Fipronil induces lung inflammation in vivo and cell death in vitro

Polyethylene glycol used as a dispersant potentiates the toxicity of insecticides in mammalian cells rather than insects

Insecticides are used in household products with various dispersants such as polyethylene glycol (PEG) and polyoxyethylene lauryl ether (PLE) to improve solubility. Although certain effects are expected, the combination effects of insecticides and dispersants remain elusive. Here, five different classes of insecticides (i.e., dinotefuran, fipronil, hydramethylnon, indoxacarb, and etofenprox) were dispersed in water, PEG, and PLE, and their lung inflammation potential was evaluated by bronchoalveolar lavage fluid analysis 24 h after intratracheal instillation into the lungs of rats. All chemicals dispersed in water caused no inflammation. However, among the five chemicals dispersed in PEG and PLE, only hydramethylnon showed significant neutrophilic inflammation and hydramethylnon in PEG showed 4-fold higher inflammogenic potential than that in PLE. The in vitro cytotoxic potential of hydramethylnon in PEG was 10-17 fold (in A549) or 12-14 fold (in dTHP-1) higher than that of hydramethylnon in PLE, and greater than 370 fold (in A549) or 65-169 fold (in dTHP-1) higher than that in water. PEG toxicity increased due to the micellar formulation of hydramethylnon in PEG, increasing cellular uptake by simple diffusion. Therefore, the observed potentiation effect highlights that the combination effect of formulation of hydrophobic compounds with dispersants should be carefully evaluated.

In Vivo Exposure of Deltamethrin Dysregulates the NFAT Signalling Pathway and Induces Lung Damage

Deltamethrin is an insecticide used to control harmful agricultural insects that otherwise damage crops and to control vector-borne diseases. Long-term exposure to deltamethrin results in the inflammation of the lungs. The present study elucidates the molecular mechanism underlying the deltamethrin-induced lung damage. The lung samples were extracted from the Swiss albino mice following the treatment of low (2.5 mg/kg) and high (5 mg/kg) doses of deltamethrin. The mRNA expression of TCR, IL-4, and IL-13 showed upregulation, while the expression of NFAT and FOS was downregulated following a low dose of deltamethrin. Moreover, the expression of TCR was downregulated with the exposure of a high dose of deltamethrin. Furthermore, the immunohistochemistry data confirmed the pattern of protein expression for TCR, FOS, IL-4, and IL-13 following a low dose of deltamethrin exposure. However, no change was seen in the TCR, NFAT, FOS, JUN, IL-4, and IL-13 immunopositive cells of the high-dose treatment group. Also, ELISA results showed increased expression of IL-13 in the BAL fluid of animals exposed to low doses of deltamethrin. Overall, the present study showed that deltamethrin exposure induces lung damage and immune dysregulation via dysregulating the NFAT signalling pathway.

Assessing the Risks of Pesticide Exposure: Implications for Endocrine Disruption and Male Fertility

Pesticides serve as essential tools in agriculture and public health, aiding in pest control and disease management. However, their widespread use has prompted concerns regarding their adverse effects on humans and animals. This review offers a comprehensive examination of the toxicity profile of pesticides, focusing on their detrimental impacts on the nervous, hepatic, cardiac, and pulmonary systems, and their impact on reproductive functions. Additionally, it discusses how pesticides mimic hormones, thereby inducing dysfunction in the endocrine system. Pesticides disrupt the endocrine system, leading to neurological impairments, hepatocellular abnormalities, cardiac dysfunction, and respiratory issues. Furthermore, they also exert adverse effects on reproductive organs, disrupting hormone levels and causing reproductive dysfunction. Mechanistically, pesticides interfere with neurotransmitter function, enzyme activity, and hormone regulation. This review highlights the effects of pesticides on male reproduction, particularly sperm capacitation, the process wherein ejaculated sperm undergo physiological changes within the female reproductive tract, acquiring the ability to fertilize an oocyte. Pesticides have been reported to inhibit the morphological changes crucial for sperm capacitation, resulting in poor sperm capacitation and eventual male infertility. Understanding the toxic effects of pesticides is crucial for mitigating their impact on human and animal health, and in guiding future research endeavors.

Regional variations in allergen-induced airway inflammation correspond to changes in soluble guanylyl cyclase heme and expression of heme oxygenase-1

Asthma is characterized by airway remodeling and hyperreactivity. Our earlier studies determined that the nitric oxide (NO)-soluble guanylyl cyclase (sGC)-cGMP pathway plays a significant role in human lung bronchodilation. However, this bronchodilation is dysfunctional in asthma due to high NO levels, which cause sGC to become heme-free and desensitized to its natural activator, NO. In order to determine how asthma impacts the various lung segments/lobes, we mapped the inflammatory regions of lungs to determine whether such regions coincided with molecular signatures of sGC dysfunction. We demonstrate using murine models of asthma (OVA and CFA/HDM) that the inflamed segments of these murine lungs can be tracked by upregulated expression of HO1 and these regions in turn overlap with regions of heme-free sGC as evidenced by a decreased sGC-α1β1 heterodimer and an increased response to heme-independent sGC activator, BAY 60-2770, relative to naïve uninflamed regions. We also find that NO generated from iNOS upregulation in the inflamed segments has a higher impact on developing heme-free sGC as increasing iNOS activity correlates linearly with elevated heme-independent sGC activation. This excess NO works by affecting the epithelial lung hemoglobin (Hb) to become heme-free in asthma, thereby causing the Hb to lose its NO scavenging function and exposing the underlying smooth muscle sGC to excess NO, which in turn becomes heme-free. Recognition of these specific lung segments enhances our understanding of the inflamed lungs in asthma with the ultimate aim to evaluate potential therapies and suggest that regional and not global inflammation impacts lung function in asthma.

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

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

A rapid evidence assessment of the potential risk to the environment presented by active ingredients in the UK's most commonly sold companion animal parasiticides

A number of parasiticides are commercially available as companion animal treatments to protect against parasite infestation and are sold in large volumes. These treatments are not intended to enter the wider environment but may be washed off or excreted by treated animals and have ecotoxic impacts. A systematic literature review was conducted to identify the existing evidence for the toxicity of the six most used parasiticides in the UK: imidacloprid, fipronil, fluralaner, afoxolaner, selamectin, and flumethrin. A total of 17,207 published articles were screened, with 690 included in the final evidence synthesis. All parasiticides displayed higher toxicity towards invertebrates than vertebrates, enabling their use as companion animal treatments. Extensive evidence exists of ecotoxicity for imidacloprid and fipronil, but this focuses on exposure via agricultural use and is not representative of environmental exposure that results from use in companion animal treatments, especially in urban greenspace. Little to no evidence exists for the ecotoxicity of the remaining parasiticides. Despite heavy usage, there is currently insufficient evidence to understand the environmental risk posed by these veterinary treatments and further studies are urgently needed to quantify the levels and characterise the routes of environmental exposure, as well as identifying any resulting environmental harm.

Impairment of apoptosis pathway via Apaf1 downregulation during chlorpyrifos and/or cypermethrin induced lung damage

Chlorpyrifos is an organophosphate and the cypermethrin is type 2 pyrethroid insecticide that are used for indoor and outdoor pest control. The present study aimed to investigate differential transcriptional profiling to identify the candidate gene associated with lung injury following exposure to chlorpyrifos and/or cypermethrin in a mouse model system. Swiss male albino mice (n = 24) were divided into three treatment groups (n = 6 each) that were given chlorpyrifos (2.76 mg kg^-1 body weight), cypermethrin (2 mg kg^-1 body weight) and the combination of both pesticides orally dissolved in corn oil and one control group (n = 6) that received corn oil for 90 days. The pulmonary expression of the Apaf1 was observed using RT2 Profiler PCR Array. The results showed that chronic exposure to chlorpyrifos, cypermethrin and their combination downregulated (67, 63 and 66 genes) and upregulated (4, 2 and 2 genes), respectively. The pulmonary expression of Apaf1 that plays important role in apoptosis was found to be downregulated. The immunohistochemistry depicted reduced expression of Apaf1 in both airway epithelium and alveolar septa following exposure to chlorpyrifos and/or cypermethrin. In conclusion, results demonstrated that exposure to chlorpyrifos, cypermethrin and their combination cause lung damage by the dysregulation of Apaf1 gene expression.

Exposures to 2,4-Dichlorophenoxyacetic acid with or without endotoxin upregulate small cell lung cancer pathway

Background

Pesticide residues in food and environment along with airborne contaminants such as endotoxins pose health risk. Although herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) has been associated with increased risk of lung cancers such as small cell lung cancer (SCLC) among agricultural workers, there are no data on the SCLC signaling pathway upon 2,4-D exposure without LPS or in combination with endotoxin.

Methods

We exposed Swiss albino mice (N = 48) orally to high (9.58 mg kg^− 1) and low (5.12 mg kg^− 1) dosages of 2,4-D dissolved in corn oil for 90 days followed by E. coli lipopolysaccharide (LPS) or normal saline solution (80 μl/animal). Lung samples and broncho-alveolar fluid (BALF) were subjected to Total histological score (THS) and total leucocyte count (TLC) and differential leucocytes count (DLC) analyses, respectively. We used microarray and bioinformatics tools for transcriptomic analyses and differentially expressed genes were analyzed to predict the top canonical pathways followed by validation of selected genes by qRT-PCR and immunohistochemistry.

Results

Total histological score (THS) along with BALF analyses showed lung inflammation following long term dietary exposure to high or low doses of 2,4-D individually or in combination with LPS. Microarray analysis revealed exposure to high dose of 2,4-D without or with LPS upregulated 2178 and 2142 and downregulated 1965 and 1719 genes, respectively (p < 0.05; minimum cut off 1.5 log fold change). The low dose without or with LPS upregulated 2133 and 2054 and downregulated 1838 and 1625 genes, respectively. Bioinformatics analysis showed SCLC as topmost dysregulated pathway along with differential expression of Itgb1, NF-κB1, p53, Cdk6 and Apaf1. Immunohistological and quantitative real time PCR (qRT-PCR) analyses also supported the transcriptomic data.

Conclusions

Taken together, the data show exposures to high and low dose of 2,4-D with/without LPS induced lung inflammation and altered pulmonary transcriptome profile with the involvement of the SCLC pathway. The data from the study provide the insights of the potential damage on lungs caused by 2,4-D and help to better understand the mechanism of this complex relation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12995-021-00304-4.

Study of ethion and lipopolysaccharide interaction on lung in a mouse model

Ethion is an organophosphate used commonly in India despite being banned in many other countries. The present study was designed to study the interaction of ethion and lipopolysaccharide (LPS) together on lung after single low dose ethion exposure. Mice (n = 20) were alienated into control and treatment groups (n = 10 each). The treatment group was orally fed ethion (8 mg/kg/animal/day) dissolved in corn oil. The animals (n = 5 each) from both the groups were challenged with 80 μg Escherichia coli lipopolysaccharide (LPS) intranasally and the remaining animals (n = 5 each) were administered normal saline solution after 24 h. Ethion along with LPS induced lung inflammation as indicated by increased neutrophils and total leukocyte count (TLC) in broncheoalveolar lavage fluid. Ethion induced histomorphological alterations in lung as shown by increased pulmonary inflammation score in histopathology. Real time PCR analysis showed that ethion followed by LPS resulted significant (p < 0.05) increase in pulmonary Toll-like receptor (TLR)-4 (48.53 fold), interleukin (IL)-1β (7.05 fold) and tumor necrosis factor (TNF)-α (5.74 fold) mRNA expression. LPS co-exposure suggested synergistic effect on TLR4 and TNF-α mRNA expression. Ethion alone or in combination with LPS resulted genotoxicity in blood cells as detected by comet assay. The data suggested single dietary ethion exposure alone or in conjunction with LPS causes lung inflammation and genotoxicity in blood cells.

Investigating the effects of fipronil on male fertility: Insight into the mechanism of capacitation

Fipronil (FPN) is a widely used phenylpyrazole pesticide for the control of insects and removal of veterinary pet fleas, ticks, etc. Although FPN presents moderate hazards to human health, people are readily exposed in daily life. FPN acts by impairing the central nervous systems of insects by blocking gamma-aminobutyric acid (GABA) and glutamate-activated chloride channels. A previous study demonstrated that GABA and GABA_AR are present in spermatozoa and play various roles in the process of sperm capacitation, which is required for fertilization. However, the effects of FPN on mammalian fertility are not yet fully understood. Therefore, the present study was designed to investigate the effects of FPN on spermatozoa. Herein, we treated various concentrations of FPN (0.1, 1, 10, 100, and 300 μM) or a control treatment with mouse spermatozoa. FPN treatment significantly reduced sperm motility, motion kinematic parameters, and intracellular ATP level, whereas the acrosome reaction was enhanced. Levels of phospho-PKA and phospho-tyrosine substrate were significantly decreased in a dose-dependent manner. Meanwhile, there was no difference between control and treatment groups in the level of GABA_AR β-3. Only the ratio of GABA_AR β-3 pS408/pS409 was significantly decreased at higher concentrations of FPN. Moreover, cleavage and blastocyst formation rates were also significantly decreased by FPN treatments. Taken together, these data suggest that FPN can directly and indirectly suppress various sperm functions. Therefore, FPN can negatively affect male fertility leading to infertility. From these results, we suggest that the use of FPN as a pesticide requires the attention of reproductive toxicity.

Developmental toxicity of fipronil in early development of zebrafish (Danio rerio) larvae: Disrupted vascular formation with angiogenic failure and inhibited neurogenesis

Fipronil has been widely used in agriculture to prevent aggressive insects from damaging agricultural products. Fipronil residues circulate in the environment and they have been detected in non-targeted organisms in aquatic environments. To study the effect of fipronil toxicity on environmental health, 6 h post fertilization (hpf) zebrafish embryos were treated with fipronil for 72 h. LC₅₀ value was obtained by applying varying concentrations of fipronil to zebrafish embryos for 72 h. As zebrafish embryos are useful vertebrate models for studying developmental and genetic findings in toxicology research, they were exposed to fipronil to study detailed elucidating mechanisms with hazardous end points of toxicity. Cell cycle arrest-related apoptosis supported pathological alterations, such as increased mortality, shortened body length, and reduced hatchability. Furthermore, observed heart defects, including edema and irregular heartbeat were caused due to abnormal blood circulation. In transgenic zebrafish models (fli1:eGFP and olig2:dsRED), disrupted blood vessel formations were indicated by eGFP⁺ endothelial cells. Moreover, neurogenic defects were observed by studying dsRED⁺ motor neurons and oligodendrocytes. This study demonstrates fipronil accumulation in aquatic environment and its ability to impair essential processes, such as angiogenesis and neurogenesis during early developmental stage of zebrafish, along with general developmental toxicity.

Pulmonary innate inflammatory responses to agricultural occupational contaminants

Agricultural workers are exposed to many contaminants and suffer from respiratory and other symptoms. Dusts, gases, microbial products and pesticide residues from farms have been linked to effects on the health of agricultural workers. Growing sets of data from in vitro and in vivo models demonstrate the role of the innate immune system, especially Toll-like receptor 4 (TLR4) and TLR9, in lung inflammation induced following exposure to contaminants in agricultural environments. Interestingly, inflammation and lung function changes appear to be discordant indicating the complexity of inflammatory responses to exposures. Whereas the recent development of rodent models and exposure systems have yielded valuable data, we need new systems to examine the combined effects of multiple contaminants in order to increase our understanding of farm-exposure-induced negative health effects.

Chronic exposure to indoxacarb and pulmonary expression of toll-like receptor-9 in mice

AIM

Chronic exposure to indoxacarb and pulmonary expression of toll-like receptor 9 (TLR-9) in mice.

MATERIALS AND METHODS

In this study, healthy male Swiss albino mice (n=30) aging 8-10 weeks were used to evaluate TLR-9 expression in lungs of mice following indoxacarb exposure with and without lipopolysaccharide (LPS). Indoxacarb was administered orally dissolved in groundnut oil at 4 and 2 mg/kg/day for 90 days. On day 91, five animals from each group were challenged with LPS/normal saline solution at 80 µg/animal. The lung tissues were processed for real time and immunohistochemical studies.

RESULTS

LPS resulted increase in fold change m-RNA expression level of TLR-9 as compare to control, while indoxacarb (4 mg/kg) alone and in combination with LPS resulted 16.21-fold change and 29.4-fold change increase in expression of TLR-9 m-RNA, respectively, as compared to control. Similarly, indoxacarb (2 mg/kg) alone or in combination with LPS also altered TLR-9 expression. Further at protein level control group showed minimal expression of TLR-9 in lungs as compare to other groups, however, LPS group showed intense positive staining in bronchial epithelium as well as in alveolar septal cells. Indoxacarb at both doses individually showed strong immuno-positive reaction as compare to control, however when combined with LPS resulted intense staining in airway epithelium as compare to control.

CONCLUSION

Chronic oral administration of indoxacarb for 90 days (4 and 2 mg/kg) alters expression of TLR-9 at m-RNA and protein level and co-exposure with LPS exhibited synergistic effect.