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Effects of 17α-ethinylestradiol (EE2) on molecular signaling cascades in mummichog (Fundulus heteroclitus)

ABSTRACT: The objective of this study was to gain mechanistic insight into how mummichog are able to produce eggs during exposures to high levels of EE2. Mummichog were exposed to 0, 50 or 250 ng/L of EE2 for 14 d. A mummichog microarray was used to identify genomic responses associated with high EE2 exposure, and effects of EE2 on target genes involved in lipid mobilization and transport and steroidogenesis, two important (EE2 regulated) pathways involved in egg production, were measured using real-time PCR. In addition, changes at higher level biological endpoints such as plasma steroid production and gonad morphology were measured to examine downstream responses to EE2. There were no differences in gonadosomatic index, liversomatic index, gonad development, or plasma estradiol levels after exposure to EE2, although testosterone decreased with EE2 exposures. Similar to other species, mummichog showed alterations to plasma steroid levels, and similar processes at the molecular level were identified as being altered by EE2, including cell processes associated with lipids. However, unlike other species, mummichog showed no differences in GSI or ovarian development. Fatty acids were affected at both the transcript and translation level, which suggests they are a major target of estrogens. Lipids are important for both growth and reproduction, and provide oocytes with nutrients. Interestingly, mummichog showed no effect on apolipoprotein expression, which is important in lipid transport. Therefore, it is hypothesized that mummichog are normally able to transport lipids for energy and nutrients to the ovary, while this is affected in other species. Novel gene regulatory networks for protein modification targets were also constructed to learn more about the potential roles of estrogens in the teleost liver. Although post-translational modifications (PTMs) are important regulatory mechanisms, the roles of PTMs in protein regulation in fish and the susceptibility of PTMs to aquatic pollutants are largely unexplored and may offer novel insight into mechanisms of endocrine disruption.

ORGANISM(S): Fundulus heteroclitus

PROVIDER: GSE48945 | GEO | 2013/07/18

SECONDARY ACCESSION(S): PRJNA212375

REPOSITORIES: GEO

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Project description:The objective of this study was to gain mechanistic insight into how mummichog are able to produce eggs during exposures to high levels of EE2. Mummichog were exposed to 0, 50 or 250 ng/L of EE2 for 14 d. A mummichog microarray was used to identify genomic responses associated with high EE2 exposure, and effects of EE2 on target genes involved in lipid mobilization and transport and steroidogenesis, two important (EE2 regulated) pathways involved in egg production, were measured using real-time PCR. In addition, changes at higher level biological endpoints such as plasma steroid production and gonad morphology were measured to examine downstream responses to EE2. There were no differences in gonadosomatic index, liversomatic index, gonad development, or plasma estradiol levels after exposure to EE2, although testosterone decreased with EE2 exposures. Similar to other species, mummichog showed alterations to plasma steroid levels, and similar processes at the molecular level were identified as being altered by EE2, including cell processes associated with lipids. However, unlike other species, mummichog showed no differences in GSI or ovarian development. Fatty acids were affected at both the transcript and translation level, which suggests they are a major target of estrogens. Lipids are important for both growth and reproduction, and provide oocytes with nutrients. Interestingly, mummichog showed no effect on apolipoprotein expression, which is important in lipid transport. Therefore, it is hypothesized that mummichog are normally able to transport lipids for energy and nutrients to the ovary, while this is affected in other species. Novel gene regulatory networks for protein modification targets were also constructed to learn more about the potential roles of estrogens in the teleost liver. Although post-translational modifications (PTMs) are important regulatory mechanisms, the roles of PTMs in protein regulation in fish and the susceptibility of PTMs to aquatic pollutants are largely unexplored and may offer novel insight into mechanisms of endocrine disruption. Mummichog were exposed to 0, 50, and 250 ng/L EE2 for 14 days. Microarray analysis was performed with five biological replicated (5 control, 5 EE2 50 ng/L, 5 EE2 250 ng/L). Female liver tissue was used for the analysis.

Project description:17alpha-ethinylestradiol (EE2) is one of the most potent estrogens that have the ability to interfere with the endocrine system of fish. The objective was to investigate the effects and mechanisms of action caused by 60 days of dietary exposure to 0.2 mg EE2/kg and 0.07 mg EE2/kg feed in female largemouth bass (LMB) during the reproductive season. Microarrays and pathway analyses were performed on hepatic tissues to identify genes and biological processes altered in female LMB by EE2 exposure. The hypothesis was that the two concentrations of EE2 would produce dose-response changes in sensitive genes. Body and ovary weights were measured and blood was collected for measurement of plasma steroid hormones (17beta-estradiol (E2), testosterone (T)) and vitellogenin (VTG) using ELISA. The 0.2 mg EE2/kg feed exposure reduced the gonadosomatic index (GSI) by 75%, and plasma levels of E2 and T were reduced by over 90%. Plasma VTG was increased by approximately 100% (from 4 to 8mg/ml) by the 0.2 mg/kg treatment. T levels, from the 0.07 mg EE2/kg feed, reduced GSI by approximately 30% and circulating E2 and T by ~80% but did not affect VTG concentrations. We found 1,594 and 1,165 genes were significantly affected (p<0.05) by the 0.07 mg EE2/kg feed and 0.2 mg EE2/kg feed, respectively. Gene ontology (GO) analysis revealed that there were different biological processes regulated by the two concentrations of EE2. Pathway analysis showed that the 0.07 mg EE2/kg feed exposure caused differential regulation of genes associated with fatty acid biosynthesis and glycolysis, indicating some metabolic effects. In contrast, the 0.2 mg EE2/kg feed exposure altered transcription of genes involved in immune response and apoptosis, suggesting a toxic response at this concentration. These results suggest that the two concentrations demonstrated distinct physiological responses, with the higher concentration inducing complete endocrine disruption in LMB. These findings demonstrate the usefulness of microarrays to identify possible biomarkers and modes of toxic action to dietary exposure in LMB. Two concentrations of EE2 would produce dose-response changes in sensitive genes. Female LMB were fed 5 days per week for 60 days with floating pellets that contained 0.07 or 0.2 mg/kg of EE2.

Project description:Genomic, proteomic, and metabolomic technologies continue to receive increasing interest from environmental toxicologists. This interest is due to the great potential of these technologies to identify detailed modes of action and to provide assistance in the evaluation of a contaminant?s risk to aquatic organisms. Our experimental model is the zebrafish (Danio rerio) exposed to reference endocrine disrupting compounds in order to investigate compound-induced changes in gene transcript profiles. Adult, female zebrafish were exposed to 0, 15, 40, and 100 ng/L of 17 alpha-ethynylestradiol (EE2) and concentration and time-dependent changes in hepatic gene expression were examined using Affymetrix GeneChip® Zebrafish Genome Microarrays. At 24, 48, and 168 hours, fish were sacrificed and liver mRNA was extracted for gene expression analysis (24 and 168 hours only). In an effort to link gene expression changes to effects on higher levels of biological organization, body and ovary weights were measured and blood was collected for measurement of plasma steroid hormones (17 beta-estradiol (E2), testosterone (T)) and vitellogenin (VTG) using ELISA. EE2 exposure significantly affected GSI, E2, T, VTG and gene expression. We observed 1575 genes that were significantly affected (up- or down-regulated by at least 1.5-fold (p ? 0.001) in a concentration-dependent manner by EE2 exposure at either 24 or 168 hours. EE2 exposure altered transcription of genes involved in steroid hormone homeostasis, cholesterol homeostasis, retinoic acid metabolism, and cell growth and proliferation. Plasma VTG was significantly increased at 24, 48, and 168 hours (p<0.05) at 40 and 100 ng/L and at 15 ng/L at 168 hours. E2 and T were significantly reduced following EE2 exposure at 48 and 168 hours. GSI was decreased in a dose-dependent manner at 168 hours. In this study, we identified genes involved in a variety of biological functions that have the potential to be used as markers of exposure to estrogenic substances. Future work will evaluate the use of these genes in zebrafish exposed to weak estrogens to determine if these genes are indicative of exposure to estrogens with varying potencies.

Project description:Environmental estrogens are ubiquitous in aquatic systems worldwide. In wild fish inhabiting wastewater effluent with estrogenic components, the presence of both oocytes and spermatogenic tissue in the testes has been documented. However, the molecular networks underlying the manifestation of the intersex condition are not completely characterized. In this study, we used an environmentally relevant concentration of 17alpha-ethinylestradiol (EE2), the active component of the birth control pill, to determine the response of the fathead minnow testis transcriptome after 96 hrs. The goal was to capture early molecular initiating events that may lead to the intersex condition following exposure to an estrogen that is present in wastewater effluent. There were no effects of EE2 on morphometric endpoints such as gonadosomatic index nor proportion of gametes within the testes. However, in vitro production of 11-ketotestosterone and testosterone in the testis was decreased relative to controls following EE2 exposure. Gene expression profiling revealed that there were 10 transcripts that were differentially expressed in the testis using a 8x60K fathead minnow microarray, the most dramatic change being that of coagulation factor XIII A chain (20-fold increase). Transcripts that included guanine nucleotide binding protein (Beta Polypeptide 2), peroxisome proliferator-activated receptor delta, and WNK lysine deficient protein kinase 1a, were down-regulated by EE2. Subnetwork enrichment analysis revealed that EE2 suppressed transcriptional networks associated with reproduction such as steroid metabolism, hormone biosynthesis, and sperm mobility. Most interesting was that gene networks associated with doublesex and mab-3 related transcription factor 1 (dmrt1) were suppressed in the adult testis, despite the fact that dnmt1 itself was not differentially expressed from controls. Moreover cell processes involving forkhead box L2 (foxL2) such as ovarian follicle development and granulosa cell development were increased in expression in the testis. Cell processes that included glucose homeostasis, response to heavy metal, amino acid catabolism, and the cyclooxygenase pathway were decreased with EE2 while lymphocyte chemotaxis, intermediate filament polymerization, glucocorticoid metabolism, carbohydrate utilization, and anterior/posterior axis specification were increased, shedding light on the transcriptional responses that may be perturbed prior to gonadal remodelling following exposure to estrogenic contaminants. These data demonstrate that low concentrations of EE2 rapidly suppresses male hormone secretion, suppresses gene networks related to male sex differentiation, and induces transcriptional networks related to female sexual differentiation in the adult testis. These responses are hypothesized to be the molecular initiating events that occur prior to the development of the intersex phenotype after prolonged exposures to estrogens.

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Effects of 17α-ethinylestradiol (EE2) on molecular signaling cascades in mummichog (Fundulus heteroclitus)

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