Weight of evidence evaluation of the metabolism disrupting effects of triphenyl phosphate using an expert knowledge elicitation approach.

Identification of Endocrine-Disrupting Chemicals (EDCs) in a regulatory context requires a high level of evidence. However, lines of evidence (e.g. human, in vivo, in vitro or in silico) are heterogeneous and incomplete for quantifying evidence of the adverse effects and mechanisms involved. To date, for the regulatory appraisal of metabolism-disrupting chemicals (MDCs), no harmonised guidance to assess the weight of evidence has been developed at the EU or international level. To explore how to develop this, we applied a formal Expert Knowledge Elicitation (EKE) approach within the European GOLIATH project. EKE captures expert judgment in a quantitative manner and provides an estimate of uncertainty of the final opinion. As a proof of principle, we selected one suspected MDC -triphenyl phosphate (TPP) - based on its related adverse endpoints (obesity/adipogenicity) relevant to metabolic disruption and a putative Molecular Initiating Event (MIE): activation of peroxisome proliferator activated receptor gamma (PPARγ). We conducted a systematic literature review and assessed the quality of the lines of evidence with two independent groups of experts within GOLIATH, with the objective of categorising the metabolic disruption properties of TPP, by applying an EKE approach. Having followed the entire process separately, both groups arrived at the same conclusion, designating TPP as a "suspected MDC" with an overall quantitative agreement exceeding 85%, indicating robust reproducibility. The EKE method provides to be an important way to bring together scientists with diverse expertise and is recommended for future work in this area.

Prenatal Exposure to Metabolism-Disrupting Chemicals, Cord Blood Transcriptome Perturbations, and Birth Weight in a Belgian Birth Cohort.

Prenatal exposure to metabolism-disrupting chemicals (MDCs) has been linked to birth weight, but the molecular mechanisms remain largely unknown. In this study, we investigated gene expressions and biological pathways underlying the associations between MDCs and birth weight, using microarray transcriptomics, in a Belgian birth cohort. Whole cord blood measurements of dichlorodiphenyldichloroethylene (p,p'-DDE), polychlorinated biphenyls 153 (PCB-153), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and transcriptome profiling were conducted in 192 mother-child pairs. A workflow including a transcriptome-wide association study, pathway enrichment analysis with a meet-in-the-middle approach, and mediation analysis was performed to characterize the biological pathways and intermediate gene expressions of the MDC-birth weight relationship. Among 26,170 transcriptomic features, we successfully annotated five overlapping metabolism-related gene expressions associated with both an MDC and birth weight, comprising BCAT2, IVD, SLC25a16, HAS3, and MBOAT2. We found 11 overlapping pathways, and they are mostly related to genetic information processing. We found no evidence of any significant mediating effect. In conclusion, this exploratory study provides insights into transcriptome perturbations that may be involved in MDC-induced altered birth weight.

Drug Metabolism of Hepatocyte-like Organoids and Their Applicability in In Vitro Toxicity Testing.

Emerging advances in the field of in vitro toxicity testing attempt to meet the need for reliable human-based safety assessment in drug development. Intrahepatic cholangiocyte organoids (ICOs) are described as a donor-derived in vitro model for disease modelling and regenerative medicine. Here, we explored the potential of hepatocyte-like ICOs (HL-ICOs) in in vitro toxicity testing by exploring the expression and activity of genes involved in drug metabolism, a key determinant in drug-induced toxicity, and the exposure of HL-ICOs to well-known hepatotoxicants. The current state of drug metabolism in HL-ICOs showed levels comparable to those of PHHs and HepaRGs for CYP3A4; however, other enzymes, such as CYP2B6 and CYP2D6, were expressed at lower levels. Additionally, EC50 values were determined in HL-ICOs for acetaminophen (24.0−26.8 mM), diclofenac (475.5−>500 µM), perhexiline (9.7−>31.5 µM), troglitazone (23.1−90.8 µM), and valproic acid (>10 mM). Exposure to the hepatotoxicants showed EC50s in HL-ICOs comparable to those in PHHs and HepaRGs; however, for acetaminophen exposure, HL-ICOs were less sensitive. Further elucidation of enzyme and transporter activity in drug metabolism in HL-ICOs and exposure to a more extensive compound set are needed to accurately define the potential of HL-ICOs in in vitro toxicity testing.

Interspecies Differences in Activation of Peroxisome Proliferator-Activated Receptor γ by Pharmaceutical and Environmental Chemicals.

Endocrine disrupting chemicals (EDCs) are able to deregulate the hormone system, notably through interactions with nuclear receptors (NRs). The mechanisms of action and biological effects of many EDCs have mainly been tested on human and mouse but other species such as zebrafish and xenopus are increasingly used as a model to study the effects of EDCs. Among NRs, peroxisome proliferator-activated receptor γ (PPARγ) is a main target of EDCs, for which most experimental data have been obtained from human and mouse models. To assess interspecies differences, we tested known human PPARγ ligands on reporter cell lines expressing either human, mouse, zebrafish, or xenopus PPARγ. Using these cell lines, we were able to highlight major interspecies differences. Known hPPARγ pharmaceutical ligands modulated hPPARγ and mPPARγ activities in a similar manner, while xPPARγ was less responsive and zfPPARγ was not modulated at all by these compounds. On the contrary, human liver X receptor (hLXR) ligands GW 3965 and WAY-252623 were only active on zfPPARγ. Among environmental compounds, several molecules activated the PPARγ of the four species similarly, e.g., phthalates (MEHP), perfluorinated compounds (PFOA, PFOS), and halogenated derivatives of BPA (TBBPA, TCBPA), but some of them like diclofenac and the organophosphorus compounds tri-o-tolyl phosphate and triphenyl phosphate were most active on zfPPARγ. This study confirms or shows for the first time the h, m, x, and zfPPARγ activities of several chemicals and demonstrates the importance of the use of species-specific models to study endocrine and metabolism disruption by environmental chemicals.

Endocrine Disrupting Chemicals: Current Understanding, New Testing Strategies and Future Research Needs.

Endocrine disrupting chemicals (EDCs) are exogenous chemicals which can disrupt any action of the endocrine system, and are an important class of substances which play a role in the Developmental Origins of Health and Disease (DOHaD) [...].

The GOLIATH Project: Towards an Internationally Harmonised Approach for Testing Metabolism Disrupting Compounds.

The purpose of this project report is to introduce the European "GOLIATH" project, a new research project which addresses one of the most urgent regulatory needs in the testing of endocrine-disrupting chemicals (EDCs), namely the lack of methods for testing EDCs that disrupt metabolism and metabolic functions. These chemicals collectively referred to as "metabolism disrupting compounds" (MDCs) are natural and anthropogenic chemicals that can promote metabolic changes that can ultimately result in obesity, diabetes, and/or fatty liver in humans. This project report introduces the main approaches of the project and provides a focused review of the evidence of metabolic disruption for selected EDCs. GOLIATH will generate the world's first integrated approach to testing and assessment (IATA) specifically tailored to MDCs. GOLIATH will focus on the main cellular targets of metabolic disruption-hepatocytes, pancreatic endocrine cells, myocytes and adipocytes-and using an adverse outcome pathway (AOP) framework will provide key information on MDC-related mode of action by incorporating multi-omic analyses and translating results from in silico, in vitro, and in vivo models and assays to adverse metabolic health outcomes in humans at real-life exposures. Given the importance of international acceptance of the developed test methods for regulatory use, GOLIATH will link with ongoing initiatives of the Organisation for Economic Development (OECD) for test method (pre-)validation, IATA, and AOP development.

Method Development for Effect-Directed Analysis of Endocrine Disrupting Compounds in Human Amniotic Fluid.

The developing fetus represents a highly sensitive period of exposure to endocrine disrupting compounds (EDCs). However, risk assessment of EDCs is hampered by the lack of data on direct in utero exposure. In this study, we developed a robust analytical methodology for the identification of a wide range of known and unknown EDCs in full-term amniotic fluid (AF). First, a method for extraction and fractionation of a broad range of polar and nonpolar EDCs was developed and validated. Maximal recoveries of reference compounds and minimal interference from the matrix were achieved with a combination of solid phase extraction and dispersive liquid/liquid extraction. Bioassay analysis using cell-based reporter gene assays revealed estrogenic, androgenic, and dioxin-like activity in AF extract corresponding to 1.4 nmol EEQ/L, 76.6 pmol DHT-EQ/L, and 10.1 pmol TEQ/L, respectively. Targeted analysis revealed 13 xenobiotics, phytoestrogens, and endogenous hormones in the AF extract that partly contributed to the bioassay activity. Separation of the complex mixture of chemicals in the AF extract with reversed-phase chromatographic fractionation and subsequent bioassay analysis revealed activity in fractions over a wide range of polarity, indicating diverse (unidentified) substances with potential ED activity. The method developed here represents the first methodological step in an effect-directed analysis approach to identify unknown biologically active compounds in the fetal environment.

Thyroid-stimulating hormone levels in newborns and early life exposure to endocrine-disrupting chemicals: analysis of three European mother-child cohorts.

BackgroundVarious studies have reported interactions between thyroid hormones and early life chemical exposure. Our objective was to analyze the associations between markers of endocrine-disrupting chemical exposure and thyroid function in newborns, determined through heel prick blood spots.MethodsThree European mother-child cohorts (FLEHSI-Belgium, HUMIS-Norway, and the PCB cohort-Slovakia. Total n=1,784) were pooled for the purpose of this study. Data on thyroid-stimulating hormone (TSH) were obtained from national neonatal screening registries, and samples of cord plasma and/or breast milk were collected to determine exposure to various chemicals. Multiple regression models were composed with exposure and cohort as fixed factors, and adjustments were made for a priori defined covariates.ResultsMedian TSH concentrations were 1, 1.10, and 2.76 mU/l for the Belgian, Norwegian, and Slovak cohorts, respectively. For polychlorinated biphenyl (PCB)-153 and dichlorodiphenyldichloroethylene (p,p'-DDE), children in the third exposure quartile had a 12-15% lower TSH at birth. Results remained unchanged after additional adjustment for birth weight and gestational weight gain. No effect on TSH was observed for the other compounds.ConclusionEarly life exposure to PCB-153 and p,p'-DDE impacts newborn TSH levels. Higher exposure levels were associated with 12-15% lower TSH levels.

Determination of monoamine neurotransmitters in zebrafish (Danio rerio) by gas chromatography coupled to mass spectrometry with a two-step derivatization.

A sensitive analytical method for the determination of monoamine neurotransmitters (MNTs) in zebrafish larvae was developed using gas chromatography coupled to mass spectrometry. Six MNTs were selected as target compounds for neurotoxicity testing. MNTs underwent a two-step derivatization with hexamethyldisilazane (HDMS) for O-silylation followed by N-methyl-bis-heptafluorobutyramide (MBHFBA) for N-perfluoroacylation. Derivatization conditions were optimized by an experimental design approach. Method validation showed linear calibration curves (r 2 > 0.9976) in the range of 1-100 ng for all the compounds. The recovery rates were between 92 and 119%. The method was repeatable and reproducible with relative standard deviations (RSD) in the range of 2.5-9.3% for intra-day and 4.8-12% for inter-day variation. The limits of detection and the limits of quantitation were 0.4-0.8 and 1.2-2.7 ng/mL, respectively. The method was successfully applied to detect and quantify trace levels of MNTs in 5-day-old zebrafish larvae that were exposed to low concentrations of neurotoxic chemicals such as pesticides and methylmercury. Although visual malformations were not detected, the MNT levels varied significantly during early zebrafish development. These results show that exposure to neurotoxic chemicals can alter neurotransmitter levels and thereby may influence early brain development. Graphical abstract ᅟ.

Correction to: Parma consensus statement on metabolic disruptors.

CORRECTION: After publication of the article [1], it has been brought to our attention that the thirteenth author of this article has had their name spelt incorrectly. In the original article the spelling "Laura Rizzir" was used. In fact the correct spelling should be "Laura Rizzi".

Effects of Hydroxylated Polybrominated Diphenyl Ethers in Developing Zebrafish Are Indicative of Disruption of Oxidative Phosphorylation.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been detected in humans and wildlife. Using in vitro models, we recently showed that OH-PBDEs disrupt oxidative phosphorylation (OXPHOS), an essential process in energy metabolism. The goal of the current study was to determine the in vivo effects of OH-PBDE reported in marine wildlife. To this end, we exposed zebrafish larvae to 17 OH-PBDEs from fertilisation to 6 days of age, and determined developmental toxicity as well as OXPHOS disruption potential with a newly developed assay of oxygen consumption in living embryos. We show here that all OH-PBDEs tested, both individually and as mixtures, resulted in a concentration-dependant delay in development in zebrafish embryos. The most potent substances were 6-OH-BDE47 and 6'-OH-BDE49 (No-Effect-Concentration: 0.1 and 0.05 µM). The first 24 h of development were the most sensitive, resulting in significant and irreversible developmental delay. All substances increased oxygen consumption, an effect indicative of OXPHOS disruption. Our results suggest that the induced developmental delay may be caused by disruption of OXPHOS. Though further studies are needed, our findings suggest that the environmental concentrations of some OH-PBDEs found in Baltic Sea wildlife in the Baltic Sea may be of toxicological concern.

Altered Adipogenesis in Zebrafish Larvae Following High Fat Diet and Chemical Exposure Is Visualised by Stimulated Raman Scattering Microscopy.

Early life stage exposure to environmental chemicals may play a role in obesity by altering adipogenesis; however, robust in vivo methods to quantify these effects are lacking. The goal of this study was to analyze the effects of developmental exposure to chemicals on adipogenesis in the zebrafish (Danio rerio). We used label-free Stimulated Raman Scattering (SRS) microscopy for the first time to image zebrafish adipogenesis at 15 days post fertilization (dpf) and compared standard feed conditions (StF) to a high fat diet (HFD) or high glucose diet (HGD). We also exposed zebrafish embryos to a non-toxic concentration of tributyltin (TBT, 1 nM) or Tris(1,3-dichloroisopropyl)phosphate (TDCiPP, 0.5 µM) from 0-6 dpf and reared larvae to 15 dpf under StF. Potential molecular mechanisms of altered adipogenesis were examined by qPCR. Diet-dependent modulation of adipogenesis was observed, with HFD resulting in a threefold increase in larvae with adipocytes, compared to StF and HGD. Developmental exposure to TBT but not TDCiPP significantly increased adipocyte differentiation. The expression of adipogenic genes such as pparda, lxr and lepa was altered in response to HFD or chemicals. This study shows that SRS microscopy can be successfully applied to zebrafish to visualize and quantify adipogenesis, and is a powerful approach for identifying obesogenic chemicals in vivo.

Exposure to endocrine disrupting chemicals perturbs lipid metabolism and circadian rhythms.

A growing body of evidence indicates that exposure to environmental chemicals can contribute to the etiology of obesity by inappropriately stimulating adipogenesis as well as perturbing lipid metabolism and energy balance. One potential mechanism by which chemical exposure can influence lipid metabolism is through disturbance of circadian rhythms, endogenously-driven cycles of roughly 24hr in length that coordinate biochemical, physiological, and behavioral processes in all organisms. Here we show for the first time that exposure to endocrine disrupting compounds (EDCs), including the pesticide tributyltin, two commercial flame retardants, and a UV-filter chemical found in sunscreens, can perturb both circadian clocks and lipid metabolism in vertebrates. Exposure of developing zebrafish to EDCs affects core clock activity and leads to a remarkable increase in lipid accumulation that is reminiscent of the effects observed for longdaysin, a known disruptor of circadian rhythms. Our data reveal a novel obesogenic mechanism of action for environmental chemicals, an observation which warrants further research. Because circadian clocks regulate a wide variety of physiological processes, identification of environmental chemicals capable of perturbing these systems may provide important insights into the development of environmentally-induced metabolic disease.

Zebrafish embryos as a screen for DNA methylation modifications after compound exposure.

Modified epigenetic programming early in life is proposed to underlie the development of an adverse adult phenotype, known as the Developmental Origins of Health and Disease (DOHaD) concept. Several environmental contaminants have been implicated as modifying factors of the developing epigenome. This underlines the need to investigate this newly recognized toxicological risk and systematically screen for the epigenome modifying potential of compounds. In this study, we examined the applicability of the zebrafish embryo as a screening model for DNA methylation modifications. Embryos were exposed from 0 to 72 h post fertilization (hpf) to bisphenol-A (BPA), diethylstilbestrol, 17α-ethynylestradiol, nickel, cadmium, tributyltin, arsenite, perfluoroctanoic acid, valproic acid, flusilazole, 5-azacytidine (5AC) in subtoxic concentrations. Both global and site-specific methylation was examined. Global methylation was only affected by 5AC. Genome wide locus-specific analysis was performed for BPA exposed embryos using Digital Restriction Enzyme Analysis of Methylation (DREAM), which showed minimal wide scale effects on the genome, whereas potential informative markers were not confirmed by pyrosequencing. Site-specific methylation was examined in the promoter regions of three selected genes vasa, vtg1 and cyp19a2, of which vasa (ddx4) was the most responsive. This analysis distinguished estrogenic compounds from metals by direction and sensitivity of the effect compared to embryotoxicity. In conclusion, the zebrafish embryo is a potential screening tool to examine DNA methylation modifications after xenobiotic exposure. The next step is to examine the adult phenotype of exposed embryos and to analyze molecular mechanisms that potentially link epigenetic effects and altered phenotypes, to support the DOHaD hypothesis.

Changes in Neurotransmitter Profiles during Early Zebrafish (Danio rerio) Development and after Pesticide Exposure.

During early development, neurotransmitters are important stimulants for the development of the central nervous system. Although the development of different neuronal cell types during early zebrafish (Danio rerio) development is well-studied, little is known of the levels of neurotransmitters, their precursors and metabolites during development, and how these levels are affected by exposure to environmental contaminants. A method based on hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry has been applied for the first time to zebrafish embryos and larvae to study five neurotransmitter systems in parallel, including the dopaminergic-andrenergic, glutaminergic-GABAnergic, serotoninergic, histaminergic, and cholinergic systems. Our method enables the quantification of neurotransmitters and their precursors and metabolites in whole zebrafish from the period of zygote to free-swimming larvae 6 days postfertilization (dpf). We observed a developmental stage-dependent pattern with clear differences between the first 2 days of development and the following days. Whereas the neurotransmitter levels steadily increased, the precursors showed a peak at 3 dpf. After exposure to several pesticides, significant differences in concentrations of neurotransmitters and precursors were observed. Our study revealed new insights about neurotransmitter systems during early zebrafish development and showed the usefulness of our approach for environmental neurotoxicity studies.

Demographic, Reproductive, and Dietary Determinants of Perfluorooctane Sulfonic (PFOS) and Perfluorooctanoic Acid (PFOA) Concentrations in Human Colostrum.

To determine demographic, reproductive, and maternal dietary factors that predict perfluoroalkyl substance (PFAS) concentrations in breast milk, we measured perfluorooctane sulfonic (PFOS) and perfluorooctanoic acid (PFOA) concentrations, using liquid chromatography-mass spectrometry, in 184 colostrum samples collected from women participating in a cohort study in Eastern Slovakia between 2002 and 2004. During their hospital delivery stay, mothers completed a food frequency questionnaire, and demographic and reproductive data were also collected. PFOS and PFOA predictors were identified by optimizing multiple linear regression models using Akaike's information criterion (AIC). The geometric mean concentration in colostrum was 35.3 pg/mL for PFOS and 32.8 pg/mL for PFOA. In multivariable models, parous women had 40% lower PFOS (95% CI: -56 to -17%) and 40% lower PFOA (95% CI: -54 to -23%) concentrations compared with nulliparous women. Moreover, fresh/frozen fish consumption, longer birth intervals, and Slovak ethnicity were associated with higher PFOS and PFOA concentrations in colostrum. These results will help guide the design of future epidemiologic studies examining milk PFAS concentrations in relation to health end points in children.

LInking EDCs in maternal Nutrition to Child health (LINC study) - protocol for prospective cohort to study early life exposure to environmental chemicals and child health.

BACKGROUND: The presence of chemicals in the environment is ubiquitous. Human biomonitoring studies have shown that various chemicals can be detected in the majority of the population, including pregnant women. These compounds may pass the placenta, and reach the fetus. This early life exposure in particular may be detrimental as some chemicals may disrupt the endocrine system, which is involved in various processes during development. The LINC study is a prospective birth cohort designed to study associations between early life environmental exposures and child health, including growth and neurodevelopment. The purpose of this paper is to give an overview of this cohort. METHODS AND DESIGN: Recruitment for this cohort has started in 2011 in three Dutch areas and is still ongoing. To date over 300 mother-child pairs have been included. Women are preferably included during the first trimester of pregnancy. Major congenital anomalies and twin births are reasons for exclusion. To assess exposure to environmental chemicals, cord blood, placenta, meconium and vernix are collected. Parents collect urine of the child shortly after birth and breast milk in the second month of life. Exposure to a broad range of environmental chemicals are determined in cord plasma and breast milk. Furthermore various hormones, including leptin and cortisone, are determined in cord plasma, and in heel prick blood spots (thyroxine). Data on anthropometry of the child is collected through midwives and youth health care centres on various time points until the child is 18 months of age. Furthermore cognitive development is monitored by means of the van Wiechen scheme, and information on behavioral development is collected by means of the infant behavior questionnaire and the child behavior checklist. When the child is 12 months of age, a house visit is scheduled to assess various housing characteristics, as well as hand-to-mouth behavior of the child. At this visit exposure of the child to flame retardants (with endocrine disrupting properties) in house dust is determined by means of body wipes. They are furthermore also measured in a saliva sample of the child. Next to these measurements, women receive questionnaires each trimester regarding amongst others lifestyle of the parents, general health of the parents and the child, and mental state of the mother. DISCUSSION: This study was approved by the medical ethics committee of the VU University Medical Centre. Consent for the infant is given by the mother, who is specifically required to give consent for both herself as well as her child. Results will be published regardless of the findings of this study, and will be widely disseminated among related medical stakeholders (e.g. midwives and pediatricians), policy makers, and the general public.

Prenatal exposure to endocrine disrupting chemicals and birth weight-A prospective cohort study.

Prenatal exposure to endocrine disrupting chemicals may affect fetal development through disruption of hormonal actions and epigenetic modifications, potentially predisposing individuals to later on-set health risks, such as obesity. The objective of this study was to determine associations between biological exposure markers of various endocrine disrupting chemicals and birth weight in a newly established, prospective mother-child cohort in the Netherlands. Birth weight (n = 91) was obtained from birth records, and exposure to dichlorodiphenyldichloroethylene (DDE), three di-2-ethylhexyl phthalate (DEHP) metabolites, polychlorinated biphenyl-153, perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) was determined in cord plasma. For DDE, exposure was also measured in breast milk. Linear regression analysis was used to determine associations between compounds and birth weight, which were stratified for gender and adjusted for a priori defined covariates. Increased exposure to DDE was associated with lower birth weight in boys (>95.89 ng L-1, -325.9 g, 95% CI -634.26 to -17.56), whereas in girls a tendency towards a higher birth weight was observed. Lower birth weights for boys were also observed for high exposure to MECPP, and to a certain extent also for PFOA. MEHHP and PFOS exposure on the other hand were associated with higher birth weights in boys. In girls no effects were observed for these compounds. It can be concluded that prenatal exposure to DDE, perfluorinated alkyl acids, and phthalates was associated with changes in birth weight in this population. Associations were gender specific, and appeared to be non-linear. Since the population was relatively small, results should be interpreted with caution.

Multimode sensors as new tools for molecular recognition of testosterone, dihydrotestosterone and estradiol in children's saliva.

Increased levels of testosterone (T2 ), dihydrotestosterone (DHT) and estradiol (E2 ) in children may be responsible for their early/delayed puberty and obesity conditions. Therefore, multimode sensors based on carbon matrices, such as graphite, graphene, fullerene C60 and multiwall carbon nanotubes modified with maltodextrin, were designed to assess reliably T2 , DHT and E2 in children saliva. The modes used for the assay of hormones were stochastic mode (for qualitative and quantitative determination of hormones) and differential pulse voltammetry mode (for quantitative determination of hormones). The advantage of this type of sensors, for hormone analysis, is their possibility to reach low concentration levels- are placed for children saliva under the detection limit of standard methods (e.g. ELISA used for the determination of these hormones in saliva). This made the multimode sensors an excellent tool for clinical analysis and especially for determination of substances of clinical importance in saliva samples. The proposed method is fast and simple, and no sampling of saliva is required.

Combined Transcriptomics Analysis for Classification of Adverse Effects As a Potential End Point in Effect Based Screening.

Environmental risk assessment relies on the use of bioassays to assess the environmental impact of chemicals. Gene expression is gaining acceptance as a valuable mechanistic end point in bioassays and effect-based screening. Data analysis and its results, however, are complex and often not directly applicable in risk assessment. Classifier analysis is a promising method to turn complex gene expression analysis results into answers suitable for risk assessment. We have assembled a large gene expression data set assembled from multiple studies and experiments in the springtail Folsomia candida, with the aim of selecting a set of genes that can be trained to classify general toxic stress. By performing differential expression analysis prior to classifier training, we were able to select a set of 135 genes which was enriched in stress related processes. Classifier models from this set were used to classify two test sets comprised of chemical spiked, polluted, and clean soils and compared to another, more traditional classifier feature selection. The gene set presented here outperformed the more traditionally selected gene set. This gene set has the potential to be used as a biomarker to test for adverse effects caused by chemicals in springtails to provide end points in environmental risk assessment.