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Comparison of in vitro transcriptomic points of departure with fish acute and chronic toxicity values: A case study of rainbow trout cells exposed to pesticides

ABSTRACT: There is growing scientific and regulatory interest in transcriptomic points of departure (tPOD) values from in vitro experiments as an alternative to animal test method. The objective of this study was to calculate tPOD values in rainbow trout gill cells (RTgill-W1 following OECD 249) exposed to 20 pesticides, and to evaluate how these values compare to fish acute and chronic toxicity data from the ECOTOX database. Cells were exposed to one fungicide (chlorothalonil), ten herbicides (atrazine, glyphosate, imazethapyr, metolachlor, diquat, s-metolachlor, AMPA, dicamba, dimethenamid-P, metribuzin), eight insecticides (chlorpyrifos, diazinon, permethrin, carbaryl, clothianidin, imidacloprid, thiamethoxam, chlorantraniliprole), and OECD 249 positive control 3,4-dichloroaniline. Sequencing libraries were prepared with UPXome, and tPODs calculated with ExpressAnalyst. The method identified 44,262 unique genes, with 1,115 genes having >5 counts in the 576 samples sequenced. For all chemicals, tPODs were derived and tPOD mode values ranged from 0.003 to 141µM with an average of 37µM. There were significant correlations between these tPOD mode values (x-value) and in vitro cytotoxicity EC50s from RTgill-W1 cells (y=1.1x+0.89, R2=0.85, p<0.001; n=11), rainbow trout acute toxicity LC50s (y=0.9x+0.59, R2=0.56, p<0.001; n=20), fish chronic sub-lethal effect concentrations (y=0.62x+0.38, R2=0.36, p=0.01; n=16) and fish chronic lethal effect concentrations (y=0.77x-0.28, R2=0.57, p=0.002; n=14). Bland–Altman plot statistical analyses of these comparisons also showed good agreement. Overall, these data demonstrate that tPOD values can be derived from an experimental platform that links together elements of OECD 249 with a transcriptomic method with high throughput potential. The findings support the notion that tPODs from short-term in vitro studies may be comparable to effect concentration data from in vivo studies of fish exposed for chronic durations.

ORGANISM(S): Oncorhynchus mykiss

PROVIDER: GSE283712 | GEO | 2025/01/01

REPOSITORIES: GEO

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Project description:Current methods to support chemical hazard assessment face significant challenges given the rapidly growing number of compounds of emerging concern (CEC) requiring assessment. Standard testing strategies rely upon live animal testing, which are time-consuming, expensive, and ethically questionable. These concerns serve as an impetus to develop new approach methodologies (NAMs) that do not rely on live animal tests. This study explored the application of the molecular benchmark dose (BMD) approach in a 7-day embryo-larval fathead minnow (FHM) assay to derive determine transcriptomic points-of-departure (tPODs) which can be useds to predict apical BMDs of fluoxetine (FLX), a highly prescribed and potent selective serotonin reuptake inhibitor frequently detected in surface waters. Fertilized FHM embryos were exposed to graded concentrations of FLX (confirmed at <LOD, 0.19, 0.74, 3.38, 10.2, 47.5 µg/L) for 32 days. Subsets of fish were subjected to omics and locomotor analyses at 7 days post-fertilization (dpf) and to histological and biometric measurements at 32 dpf. Enrichment analyses of transcriptomics and proteomics data revealed significant perturbations in gene sets associated with serotonergic and axonal functions. BMD analysis resulted in tPOD values of 0.56 µg/L (median of the 20 most sensitive gene-level BMDs), 5.0 µg/L (tenth percentile of all gene-level BMDs), 7.51 µg/L (mode of the first peak of all gene-level BMDs) , and 5.66 µg/L (pathway-level BMD). These tPODs are protective of apical locomotor and reduced weight effects (LOEC of 10.2 µg/L) observed in this study and are well within the range of chronic apical BMDs of FLX reported in the literature. Furthermore, the distribution of gene-level BMDs followed a bimodal pattern, revealing disruption of sensitive neurotoxic pathways at low concentrations and metabolic pathway perturbations at higher concentrations. This is one of the first studies to derive tPODs for FLX using a short-term embryo assay at a life stage not considered to be a live animal under current legislations.

Project description:Traditional toxicity testing has been unable to keep pace with the introduction of new chemicals into commerce. Consequently, there are limited or no toxicity data upon which to base a risk assessment for many chemicals to which fish and wildlife may be exposed. Per- and polyfluoroalkyl substances (PFAS) are emblematic of this issue in that most the ecological hazards of most PFAS remain uncharacterized. The present study employed a high throughput assay to identify the concentration at which 20 PFAS, with diverse properties, elicited a concerted gene expression response in larval fathead minnows (Pimephales promelas, 5-6 days post-fertilization) exposed for 24 h. Based on a reduced transcriptome approach that measured whole body expression of 1832 genes, the median transcriptomic point of departure (tPOD) for the 20 PFAS tested was 10 µM. Longer chain carboxylic acids (12-13 C-F) and an eight C-F di-alcohol, N-alkyl sulfonamide, and telomer sulfonic acid were among the most potent PFAS, eliciting gene expression responses at concentrations below 1 µM. With a few exceptions, larval fathead minnow tPODs were concordant with those based on whole transcriptome response in human cell lines. However, larval fathead minnow tPODs were often greater than those for Daphnia magna exposed to the same PFAS. The tPODs overlapped concentrations at which other sub-lethal effects have been reported in fish (available for 10 PFAS; including a range of species, life stages, and study designs). Nonetheless, fathead minnow tPODs were all orders of magnitude higher than aqueous PFAS concentrations detected in tributaries of the North American Great Lakes suggesting a substantial margin of safety in those systems, even for PFAS with significant potential for bioaccumulation. Overall, results broadly support the use of a fathead minnow larval transcriptomics assay to derive screening level potency estimates for use in ecological risk-based prioritization. Traditional toxicity testing has been unable to keep pace with the introduction of new chemicals into commerce. Consequently, there are limited or no toxicity data upon which to base a risk assessment for many chemicals to which fish and wildlife may be exposed. Per- and polyfluoroalkyl substances (PFAS) are emblematic of this issue in that most the ecological hazards of most PFAS remain uncharacterized. The present study employed a high throughput assay to identify the concentration at which 20 PFAS, with diverse properties, elicited a concerted gene expression response in larval fathead minnows (Pimephales promelas, 5-6 days post-fertilization) exposed for 24 h. Based on a reduced transcriptome approach that measured whole body expression of 1832 genes, the median transcriptomic point of departure (tPOD) for the 20 PFAS tested was 10 µM. Longer chain carboxylic acids (12-13 C-F) and an eight C-F di-alcohol, N-alkyl sulfonamide, and telomer sulfonic acid were among the most potent PFAS, eliciting gene expression responses at concentrations below 1 µM. With a few exceptions, larval fathead minnow tPODs were concordant with those based on whole transcriptome response in human cell lines. However, larval fathead minnow tPODs were often greater than those for Daphnia magna exposed to the same PFAS. The tPODs overlapped concentrations at which other sub-lethal effects have been reported in fish (available for 10 PFAS; including a range of species, life stages, and study designs). Nonetheless, fathead minnow tPODs were all orders of magnitude higher than aqueous PFAS concentrations detected in tributaries of the North American Great Lakes suggesting a substantial margin of safety in those systems, even for PFAS with significant potential for bioaccumulation. Overall, results broadly support the use of a fathead minnow larval transcriptomics assay to derive screening level potency estimates for use in ecological risk-based prioritization.

Project description:We investigated the effects of chronic TCDD exposure on global gene expression in developing rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout (0.18M-BM-10.01g) were fed Biodiet starter with TCDD added at 0, 0.1, 1, 10 and 100ppb, and ten fish were sampled and pooled from each group for microarray experiments at 28 days after initiation of the exposure. Gene expression analysis was performed using the Genomics Research on All Salmonids Project (cGRASP) 16K cDNA microarrays. TCDD-responsive whole body transcripts identified in the microarray experiments have putative functions involved in various biological processes including cellular process, metabolic process, biological regulation, and response to stimulus. In addition, TCDD caused leisons in multiple organ systems in juvenile rainbow, including skin, oropharynx, liver, gas bladder, intestine, pancreas, nose and kidney. Juvenile rainbow trout (0.18M-BM-10.01g) were fed Biodiet starter (Bio-Oregon) (4% body weight per day) with TCDD added at 0, 0.1, 1, 10 and 100 ppb. Fish were sampled after 28 days. Total RNA from individual fish was isolated using TRIzol reagent (Invitrogen). Total RNA of ten control trout were pooled as a common reference which were labeled with Cy3. Total RNA of ten fish of each treatment were labeled wih Cy5. cDNA were synthesized using SuperScript II Reverse Transcriptase (Invitrogen) (1 M-NM-<g pooled RNA per synthesis). Targets were labeled using the Array 900 Expression Array Detection kit (Genisphere) following the manufacture protocol. 1M-BM-5g RNA of pooled ten control fish were labled with Cy3 and 1M-BM-5g RNA of pooled ten TCDD-treated fish were labled with Cy5, then day-swap was performed. Two arrays were run for each comparison. Microarrays were scanned at 10 M-BM-5m resolution using a ScanArray Express (PerkinElmer Life Sciences, Inc, Boston, MA). The photomultiplier tube settings (PMT) for Cy3 and Cy5 were 70 and 65-66, respectively. TIFF images of arrays were generated with ScanArray Express software (PerkinElmer). Fluorescence intensity data for Cy3 and Cy5 channels were extracted from TIFF images using ImaGene 7.5 software (BioDiscovery Inc., El Segundo, CA). Background correction, data transformation (setting background corrected values < 0.01 to 0.01), Lowess normalization, and analysis (e.g. fold-change calculations) were performed using GeneSpring GX 7.3 (Agilent Technologies, Palo Alto, CA)

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Comparison of in vitro transcriptomic points of departure with fish acute and chronic toxicity values: A case study of rainbow trout cells exposed to pesticides

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