Assessment of serum biomarkers in rats after exposure to pesticides of different chemical classes

Serum Concentrations of Fipronil and Metabolites in Japanese Pregnant Women: Relationship with Thyroid Hormone Levels

Fipronil, a widely used phenylpyrazole insecticide, is known to disrupt circulating thyroid hormone (TH) levels in rodents. Concentrations of fipronil and its metabolites (fipronil sulfone and fipronil sulfide) in serum samples collected in 2009-2011 were measured for 131 Japanese pregnant women by a sensitive and accurate liquid chromatography-tandem mass spectrometric method developed in our laboratory to relate TH levels. Fipronil sulfone was detected in all the subjects with the median being 21 ng/L (min-max: 6.8-89), but fipronil and fipronil sulfide were detected in none of the subjects (detection limit: 5.0 and 1.2 ng/L, respectively), indicating a rapid and exclusive oxidative conversion to fipronil sulfone upon exposure. The median concentration of fipronil sulfone was lower than those previously reported for general populations in other countries by one order of magnitude. There were no attributes or dietary habits of the subjects that significantly vary the serum fipronil sulfone concentrations. Multiple regression analyses found no significant association between serum concentrations of fipronil sulfone and free thyroxine- or thyroid-stimulating hormone levels, indicating the absence of adverse effects on circulating TH levels probably due to the lower exposure levels of the present subjects. The present result would be valuable for establishing a dose-effect relationship of fipronils in humans on population levels.

Probiotic bacteria alleviate chlorpyrifos-induced rat testicular and renal toxicity: A possible mechanism based on antioxidant and anti-inflammatory activity

Chlorpyrifos (CPF) has caused many potential toxicities in nontarget organisms. Fewer studies have been conducted on the effects of lactic acid bacteria (LAB) in mitigating tissue damage induced by CPF in vivo. Therefore, we investigated CPF renal and testicular toxicity and the alleviating effect of probiotic lactobacilli, based on antioxidant and anti-inflammatory activity, on induced toxicity in an animal model. Biochemical assays showed that CPF induced oxidative stress along with a change in superoxide dismutase (SOD) and catalase (CAT) activity in a tissue-dependent manner. After treatment with CPF, testicular and renal levels of TNF-α were significantly reduced and enhanced, respectively, compared to the control group. The probiotic treatment restored renal and testicular TNF-α levels and modulated and blocked the increasing effect of CPF on renal IL-1β levels. Testicular IL-1β levels in the probiotic-treated and CPF groups demonstrated similar values. Exposure to CPF significantly induced renal histopathological damage that, of course, was completely inhibited by treatment with Lactobacillus casei and the LAB mixture. In summary, CPF showed significant toxicological effects on oxidative stress and the inflammation rate in CPF-exposed rats. Therefore, supplementation with probiotic bacteria may alleviate CPF renal toxicity and mitigate its oxidative stress and inflammation effects.

Pesticide use and risk of systemic autoimmune diseases in the Agricultural Health Study

BACKGROUND

Systemic lupus erythematosus (SLE) risk has been associated with pesticide use, but evidence on specific pesticides or other agricultural exposures is lacking. We investigated history of pesticide use and risk of SLE and a related disease, Sjögren's syndrome (SS), in the Agricultural Health Study.

METHODS

The study sample (N = 54,419, 52% male, enrolled in 1993-1997) included licensed pesticide applicators from North Carolina and Iowa and spouses who completed any of the follow-up questionnaires (1999-2003, 2005-2010, 2013-2015). Self-reported cases were confirmed by medical records or medication use (total: 107 incident SLE or SS, 79% female). We examined ever use of 31 pesticides and farm tasks and exposures reported at enrollment in association with SLE/SS, using Cox regression to estimate hazard ratios (HR) and 95% confidence intervals (CI), with age as the timescale and adjusting for gender, state, and correlated pesticides.

RESULTS

In older participants (>62 years), SLE/SS was associated with ever use of the herbicide metribuzin (HR 5.33; 95%CI 2.19, 12.96) and applying pesticides 20+ days per year (2.97; 1.20, 7.33). Inverse associations were seen for petroleum oil/distillates (0.39; 0.18, 0.87) and the insecticide carbaryl (0.56; 0.36, 0.87). SLE/SS was inversely associated with having a childhood farm residence (0.59; 0.39, 0.91), but was not associated with other farm tasks/exposures (except welding, HR 2.65; 95%CI 0.96, 7.35).

CONCLUSIONS

These findings suggest that some agricultural pesticides may be associated with higher or lower risk of SLE/SS. However, the overall risk associated with farming appears complex, involving other factors and childhood exposures.

Lactiplantibacillus plantarum P9 improved gut microbial metabolites and alleviated inflammatory response in pesticide exposure cohorts

Multiple pesticide residue accumulations increase the probability of chronic metabolic diseases in humans. Thus, we applied multi-omics techniques to reveal how the gut microbiome responded to pesticide exposure. Then, we explored how probiotic Lactiplantibacillus plantarum P9 (P9) consumption impacted the gut microbiota and immune factors after high pesticide exposure. Multi-omics results indicated frequent exposure to pesticides did not alter the composition of the intestinal microbiota, but it did increase the abundance of Lipopolysaccharide in the gut, which might contribute to chronic inflammation. Supplementation with P9 maintained the homeostasis of the gut microbiota and reduced the abundance of pathogens in the high pesticide-exposed subjects. By detecting metabolites, we observed uridine and 5-oxoproline concentrations increased significantly after P9 consumption. Furthermore, P9 alleviated immune factors disorder and promoted pesticide residue excretion. Our findings provide new insights into the application of probiotics for pesticide detoxification, and suggest probiotics as daily supplements for pesticide exposure prevention.

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High-frequency pesticide exposure induced inflammatory responses to occur

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P9 maintained gut microbiota homeostasis in subjects with high pesticide exposure

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P9 significantly increased the level of beneficial metabolites in the subjects

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P9 reduced inflammatory response and promoted excretion of pesticide residues

Subacute toxicity of chlorpyrifos on histopathological damages, antioxidant activity, and pro-inflammatory cytokines in the rat model

Chlorpyrifos (CPF) is an extensively used organophosphorus pesticide for agricultural, industrial, and domestic purposes. Previous studies have reported the adverse effects of CPF, such as intoxication incidents, endocrine disruption, cardiovascular diseases, as well as histopathological and oxidative damage. The aims of the present study were to elucidate short time subacute toxicity of CPF in male rats. Sprague-Dawley male rats (n = 32) were divided into four groups (n = 8) and received CPF as 3.25 mg/kg body weight (b.w) (Group A), 6.75 mg/kg b.w (Group B), 13.5 mg/kg b.w (Group C), and corn oil (control or Group D) daily via gavage for 15 days. The rats were sacrificed and oxidative damages, pro-inflammatory cytokines (TNF-α, IL-1β), and histopathological changes were determined in the lung, liver, kidney, heart, and testis tissues as well as plasma. According to our result, administration of CPF caused a significant increase in malondialdehid level and catalase activity while a significant decrease in superoxide dismutase activity in all tissues. In addition, a significant decrease in TNF-α observed in all tissues and plasma duo to the CPF. Histopathological evaluation of CPF-treated samples revealed a dose-dependent tissue toxicity in the liver, heart, lung, and kidney with less sensitivity of testicular and kidney tissues. These results suggest the potential of CPF in inducing oxidative stress at low doses and short duration time with similar trends in different tissues. As well as, due to the effects of CPF on some pro-inflammatory mediators, more comprehensive studies are recommended.

Chronic environmentally relevant levels of pesticides disrupt energy reserves, feeding rates, and life-cycle responses in the amphipod Hyalella meinerti

When pesticides reach the aquatic environment, they can distribute in water and sediment, increasing the risks to benthic organisms, such as amphipods that play a key role in the aquatic food webs. Thus, the present study assessed the consequences of exposure to the insecticide fipronil and herbicide 2,4-D (alone and in mixture) on biochemical markers, feeding rates and the partial life-cycle of Hyalella meinerti. Three concentrations of fipronil (0.1, 0.3, and 0.7 µg L^-1) and 2,4-D (19, 124, and 654 µg L^-1), and six mixture combinations were assessed. The first experiment was carried out with males and females separately assessing the feeding rates, total carbohydrate content, and lipid profile. The second (partial life-cycle) lasted 49 days, and the survival, growth, and reproductive endpoints were assessed. Both pesticides and their mixture caused decreases in feeding rates, mainly in females. Females also suffered a change in the total carbohydrate content. In addition, there were changes in the percentage of triacylglycerol and phospholipids in males and females. Furthermore, alterations occurred in the percentual of triacylglycerol and phospholipids to both sexes. In the second experiment, fipronil and the mixtures caused decreases in the survival of H. meinerti over time. Exposure to 2,4-D, fipronil, and their mixture impaired the 28-day growth leading to biomass loss ranging from 17-23%, 54-60%, and 22-49%, respectively. The insecticide and mixture caused increases in time to sexual maturation of up to 10 and 6 days, respectively, and reduced the number of formed couples. Furthermore, fipronil decreased reproduction up to 36 times and no juveniles were produced in some mixture combinations. In addition, the pesticides on isolation decreased the juvenile size. Finally, exposure to both pesticides, alone or in a mixture, decreased the intrinsic rate of population growth. The results were observed in concentrations already quantified in water bodies, with risks for ecosystems functioning due to the importance of amphipods in aquatic ecosystems.

Pesticide-induced metabolic changes are amplified by food stress

In natural ecosystems, long-term detrimental effects of pesticides may occur at very low concentrations, below those considered safe by the governmental risk assessment. Mechanisms potentially responsible for this unexpected sensitivity include environmental stress-factors such as food deficiency. To understand this so called "effect-paradox", we investigated how food stress interacts with insecticide-induced biochemical fingerprints. Therefore, we measured metabolomic perturbations in Daphnia magna following a 24 h exposure to esfenvalerate under high and low food conditions. In total, 160 metabolites covering the groups of amino acids, fatty acids, lipids, and sugars were analyzed. At 0.001 μg/L esfenvalerate - a factor of >200 below the acute lethal concentration (LC₅₀) - the endogenous metabolome was significantly affected. Further, the effect under low food conditions was considerably stronger compared to high food conditions. Individual metabolites showed up to 7-fold stronger effects under low food conditions. In general, the metabolomic changes were largely dose-specific and increased over seven days after contamination. We conclude that the metabolic profiles are altered for at least seven days after a pulse exposure, and therefore might be a key process to understanding population level changes at ultra-low pesticide concentrations in the field.

In vitro assessment of pesticides capacity to act as agonists/antagonists of the thyroid hormone nuclear receptors

Chemicals acting as thyroid hormone disruptors (THDs) are of a particular concern for public health, considering the importance of this hormone in neurodevelopment and metabolic processes. They might either alter the circulating level of thyroid hormone (TH) or interfere with the cellular response to the hormonal stimulation. In order to assess this later possibility we selected 39 pesticides and combined several in vitro tests. Reporter assays respectively addressed the transactivation capacity of the full-length TH nuclear receptor TRα1, the transactivation capacity of its C-terminal ligand binding domain, or the ability of the hormone to destabilize the interaction between TRα1 and the transcriptional corepressor NcoR. Although some pesticides elicit a cellular response, which sometimes interferes with TH signaling, RNA-seq analysis provided no evidence that they can act as TRα1 agonists or antagonists. Their neurodevelopmental toxicity in mammals cannot be explained by an alteration of the response to TH.

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Pesticides were tested for their capacity to interfere with thyroid hormone receptors

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Three reporter assays were combined to identify possible agonists/antagonists

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The tested pesticides are not major disruptors of thyroid hormone signaling

Xenopus laevis and human type 3 iodothyronine deiodinase enzyme cross-species sensitivity to inhibition by ToxCast chemicals

Deiodinase enzymes are critical for tissue-specific and temporal control of activation or inactivation of thyroid hormones during vertebrate development, including amphibian metamorphosis. We previously screened ToxCast chemicals for inhibitory activity toward human recombinant Type 3 iodothyronine deiodinase enzyme (hDIO3) and subsequently produced Xenopus laevis recombinant dio3 enzyme (Xldio3) with the goals to identify specific chemical inhibitors of Xldio3, to evaluate cross-species sensitivity and explore whether the human assay results are predictive of the amphibian. We identified a subset of 356 chemicals screened against hDIO3 to test against Xldio3, initially at a single concentration (200 μM), and further tested 79 in concentration-response mode. Most chemicals had IC₅₀ values lower for hDIO3 than for Xldio3 and many had steep Hill slopes (a potential indication of non-specific inhibition). However, eight of the most potent chemicals are likely specific inhibitors, with IC₅₀ values of 14 μM or less, Hill slopes near -1 and curves not significantly different between species likely due to conservation of catalytically active amino acids. Controlling for assay conditions, human in vitro screening results can be predictive of activity in the amphibian assay. This study lays the groundwork for future studies using recombinant non-mammalian proteins to test cross-species sensitivity to chemicals. DISCLAIMER: The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Pharmacological Actions of Carbamate Insecticides at Mammalian Melatonin Receptors

Integrated in silico chemical clustering and melatonin receptor molecular modeling combined with in vitro 2-[125I]-iodomelatonin competition binding were used to identify carbamate insecticides with affinity for human melatonin receptor 1 (hMT1) and human melatonin receptor 2 (hMT2). Saturation and kinetic binding studies with 2-[125I]-iodomelatonin revealed lead carbamates (carbaryl, fenobucarb, bendiocarb, carbofuran) to be orthosteric ligands with antagonist apparent efficacy at hMT1 and agonist apparent efficacy at hMT2 Furthermore, using quantitative receptor autoradiography in coronal brain slices from C3H/HeN mice, carbaryl, fenobucarb, and bendiocarb competed for 2-[125I]-iodomelatonin binding in the suprachiasmatic nucleus (SCN), paraventricular nucleus of the thalamus (PVT), and pars tuberalis (PT) with affinities similar to those determined for the hMT1 receptor. Carbaryl (10 mg/kg i.p.) administered in vivo also competed ex vivo for 2-[125I]-iodomelatonin binding to the SCN, PVT, and PT, demonstrating the ability to reach brain melatonin receptors in C3H/HeN mice. Furthermore, the same dose of carbaryl given to C3H/HeN mice in constant dark for three consecutive days at subjective dusk (circadian time 10) phase-advanced circadian activity rhythms (mean = 0.91 hours) similar to melatonin (mean = 1.12 hours) when compared with vehicle (mean = 0.04 hours). Carbaryl-mediated phase shift of overt circadian activity rhythm onset is likely mediated via interactions with SCN melatonin receptors. Based on the pharmacological actions of carbaryl and other carbamate insecticides at melatonin receptors, exposure may modulate time-of-day information conveyed to the master biologic clock relevant to adverse health outcomes. SIGNIFICANCE STATEMENT: In silico chemical clustering and molecular modeling in conjunction with in vitro bioassays identified several carbamate insecticides (i.e., carbaryl, carbofuran, fenobucarb, bendiocarb) as pharmacologically active orthosteric melatonin receptor 1 and 2 ligands. This work further demonstrated that carbaryl competes for melatonin receptor binding in the master biological clock (suprachiasmatic nucleus) and phase-advances overt circadian activity rhythms in C3H/HeN mice, supporting the relevance of circadian effects when interpreting toxicological findings related to carbamate insecticide exposure.

Avaliação neurocomportamental e níveis de acetilcolinesterase cerebral em ratos expostos subcronicamente ao fipronil

RESUMO O fipronil é um inseticida de toxicidade seletiva amplamente empregado na agricultura e na medicina veterinária. Porém, há relatos de efeitos neurotóxicos dessa substância, que geram prejuízos para vertebrados. Avaliou-se a atividade locomotora, a coordenação motora e a atividade da enzima acetilcolinesterase cerebral em ratos expostos ao fipronil. Ratos Wistar machos adultos (n=15) receberam fipronil em dose de 30mg/kg, por via oral, durante 15 dias; o grupo controle (n=15) foi tratado com solução fisiológica, por via oral, no mesmo período. No 16° dia de experimentação, os animais foram submetidos aos testes de arena de campo aberto e hole board. No 17° dia, foram anestesiados e eutanasiados, procedendo-se à coleta de órgãos, e posteriormente foi feita a avaliação da AChE cerebral. A exposição ao fipronil não provocou alterações significativas sobre a coordenação motora e a atividade locomotora, porém gerou inibição significativa da atividade da acetilcolinesterase cerebral. Esses achados sugerem que o fipronil pode provocar efeitos neurotóxicos em curto prazo, os quais podem ser exacerbados caso a exposição seja prolongada.

Transcriptomic modifications of the thyroid gland upon exposure to phytosanitary-grade fipronil: Evidence for the activation of compensatory pathways

Fipronil is a phenylpyrazole insecticide used for the control of a variety of pest for domestic, veterinary and agricultural uses. Fipronil exposure is associated to thyroid disruption in the rat. It increases thyroid hormone (TH) hepatic clearance. The effect on thyroxine (T4) clearance is about four fold higher than the effect on T4 plasma concentrations suggesting that the thyroid gland might develop compensatory mechanisms. The aim of this study was to document the potential effects of fipronil treatment on the thyroid transcriptome together with its effects on TSH and TH blood levels under well characterized internal exposure to fipronil and its main metabolite fipronil sulfone. Fipronil (3 mg/kg/d by gavage for 14 days) clearance increased while its half-life decreased (about 10 fold) throughout treatment. Fipronil treatment in adult female rats significantly decreased total T4 and free triiodothyronine (T3) concentrations. Key genes related to thyroid hormone synthesis and/or cellular dynamic were modulated by fipronil exposure. RT-PCR confirmed that thyroglobulin gene expression was upregulated. A trend toward higher Na/I symporter expression was also noted, while sulfotransferase 1a1 gene expression was down-regulated. The expression of genes potentially involved in thyroid cell dynamic were upregulated (e.g. prostaglandin synthase 1, amphiregulin and Rhoa). Our results indicate that both pathways of TH synthesis and thyroid cell dynamics are transcriptional targets of fipronil and/or its main sulfone metabolite. The underlying mechanisms remain to be elucidated.

Pesticides With Potential Thyroid Hormone-Disrupting Effects: A Review of Recent Data

Plant Protection Products, more commonly referred to as pesticides and biocides, are used to control a wide range of yield-reducing pests including insects, fungi, nematodes, and weeds. Concern has been raised that some pesticides may act as endocrine disrupting chemicals (EDCs) with the potential to interfere with the hormone systems of non-target invertebrates and vertebrates, including humans. EDCs act at low doses and particularly vulnerable periods of exposure include pre- and perinatal development. Of critical concern is the number of pesticides with the potential to interfere with the developing nervous system and brain, notably with thyroid hormone signaling. Across vertebrates, thyroid hormone orchestrates metamorphosis, brain development, and metabolism. Pesticide action on thyroid homeostasis can involve interference with TH production and its control, displacement from distributor proteins and liver metabolism. Here we focused on thyroid endpoints for each of the different classes of pesticides reviewing epidemiological and experimental studies carried out both in in vivo and in vitro. We conclude first, that many pesticides were placed on the market with insufficient testing, other than acute or chronic toxicity, and second, that thyroid-specific endpoints for neurodevelopmental effects and mixture assessment are largely absent from regulatory directives.

[Thyroid disruptors and their consequences on brain development and behavior]

An increase in the prevalence of many diseases affecting the nervous system in both children and adults has been reported. Some of these diseases are related to endocrine dysfunction, notably of the thyroid axis. Examples in children are attention deficit/hyperactivity disorders and Autism Spectrum Disorders, diagnosed but most often affecting the whole life, and multiple sclerosis or Alzheimer's disease in adults. It is becoming increasingly clear that embryonic exposure to thyroid hormone disruptors can lead to short- and long-term consequences, that often escape conventional neonatal diagnosis. Endocrine disruptors comprise a wide range of molecules, plasticizers, some pesticides, surfactants, flame-retardants, etc., many of which can interfere with thyroid hormone synthesis or their actions. We here report briefly the history of endocrine disruptors, their properties and the consequences on neuronal development of embryonic exposure to some of them.

Identification of pesticide exposure-induced metabolic changes in mosquito larvae

The European regulatory framework for pesticides generally applies an assessment factor of up to 100 below the acute median lethal concentration (LC50) in laboratory tests to predict the regulatory acceptable concentrations (RACs). However, long-term detrimental effects of pesticides in the environment occur far below the RACs. Here, we explored the metabolic changes induced by exposure to the neonicotinoid insecticide clothianidin in larvae of the mosquito Culex pipiens. We exposed the test organisms to the insecticide for 24 h and then measured the levels of 184 metabolites immediately and 48 h after the pulse contamination. We established a link between the exposure to clothianidin and changes in the level of three specific classes of metabolites involved in energy metabolism, namely, glycerophospholipids, acylcarnitines and biogenic amines. Remarkably, exposure to concentrations considered to be safe according to the regulatory framework (2-4 orders of magnitude lower than the acute LC50), induced longer-term effects than exposure to the highest concentration. These results suggest that a specific detoxification mechanism was only triggered by the highest concentration. We conclude that even very low insecticide concentrations increase the energy demands of exposed organisms, which potentially translates into a decline in sensitive species in the field.

Changes in the metabolome and microRNA levels in biological fluids might represent biomarkers of neurotoxicity: A trimethyltin study

Neurotoxicity has been linked with exposure to a number of common drugs and chemicals, yet efficient, accurate, and minimally invasive methods to detect it are lacking. Fluid-based biomarkers such as those found in serum, plasma, urine, and cerebrospinal fluid have great potential due to the relative ease of sampling but at present, data on their expression and translation are lacking or inconsistent. In this pilot study using a trimethyl tin rat model of central nervous system toxicity, we have applied state-of-the-art assessment techniques to identify potential individual biomarkers and patterns of biomarkers in serum, plasma, urine or cerebral spinal fluid that may be indicative of nerve cell damage and degeneration. Overall changes in metabolites and microRNAs were observed in biological fluids that were associated with neurotoxic damage induced by trimethyl tin. Behavioral changes and magnetic resonance imaging T₂ relaxation and ventricle volume changes served to identify animals that responded to the adverse effects of trimethyl tin. Impact statement These data will help design follow-on studies with other known neurotoxicants to be used to assess the broad applicability of the present findings. Together this approach represents an effort to begin to develop and qualify a set of translational biochemical markers of neurotoxicity that will be readily accessible in humans. Such biomarkers could prove invaluable for drug development research ranging from preclinical studies to clinical trials and may prove to assist with monitoring of the severity and life cycle of brain lesions.

Exploration of potential biomarkers and related biological pathways for PCB exposure in maternal and cord serum: A pilot birth cohort study in Chiba, Japan

Polychlorinated biphenyls (PCBs) have been associated with adverse human reproductive and fetal developmental measures or outcomes because of their endocrine-disrupting effects; however, the biological mechanisms of adverse effects of PCB exposure in humans are not currently well established. In this study, we aimed to identify the biological pathways and potential biomarkers of PCB exposure in maternal and umbilical cord serum using a hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS) metabolomics platform. The median concentration of total PCBs in maternal (n=93) and cord serum (n=93) were 350 and 70pgg^-1 wet wt, respectively. PCB levels in maternal and fetal serum from the Chiba Study of Mother and Children's Health (C-MACH) cohort are comparable to those of earlier cohort studies conducted in Japan, the USA, and European countries. We used the random forest model with the metabolome profile to predict exposure levels of PCB (first quartile [Q1] and fourth quartile [Q4]) for pregnant women and fetuses. In the prediction model for classification of Q1 versus Q4 (area-under-curve [AUC]: pregnant women=0.812 and fetuses=0.919), citraconic acid level in maternal serum and ethanolamine, p-hydroxybenzoate, and purine levels in cord serum had >0.70 AUC values. These candidate biomarkers and metabolite included in composited models were related to glutathione and amino acid metabolism in maternal serum and the amino acid metabolism and ubiquinone and other terpenoid-quinone biosynthesis in cord serum (FDR <0.10), indicating disruption of metabolic pathways by PCB exposure in pregnant women and fetuses. These results showed that metabolome analysis might be useful to explore potential biomarkers and related biological pathways for PCB exposure. Thus, more detailed studies are needed to verify sensitivity of the biomarkers and clarify the biochemical changes resulting from PCB exposure.

Pesticide Mixture Toxicity in Surface Water Extracts in Snails (Lymnaea stagnalis) by an in Vitro Acetylcholinesterase Inhibition Assay and Metabolomics

Many chemicals in use end up in the aquatic environment. The toxicity of water samples can be tested with bioassays, but a metabolomic approach has the advantage that multiple end points can be measured simultaneously and the affected metabolic pathways can be revealed. A current challenge in metabolomics is the study of mixture effects. This study aims at investigating the toxicity of an environmental extract and its most abundant chemicals identified by target chemical analysis of >100 organic micropollutants and effect-directed analysis (EDA) using the acetylcholinesterase (AChE) bioassay and metabolomics. Surface water from an agricultural area was sampled with a large volume solid phase extraction (LVSPE) device using three cartridges containing neutral, anionic, and cationic sorbents able to trap several pollutants classes like pharmaceuticals, pesticides, PAHs, PCBs, and perfluorinated surfactants. Targeted chemical analysis and AChE bioassay were performed on the cartridge extracts. The extract of the neutral sorbent cartridge contained most of the targeted chemicals, mainly imidacloprid, thiacloprid, and pirimicarb, and was the most potent AChE inhibitor. Using an EDA approach, other AChE inhibiting candidates were identified in the neutral extract, such as carbendazim and esprocarb. Additionally, a metabolomics experiment on the central nervous system (CNS) of the freshwater snail Lymnaea stagnalis was conducted. The snails were exposed to the extract, the three most abundant chemicals individually, and a mixture of these. The extract disturbed more metabolic pathways than the three most abundant chemicals individually, indicating the contribution of other chemicals. Most pathways perturbed by the extract exposure overlapped with those related to exposure to neonicotinoids, like the polyamine metabolism involved in CNS injuries. Metabolomics for the straightforward comparison between a complex mixture and single compound toxicity is still challenging but, compared to traditional biotesting, is a promising tool due to its increased sensitivity.

Gene expression profiling to identify the toxicities and potentially relevant disease outcomes due to endosulfan exposure

Endosulfan, one of the most toxic organochlorine pesticides, belongs to a group of persistent organic pollutants. Gene expression profiling offers a promising approach in health hazard identification of chemicals. The aim of this study was to use gene expression profiling to identify the toxicities and potentially relevant human diseases due to endosulfan exposure. We performed DNA microarray analysis to analyze gene expression profiles in human endothelial cells exposed to 20, 40 and 60 μM endosulfan in combination with an endothelial phenotype. Microarray results showed that endosulfan increased the number of altered genes in a dose-dependent manner, and changed the expression of 161 genes across all treatment groups. qRT-PCR closely matched the microarray data for the genes tested. Significantly enriched biological processes for overlapping down-regulated genes include the neurological system process, signal transduction, and homeostatic process in all the dose groups. These down-regulated genes were associated with cytoskeleton organization and DNA repair at low doses, and involved in cell cycle, apoptosis, p53 pathway and carcinogenesis at high doses. Those up-regulated genes were linked to the inflammatory response and transcriptional misregulation in cancer at higher doses. These findings are consistent with our established endothelial phenotypes. Endosulfan may be relevant to human diseases including liver cancer, prostate cancer and leukemia using the NextBio Human Disease Atlas. These results provide molecular evidence supporting the toxicities and carcinogenic potential of endosulfan in humans.

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

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

Taxonomic applicability of inflammatory cytokines in adverse outcome pathway (AOP) development

Cytokines, low-molecular-weight messenger proteins that act as intercellular immunomodulatory signals, have become a mainstream preclinical marker for assessing the systemic inflammatory response to external stressors. The challenge is to quantitate from healthy subjects cytokine levels that are below or at baseline and relate those dynamic and complex cytokine signatures of exposures with the inflammatory and repair pathways. Thus, highly sensitive, specific, and precise analytical and statistical methods are critically important. Investigators at the U.S. Environmental Protection Agency (EPA) have implemented advanced technologies and developed statistics for evaluating panels of inflammatory cytokines in human blood, exhaled breath condensate, urine samples, and murine biological media. Advanced multiplex, bead-based, and automated analytical platforms provided sufficient sensitivity, precision, and accuracy over the traditional enzyme-linked immunosorbent assay (ELISA). Thus, baseline cytokine levels can be quantified from healthy human subjects and animals and compared to an in vivo exposure response from an environmental chemical. Specifically, patterns of cytokine responses in humans exposed to environmental levels of ozone and diesel exhaust, and in rodents exposed to selected pesticides (such as fipronil and carbaryl), were used as case studies to generally assess the taxonomic applicability of cytokine responses. The findings in this study may aid in the application of measureable cytokine markers in future adverse outcome pathway (AOP)-based toxicity testing. Data from human and animal studies were coalesced and the possibility of using cytokines as key events (KE) to bridge species responses to external stressors in an AOP-based framework was explored.

Identification of fipronil metabolites by time-of-flight mass spectrometry for application in a human exposure study

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