Reactive oxygen species and mitogen-activated protein kinase induce apoptotic death of SH-SY5Y cells in response to fipronil

Toxicoproteomic study of fipronil in SH-SY5Y cells reveals induction of endoplasmic reticulum stress and necrotic cell death as neurodegenerative mechanisms

Exposure to pesticides has been considered as a risk factor for developing neurodegenerative diseases. The increasing use of fipronil, a phenylpyrazole insecticide, poses a risk to human health. This study aims to use toxicoproteomics for exploring neurodegenerative mechanism of fipronil in SH-SY5Y human neuroblastoma cells. In this study, fipronil at sub-cytotoxic and cytotoxic concentrations (43 and 78 μM) caused increases in superoxide level from 3 to 48 h after treatment, while intracellular glutathione level was decreased at 48 h. Neurite outgrowth of the cells was impaired by fipronil at both concentrations, while significant increase of cell death via apoptosis and necrosis modes were observed with fipronil at cytotoxic concentration. Pretreatment with antioxidant N-acetylcysteine (NAC) effectively relieved impairment of neurite outgrowth and induction of cell death by fipronil. Proteomic analysis showed that expression of proteins involving endoplasmic reticulum (ER) stress and unfolded protein responses were predominantly affected by fipronil. Immunoblotting confirmed the increased expression of ER stress markers, GRP78/BiP (78 kDa glucose-regulated protein/Binding immunoglobulin protein) and PDI (protein disulfide isomerase), in fipronil-treated cells. Improved understanding of the neurotoxic mechanism of fipronil may help in developing a strategy for reducing risk of neurodegenerative development from intense and prolonged use of fipronil.

Fipronil Triggers Immunotoxicity Through Reactive Oxygen Species-Driven Mitochondrial Apoptosis in Thymocytes

Fipronil (FPN), a widely used pesticide, is associated with significant immunotoxic effects, particularly impacting thymocyte survival and immune homeostasis. This study explores the mechanistic pathways underlying FPN-induced apoptosis and oxidative stress. Short-term FPN exposure (1-10 mg/kg) notably suppressed the expression of both anti-apoptotic (Bcl-2, Bcl-6, Mcl-1) and pro-apoptotic (Bnip3, Bim) genes in thymic tissues in vivo. Additionally, in isolated primary thymocytes, FPN directly decreased the expression of Bcl-2, Bcl-6, Mcl-1, and Bnip3 expression, coupled with a significant increase in pro-apoptotic Bim expression in a dose-dependent manner. FPN treatment directly led to elevated reactive oxygen species (ROS), lipid peroxidation, mitochondrial membrane depolarization, reduced cellular metabolic activity, and depleted intracellular calcium and glutathione (GSH) levels, indicating mitochondrial dysfunction and oxidative stress. Annexin V/PI staining confirmed that FPN induced late-stage apoptosis and necrosis in primary thymocytes. These findings elucidate the immunotoxic effects of FPN on thymocytes, highlighting its detrimental impact on immune system integrity, thymic development, and T cell maturation through oxidative damage and mitochondrial-mediated apoptosis.

An adverse outcome pathway-based approach to assess the neurotoxicity by combined exposure to current-use pesticides

Exposure to multiple pesticides in daily life has become an important public health concern. However, the combined effects of pesticide mixtures have not been fully elucidated by the conventional toxicological testing used for individual chemicals. Grouping of chemicals by mode of action using common key events (KEs) in the adverse outcome pathway (AOP) as endpoints could be applied for efficient risk assessment of combined exposure to multiple chemicals. The purpose of this study was to investigate whether exposure to multiple pesticides has synergistic neurotoxic effects on mammalian nervous systems. According to the AOP-based approach, we evaluated the effects of 10 current-use pesticides (4 neonicotinoids, 4 pyrethroids and 2 phenylpyrazoles) on the common KEs in AOPs for neurotoxicity, such as KEs involving mitochondrial and proteolytic functions, in a mammalian neuronal cell model. Our data showed that several pyrethroids and phenylpyrazoles partly shared the effects on several common KEs, including decreases in mitochondrial membrane potential and proteasome activity and increases in autophagy activity. Furthermore, we also found that combined exposure to a type-I pyrethroid permethrin or a type-II pyrethroid deltamethrin and the phenylpyrazole fipronil decreased the cell viability and the benchmark doses much more than either single exposure, indicating that the pair exhibited synergistic effects, since the combination indexes were less than 1. These findings revealed that novel pairs of different classes of pesticides with similar effects on common KEs exhibited synergistic neurotoxicity and provide new insights into the risk assessment of combined exposure to multiple chemicals.

Avoidance responses by Danio rerio reveal interactive effects of warming, pesticides and their mixtures

Temperature variations and thermal extremes events caused by climate change can have profound implications for the toxicity of pesticides in aquatic organisms. Using an innovative system (Heterogeneous Multi-Habitat Test System - HeMHAS) that allows the simulation of different scenarios within a spatially heterogeneous landscape, the effects on the habitat selection of Danio rerio fish caused by the pesticides fipronil and 2,4-D were studied as single compounds and in mixture and integrated with air temperature variation (20, 24 and 28 °C). As a result, D. rerio detected and avoided both pesticides at air temperatures of 20 and 24 °C; however, at 28 °C no significant difference was observed in habitat choice by fish. Additionally, when pesticides were mixed in a heterogeneously contaminated landscape, it was observed that D. rerio detected contamination and preferred the clean zone at 20 and 24 °C; however, at 28 °C the potential to escape from the most contaminated areas was impaired. Thus, contamination by both pesticides made the habitat selection behavior of fish at 20 and 24 °C more noticeable. In addition, the association between pesticides and temperature showed negative effects on the response of fish to detect and escape from contaminated environments, suggesting the influence of temperature in altering the ability of the organism to provide an efficient response to stress.

Antitumor activity of copper(II) complexes with Schiff bases derived from N'-tosylbenzene-1,2-diamine

The electrochemical oxidation of anodic metal copper in a solution of the ligands N-[(5-tert-butyl-2-hydroxyphenyl)methylidine]-N'-tosylbenzene-1,2-diamine [H₂L¹] and N-[(3,5-di-tert-butyl-2-hydroxyphenyl)methylidine]-N'-tosylbenzene-1,2-diamine, [H₂L²] afforded homoleptic [CuL] compounds or solvate [CuLS] complexes. The addition to the electrochemical cell of coligands (L') such as 2,2'-bipyridine (2-bpy), 4,4'-bipyridine(4-bpy) or 1,10-phenanthroline (phen) allowed the synthesis, in one step, of heteroleptic [CuLL'] compounds, namely [CuL¹(H₂O)] (1), [CuL¹(2,2'-bpy)]⋅CH₃CN (2), [CuL¹(phen)]·H₂O (3), [Cu₂L¹₂(4,4'-bpy)] (4), [CuL²(CH₃OH)] (5), [CuL²(2,2'-bpy)] (6), [CuL²(phen)] (7) and [Cu₂L²₂(4,4'-bpy)] (8). The crystal structures of both ligands, H₂L¹, H₂L², and those of the complexes (2), (4), (5), (6) and (7) have been determined by X-ray diffraction techniques. Coordination polyhedron around metal atom is square planar for [CuL²(CH₃OH)] (5) and [Cu₂L¹₂(4,4'-bpy)] (4) and square pyramid for the other complexes with additional chelating ligands. The cytotoxic activity of this new series of copper(II) complexes against the SH-SY5Y neuroblastoma cell line and U87-MG and U373-MG glioblastoma cell lines has been investigated. Most of the test compounds showed higher activity than cisplatin in the three cell lines. Among this series, compound [CuL¹(phen)] (3) displayed the highest activity with IC₅₀ equal to 1.77 μM on SH-SY5Y whereas compound [Cu₂L¹₂(4.4'-bpy)] (4) resulted the most potent compounds on U87 MG and U373 MG glioblastoma cell lines. Studies on the cytotoxic activity of these derivatives suggest that these compounds induce cell death by a mechanism other than apoptosis.

Pathogenicity of Beauveria bassiana PfBb and Immune Responses of a Non-Target Host, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Exploring the pathogenicity of a new fungus strain to non-target host pests can provide essential information on a large scale for potential application in pest control. In this study, we tested the pathogenicity of Beauveria bassiana PfBb on the important agricultural pest Spodoptera frugiperda (Lepidoptera: Noctuidae) by determining the relative activities of protective enzymes and detoxifying enzymes in different larval instars. Our results show that the B. bassiana PfBb strain could infect all six larval instars of S. frugiperda, and its virulence to S. frugiperda larvae gradually increased with an increase in spore concentration. Seven days after inoculation, the LC₅₀ of B. bassiana PfBb was 7.7 × 10⁵, 5.5 × 10⁶, 2.2 × 10⁷, 3.1 × 10⁸, 9.6 × 10⁸, and 2.5 × 10¹¹ spores/mL for first to sixth instars of S. frugiperda, respectively, and the LC₅₀ and LC₉₀ of B. bassiana PfBb for each S. frugiperda instar decreased with infection time, indicating a significant dose effect. Furthermore, the virulence of B. bassiana PfBb to S. frugiperda larvae gradually decreased with an increase in larval instar. The activities of protective enzymes (i.e., catalase, peroxidase, and superoxide dismutase) and detoxifying enzymes (i.e., glutathione S-transferases, carboxylesterase, and cytochrome P450) in S. frugiperda larvae of the first three instars infected with B. bassiana PfBb changed significantly with infection time, but such variations were not obvious in the fifth and sixth instars. Additionally, after being infected with B. bassiana PfBb, the activities of protective enzymes and detoxification enzymes in S. frugiperda larvae usually lasted from 12 to 48 h, which was significantly longer than the control. These results indicate that the pathogenicity of B. bassiana PfBb on the non-target host S. frugiperda was significant but depended on the instar stage. Therefore, the findings of this study suggest that B. bassiana PfBb can be used as a bio-insecticide to control young larvae of S. frugiperda in an integrated pest management program.

Ameliorative effects of the phytochemicals in dates (Phoenix dactylifera) against the toxicological changes induced by fipronil in male albino rats

Scientific evidence has shown that fipronil induces oxidative stress and genotoxicity. Our study aimed to evaluate the potential oxidation in redox parameters and DNA, as well as determine the protective effect of date extract of increasing resistance to cellular damage. 30 Male albino rats were divided into six groups ( n = 5): 1) control group; 2) treatment group with date extract (1 g/kg B.W.); 3) treatment group with 1/20 LD50 of fipronil; 4) treatment group with 1/40 LD50 of fipronil; 5) treatment group with 1/20 LD50 of fipronil + 1 g/kg date extract; and 6) treatment group with 1/40 LD50 of fipronil + 1 g/kg dates extract. Date extract showed a high content of phenolic compounds and antioxidant properties. Fipronil increased 8-hydroxy-2-deoxyguanosine levels and lipid peroxidation by malondialdehyde but decreased the total antioxidant capacity in plasma. Moreover, glutathione, catalase, and superoxide dismutase levels in the liver and kidney decreased, along with histopathological abnormalities. Additionally, tail moment parameters of liver DNA and micronucleus frequencies in the bone marrow increased. This study showed that fipronil-induced various health hazards in vivo, whereas date extract alleviated the said toxicological effects. However, date extract failed to reduce genotoxicity.

The SH-SY5Y human neuroblastoma cell line, a relevant in vitro cell model for investigating neurotoxicology in human: focus on organic pollutants

Investigation of the toxicity triggered by chemicals on the human brain has traditionally relied on approaches using rodent in vivo models and in vitro cell models including primary neuronal cultures and cell lines from rodents. The issues of species differences between humans and rodents, the animal ethical concerns and the time and cost required for neurotoxicity studies on in vivo animal models, do limit the use of animal-based models in neurotoxicology. In this context, human cell models appear relevant in elucidating cellular and molecular impacts of neurotoxicants and facilitating prioritization of in vivo testing. The SH-SY5Y human neuroblastoma cell line (ATCC® CRL-2266^TM) is one of the most used cell lines in neurosciences, either undifferentiated or differentiated into neuron-like cells. This review presents the characteristics of the SH-SY5Y cell line and proposes the results of a systematic review of literature on the use of this in vitro cell model for neurotoxicity research by focusing on organic environmental pollutants including pesticides, 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), flame retardants, PFASs, parabens, bisphenols, phthalates, and PAHs. Organic environmental pollutants are widely present in the environment and increasingly known to cause clinical neurotoxic effects during fetal & child development and adulthood. Their effects on cultured SH-SY5Y cells include autophagy, cell death (apoptosis, pyroptosis, necroptosis, or necrosis), increased oxidative stress, mitochondrial dysfunction, disruption of neurotransmitter homeostasis, and alteration of neuritic length. Finally, the inherent advantages and limitations of the SH-SY5Y cell model are discussed in the context of chemical testing.

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.

Fipronil induced oxidative stress in neural tissue of albino rat with subsequent apoptosis and tissue reactivity

Fipronil (FIP) insecticide is extensively used in agriculture, public health and veterinary medicine. Although it is considered as a neurotoxin to insects (target organisms) and exhibits neurological signs upon vertebrates (non-target organisms) exposure, slight is known about its potential neurotoxic effects and its molecular mechanisms on vertebrates. The current study is designed to assess oxidative stress as a molecular mechanism of FIP neurotoxicity subordinated with apoptosis and neural tissue reactivity. Ten adult male albino rats received 10 mg/kg body weight fipronil technical grade by oral gavage daily for 45 days (subacute exposure). Brain neural tissue regions (hippocampus, cerebellum and caudate putamen) were processed to examine oxidative stress induced cellular macromolecular alterations as MDA, PCC and DNA fragmentation. Besides, TNF-α and Bcl-2 gene expression and immunoreactivity for caspase-3 (active form), iNOS and GFAP were evaluated. Also, histopathological assessment was conducted. We found that FIP significantly raised MDA, PCC and DNA fragmentation (p ≤ 0.05). Also, it significantly upregulated TNF-α and non-significantly down-regulated Bcl-2 gene expression (p ≤ 0.05). Further, significant increased immunoreactivity to GFAP, iNOS and caspase-3 (active form) in these brain neural tissue regions in FIP treated group was noticed (p ≤ 0.05). Histopathological findings, including alterations in the histological architecture and neuronal degeneration, were also observed in these brain regions of FIP treated group. In conclusion, we suggest the ability of FIP to induce oxidative stress mediated macromolecular alterations, leading to apoptosis and tissue reaction in these brain regions which showed variable susceptibility to FIP toxic effects.

Boswellia serrata suppress fipronil-induced neuronal necrosis and neurobehavioral alterations via promoted inhibition of oxidative/inflammatory/apoptotic pathways

Boswellic acid (BA) is a pentacyclic terpenoid derived from the gum-resin of Boswellia serrate. It is known for its strong antioxidant, anti-inflammatory, and anticancer properties. It has improved spatial learning and provides neuroprotection against trimethyltin-induced memory impairment. The aim of this study is to evaluate the possible neuroprotective activity of B. serrata extract (BSE) containing BA against fipronil (FPN)-induced neurobehavioral toxicity in Wister male albino rats. Sixty male rats were allocated equally into six groups. The first group served as control; the second and third groups received BSE at two different oral doses (250 or 500 mg/kg body weight [BW], respectively). The fourth group was orally intoxicated with FPN (20 mg/kg BW), whereas the fifth and sixth groups served as preventive groups and co-treated with FPN (20 mg/kg BW) and BSE (250 or 500 mg/kg BW, respectively). The experiment was conducted over 8 weeks period. Results revealed that co-treatment with BSE led to significant (p > 0.05) dose-dependent reduction in malondialdehyde (MDA), nitric oxide (NO), interleukin-6 (IL6), tumor necrosis factors-alpha (TNF-α), nuclear factor Kappa-B (NF-κB), Cyclooxegenase-2 (COX-2), prostaglandin E2 (PGE2), serotonin, and acetylcholine (ACh). Conversely, significant (p > 0.05) up regulation of catalase (CAT), glutathione peroxidase (GSH-Px), gamma-aminobutyric acid (GABA), and acetylcholine esterase (AChE) has reported in BSE-co-treated groups. In addition, significant (p > 0.05) promotion in neurobehaviours, histopathologic imaging of the cerebral, cerebellar, and hippocampal regions, and immunohistochemical expression of caspase-3 and glial fibrillary acidic protein (GFAP) were also reported in the BSE-treated groups in a dose-dependent manner. In conclusion, BSE (500 mg/kg BW) is a natural, promising neuroprotective agent that can mitigate FPN-induced neurobehavioral toxicity via the suppression of oxidative, inflammatory, and apoptotic pathways and relieve neuronal necrosis and astrogliosis.

Acute exposure to fipronil induces oxidative stress, apoptosis and impairs epithelial homeostasis in the midgut of the stingless bee Partamona helleri Friese (Hymenoptera: Apidae)

Partamona helleri is an important pollinator in natural and agricultural ecosystems in the neotropics. However, the foraging activity of this bee increases its risk of exposure to pesticides, which may affect both the individuals and the colony. Thus, this study aims to evaluate the side effects of LC₅₀ of fipronil (0.28 ng a.i. μL^-1) on the midgut morphology, antioxidant activity and some pathways of cell death, proliferation and differentiation in workers of P. helleri, after 24 h of oral exposure. Fipronil caused morphological alterations in the midgut of the bees. The activities of the detoxification enzymes superoxide dismutase, catalase and glutathione S-transferase increased after exposure, which suggests the occurrence of a detoxification mechanism. Furthermore, exposure to fipronil changed the number of positive cells for signaling-pathway proteins in the midgut of bees, which indicates the induction of cell death by the apoptotic pathway and impairment of the midgut epithelial regeneration. These results demonstrate that fipronil may negatively affect the morphology and physiology of the midgut of the stingless bee P. helleri and impose a threat to the survival of non-target organisms.

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.

Ameliorative Role of Cerium Oxide Nanoparticles Against Fipronil Impact on Brain Function, Oxidative Stress, and Apoptotic Cascades in Albino Rats

Fipronil (FIP) is an N-phenylpyrazole insecticide that is used extensively in public health and agriculture against a wide range of pests. Exposure to FIP is linked to negative health outcomes in humans and animals including promoting neuronal cell injury, which results in apoptosis through the production of reactive oxygen species (ROS). Therefore, the purpose of the current study was to investigate the neuroprotective effects of cerium oxide nanoparticles (CeNPs) on neuronal dysfunction induced by FIP in albino rats. Male rats were randomly classified into four groups: control, FIP (5 mg/kg bwt), CeNPs (35 mg/kg bwt), and FIP + CeNPs (5 (FIP) + 35 (CeNPs) mg/kg bwt), which were treated orally once daily for 28 consecutive days. Brain antioxidant parameters, histopathology, and mRNA expression of genes related to brain function were evaluated. The results revealed oxidative damage to brain tissues in FIP-treated rats indicated by the elevated levels of malondialdehyde (MDA) and nitric oxide (NO) levels and reduced activities of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx). On the other hand, the FIP’s group that was treated with CeNPs showed decrease in MDA and NO levels and increase in SOD and GPx enzymes activity. Besides, FIP-treated rats showed decreased butyrylcholinesterase (BuChE) activity in comparison to the FIP + CeNPs group. Moreover, FIP caused up-regulation of the expression of neuron-specific enolase (NSE), caspase-3, and glial fibrillary acidic protein (GFAP) but down-regulation of B-cell lymphoma-2 (BCL-2) expression. But the FIP + CeNPs group significantly down-regulated the GFAP, NSE, and caspase-3 and up-regulated the gene expression of BCL-2. Additionally, the FIP-treated group of rats had clear degenerative lesions in brain tissue that was reversed to nearly normal cerebral architecture by the FIP + CeNPs treatment. Immunohistochemical examination of brain tissues of rats-treated with FIP showed abundant ionized calcium-binding adaptor molecule 1 (Iba-1) microglia and caspase-3 and apoptotic cells with nearly negative calbindin and synaptophysin reaction, which were countered by FIP + CeNPs treatment that revealed a critical decrease in caspase-3, Iba-1 reaction with a strong calbindin positive reaction in most of the Purkinje cells and strong synaptophysin reaction in the cerebrum and cerebellum tissues. Based on reported results herein, CeNPs treatment might counteract the neurotoxic effect of FIP pesticide via an antioxidant-mediated mechanism.

Developmental Neurotoxicity of Fipronil and Rotenone on a Human Neuronal In Vitro Test System

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.

Luteolin attenuates Fipronil-induced neurotoxicity through reduction of the ROS-mediated oxidative stress in rat brain mitochondria

Luteolin (LUT) as a natural compound found in vegetables and fruits has various pharmacological effects. Fipronil (FPN), as a pesticide, has been considered for its effect on the antioxidant system and induction of oxidative stress. This study was designed to investigate the protective effects of LUT against the oxidative stress and mitochondrial toxicity induced by FPN on the rat brain. Several parameters such as mitochondrial reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP) collapse, mitochondrial swelling, cytochrome c release, mitochondrial glutathione (GSH), lipid peroxidation (LPO) and Adenosine triphosphate (ATP) levels were assessed. Results indicated that the administration of LUT (25 μM) significantly improved oxidative stress and mitochondrial damages induced via FPN (6, 12 and 24 μM) in isolated mitochondria from the brain. These results show that LUT exerted protective effects against FPN-induced neurotoxicity in vitro through improving oxidative stress and mitochondrial damages.

Fipronil and 2,4-D effects on tropical fish: Could avoidance response be explained by changes in swimming behavior and neurotransmission impairments?

Brazil is the largest producer of sugarcane, a crop largely dependent on chemical control for its maintenance. The insecticide fipronil and herbicide 2,4-D stand out among the most commonly used pesticides and, therefore, environmental consequences are a matter of concern. The present study aimed to investigate the toxicity mechanisms of Regent® 800 WG (a.i. fipronil) and DMA® 806 BR (a.i. 2,4-D) pesticides using forced and non-forced exposures through an integrative approach: firstly, to assess whether contamination by fipronil and 2,4-D can trigger the avoidance behavior of the fish Danio rerio (zebrafish) and Hyphessobrycon eques (serpae tetra or mato-grosso). Additionally, the effects on fish were analyzed considering the swimming behavior together with a biomarker of neurotoxicity, the activity of acetylcholinesterase (AChE). In avoidance tests with pesticide gradients, D. rerio avoided the highest concentrations of the two compounds and H. eques avoided only the highest concentration of 2,4-D. The swimming behavior (distance moved) was reduced and AChE was inhibited when D. rerio was exposed to fipronil. The 2,4-D affected the swimming (maximum speed) of H. eques, but AChE was not altered. Avoidance response seemed not to have been affected by possible effects of contaminants on swimming behavior and Ache activity. This study showed the importance of knowing the avoidance capacity, swimming behavior and neurotoxic effects of pesticides on fish in an integrated and realistic context of exposure in environments contaminated with pesticides and can be useful as ecologically relevant tools for ecological risk assessment.

Ginseng attenuates fipronil-induced hepatorenal toxicity via its antioxidant, anti-apoptotic, and anti-inflammatory activities in rats

Fipronil (FPN) is a relatively new and broad spectrum insecticide that induces toxic effects to animals and humans through induction of oxidative stress. Ginseng is a medicinal plant that has antioxidant, anti-inflammatory, and anti-apoptotic activities. Thus, the current study was conducted to evaluate the anti-toxic potential of ginseng aqueous extract (GAE) against FPN-induced hepatorenal toxicity in rats. Thirty-two male Wistar albino rats were randomly allocated into four equal groups. Rats of the control group received distilled water. The second group was administrated with GAE at a dose of 200 mg/kg b.w. orally day by day for 6 weeks. The third group was intoxicated with FPN at a dose of 4.85 mg/kg b.w. orally day by day for 6 weeks. The fourth group was administrated with GAE 2 h before FPN intoxication. Intoxication of rats with FPN significantly elevated the activities of serum alanine aminotransferase and aspartate aminotransferase and serum levels of urea and creatinine, as well as increased malondialdehyde level and protein expressions of caspase-3 and cyclooxygenase-2 in hepatic and renal tissues. However, it significantly decreased hepatic and renal GSH content and catalase activity. In addition, it induced histopathological alterations in hepatic and renal tissue architectures. Conversely, concomitant oral administration of GAE ameliorated the FPN-induced biochemical, pathological, and histochemical alterations in both hepatic and renal tissues. This study indicated that ginseng attenuates FPN-induced hepatorenal toxicity, possibly via its antioxidant, anti-apoptotic, and anti-inflammatory properties. Graphical Abstract CAL ABSTRACTPHIRAG.

Oxidative stress, hematological and biochemical alterations induced by sub-acute exposure to fipronil (COACH®) in albino mice and ameliorative effect of selenium plus vitamin E

Fipronil (FIP) is a highly effective, broad-use insecticide that belongs to the phenylpyrazole chemical group. It is extensively used in the agriculture and veterinary medicine for controlling a wide variety of pests. Though FIP showed lower toxicity in vertebrates than in insects, it was recognized to have a variety of toxic effects in mammals. The present study was undertaken to evaluate FIP-induced alterations in the blood biochemical markers and oxidative stress parameters in male albino mice via oral sub-acute toxicity exposure. The possible ameliorative effect of the pretreatment with selenium plus α-tocopherol (vitamin E) against the harmful effects of FIP was also investigated. Mice in FIP-test groups were exposed to different sublethal doses, i.e., 1.43, 2.87, and 4.78 mg active ingredient (AI)/kg body weight (b.w.), equal to 1/100, 1/50, and 1/30 LD₅₀ of FIP, respectively, for 28 days. Mice in the amelioration groups were orally administered with selenium + vitamin E (0.3 mg + 22.5 mg/kg b.w., respectively) 14 days prior to exposure to the higher dose (4.78 mg/kg) of FIP for another 14 days. Fipronil exposure at medium and high doses showed lowered values of red blood cell count (RBC), hematocrit (HCT), hemoglobin (HGB), white blood cell (WBC), and platelet (PLT) counts after 28-day exposure, compared to the control. All three doses caused significant increases in levels of liver-function biomarkers, i.e., aspartate amino transaminase (AST), alanine amino transaminase (ALT), alkaline phosphatase (ALP), cholesterol, and bilirubin levels compared to the control. Levels of biomarkers related to kidney functions, i.e., urea, uric acid, and creatinine, increased significantly than these of the control. Likewise, the oxidative stress indices, i.e., hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), significantly increased at the higher and medium doses, while antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD), decreased significantly. On the other hand, prior administration of selenium + vitamin E in the FIP-exposed mice led to restore values of most hematological parameters nearly to these of the control. Also, the levels of AST, total protein, and creatinine seemed to be restored to the control values. Interestingly, pretreatment with selenium + vitamin E restored the levels of antioxidant enzymes, CAT and SOD, to the control values, whereas, oxidative stress indices, H₂O₂ and MDA, remained significantly high. It is our thought that the sublethal dose less than 1.43 mg/kg b.w. of commercial formulation of FIP (COACH^® 200 SC) could be considered as no-observed-adverse-effect-level(NOAEL) under our present experimental conditions at short-term toxicity study. On the other hand, the higher sublethal doses, 4.78 and 2.87 mg/kg b.w., induced significant adverse effects in biomarkers and may be deleterious to human health following long-term exposure.

Evaluation of the genotoxicity of neurotoxic insecticides using the micronucleus test in Tradescantia pallida

Neonicotinoids and phenylpyrazoles are classes of neurotoxic insecticides which are able to bind at different ligand sites of neural receptors, leading to the deregulation of insect neural activity and hence resulting in death. The misuse or indiscriminate use of these chemicals is directly associated with several toxicological effects in biota and at different trophic levels. Based on this premise, the aim of the present study was to evaluate and compare the genotoxic capacity of different concentrations of thiamethoxam (TMX), acetamiprid (ACP), imidacloprid (IMI) and fipronil (FP) through the Micronucleus Test in Tradescantia pallida (Trad-MCN). After acclimatization (24 h), T. pallida stems were treated with stablished concentrations of TMX, ACP, IMI and FP for 8 h. Then, the stems of the model organism were submitted to a recovery phase (24 h). The young inflorescences were harvested and fixed in Carnoy solution and, after 24 h, were conserved in ethanol 70% until the analyzes. The obtained anthers were macerated on slides for microscopy, stained with acetic carmine dye and covered with coverslips before analysis by light microscopy. Considering the insecticides, the micronuclei (MN) frequency in plants treated at concentrations of 0.2 and 0.4 g L^-1 for TMX, 0.2; 0.4 and 0.8 g L^-1 for ACP, 0.1; 0.2; 0.4; 0.8 and 1.6 g L^-1 for IMI and 0.2; 0.4; 0.8 and 1.6 g L^-1 for FP differed statistically (p < 0.05, Tukey) from the MN frequency of the negative control. All chemicals evaluated revealed genotoxic activity in T. pallida at the highest concentrations.

Butylene fipronil induces apoptosis in PC12 murine nervous cells via activation of p16-CDK4/6-cyclin D1 and mitochondrial apoptotic pathway

Butylene fipronil (BFPN) is a phenylpyrazole insecticide, acting at the γ-aminobutyric acid (GABA) receptor. Here, we show that BFPN inducedcytotoxicity in PC12 murinenervous cells, which lacks GABA receptor. Treatment with BFPN for 48 hours significantly enhanced G0/G1 arrest and induced apoptosis. BFPN decreased the expression of cyclin-dependent kinase (CDK4 and CDK6) and increased P16 and cyclin D1. Simultaneously, Bcl-2 protein was declined while Bax and cytochrome c were significantly enhanced in BFPN-treated groups. The apoptotic enzymes caspase-8, -9, and -3 were also activated by BFPN. Furthermore, treatment with BFPN significantly stimulated reactive oxygen species (ROS) generation, and pretreatment with antioxidant diphenyleneiodonium, substantially reduced cell death. Overall, these results suggest that BFPN is effective to induce G0/G1-phase arrest and apoptosis in PC12 murine nervous cell. Stimulating ROS generation and activation of P16-CDK4/6-cyclin D1 and mitochondrial apoptotic pathway may participate in the cytotoxicity of BFPN.

The effect of α-tocopherol and dithiothreitol in ameliorating emamectin benzoate cytotoxicity in human K562 cells involving the modulation of ROS accumulation and NF-κB signaling

Emamectin benzoate (EMB) toxicity contributes a potential risk to environment and human health. To investigate the effect of α-tocopherol (VitE) and dithiothreitol (DTT) in ameliorating EMB-induced cytotoxicity in human K562 cells, in vitro cultured human K562 cells were incubated with different concentrations of EMB in supplement with VitE and DTT when the cells were in the logarithmic phase. Next, the cell growth inhibition was evaluated using the MTT assay and cellular morphology observation. Reactive oxygen species (ROS) production was monitored using DCFH-DA probe and NF-κB signaling was determined using Western blotting. The results demonstrated that treatment with EMB (time- and concentration-dependent) showed significantly greater inhibition on K562 cell viability, heavier chromatin condensation and DNA fragmentation, and stronger suppression of NF-κB/p105 and p65/RelA expression of K562 cells than the control group (p < 0.01). The supplementation of VitE or DTT could help protect K562 cells against EMB-induced cytotoxicity by improving cell viability, preventing ROS accumulation and up-regulating NF-κB signaling through their ameliorating effects against oxidative stress induced by EMB. VitE had a stronger synergistic effect in limiting EMB cytotoxicity than DTT. Our findings indicate that VitE and DTT are potent antioxidants for human K562 cells, offering a promising means of ameliorating EMB cytotoxicity.

Thymoquinone and diallyl sulfide protect against fipronil-induced oxidative injury in rats

Fipronil (FPN) is a phenylpyrazole insecticide, widely used for agricultural and veterinary activities. Early reports indicated that FIP organ toxicity is primarily mediated by the induction of oxidative stress. Both thymoquinone (TQ) and diallyl sulfide (DAS) are natural antioxidants with established health benefits. This study investigated the potential ameliorative effects of DAS and TQ against FPN-induced toxicity in rats. Thirty-two male Wistar rats (150-180 g) were randomized into four treatment groups, receiving (I) saline, (II) FPN (10 mg/kg bw), (III) FPN with DAS (200 mg/kg bw), and (IV) FPN with TQ (10 mg/kg bw). All treatments were administered once daily for 28 days. The results showed that compared to the control rats, FPN-treated rats had significantly increased (p < 0.05) serum levels of uric acid, urea, creatinine, cholesterol, aspartate transferase, alanine transferase, alkaline phosphatase, lactate dehydrogenase, and γ-glutamyl transferase. Moreover, FPN significantly reduced (p < 0.05) the serum levels of total proteins, albumin, and triglycerides. In addition, compared with the control group, FPN-treated rats had significantly elevated (p < 0.05) malondialdehyde and nitric oxide levels, as well as significantly reduced glutathione concentration and activities of glutathione peroxidase, superoxide dismutase, and catalase enzymes in the hepatic, renal, and brain tissues. Cotreatment with DAS or TQ significantly ameliorated (p < 0.05) the FPN-induced alterations in all the previously mentioned parameters with more frequent restoration of normal control ranges in the TQ group. In conclusion, both DAS and TQ alleviated the oxidative injury of FPN, probably by enhancing tissue antioxidant defenses.

PEST-containing nuclear protein mediates the proliferation, migration, and invasion of human neuroblastoma cells through MAPK and PI3K/AKT/mTOR signaling pathways

Background

PEST-containing nuclear protein (PCNP), a novel nuclear protein, is involved in cell proliferation and tumorigenesis. However, the precise mechanism of action of PCNP in the process of tumor growth has not yet been fully elucidated.

Methods

ShRNA knockdown and overexpression of PCNP were performed in human neuroblastoma cells. Tumorigenic and metastatic effects of PCNP were examined by tumor growth, migration, and invasion assays in vitro, as well as xenograft tumor assay in vivo.

Results

PCNP over-expression decreased the proliferation, migration, and invasion of human neuroblastoma cells and down-regulation of PCNP showed reverse effects. PCNP over-expression increased protein expressions of cleaved caspase-3, cleaved caspase-8, cleaved caspase-9, and cleaved poly adenosine diphosphate-ribose polymerase, as well as ratios of B-cell lymphoma-2 (Bcl-2)-associated X protein/Bcl-2 and Bcl-2-associated death promoter/B-cell lymphoma-extra large in human neuroblastoma cells, however PCNP knockdown exhibited reverse trends. PCNP over-expression increased phosphorylations of extracellular signal-regulated protein kinase 1/2, p38, c-Jun N-terminal kinase, as well as decreased phosphorylations of phosphatidylinositol 3-kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR), nevertheless PCNP knockdown exhibited opposite effects. Furthermore, PCNP over-expression significantly reduced the growth of human neuroblastoma xenograft tumors by down-regulating angiogenesis, whereas PCNP knockdown markedly promoted the growth of human neuroblastoma xenograft tumors through up-regulation of angiogenesis.

Conclusions

PCNP mediates the proliferation, migration, and invasion of human neuroblastoma cells through mitogen-activated protein kinase and PI3K/AKT/mTOR signaling pathways, implying that PCNP is a therapeutic target for patients with neuroblastoma.

Disruption of oxidative balance in the gut of the western honeybee Apis mellifera exposed to the intracellular parasite Nosema ceranae and to the insecticide fipronil

The causes underlying the increased mortality of honeybee colonies remain unclear and may involve multiple stressors acting together, including both pathogens and pesticides. Previous studies suggested that infection by the gut parasite Nosema ceranae combined with chronic exposure to sublethal doses of the insecticide fipronil generated an increase in oxidative stress in the midgut of honeybees. To explore the impact of these two stressors on oxidative balance, we experimentally infected bees with N. ceranae and/or chronically exposed to fipronil at low doses for 22 days, and we measured soluble reactive oxygen species (ROS) and ROS damage by quantifying both protein and lipid oxidation in the midgut. Our results revealed a disruption of the oxidative balance, with a decrease in both the amount of ROS and ROS damage in the presence of the parasite alone. However, protein oxidation was significantly increased in the N. ceranae/fipronil combination, revealing an increase in oxidative damage and suggesting higher fipronil toxicity in infected bees. Furthermore, our results highlighted a temporal order in the appearance of oxidation events in the intestinal cells and revealed that all samples tended to undergo protein oxidation during ageing, regardless of treatment.

Involvement of vimentin in neurite outgrowth damage induced by fipronil in SH-SY5Y cells

Fipronil, a phenylpyrazole insecticide, is more selective in its potency towards insects than humans and is thus commonly used. In this study, we demonstrated that exposure to fipronil may pose a human health risk. We observed in vitro the shortening of neurite outgrowths of SH-SY5Y neuroblastoma cells upon treatment with fipronil, even at a non-cytotoxic concentration. Fipronil induced apoptosis involving caspase-6, which is an apoptotic effector highly implicated in neurodegenerative diseases. Moreover, at a concentration that did not induce apoptosis, mitochondrial dysfunction and autophagic vacuole formation were detected. Interestingly using proteomics, we identified vimentin to be dramatically expressed by SH-SY5Y cells as a response to fipronil treatment. Not only did the expression of total vimentin increase, different isoforms were observed, indicating alterations in post-translational modifications. Vimentin was localized at the neurite outgrowth, possibly to repair the damage in cellular structure. However at high concentrations of fipronil, vimentin was found in less defined fibrils, in bridge-like formation, and dense surrounding vacuoles. In all, our results indicate that vimentin plays an important role in fipronil-induced neurotoxicity in SH-SY5Y cells.

Biochemical effects of fipronil and its metabolites on lipid peroxidation and enzymatic antioxidant defense in tadpoles (Eupemphix nattereri: Leiuperidae)

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^-1. We assessed the activities of the antioxidant enzymes glutathione S-transferase (GST), glucose 6-phosphate dehydrogenase (G6PDH) and catalase (CAT) and lipid peroxidation (malondialdehyde, MDA). The results showed that fipronil has an inherent capacity to cause oxidative stress in tadpoles, as evidenced by a decrease in CAT activity and an increase in lipid peroxidation levels at all concentrations tested. Fipronil sulfone also produced elevated MDA levels at two of the tested concentrations and increased G6PDH activity in tadpoles exposed to the highest concentration of this metabolite but did not affect MDA levels. Our data showed that fipronil and its degradation products promoted oxidative stress in Eupemphix nattereri tadpoles exposed to environmentally relevant concentrations and could lead to a decrease in the long-term physiological performance of these animals, leading to detrimental effects at the population level.

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 induced oxidative stress involves alterations in SOD1 and catalase gene expression in male mice liver: Protection by vitamins E and C

In the present investigation, hepatic oxidative stress induced by fipronil was evaluated in male mice. We also investigated whether pretreatment with antioxidant vitamins E and C could protect mice against these effects. Several studies conducted in cell lines have shown fipronil as a potent oxidant; however, no information is available regarding its oxidative stress inducing potential in an animal model. Out of 8 mice groups, fipronil was administered to three groups at low, medium, and high dose based on its oral LD50 (2.5, 5, and 10 mg/kg). All three doses of fipronil caused a significant increase in the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) level with concomitant increase in the absolute and relative weight of liver. High dose of fipronil caused significant down-regulation in the hepatic mRNA expression of superoxide dismutase 1 (SOD1) and catalase (0.412 ± 0.01 and 0.376 ± 0.05-fold, respectively) as well as an increase in the lipid peroxidation (LPO). Also, decrease in the activity of antioxidant enzymes; SOD, catalase, and glutathione-S-transferase (GST) and the content of nonantioxidant enzymes; glutathione and total thiol were recorded. Histopathological examination of liver revealed dose dependant changes such as severe fatty degeneration and vacuolation leading to hepatocellular necrosis. Prior administration of vitamin E or vitamin C against fipronil high dose caused decrease in lipid peroxidation and increased activity of antioxidant enzymes. Severe reduction observed in functional activities of antioxidant enzymes was aptly substantiated by down-regulation seen in their relative mRNA expression. Thus results of the present study imply that liver is an important target organ for fipronil and similar to in vitro reports, it induces oxidative stress in the mice liver, which in turn could be responsible for its hepatotoxic nature. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1147-1158, 2016.

Drone exposure to the systemic insecticide Fipronil indirectly impairs queen reproductive potential

A species that requires sexual reproduction but cannot reproduce is doomed to extinction. The important increasing loss of species emphasizes the ecological significance of elucidating the effects of environmental stressors, such as pesticides, on reproduction. Despite its special reproductive behavior, the honey bee was selected as a relevant and integrative environmental model because of its constant and diverse exposure to many stressors due to foraging activity. The widely used insecticide Fipronil, the use of which is controversial because of its adverse effects on honey bees, was chosen to expose captive drones in hives via syrup contaminated at 0.1 μg/L and gathered by foragers. Such environmental exposure led to decreased spermatozoa concentration and sperm viability coupled with an increased sperm metabolic rate, resulting in drone fertility impairment. Subsequently, unexposed queens inseminated with such sperm exhibited fewer spermatozoa with lower viability in their spermatheca, leaving no doubt about the detrimental consequences for the reproductive potential of queens, which are key for colony sustainability. These findings suggest that pesticides could contribute to declining honey bee populations through fertility impairment, as exemplified by Fipronil. More broadly, reproductive disorders should be taken into consideration when investigating the decline of other species.

The critical role of oxidative stress in the toxicity and metabolism of quinoxaline 1,4-di-N-oxides in vitro and in vivo

Quinoxaline 1,4-dioxide derivatives (QdNOs) have been widely used as growth promoters and antibacterial agents. Carbadox (CBX), olaquindox (OLA), quinocetone (QCT), cyadox (CYA) and mequindox (MEQ) are the classical members of QdNOs. Some members of QdNOs are known to cause a variety of toxic effects. To date, however, almost no review has addressed the toxicity and metabolism of QdNOs in relation to oxidative stress. This review focused on the research progress associated with oxidative stress as a plausible mechanism for QdNO-induced toxicity and metabolism. The present review documented that the studies were performed over the past 10 years to interpret the generation of reactive oxygen species (ROS) and oxidative stress as the results of QdNO treatment and have correlated them with various types of QdNO toxicity, suggesting that oxidative stress plays critical roles in their toxicities. The major metabolic pathways of QdNOs are N→O group reduction and hydroxylation. Xanthine oxidoreductase (XOR), aldehyde oxidase (SsAOX1), carbonyl reductase (CBR1) and cytochrome P450 (CYP) enzymes were involved in the QdNOs metabolism. Further understanding the role of oxidative stress in QdNOs-induced toxicity will throw new light onto the use of antioxidants and scavengers of ROS as well as onto the blind spots of metabolism and the metabolizing enzymes of QdNOs. The present review might contribute to revealing the QdNOs toxicity, protecting against oxidative damage and helping to improve the rational use of concurrent drugs, while developing novel QdNO compounds with more efficient potentials and less toxic effects.

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.

Clearance of Damaged Mitochondria Through PINK1 Stabilization by JNK and ERK MAPK Signaling in Chlorpyrifos-Treated Neuroblastoma Cells

Mitochondrial quality control and clearance of damaged mitochondria through mitophagy are important cellular activities. Studies have shown that PTEN-induced putative protein kinase 1 (PINK1) and Parkin play central roles in triggering mitophagy; however, little is known regarding the mechanism by which PINK1 modulates mitophagy in response to reactive oxygen species (ROS)-induced stress. In this study, chlorpyrifos (CPF)-induced ROS caused mitochondrial damage and subsequent engulfing of mitochondria in double-membrane autophagic vesicles, indicating that clearance of damaged mitochondria is due to mitophagy. CPF treatment resulted in PINK1 stabilization on the outer mitochondrial membrane and subsequently increased Parkin recruitment from the cytosol to the abnormal mitochondria. We found that PINK1 physically interacts with Parkin in the mitochondria of CPF-treated cells. Furthermore, a knockdown of PINK1 strongly inhibited the LC3-II protein level by blocking Parkin recruitment. This indicates that CPF-induced mitophagy is due to PINK1 stabilization in mitochondria. We observed that PINK1 stabilization was selectively regulated by ROS-mediated c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling activation but not p38 signaling. In the mitochondria of CPF-exposed cells, pretreatment with specific inhibitors of JNK and ERK1/2 significantly decreased PINK1 stabilization and Parkin recruitment and blocked the LC3-II protein level. Specifically, JNK and ERK1/2 inhibition also dramatically blocked the interaction between PINK1 and Parkin. Our results demonstrated that PINK1 regulation plays a critical role in CPF-induced mitophagy. The simple interpretation of these results is that JNK and ERK1/2 signaling regulates PINK1/Parkin-dependent mitophagy in the mitochondria of CPF-treated cells. Overall, this study proposes a novel molecular regulatory mechanism of PINK1 stabilization under CPF exposure.

Firpronil induced spermotoxicity is associated with oxidative stress, DNA damage and apoptosis in male rats

The present study is the first to investigate and characterize the fipronil (FPN) induced spermotoxicity in male rats. Male rats were orally given FPN (2.5, 5.0 and 10 mg/kg/day) for 4 weeks. Epididymal sperms were collected and remaining testis was processed for histopathological evaluation. FPN treatment significantly reduced sperm density, motility, viability and per cent intact acrosome along with concomitant increase in spermatozoa abnormalities. Exposure of FPN caused excessive ROS generation, lipid peroxidation and alteration in mitochondrial membrane potential leading to apoptosis of spermatozoa in dose dependent manner. Higher FPN doses (5 and 10 mg/kg) markedly reduced the DNA integrity of spermatozoa. These data suggest that FPN causes male reproductive toxicity through oxidative stress induced DNA damage and apoptosis of spermatozoa.

Meloxicam inhibits fipronil-induced apoptosis via modulation of the oxidative stress and inflammatory response in SH-SY5Y cells

Oxidative stress and inflammatory responses have been identified as key elements of neuronal cell apoptosis. In this study, we investigated the mechanisms by which inflammatory responses contribute to apoptosis in human neuroblastoma SH-SY5Y cells treated with fipronil (FPN). Based on the cytotoxic mechanism of FPN, we examined the neuroprotective effects of meloxicam against FPN-induced neuronal cell death. Treatment of SH-SY5Y cells with FPN induced apoptosis via activation of caspase-9 and -3, leading to nuclear condensation. In addition, FPN induced oxidative stress and increased expression of cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNF-α) via inflammatory stimulation. Pretreatment of cells with meloxicam enhanced the viability of FPN-exposed cells through attenuation of oxidative stress and inflammatory response. FPN activated mitogen activated protein kinase (MAPK) and inhibitors of MAPK abolished FPN-induced COX-2 expression. Meloxicam also attenuated FPN-induced cell death by reducing MAPK-mediated pro-inflammatory factors. Furthermore, we observed both nuclear accumulation of p53 and enhanced levels of cytosolic p53 in a concentration-dependent manner after FPN treatment. Pretreatment of cells with meloxicam blocked the translocation of p53 from the cytosol to the nucleus. Together, these data suggest that meloxicam may exert anti-apoptotic effects against FPN-induced cytotoxicity by both attenuating oxidative stress and inhibiting the inflammatory cascade via inactivation of MAPK and p53 signaling.

Fipronil induces apoptosis through caspase-dependent mitochondrial pathways in Drosophila S2 cells

Fipronil is the first phenylpyrazole insecticide widely used in controlling pests, including pyrethroid, organophosphate and carbamate insecticides. It is generally accepted that fipronil elicits neurotoxicity via interactions with GABA and glutamate receptors, although alternative mechanisms have recently been proposed. This study evaluates the genotoxicity of fipronil and its likely mode of action in Drosophila S2 cells, as an in vitro model. Fipronil administrated the concentration- and time-dependent S2 cell proliferation. Intracellular biochemical assays showed that fipronil-induced S2 cell apoptosis coincided with a decrease in the mitochondrial membrane potential and an increase reactive oxygen species generation, a significant decrease of Bcl-2 and DIAP1, and a marked augmentation of Cyt c and caspase-3. Because caspase-3 is the major executioner caspase downstream of caspase-9 in Drosophila, enzyme activity assays were used to determine the activities of caspase-3 and caspase-9. Our results indicated that fipronil effectively induced apoptosis in Drosophila S2 cells through caspase-dependent mitochondrial pathways.

Sub-chronic exposure to fipronil induced oxidative stress, biochemical and histopathological changes in the liver and kidney of male albino rats

Fipronil (FPN) is a broad-spectrum N-phenylpyrazole insecticide and has been used in agriculture and public health since the mid-1990s. The present study was designed to investigate the adverse effects of sub-chronic exposure to the FPN on the liver and kidney of male rats at three concentrations 0.1, 1 and 10 mg/L in drinking water for 45 days. Serum aspartate aminotransferases (AST), alanine aminotransferases (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) activity and levels of uric acid, creatinine and total protein were significantly increased in FPN-treated rats. Oxidative stress biomarkers such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reduced (GSH) were significantly decreased, while lipid peroxidation (LPO) was significantly increased in treating rats in a concentration dependent manner. FPN caused histopathological alterations in liver and kidney of male rats. From our results, it can be concluded that FPN induced lipid peroxidation, oxidative stress, liver, and kidney injury in rats. These pathophysiological changes in liver and kidney tissues could be due to the toxic effect of FPN that associated with a generation of free radicals.

Fipronil induced oxidative stress in kidney and brain of mice: protective effect of vitamin E and vitamin C

Fipronil is a relatively new insecticide of the phenpyrazole group. Fipronil-induced effects on antioxidant system and oxidative stress biomarkers are yet to be studied in vivo. The present study was undertaken to evaluate fipronil-induced alterations in the blood biochemical markers and tissue antioxidant enzymes after oral exposure in mice and to explore possible protective effect of pre-treatment of antioxidant vitamins against these alterations. Mice were divided into eight groups containing control, test and amelioration groups. Mice in the test groups were exposed to different doses of fipronil, i.e., 2.5, 5 and 10 mg/kg bw, respectively for 28 days. Mice in the amelioration groups were treated with vitamin E or vitamin C (each at 100 mg/kg) 2 h prior to high dose (10 mg/kg) of fipronil. Fipronil exposure at three doses caused significant increase in the blood biochemical markers, lipid peroxidation and prominent histopathological alterations; while level of antioxidant enzymes was severely decreased both in kidney and brain tissues. Prior administration of vitamin E or vitamin C in the fipronil exposed mice led to decrease in lipid peroxidation and significant increase in activities of antioxidants, viz., glutathione, total thiol, superoxide dismutase and catalase. Vitamin E and vitamin C administration in fipronil exposed mice also improved histological architecture of the kidney and brain when compared with fipronil alone treated groups. Thus, results of the present study demonstrated that in vivo fipronil exposure induces oxidative stress and pre-treatment with vitamin E or C can protect mice against this oxidative insult.

Modification of the brain proteome of Africanized honeybees (Apis mellifera) exposed to a sub-lethal doses of the insecticide fipronil

Fipronil is a phenylpyrazole insecticide that is widely used in Brazilian agriculture for pest control. Although honeybees are not targets of fipronil, studies indicate that this pesticide can be harmful to honeybees. To assess the effects of fipronil in the brain of Africanized Apis mellifera workers, this study focused on the toxico-proteome profiling of the brain of newly emerged and aged honeybee workers that were exposed to a sub-lethal dose (10 pg fipronil per day. i.e. (1)/100 of LD50/bee/day during 5 days) of the insecticide. Proteomic analysis identified 25 proteins that were differentially up-regulated or down-regulated when the fipronil-exposed and non-exposed groups were compared. These proteins are potentially related to pathogen susceptibility, neuronal chemical stress, neuronal protein misfolding, and occurrence of apoptosis, ischemia, visual impairment, damaged synapse formation, brain degeneration, memory and learning impairment. The exposure of honeybees to a very low dose of fipronil, even for a short period of time (5 days), was sufficient to cause a series of important neuroproteomic changes in the brains of honeybees.

In vitro impact of five pesticides alone or in combination on human intestinal cell line Caco-2

In Burkina Faso, as in most Sahelian countries, the failure to follow good agricultural practices coupled with poor soil and climate conditions in the locust control context lead to high environmental contaminations with pesticide residues. Thus, consumers being orally exposed to a combination of multiple pesticide residues through food and water intake, the digestive tract is a tissue susceptible to be directly exposed to these food contaminants. The aim of our work was to compare in vitro the impact of five desert locust control pesticides (Deltamethrin DTM, Fenitrothion FNT, Fipronil FPN, Lambda-cyalothrine LCT, and Teflubenzuron TBZ) alone and in combination on the human intestinal Caco-2 cells viability and function. Cells were exposed to 0.1–100 μM pesticides for 10 days alone or in mixture (MIX). Our results showed a cytotoxic effect of DTM, FNT, FPN, LCT, and TBZ alone or in combination in human intestinal Caco-2 cells. The most efficient were shown to be FPN and FNT impacting the cell layer integrity and/or barrier function, ALP activity, antioxidant enzyme activity, lipid peroxidation, Akt activation, and apoptosis. The presence of antioxidant reduced lipid peroxidation level and attenuated the pesticides-induced cell toxicity, suggesting that key mechanism of pesticides cytotoxicity may be linked to their pro-oxidative potential. A comparative analysis with the predicted cytotoxic effect of pesticides mixture using mathematical modeling shown that the combination of these pesticides led to synergistic effects rather than to a simple independent or dose addition effect.

Use of herbal medicines and natural products: an alternative approach to overcoming the apoptotic resistance of pancreatic cancer

Pancreatic cancer has a poor prognosis with a 5-year survival rate of <5%. It does not respond well to either chemotherapy or radiotherapy, due partly to apoptotic resistance (AR) of the cancer cells. AR has been attributed to certain genetic abnormalities or defects in apoptotic signaling pathways. In pancreatic cancer, significant mutations of K-ras and p53, constitutive activation of NFκB, over-expression of heat shock proteins (Hsp90, Hsp70), histone deacetylase (HDACs) and the activities of other proteins (COX-2, Nrf2 and bcl-2 family members) are closely linked with resistance to apoptosis and invasion. AR has also been associated with aberrant signaling of MAPK, PI3K-AKT, JAK/STAT, SHH, Notch, and Wnt/β-catenin pathways. Strategies targeting these signaling molecules and pathways provide an alternative for overcoming AR in pancreatic cancer. The use of herbal medicines or natural products (HM/NPs) alone or in combination with conventional anti-cancer agents has been shown to produce beneficial effects through actions upon multiple molecular pathways involved in AR. The current standard first-line chemotherapeutic agents for pancreatic cancer are gemcitabine (Gem) or Gem-containing combinations; however, the efficacy is dissatisfied and this limitation is largely attributed to AR. Meanwhile, emerging data have pointed to a combination of HM/NPs that may augment the sensitivity of pancreatic cancer cells to Gem. Greater understanding of how these compounds affect the molecular mechanisms of apoptosis may propel development of HM/NPs as anti-cancer agents and/or adjuvant therapies forward. In this review, we give a critical appraisal of the use of HM/NPs alone and in combination with anti-cancer drugs. We also discuss the potential regulatory mechanisms whereby AR is involved in these protective pathways.

Survival and swimming behavior of insecticide-exposed larvae and pupae of the yellow fever mosquito Aedes aegypti

BACKGROUND

The yellow fever mosquito Aedes aegypti is essentially a container-inhabiting species that is closely associated with urban areas. This species is a vector of human pathogens, including dengue and yellow fever viruses, and its control is of paramount importance for disease prevention. Insecticide use against mosquito juvenile stages (i.e. larvae and pupae) is growing in importance, particularly due to the ever-growing problems of resistance to adult-targeted insecticides and human safety concerns regarding such use in human dwellings. However, insecticide effects on insects in general and mosquitoes in particular primarily focus on their lethal effects. Thus, sublethal effects of such compounds in mosquito juveniles may have important effects on their environmental prevalence. In this study, we assessed the survival and swimming behavior of A. aegypti 4th instar larvae (L4) and pupae exposed to increasing concentrations of insecticides. We also assessed cell death in the neuromuscular system of juveniles.

METHODS

Third instar larvae of A. aegypti were exposed to different concentrations of azadirachtin, deltamethrin, imidacloprid and spinosad. Insect survival was assessed for 10 days. The distance swam, the resting time and the time spent in slow swimming were assessed in 4th instar larvae (L4) and pupae. Muscular and nervous cells of L4 and pupae exposed to insecticides were marked with the TUNEL reaction. The results from the survival bioassays were subjected to survival analysis while the swimming behavioral data were subjected to analyses of covariance, complemented with a regression analysis.

RESULTS

All insecticides exhibited concentration-dependent effects on survival of larvae and pupae of the yellow fever mosquito. The pyrethroid deltamethrin was the most toxic insecticide followed by spinosad, imidacloprid, and azadirachtin, which exhibited low potency against the juveniles. All insecticides except azadirachtin reduced L4 swimming speed and wriggling movements. A similar trend was also observed for swimming pupa, except for imidacloprid, which increased the swimming activity of pupa. Curiously, the insecticides did not affect cell damage in the neuromuscular system of larvae and pupae.

CONCLUSIONS

Deltamethrin and spinosad were the main compounds to exhibit lethal effects, which allowed the control of A. aegypti larvae and pupae, and impair their swimming potentially compromising foraging and predation likelihood.