fipronil-sulfone and fipronil

Fipronil (FIP) is a broad-spectrum insecticide used in the industrial, residential and agricultural sectors, which presents environmental and human health risks. Studies report its presence in aquatic environments in several countries, but in Brazil reports are scarce. The aim of this work was to evaluate the presence of fipronil and fipronil sulfone in surface waters through a validated analytical method by LC-MS according to INMETRO and USEPA in eight sampling sites in two seasons (summer and autumn, 2020) in Guandu River basin, in the state of Rio de Janeiro. FIP was quantified in the concentration range of 0.132-2.44 μg/L, while FIP-S was detected in most samples. This is the first study on the occurrence of FIP and FIP-S in the Guandu River basin, presenting values high enough to justify the need for monitoring studies in a region of great importance for the city of Rio de Janeiro.

Topics: Brazil; Chromatography, High Pressure Liquid; Environmental Monitoring; Humans; Pyrazoles; Rivers; Sulfones; Tandem Mass Spectrometry

Topics: Electrochemical Techniques; Electrodes; Imides; Limit of Detection; Pyrazoles; Reproducibility of Results; Titanium

In 2017 a large-scale fipronil contamination in eggs occurred in several European countries. Fipronil and its metabolites have the potential to be transferred into the eggs of laying hens, thereby entering the human food chain. Here, first the metabolism of fipronil was measured in vitro using chicken liver S9. The results show that fipronil is mainly metabolised into fipronil sulfone and the clearance obtained in vitro was extrapolated to in vivo liver clearance. In a second step a physiologically based kinetic model was developed with a focus on fipronil and its major sulfone metabolite and the model outcome was compared to available in vivo data in eggs from the literature. The experimentally obtained clearance was used as model input to evaluate whether such an in vitro-based model can be used in an early phase of a contamination incident to predict the time-concentration curves. Overall, all model predictions were within a 10-fold difference and the estimated elimination half-life for fipronil equivalents was 14 days. In vitro experiments are definitely recommended compared to in vivo studies, since they provide a fast first insight into the behaviour of a chemical in an organism.

Topics: Animals; Chickens; Female; Insecticides; Pyrazoles

Pesticide exposure during in utero and early postnatal development can cause a wide range of neurological defects. However, relatively few insecticides have been recognized as developmental neurotoxicants, so far. Recently, discovery of the insecticide, fipronil, in chicken eggs has raised public concern. The status of fipronil as a potential developmental neurotoxicant is still under debate. Whereas several in vivo and in vitro studies suggest specific toxicity, other in vitro studies could not confirm this concern. Here, we tested fipronil and its main metabolic product, fipronil sulfone both at concentrations between 1.98 and 62.5 µM, alongside with the established developmental neurotoxicant, rotenone (0.004-10 µM) in vitro on the human neuronal precursor cell line NT2. We found that rotenone impaired all three tested DNT endpoints, neurite outgrowth, neuronal differentiation, and precursor cell migration in a dose-dependent manner and clearly separable from general cytotoxicity in the nanomolar range. Fipronil and fipronil sulfone specifically inhibited cell migration and neuronal differentiation, but not neurite outgrowth in the micromolar range. The rho-kinase inhibitor Y-27632 counteracted inhibition of migration for all three compounds (EC50 between 12 and 50 µM). The antioxidant, n-acetyl cysteine, could ameliorate the inhibitory effects of fipronil on all three tested endpoints (EC 50 between 84 and 164 µM), indicating the involvement of oxidative stress. Fipronil sulfone had a stronger effect than fipronil, confirming the importance to test metabolic products alongside original pesticides. We conclude that in vitro fipronil and fipronil sulfone display specific developmental neurotoxicity on developing human model neurons.

Topics: Cell Differentiation; Cell Line; Cell Movement; Dose-Response Relationship, Drug; Humans; Insecticides; Neuronal Outgrowth; Neurons; Neurotoxicity Syndromes; Pyrazoles; Rotenone

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.

Topics: Acetonitriles; Animals; Chickens; Chromatography, Micellar Electrokinetic Capillary; Eggs; Insecticides; Limit of Detection; Linear Models; Pyrazoles; Reproducibility of Results

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.

Topics: Administration, Oral; Amniotic Fluid; Animals; Biological Availability; Biotransformation; Dose-Response Relationship, Drug; Female; Fetal Blood; Insecticides; Male; Maternal-Fetal Exchange; Placental Circulation; Pregnancy; Pyrazoles; Rats; Toxicity Tests, Acute

A rapid and sensitive method for the simultaneous determination of fipronil and fipronil sulfone (metabolite B) in livestock products was developed. The analytes were extracted from samples with acidic acetonitrile. The crude extracts were subjected to clean-up step using neutral alumina cartridge column. The HPLC separation was performed on a C18 column with isocratic elution of acetonitrile and ammonium formate solution. For the determination of the analytes, a tandem mass spectrometry with negative ion electrospray ionization was used. In the recovery tests using 6 livestock products fortified with MRLs levels of analytes, the truenesses for fipronil and fipronil sulfone were 95 to 115 and 94 to 101% with the repeatabilities of 0.8 to 4.1 and 0.9 to 5.1 RSD%, respectively. The limits of quantification for both analytes were estimated to be 0.001 mg/kg. The developed method is considered suitable for regulatory analysis of fipronil and fipronil sulfone.

Topics: Animals; Chromatography, High Pressure Liquid; Chromatography, Liquid; Food Analysis; Livestock; Meat Products; Pyrazoles; Tandem Mass Spectrometry

Topics: Animals; Chickens; Chromatography, Gas; Chromatography, High Pressure Liquid; Eggs; Insecticides; Limit of Detection; Pyrazoles; Tandem Mass Spectrometry

The insecticide fipronil can be metabolized to its sulfone in mammalian species. Two camel single-domain antibodies (VHHs) F1 and F6, selective to fipronil and fipronil-sulfone, respectively, were generated and used to develop enzyme linked immunosorbent assays (ELISAs) for the detection of the two compounds in the sera of black-tailed prairie dogs and rats. The limits of detection of fipronil and fipronil-sulfone in the rodent sera by the corresponding ELISAs were 10 and 30 ng mL

Topics: Administration, Oral; Animals; Enzyme-Linked Immunosorbent Assay; Immunization; Insecticides; Pyrazoles; Rats; Sciuridae; Single-Domain Antibodies

Fipronil is a highly effective insecticide with extensive usages; however, its distribution and toxic/health effects in the human population after chronic exposure have not yet been clearly identified. Our objectives were to determine the levels of serum fipronil and fipronil sulfone, a primary fipronil metabolite, in a general and sensitive human population using a birth cohort of parent-infant triads in Korea. We further investigated whether in utero exposure to fipronil and fipronil sulfone can affect health outcomes in newborn infants. Blood and umbilical cord blood from 169 participants, 59 mother-neonate pairs and 51 matching biological fathers, were collected; serum fipronil and fipronil sulfone (both blood and cord blood) and serum thyroid hormones (cord blood) were measured. Demographic, physiological, behavioral, clinical, and socioeconomic data for each participant were collected via a one-on-one interview and a questionnaire survey. Fipronil sulfone was detected in the serum of mothers, fathers, and infantile cord blood, while fipronil itself was not. Maternal fipronil sulfone levels were correlated to those of matched biological fathers and newborn infants. Adjusted analyses identified significant associations between parental fipronil sulfone levels and household income. Infantile fipronil sulfone levels were significantly associated with both maternal and paternal levels as well as maternal pre-pregnant BMI. Furthermore, infantile fipronil sulfone levels were inversely associated with cord blood T3 and free T3 levels as well as 5-min Apgar scores of newborn infants. Serum fipronil sulfone was detected in a specific population of mother-neonate pairs and their matched biological fathers in a manner suggestive of regular exposure to fipronil among urban residents. The findings also suggest that serum fipronil sulfone placentally transfers to the fetus and affects infantile adverse health outcomes. This is a first of its kind study; therefore, future studies are warranted.

Topics: Adult; Apgar Score; Biological Monitoring; Female; Fetal Blood; Humans; Infant, Newborn; Insecticides; Male; Maternal Exposure; Maternal-Fetal Exchange; Paternal Exposure; Pregnancy; Pyrazoles; Republic of Korea; Thyroid Hormones

Fipronil is a most widely used insecticide. It has been found to be highly toxic to insects with alarming decline in honey bees' population. It has shown to cause severe contamination of soil and water. The present study was undertaken to understand the degradation of fipronil and its metabolite fipronil sulfone using actinomycetes. Fipronil degrading actinomycetes strain AJAG7 was isolated from fipronil contaminated agricultural field by enrichment method. Molecular identification by 16S rRNA gene sequencing identified strain AJAG7 as Streptomyces rochei. The biodegradation of fipronil and its metabolite fipronil sulfone by strain AJAG7 was examined by HPLC. Biodegradation pathway of fipronil by strain AJAG7 was deduced with GC-MS analysis. Scanning electron microscopy was used to investigate the surface morphological changes of strain AJAG7 upon fipronil degradation. Apart from fipronil degradation, low cost powder formulation of strain AJAG7 was prepared using agricultural waste to remediate the fipronil contaminated agricultural field. Results of the present study suggest that strain AJAG7 qualifies as an ideal candidate for biodegradation of fipronil contaminated environment.

Topics: Biodegradation, Environmental; Chromatography, High Pressure Liquid; Gas Chromatography-Mass Spectrometry; Pyrazoles; Soil Microbiology; Streptomyces

Fipronil is a highly effective, broad-spectrum insecticide used to control pests, globally. The increased usage has led to contamination of soil, water, fruits, and vegetables. The wide and frequent usage of fipronil across the globe calls for attention regarding risk assessment of undesirable effects on non-target microorganisms. In this context, the present study was carried to understand the impact of fipronil on non-pathogenic Escherichia coli. The non-pathogenic E. coli are important commensal of the intestinal tract of humans and animals and are also indicator organisms in the environment. Our study indicates that exposure of E. coli to fipronil (100 μM concentration) leads to significant reactive oxygen species production, loss of membrane potential and viability. Further, we have witnessed the bioaccumulation and biotransformation of fipronil by E. coli at non-lethal concentrations. The bio-transformed products (fipronil sulfone and fipronil sulfide) are also the major metabolites (along with amide) reported in the feces of the mammals when exposed to fipronil. Thus, there is a possibility that the gut E. coli might play a role in the degradation and thereby removal of fipronil. In addition, the bioaccumulation of fipronil in bacteria is of concern and need to be further explored because it can lead to biomagnification in the higher trophic level and can disturb the ecological balance. In our knowledge, this is the first report on the determination of fipronil and its metabolites in bacteria through GC-MS/MS.

Topics: Biotransformation; Chromatography, Gas; Ecology; Escherichia coli; Insecticides; Pyrazoles; Tandem Mass Spectrometry

Fipronil is a chiral insecticide employed worldwide in crops, control of public hygiene and control of veterinary pests. Humans can be exposed to fipronil through occupational, food, and environmental contamination. Therefore, the risk assessment of fipronil in humans is important to protect human health. Fipronil sulfone is the major metabolite formed during fipronil metabolism by humans. Since the CYP450 enzymes are the main ones involved in drug metabolism, the evaluation of their inhibition by fipronil and its main metabolite is important to predict drug-pesticide interactions. The aim of this work was to investigate the inhibition effects of rac-fipronil, S-fipronil, R-fipronil and fipronil sulfone on the main human CYP450 isoforms. The results showed that CYP2D6 is the only CYP450 isoform inhibited by these xenobiotics. In addition, no enantioselective differences were observed in the inhibition of CYP450 isoforms by fipronil and its individuals' enantiomers. Rac-fipronil, S-fipronil and R-fipronil are moderate CYP2D6 inhibitors showing a competitive inhibition profile. On the other hand, the metabolite fipronil sulfone showed to be a strong inhibitor of CYP2D6 also by competitive inhibition. These results highlight the importance of metabolite evaluation on pesticide safety since the metabolism of fipronil into fipronil sulfone increases the risk of pesticide-drug interactions for drugs metabolized by CYP2D6.

Topics: Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP2D6 Inhibitors; Dose-Response Relationship, Drug; Drug Interactions; Humans; Microsomes, Liver; Models, Biological; Pesticides; Protein Conformation; Pyrazoles; Risk Assessment; Structure-Activity Relationship

A novel hydrophilicity nano-titania coating modified magnetic graphene oxide (HTC-Mag-GO) has been synthesized. It has been evaluated in PRiME (process, robustness, improvements, matrix effects, ease of use) pass-through cleanup procedure for human blood prior to analysis of fipronil and its metabolites, i.e., fipronil sulphone, fipronil sulphide and fipronil desulfinyl by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Compared with the Oasis PRiME HLB cartridge, HTC-Mag-GO is much more effective for the removal of matrix effect. Furthermore, it is beneficial to protect the chromatographic column and ESI source by the HTC-Mag-GO PRiME pass-through cleanup procedure, resulting from the much cleaner blood samples. Under the optimum conditions, the results show higher cleanup efficiency of HTC-Mag-GO with recoveries in the range of 92.4%-108%. Especially, the HTC-Mag-GO is also evaluated for reuse (20 times) without much sacrifice of the cleanup efficiency. The limits of quantification (LOQs) for fipronil, fipronil sulphone, fipronil sulphide and fipronil desulfinyl are 8.9 ng/L, 7.2 ng/L, 8.0 ng/L and 42 ng/L, respectively. The developed method has also been successfully applied to monitoring fipronil and its metabolites in 120 blood samples, and fipronil sulphone is detected in six samples with concentrations in the range of 12.1 ng/L-106 ng/L. Further, the well validation results and the application to analysis of fipronil and its metabolites in real samples demonstrate the applicability to toxico kinetic studies and clinical studies.

Topics: Chromatography, Liquid; Graphite; Humans; Hydrophobic and Hydrophilic Interactions; Kinetics; Magnetic Phenomena; Nanoparticles; Oxides; Pyrazoles; Tandem Mass Spectrometry; Titanium

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.

Topics: Animals; Artemia; Dose-Response Relationship, Drug; Feeding Behavior; Female; Insecticides; Larva; Neonicotinoids; Nitro Compounds; Odonata; Pyrazoles

The aim of this study is to evaluate the toxicity of the fipronil and its metabolites, fipronil sulfone and fipronil desulfinyl on Folsomia candida. Three types of soils were used to perform the ecotoxicological tests, two natural soils (Oxisol and Entisol), and an artificial substrate (Tropical Artificial Soil). The treatments consisted of increasing doses of a veterinary medicinal product with active ingredient based on fipronil, and of its two main metabolites, fipronil sulfone and fipronil desulfinyl. The doses of fipronil were 0.00, 0.02, 0.04, 0.08, 0.15, 0.30, 0.60, and 1.00 mg kg

Topics: Animals; Antiparasitic Agents; Arthropods; Lethal Dose 50; No-Observed-Adverse-Effect Level; Pyrazoles; Reproduction; Soil Pollutants; Veterinary Drugs

Occupational medical surveillance is highly desirable in manufacturing facilities where exposure to chemicals is significant. The insecticide fipronil is generally considered safe for humans but with increasing use, exposure to fipronil is of concern. Identification of urinary metabolites of fipronil may allow development of affordable, cheap and rapid procedures for human exposure evaluation. In this study we developed a fast and easy approach for synthesis of hydroxy-fipronil, a potential urinary metabolite of fipronil. This standard was used to develop a sensitive analytical LC-MS/MS method with a limit of quantification (LOQ) of 0.4ng/mL. Fipronil sulfone, a known metabolite, and hydroxy-fipronil were quantified in urine samples from rats treated with a fipronil containing diet. Fipronil sulfone concentration centered around 20ng/mL, while the concentration of hydroxy-fipronil was dose-dependent ranging in 10-10,000ng/mL and thus being a more sensitive marker of fipronil exposure. A fipronil immunoassay with cross-reactivity to hydroxy-fipronil showed a good correlation in signal intensity with LC-MS data. It was also used to demonstrate the applicability of the method for sample screening in the evaluation of exposure levels.

Topics: Animals; Chromatography, Liquid; Insecticides; Limit of Detection; Pyrazoles; Rats; Tandem Mass Spectrometry

Amphibians are very sensitive to environmental change and pollution because they have both aquatic and terrestrial life cycle stages and high skin permeability. Particularly during the larval stages, when these animals are restricted to small, transient ponds, exposure to high concentrations of pesticides is inevitable in agricultural areas. Given that pesticide application increases during the summer, which coincides with the reproductive season and the occurrence of most neotropical tadpoles in their natural environment, strong indications exist that tadpoles are developing in contaminated ponds. Fipronil is one of the primary insecticides used in sugarcane cultivation in Brazil, and little is known about its toxic effects on non-target organisms such as tadpoles. The purpose of this study was to evaluate the effects of fipronil and its metabolites on oxidative stress in Eupemphix nattereri tadpoles after exposure in water and sediment at concentrations of 35, 120 and 180µgkg

Topics: Amphibian Proteins; Animals; Antioxidants; Anura; Catalase; Glucosephosphate Dehydrogenase; Glutathione Transferase; Insecticides; Larva; Lipid Peroxidation; Malondialdehyde; Pyrazoles; Soil Pollutants

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.

Topics: Antioxidants; Cell Line, Tumor; Cell Survival; Cytoprotection; Dose-Response Relationship, Drug; Humans; Inhibitory Concentration 50; Insecticides; Lipid Peroxidation; Malondialdehyde; Neurons; Neuroprotective Agents; Nitric Oxide; Oxidative Stress; Pyrazoles

An enrichment culture technique was used for the isolation of bacteria capable of utilizing fipronil as a sole source of carbon and energy. Based on morphological, biochemical characteristics and phylogenetic analysis of 16S rRNA sequence, the bacterial strains were identified as Acinetobacter calcoaceticus and Acinetobacter oleivorans. Biodegradation experiments were conducted in loamy sand soil samples fortified with fipronil (50 µg kg(-1)) and inoculated with Acinetobacter sp. cells (45 × 10(7) CFU mL(-1)) for 90 days. Soil samples were periodically analyzed by gas liquid chromatography equipped with electron capture detector. Biodegradation of fipronil fitted well with the pseudo first-order kinetics, with rate constant value between 0.041 and 0.051 days(-1). In pot experiments, fipronil and its metabolites fipronil sulfide, fipronil sulfone and fipronil amide were found below quantifiable limit in soil and root, shoot and leaves of Zea mays. These results demonstrated that A. calcoaceticus and A. oleivorans may serve as promising strains in the bioremediation of fipronil-contaminated soils.

Topics: Acinetobacter calcoaceticus; Biodegradation, Environmental; Chromatography, Gas; Insecticides; Phylogeny; Plant Roots; Pyrazoles; RNA, Ribosomal, 16S; Soil; Soil Microbiology; Soil Pollutants; Zea mays

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.

Topics: Anguilla; Animals; Environmental Exposure; Environmental Monitoring; Germany; Insecticides; Pyrazoles; Rivers; Water Pollutants, Chemical

Fipronil is a recalcitrant phenylpyrazole-based pesticide used for flea/tick treatment and termite control that is distributed in urban aquatic environments via stormwater and contributes to stream toxicity. We discovered that fipronil is rapidly metabolized (t

Topics: Biotransformation; Hydroxylation; Insecticides; Kinetics; Pyrazoles; Trametes

Enantiomers of chiral pesticides often have different bioactivity, toxicity and environmental behaviours. Fipronil has been used in racemate for agricultural purposes against soil insects, leading to increased inputs into soil environments and complex biota exposures. To understand the potential risk associated with fipronil enantiomer exposure, subchronic toxicity and bioaccumulation tests with earthworms (Eisenia foetida) in fipronil-spiked soils were evaluated under laboratory conditions.. Enantioselective toxicity was measured in E. foetida biomass after 28 days of subchronic exposure, with increased toxicity from racemate and S-fipronil compared with R-fipronil. The bioaccumulation of fipronil in earthworm tissues was also enantioselective, with a preferential accumulation of S-fipronil, and the enantiomer fraction was approximately 0.56-0.60. During soil exposure, fipronil was transformed primarily into fipronil sulfide, sulfone and amide, and E. foetida rapidly accumulated fipronil and sulfone.. This work demonstrates the enantioselective subchronic toxicity and bioaccumulation of enantiomers of fipronil in E. foetida. The earthworm tissues exhibited a relative enrichment of fipronil and fipronil sulfone, and these compounds might biomagnify (with a biota-to-soil accumulation factor of ≥1.0 kgOCkglip-1), allowing for the possible trophic transfer and/or bioaccumulation of all these chemicals if earthworms were consumed by predator organisms.

Topics: Animals; Biological Availability; Insecticides; Oligochaeta; Pyrazoles; Soil Pollutants; Stereoisomerism

There is a rising concern about the ecological safety and potential health risks caused by pesticides that are commonly present in the environment. Previous studies have shown that metabolites of pesticides sometimes possess more potent endocrine activity than the parent compounds. However very little efforts had been devoted to evaluate the environmental risks of pesticide metabolites. In the present study, we evaluated the agonistic and antagonistic activities of fipronil and its metabolite, fipronil sulfone, and compared by in vitro reporter gene assays using CHO-K1 cells. For estrogenic and antiestrogenic activities, both fipronil and fipronil sulfone showed no agonistic activities but exhibited the similarly antagonistic activities via estrogen receptor α (ERα), with the RIC20 of 6.4 × 10(-7)M and 9.8 × 10(-7)M, respectively. In the thyroid hormone receptor (TR) assay, only fipronil sulfone showed anti-thyroid hormone activity with the RIC20 of 8.2 × 10(-7)M. Furthermore, molecular docking was employed to support the results in TR assay with lower MolDock score for fipronil sulfone. Data provided here suggested that it is of great significance to study the endocrine-disrupting effects of pesticide's metabolites, especially those with persistence in environment and high toxicity to non-targeted organisms.

Topics: Animals; CHO Cells; Cricetulus; Endocrine Disruptors; Estrogen Receptor alpha; Genes, Reporter; Insecticides; Molecular Docking Simulation; Pyrazoles; Thyroid Hormone Receptors beta

Fipronil is a phenylpyrazole insecticide commonly used in residential and agricultural applications. To understand more about the potential risks for human exposure associated with fipronil, urine and serum from dosed Long Evans adult rats (5 and 10mg/kg bw) were analyzed to identify metabolites as potential biomarkers for use in human biomonitoring studies. Urine from treated rats was found to contain seven unique metabolites, two of which had not been previously reported-M4 and M7 which were putatively identified as a nitroso compound and an imine, respectively. Fipronil sulfone was confirmed to be the primary metabolite in rat serum. The fipronil metabolites identified in the respective matrices were then evaluated in matched human urine (n=84) and serum (n=96) samples from volunteers with no known pesticide exposures. Although no fipronil or metabolites were detected in human urine, fipronil sulfone was present in the serum of approximately 25% of the individuals at concentrations ranging from 0.1 to 4ng/mL. These results indicate that many fipronil metabolites are produced following exposures in rats and that fipronil sulfone is a useful biomarker in human serum. Furthermore, human exposure to fipronil may occur regularly and require more extensive characterization.

Topics: Adult; Aged; Animals; Biomarkers; Environmental Exposure; Environmental Monitoring; Female; Housing; Humans; Male; Mass Spectrometry; Middle Aged; Models, Animal; Pesticides; Pyrazoles; Rats; Rats, Long-Evans; Young Adult

A method for the identification and quantification of pesticide residues in water, soil, and sediment samples has been developed, validated, and applied for the analysis of real samples. The specificity was determined by the retention time and the confirmation and quantification of analyte ions. Linearity was demonstrated over the concentration range of 20 to 120 µg L(-1), and the correlation coefficients varied between 0.979 and 0.996, depending on the analytes. The recovery rates for all analytes in the studied matrix were between 86% and 112%. The intermediate precision and repeatability were determined at three concentration levels (40, 80, and 120 µg L(-1)), with the relative standard deviation for the intermediate precision between 1% and 5.3% and the repeatability varying between 2% and 13.4% for individual analytes. The limits of detection and quantification for fipronil, fipronil sulfide, fipronil-sulfone, and fipronil-desulfinyl were 6.2, 3.0, 6.6, and 4.0 ng L(-1) and 20.4, 9.0, 21.6, and 13.0 ng L(-1), respectively. The method developed was used in water, soil, and sediment samples containing 2.1 mg L(-1) and 1.2% and 5.3% of carbon, respectively. The recovery of pesticides in the environmental matrices varied from 88.26 to 109.63% for the lowest fortification level (40 and 100 µg kg(-1)), from 91.17 to 110.18% for the intermediate level (80 and 200 µg kg(-1)), and from 89.09 to 109.82% for the highest fortification level (120 and 300 µg kg(-1)). The relative standard deviation for the recovery of pesticides was under 15%.

Topics: Brazil; Gas Chromatography-Mass Spectrometry; Geologic Sediments; Limit of Detection; Pesticide Residues; Pyrazoles; Sensitivity and Specificity; Soil; Soil Pollutants; Water; Water Pollutants, Chemical

Persistence of fipronil, a new molecule in extensive use against various insect pests is causing serious problems to the environment. Bacillus firmus was isolated by selective enrichment from soil samples collected from sugar fields with known history of pesticide usage and evaluated for metabolization of fipronil in clay loam soil. Soil samples in 50 g aliquotes were fortified with fipronil @ 0.50-1.50 mg kg(-1) and inoculated with B. firmus cells (45×10(7) CFU mL(-1)) and incubated at 25 °C. Each sample in triplicates was drawn periodically up to 56 d and residual fipronil contents analyzed by gas liquid chromatograph. Fipronil residues were not detected after 35 d at lower doses of fipronil (@ 0.50, 0.75 and 1.00 mg kg(-1)). However, at higher doses (@ 1.25 and 1.50 mg kg(-1)) than this total metabolization of fipronil could be observed after 35 and 42 d, respectively. Thus whereas, B. firmus proved its potential in efficient metabolization of fipronil, the period required for the same was dose dependent. Amongst various metabolites of fipronil degradation, fipronil sulfide was found to be the main metabolite followed by fipronil sulfone and fipronil amide. Though, desulfinyl metabolite earlier reported as one of the main metabolite of fipronil degradation, the existence of the same was not detected in any of the treatment.

Topics: Bacillus; Biodegradation, Environmental; Chromatography, Gas; Insecticides; Pyrazoles; RNA, Ribosomal, 16S; Soil Microbiology; Soil Pollutants

Fipronil is described as a thyroid disruptor in rat. Based on the hypothesis that this results from a perturbation of hepatic thyroid hormone metabolism, our goal was to investigate the pathways involved in fipronil-induced liver gene expression regulations. First, we performed a microarray screening in the liver of rats treated with fipronil or vehicle. Fipronil treatment led to the upregulation of several genes involved in the metabolism of xenobiotics, including the cytochrome P450 Cyp2b1, Cyp2b2 and Cyp3a1, the carboxylesterases Ces2 and Ces6, the phase II enzymes Ugt1a1, Sult1b1 and Gsta2, and the membrane transporters Abcc2, Abcc3, Abcg5, Abcg8, Slco1a1 and Slco1a4. Based on a large overlap with the target genes of constitutive androstane receptor (CAR) and pregnane X receptor (PXR), we postulated that these two nuclear receptors are involved in mediating the effects of fipronil on liver gene expression in rodents. We controlled that liver gene expression changes induced by fipronil were generally reproduced in mice, and then studied the effects of fipronil in wild-type, CAR- and PXR-deficient mice. For most of the genes studied, the gene expression modulations were abolished in the liver of PXR-deficient mice and were reduced in the liver of CAR-deficient mice. However, CAR and PXR activation in mouse liver was not associated with a marked increase of thyroid hormone clearance, as observed in rat. Nevertheless, our data clearly indicate that PXR and CAR are key modulators of the hepatic gene expression profile following fipronil treatment which, in rats, may contribute to increase thyroid hormone clearance.

Topics: Animals; Constitutive Androstane Receptor; Female; Gene Expression Regulation; Liver; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Pregnane X Receptor; Pyrazoles; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Receptors, Steroid; Species Specificity; Thyroid Hormones; Transcriptome

In the scientific literature, little attention has been paid to the disposition of fipronil, a phenyl pyrazole insecticide. In this study, the tissue distribution, the metabolic fate, and the elimination of fipronil was investigated in rats using radiolabeled fipronil. When a single oral dose of (14)C-fipronil (10 mg kg(-1) b.w.) was given to rats, the proportion of dose eliminated in urine and feces 72 h after dosing was ca 4% for each route. At the end of the experiment the highest levels of radioactivity were found in adipose tissue and adrenals. The main part of the radioactivity present in investigated tissues (adipose tissue, adrenals, liver, kidney, testes) was due to fipronil-sulfone. Five additional metabolites, isolated from urine were characterized by LC-MS/MS. Most of them are formed by the loss of the trifluoromethylsulphinyl group and subsequent hydroxylation and/or conjugation to glucuronic acid or sulfate. In conclusion, the retention of the metabolite fipronil sulfone in tissues following fipronil administration raises the question of the potential toxicity of this insecticide.

Topics: Animals; Insecticides; Male; Pyrazoles; Rats; Tissue Distribution

In rats, the widely used insecticide fipronil increases the clearance of thyroxine (T(4)). This effect is associated with a high plasma concentration of fipronil sulfone, the fipronil main metabolite in several species including rats and humans. In sheep, following fipronil treatment, fipronil sulfone plasma concentration and thyroid disruption are much lower than in rats. We postulated that fipronil biotransformation into fipronil sulfone by hepatic cytochromes P450 (CYP) could act as a potential thyroid disruptor. The aim of this study was to determine if fipronil sulfone treatment could reproduce the fipronil treatment effects on T(4) clearance and CYP induction in rats. Fipronil and fipronil sulfone treatments (3.4 μmol/kg/day per os, 14 days) increased total and free T(4) clearances to the same extent in THX + T(3), euthyroid-like rats. Both treatments induced a 2.5-fold increase in Ugt1a1 and Sult1b1 messenger RNA (mRNA) expressions and a twofold increase in UGT1A activity suggesting that T(4) elimination was mediated, at least in part, by hepatic uridine 5'-diphospho-glucuronosyltransferases (UGT) and/or sulfotransferases (SULT) induction. Both treatments induced a 10-fold increase in Cyp3a1 and Cyp2b2 mRNA expressions concomitant with a threefold increase in CYP3A immunoreactivity and a 1.7-fold increase in antipyrine clearance, a biomarker of CYP3A activity. All these results showed that fipronil sulfone treatment could reproduce the fipronil treatment effects on T(4) clearance and hepatic enzyme induction in rats. The potential of fipronil sulfone to act as a thyroid disruptor is all the more critical because it persists much longer in the organism than fipronil itself.

Topics: Animals; Cytochrome P-450 Enzyme System; Endocrine Disruptors; Enzyme Induction; Female; Gene Expression Regulation, Enzymologic; Glucuronosyltransferase; Insecticides; Liver; Pyrazoles; Rats; Rats, Wistar; Sulfotransferases; Thyroid Gland; Thyroid Hormones; Thyroidectomy

Fipronil represents a chemical class of insecticides acting at the γ-aminobutyric acid receptor in pests. [corrected] Fipronil has been associated with a significant increase in the incidence of thyroid gland tumors concomitant with prolonged exposure to thyroid-stimulating hormone (TSH) in rats. An association between human TSH concentration and thyroid cancer has been also reported. The primary objective of this study was to test the hypothesis that chronic occupational fipronil exposure may be associated with abnormal thyroid function tests.. In 2008, 159 workers of a factory manufacturing fipronil-containing veterinary drugs were assessed. Serum concentrations of TSH, total thyroxine, free thyroxine, fipronil, and fipronil sulfone were measured.. A positive and significant correlation was observed between serum fipronil or fipronil sulfone levels and duration of fipronil exposure. Serum fipronil sulfone concentration was negatively correlated with TSH concentration in fipronil-exposed workers, but with no significant increase in thyroid function test abnormalities.. This study did not show that chronic fipronil exposure was associated with an increase of thyroid function test abnormalities. But, despite the fact that fipronil exposure in rats has been associated with increased serum TSH, fipronil sulfone concentrations were negatively correlated with serum TSH concentrations in fipronil-exposed workers, raising the possibility that fipronil has a central inhibitory effect on TSH secretion in humans. Close occupational medical surveillance, therefore, appears to be required in factory workers manufacturing fipronil-containing veterinary drugs. Larger epidemiological studies as well as investigations on possible thyroid-disrupting mechanisms of fipronil are also required.

Topics: Adult; Female; Humans; Insecticides; Male; Occupational Exposure; Pyrazoles; Thyroid Function Tests; Thyroid Gland; Thyrotropin; Thyroxine

In rat, fipronil treatment increases the elimination of thyroid hormones (TH). Relevance of this mechanism for the risk of fipronil for human health is subject to controversy because of the specificities of adult rat for TH plasma binding properties which often lead to the assumption that rats are more sensitive than human to thyroid disruption. This study aimed at determining if the mechanism of fipronil-induced thyroid disruption is altered in sheep a species more relevant to human from the standpoint of TH plasma binding. TSH, total triiodothyronine and free and total tetra-iodothyronine 24 h secretory profiles were not modified by fipronil treatment (5 mg/kg every 4 days per os) in rams. In euthyroid-like thyroidectomised ewes, the effect of this treatment was limited to a moderate increase in free T4 clearance. In contrast with the rat, fipronil treatment (0.5 mg/kg/day, IV for 14 days) had no effect on antipyrine clearance, a marker for hepatic cytochrome activity, in ewes. The differences between rat and sheep for the potential of fipronil as a thyroid disruptor might be related to the difference in the exposure to the toxicant, the actual exposure to the sulfone metabolite of fipronil being lower in sheep than in rat.

Topics: Animals; Area Under Curve; Disease Models, Animal; Female; Insecticides; Male; Pyrazoles; Random Allocation; Rats; Sheep; Thyroid Diseases; Thyroid Gland; Thyrotropin; Thyroxine; Triiodothyronine

Fipronil is an insecticide extensively used to treat pets, which has been identified as a potential thyroid disruptor in the rat. In this species, fipronil is mainly metabolized to fipronil sulfone and plasma concentrations of fipronil sulfone can be at least 20-fold higher than those of fipronil. Investigations of fipronil and fipronil sulfone exposure in blood remain sparse because of the lack of convenient and suitable analytical methods. We have developed and validated an LC/UV/MS/MS method to quantify both fipronil and fipronil sulfone within a wide range of concentrations in rat plasma. The double detection UV and MS coupled on-line enabled the concentrations to be measured over a 3 Log range (2.5-2500 ng/mL). The volume of sample required for the extraction by solid phase extraction was reduced to 75 microL with a recovery higher than 70%. The two-detection method agreement, evaluated with a Bland-Altman plot, was good for concentrations between 50 and 150 ng/mL. The method was applied to monitor plasma concentrations following a commonly used dosage regimen for the toxicological evaluation of fipronil in rats.

Topics: Animals; Chromatography, High Pressure Liquid; Female; Insecticides; Pyrazoles; Rats; Rats, Wistar; Sensitivity and Specificity; Tandem Mass Spectrometry

Fipronil is the active ingredient in a number of widely used insecticides. Human exposure to fipronil leads to symptoms (headache, nausea and seizures) typically associated with the antagonism of GABA(A) receptors in the brain. In this study, we have examined the modulation of the common brain GABA(A) receptor subtype by fipronil and its major metabolite, fipronil sulphone.. Whole-cell and single-channel recordings were made from HEK 293 cells transiently expressing rat alpha1beta2gamma2L GABA(A) receptors.. The major effect of fipronil was to increase the rate of current decay in macroscopic recordings. In single-channel recordings, the presence of fipronil resulted in shorter cluster durations without affecting the intracluster open and closed time distributions or the single-channel conductance. The alpha1V256S mutation, previously shown alleviate channel inhibition by inhibitory steroids and several insecticides, had a relatively small effect on channel block by fipronil. The mode of action of fipronil sulphone was similar to that of its parent compound but the metabolite was less potent at inhibiting the alpha1beta2gamma2L receptor.. We conclude that exposure to fipronil induces accumulation of receptors in a novel, long-lived blocked state. This process proceeds in parallel with and independently of, channel desensitization. The lower potency of fipronil sulphone indicates that the conversion serves as a detoxifying process in mammalian brain.

Topics: Animals; Cell Line; Cloning, Molecular; Electrophysiology; GABA-A Receptor Antagonists; Humans; Insecticides; Ion Channel Gating; Molecular Structure; Patch-Clamp Techniques; Pyrazoles; Rats; Receptors, GABA-A; Recombinant Proteins