μM) and fipronil sulfone (3 and 10μM) reaching control levels. Fipronil (100μM) and fipronil sulfone (3μM) treatments induced a 4.7- and 5-fold increases in lipid peroxides measured as malondialdehyde (MDA) and a 2.2- and 2.0-fold increases in the levels of nitric oxide (NO). These results suggest that oxidative stress observed may be one of the major mechanisms of fipronil-induced neurotoxicity and it may be attributed in part to fipronil disposition and metabolism. Our results led us postulate that metabolite fipronil sulfone might be responsible for the fipronil-induced toxicity rather than fipronil itself.

Fipronil induces lung inflammation in vivo and cell death in vitro

Background

Fipronil is an insecticide that acts at the gamma-aminobutyric acid receptor and glutamate-gated chloride channels in the central nervous systems of target organisms. The use of fipronil is increasing across the globe. Presently, very little data exist on the potential impact of exposure to fipronil on the lungs.

Methods

We studied effects of intranasal (N = 8) and oral (N = 8) treatment with fipronil (10 mg/kg) on lungs of mice. Control mice were given groundnut oil orally (N = 7) or ethanol intranasally (N = 7) as these were the vehicles for respective treatments.

Results

Hematoxylin-eosin stained lung sections showed normal histology in the control lungs compared to the thickened alveolar septa, disruption of the airways epithelium and damage to vascular endothelium in the intranasal and the oral groups. Mice exposed to fipronil either orally or intranasally showed increased von Willebrand factor staining in the endothelium and septal capillaries. Compared to the control mice, TLR4 expression in airway epithelium was increased in mice treated intranasally but not orally with fipronil. Oral fipronil reduced TLR9 staining in the airway epithelium but intranasal exposure caused intense staining in the alveolar septa and airway epithelium. There were higher numbers of TLR4 positive cells in alveolar septa in lungs of mice treated intranasally (P = 0.010) compared to the respective control and orally treated mice but no significant differences between treatments for TLR9 positive stained cells (P = 0.226). The U937 macrophage cells exposed to fipronil at concentrations of 0.29 μm to 5.72 μm/ml over 3- or 24-hour showed significant increase in cell death at higher concentrations of fipronil (P < 0.0001). Western blots revealed no effect of fipronil on TLR4 (P = 0.49) or TLR9 (P = 0.94) expression on macrophage cell line.

Conclusion

While both oral or intranasal fipronil treatments induced signs of lung inflammation, the number TLR4-positive septal cells was increased only following intranasal treatment. Fipronil causes macrophage cell death without altering TLR4 and TLR9 expression in vitro.

Exposure to fipronil elevates systolic blood pressure and disturbs related biomarkers in plasma of rats

Recent reports show that fipronil affects non-target organisms, including environmental species populations and potentially humans. We aimed to examine if fipronil exposure affects the systolic blood pressure and related biomarkers. Thus, fipronil was orally administered to rats (30 mg/kg/day) during 15 days (Fipronil group) or physiological solution (Control group). While fipronil increased significantly the systolic blood pressure (158±13 mmHg), no significant changes were observed in Control group (127±3 mmHg). Significantly, higher levels of fipronil in plasma were observed in Fipronil group (0.46±0.09 μg/mL versus 0.17±0.11 μg/mL in Control group). Fipronil group showed lower weight gain compared with Control group. While fipronil resulted in higher concentrations of endothelin-1, reduced antioxidant capacity and lower levels of circulating matrix metalloproteinase 2 (MMP-2) and nitric oxide (NO) metabolites compared to Control group, no alteration was observed in serum biomarkers of renal and hepatic/biliary functional abilities. Therefore, this study suggests that fipronil causes hypertension and endothelin-1 plays a key role. Also, these findings suggest that reductions of both MMP-2 and NO may contribute with the elevation of systolic blood pressure observed with fipronil.

Fipronil Compound Consumption Presenting as Status Epilepticus

Fipronil is a broadspectrum N-phenylpyrazole insecticide with gamma-aminobutyric acid type A receptor inhibitory action causing hyperexcitability of central nervous system. There is no literature reported in the past concerning its acute toxicity in human beings. A case report is useful for workers in medical and veterinary field. Hence, we are reporting a case in which young male intoxicated with fipronil compound was presented to the emergency department for having generalized tonic-clonic seizures and subsequently with the features of delirium for few days. This patient was treated with benzodiazepines which controlled the seizures and antipsychotics were given for few days for treating the psychosis.

In utero and lactational exposure to fipronil in female rats: Pregnancy outcomes and sexual development

Fipronil, a phenylpyrazole insecticide, is used in agriculture, veterinary medicine, and public health. Because this insecticide is considered a potential endocrine disruptor, the aim of this study was to examine the influence of perinatal exposure to fipronil on neonatal female reproductive system development. Pregnant rats were exposed (via gavage) daily to fipronil (0.03, 0.3, or 3 mg/kg) from gestational day 15 to day 7 after birth, and effects on the reproductive functions assessed on postnatal day (PND) 22. No signs of maternal toxicity were observed during daily treatment with fipronil. Perinatal exposure to the highest dose of fipronil (3 mg/kg) delayed the age of vaginal opening (VO) and first estrus without markedly affecting the anogenital distance (AGD). Further, exposure to 0.3 mg/kg fipronil produced a significantly shorter estrus cycle and reduced number of cycles during the period of evaluation. However, the other reproductive parameters analyzed, including fertility, hormone levels, sexual behavior, and histology of ovaries and uterus, displayed no marked alterations. In this experimental model, fipronil interfered with development of neonatal female reproductive system as evidenced by delay in VO and estrus cycle alterations without apparent significant effects on fertility. Further studies are needed to identify the mechanisms of action associated with the observed female reproductive system changes.