RESUMEN

Single-use plastic production is higher now than ever before. Much of this plastic is released into aquatic environments, where it is eventually weathered into smaller nanoscale plastics. In addition to potential direct biological effects, nanoplastics may also modulate the biological effects of hydrophobic persistent organic legacy contaminants (POPs) that absorb to their surfaces. In this study, we test the hypothesis that developmental exposure (0-7 dpf) of zebrafish to the emerging contaminant polystyrene (PS) nanoplastics (⌀100 nm; 2.5 or 25 ppb), or to environmental levels of the legacy contaminant and flame retardant 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47; 10 ppt), disrupt organismal energy metabolism. We also test the hypothesis that co-exposure leads to increased metabolic disruption. The uptake of nanoplastics in developing zebrafish was validated using fluorescence microscopy. To address metabolic consequences at the organismal and molecular level, metabolic phenotyping assays and metabolic gene expression analysis were used. Both PS and BDE-47 affected organismal metabolism alone and in combination. Individually, PS and BDE-47 exposure increased feeding and oxygen consumption rates. PS exposure also elicited complex effects on locomotor behaviour with increased long-distance and decreased short-distance movements. Co-exposure of PS and BDE-47 significantly increased feeding and oxygen consumption rates compared to control and individual compounds alone, suggesting additive or synergistic effects on energy balance, which was further supported by reduced neutral lipid reserves. Conversely, molecular gene expression data pointed to a negative interaction, as co-exposure of high PS generally abolished the induction of gene expression in response to BDE-47. Our results demonstrate that co-exposure to emerging nanoplastic contaminants and legacy contaminants results in cumulative metabolic disruption in early development in a fish model relevant to eco- and human toxicology.

RESUMEN

Organophosphate flame retardants (OPFRs) are used in a variety of products such as clear coats, resins, and plastics; however, research into their toxicological effects is limited. p-Tert-butylphenyl diphenyl phosphate (BPDP) and isopropylphenyl phosphate (IPPP) are two OPFRs that were prioritized for whole-animal toxicological studies based on observed effects in cultured avian hepatocytes in a previous study. The present study investigates the toxicity of BPDP and IPPP in chicken embryos at different developmental stages by evaluating morphological and gene expression endpoints. Chicken eggs were exposed via air cell injection to 0-250 µg/g (nominal) of either compound and then artificially incubated. At day 11 (midincubation), liver samples were collected for mRNA expression analysis; and at day 20 (1 day prehatch), morphological measurements and liver samples for transcriptomic evaluation were collected. At 250 µg/g, gallbladder size was significantly reduced for both compounds, head/bill length and tarsus length were significantly decreased, and liver somatic index was significantly increased following IPPP exposure only. No effects on mortality were observed up to the highest administered concentration for either chemical. Using a ToxChip polymerase chain reaction array, we report significant differences in hepatic gene expression for both compounds and time points; the most pronounced transcriptomic effects occurred at midincubation. Genes related to xenobiotic metabolism, bile acid/cholesterol regulation, and oxidative stress were significantly dysregulated. Given these changes observed throughout avian embryonic development, further research into the long-term effects of BPDP and IPPP are warranted, especially as they pertain to liver cholestasis. Environ Toxicol Chem 2022;41:739-747. © 2021 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry © 2021 SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Asunto(s)

Pollos , Retardadores de Llama , Animales , Embrión de Pollo , Pollos/metabolismo , Femenino , Retardadores de Llama/metabolismo , Retardadores de Llama/toxicidad , Hígado/metabolismo , Organofosfatos/toxicidad , Fosfatos , Transcriptoma

RESUMEN

Resource limitations often require risk assessors to extrapolate chronic toxicity from acute tests using assessment factors. Transcriptomic dose-response analysis following short-term exposures may provide a more reliable and biologically-based alternative for estimating chronic toxicity. Here, we demonstrate that transcriptomic dose-response analysis in fish following short-term exposure to endocrine disrupting chemicals (EDCs) provides estimates of chronic toxicity that may be used as protective points-of-departure (POD) for risk assessment. The benchmark dose (BMD) method was used on publicly available datasets (n = 5) to determine transcriptomic PODs in fish exposed to three EDCs (bisphenol A, ethinylestradiol, and diethylstilbestrol). To test for potential bias related to data processing, our analysis compared the effect of different normalization, filtering, and BMD-grouping methods on the transcriptomic PODs. The resulting PODs were then compared to the empirically-derived chronic LOEC of each substance. Normalization and filtering methods had limited impact on the final PODs. However, we found that PODs derived from ontology- or pathway-based gene grouping methods were highly variable, whereas PODs from grouping methods that focused on the most responsive genes were more stable and provided POD estimates that were most similar to the chronic LOEC. Overall, 72% of transcriptomic PODs were within 1 order of magnitude of the chronic LOEC, regardless of data analysis method. When our recommended analysis approach was applied, the concordance improved to 100%. These results suggest that toxicogenomic dose-response analysis has the potential to be a protective decision-support tool for compounds with chronic toxicity, such as EDCs.

Asunto(s)

Disruptores Endocrinos/efectos adversos , Estrógenos/efectos adversos , Peces/metabolismo , Transcriptoma/efectos de los fármacos , Animales , Benchmarking/métodos , Compuestos de Bencidrilo/efectos adversos , Dietilestilbestrol/efectos adversos , Relación Dosis-Respuesta a Droga , Perfilación de la Expresión Génica/métodos , Fenoles/efectos adversos , Medición de Riesgo

RESUMEN

As the number of chemicals developed and used by industry increases, the inherent limitations of traditional toxicology approaches become an unavoidable issue. To help meet the demand for toxicity evaluation, new methods, such as high-throughput toxicity screening, are currently being developed to permit rapid determination of toxic, molecular, and/or biochemical effects of a wide range of chemicals. In the present study, we demonstrate the utility of an avian in vitro toxicogenomics screening approach to determine the cytotoxic and transcriptomic effects of 10 organic flame retardants (OFRs) currently of international priority for ecological risk evaluation to prioritize and inform future toxicological studies. Hepatocytes from 2 avian species, chicken and double-crested cormorant, were prepared and exposed for 24 h to various concentrations (0-300 µM) of the following 10 OFRs: Chemical Abstracts Service registration numbers 29761-21-5, 56803-37-3 (p-tert-butylphenyl diphenyl phosphate [BPDP]), 65652-41-7, 68937-41-7 (phenol, isopropylated, phosphate [3:1] [IPPP]), 95906-11-9, 19186-97-1, 26040-51-7, 35948-25-5, 21850-44-2, and 25713-60-4. Cell viability, the 7-ethoxyresorufin-O-deethylase assay, and transcriptomic analysis using species-specific ToxChip polymerase chain reaction arrays were performed to evaluate the in vitro effect of these OFRs. Of the 10 OFRs assessed, BPDP and IPPP elicited the strongest cytotoxic and transcriptomic responses in both chicken and double-crested cormorant hepatocytes and are therefore recommended as priority candidates for further wildlife toxicological investigations. Environ Toxicol Chem 2018;37:3134-3144. © 2018 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

Asunto(s)

Pollos/metabolismo , Retardadores de Llama/toxicidad , Hepatocitos/metabolismo , Pruebas de Toxicidad , Toxicogenética , Animales , Hidrocarburo de Aril Hidroxilasas/metabolismo , Proteínas Aviares/metabolismo , Canadá , Supervivencia Celular/efectos de los fármacos , Embrión de Pollo , Citocromo P-450 CYP1A1/metabolismo , Perfilación de la Expresión Génica , Hepatocitos/efectos de los fármacos , Organofosfatos/toxicidad , Estrés Oxidativo/efectos de los fármacos , Fenotipo , Receptores de Hidrocarburo de Aril/metabolismo , Hormonas Tiroideas/metabolismo , Transcriptoma/genética , Xenobióticos/metabolismo

RESUMEN

Human health risk assessment (HHRA) must be adapted to the challenges of the 21st century, and the use of toxicogenomics data in HHRA is among the changes that regulatory agencies worldwide are trying to implement. However, the use of toxicogenomics data in HHRA is still limited. The purpose of this study was to explore the availability, quality, and relevance to HHRA of toxicogenomics publications as potential barriers to their use in HHRA. We conducted a scoping review of available toxicogenomics literature, using trihalomethanes as a case study. Four bibliographic databases (including the Comparative Toxicogenomics Database) were assessed. An evaluation table was developed to characterize quality and relevance of studies included on the basis of criteria proposed in the literature. Studies were selected and analyzed by 2 independent reviewers. Only 9 studies, published between 1997 and 2015, were included in the analysis. Based on the selected criteria, critical methodological details were often missing; in fact, only 3 out of 9 studies were considered to be of adequate quality for HHRA. No studies met >3 (out of 7) criteria of relevance to HHRA (eg, adequate number of doses and sample size). This first scoping review of toxicogenomics publications on trihalomethanes shows that low availability, quality, and relevance to HHRA of toxicogenomics publications presents potential barriers to their use in HHRA. Improved reporting of methodological details and study design is needed in the future so that toxicogenomics studies can be appropriately assessed regarding their quality and value for HHRA.

Asunto(s)

Expresión Génica/efectos de los fármacos , Medición de Riesgo , Toxicogenética , Trihalometanos/toxicidad , Acceso a la Información , Bases de Datos Bibliográficas , Bases de Datos Genéticas , Humanos , Medición de Riesgo/métodos , Medición de Riesgo/normas , Toxicogenética/métodos , Toxicogenética/normas

RESUMEN

Alcohol consumption during pregnancy is still a cause of preventable birth defects and developmental disabilities. However, little is known about the impact of ethanol on preimplantation embryos and the molecular mechanisms involved. We aimed to determine the toxicogenomic impacts and the mechanisms involved in preimplantation embryonic survival following 0.2% ethanol exposure in porcine embryos. Gene expression changes were measured with a porcine embryo specific microarray and confirmed by RT-qPCR. When compared with control, ethanol exposure led to a 43% decrease in blastocyst rate and activated pathways associated with oxidative stress and nervous system damage, such as TP53 and TGF. Moreover, we observed a mitochondrial dysfunction in the exposed embryos as revealed by the decrease in Mitotracker Red fluorescence intensity (25 and 41% in 4-cell embryos and blastocysts, respectively) and a modification in the expression of GABRB3, APP, CLU, and MIOX genes. We therefore present evidence of neuronal-like adverse effects on undifferentiated cells suggesting that fetal alcohol spectrum disorder could have its origin as early as in the first week postfertilization.

Asunto(s)

Blastocisto/efectos de los fármacos , Ectogénesis/efectos de los fármacos , Etanol/toxicidad , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Mitocondrias/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Solventes/toxicidad , Mataderos , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animales , Blastocisto/citología , Blastocisto/metabolismo , Blastocisto/patología , Clusterina/genética , Clusterina/metabolismo , Pérdida del Embrión/inducido químicamente , Pérdida del Embrión/metabolismo , Pérdida del Embrión/patología , Femenino , Fertilización In Vitro , Trastornos del Espectro Alcohólico Fetal/metabolismo , Trastornos del Espectro Alcohólico Fetal/patología , Perfilación de la Expresión Génica , Inositol-Oxigenasa/genética , Inositol-Oxigenasa/metabolismo , Masculino , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Mitocondrias/metabolismo , Mitocondrias/patología , Mórula/citología , Mórula/efectos de los fármacos , Mórula/metabolismo , Mórula/patología , Receptores de GABA-A/genética , Receptores de GABA-A/metabolismo , Solventes/efectos adversos , Sus scrofa

RESUMEN

Bromodichloromethane (BDCM) is one of the trihalomethanes present in chlorinated water. Humans are thus daily exposed. Previous contradictory results failed to clearly establish the adverse effects of low concentrations of BDCM. By using the porcine preimplantation embryo as a sensitive model, we showed that exposure to low concentrations of BDCM (10 and 100ppb) during the first week of embryo development induced adverse effect on the blastocyst rate and alteration of the estradiol pathway. Our results also suggest that blastocysts exposed to BDCM present transcriptomic and epigenomic adaptive modifications compatible with the cardiac anomalies observed by previous studies of newborns exposed to BDCM during gestation. Thus, phenotypic observations and toxicogenomic adaptations of embryo to low concentration of BDCM provide insights for BDCM risk assessment. Indeed, our results support the use of sensitive toxicogenomic models using environmentally relevant concentrations to which humans are exposed in order to conduct the risk assessment.

Asunto(s)

Desarrollo Embrionario/efectos de los fármacos , Transcriptoma/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Animales , Blastocisto/efectos de los fármacos , Ciudades , Embrión de Mamíferos , Desarrollo Embrionario/genética , Estradiol/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Quebec , Medición de Riesgo , Porcinos , Trihalometanos/toxicidad

RESUMEN

Fertilization in bovines causes profound changes in the epigenetic profile that affect both DNA methylation patterns and posttranslational histone modifications. These dynamic changes have a great potential for activating pluripotency genes and unfolding certain chromatin regions to recruit different transcription factors. Surprisingly, while the fundamental function of epigenetic remodeling is well understood, the bases of the process are still unknown. Recent developments in epigenetics suggest a multistep demethylation process that would imply the prior modification of the methylated cytosine or methyl group, followed by a DNA repair mechanism implicating enzymes such as activation-induced cytidine deaminase (AICDA) and ten-eleven translocation (TET) dioxygenase. Their functions seem to differ from one species to the other, and they are not yet well characterized in large mammals. Histones have, for their part, many associated and specific lysine demethylases (KDM). Their expression profile in large mammals is not well characterized. We have been interested in characterizing the spatiotemporal expression profile for each of the genes studied to increase our understanding of the molecular interactions following fertilization in early bovine embryo stages. Bovine oocytes and embryos at various preimplantation stages were collected following in vitro fertilization protocol. Total RNA for AICDA, TET1, TET2, TET3, KDM3A, KDM4A, KDM4C, and KDM5B was extracted, reverse transcribed into cDNA, and amplified by real-time PCR. Other embryo pools were collected, and protein localization of the genes studied was characterized. TET3 dioxygenase was present in the very first embryo stages, in contrast to TET1 and AICDA. Histone demethylases KDM3A, KDM4A, and KDM4C were expressed before and after embryonic genome activation, whereas KDM5B was mainly expressed during the blastocyst period. DNA demethylation following fertilization in bovines is not accomplished by AICDA but most probably by TET3. Histone demethylation is carried out by, among others, KDM3A, KDM4A, and KDM4C, which could act in sequence to demethylate histones prior to DNA demethylation of the female chromosomes.

Asunto(s)

Blastocisto/enzimología , Metilación de ADN , Proteínas de Unión al ADN/metabolismo , Regulación del Desarrollo de la Expresión Génica/fisiología , Regulación Enzimológica de la Expresión Génica/fisiología , Histona Demetilasas con Dominio de Jumonji/metabolismo , Animales , Blastocisto/citología , Bovinos , Proteínas de Unión al ADN/genética , Femenino , Histonas/genética , Histonas/metabolismo , Histona Demetilasas con Dominio de Jumonji/genética