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Systems biology of tributyltin-induced pathogenesis in thicklip grey mullets (Chelon labrosus)

ABSTRACT: Organotin compounds are highly persistent organic pollutants that bioaccumulate in marine biota, behaving as potent endocrine disruptors. Tributyltin (TBT) has been described as an environmental obesogen, as it contributes in mammals to lipid accumulation in a mechanism mediated by PPARγ and RXR. With the aim of studying the molecular mechanisms that elicit TBT-induced pathogenesis in fish, thicklip grey mullets Chelon labrosus were exposed to low (10 ng/L) and high (500 ng/L) TBT concentrations for 1, 7 and 21 days, and gene transcription and metabolome profiles were studied. With this purpose, the multitissue transcriptome of mullet was sequenced by 454 pyrosequencing obtaining 126 Mb of sequence information. Assembly and annotation allowed spotting 8330 gene signatures on an oligonucleotide microarray that was used to identify hepatic gene transcription profiles specific to each TBT exposure set-up. Functional pathway analysis revealed that early profiles were characterized by genes related to response to organic substances and to oxidative stress and glucose metabolic processes. After 21 days of exposure, enriched GO terms in both concentrations were related to lipid homeostasis with a significant regulation of steroid metabolic and cholesterol biosynthetic processes. Also, the androgen receptor signalling pathway was regulated while PPAR signalling appeared as the most significantly regulated KEGG pathway. Neutral lipid accumulation measured by Oil-Red-O histochemistry did not show any treatment-related effect but hepatic and plasma NMR and GC-MS metabolomic analysis revealed distinctive metabolites. Aqueous profiles were characterised by lactate, glucose and alanine while GC-MS revealed a whole set of discriminating polyunsaturated fatty acids. Thus, TBT pathogenesis involves alterations of lipid metabolism through a mechanism that could involve PPARγ-regulated processes confirming the obesogen hypothesis for TBT in fish.

ORGANISM(S): Chelon labrosus

PROVIDER: GSE36811 | GEO | 2016/07/31

SECONDARY ACCESSION(S): PRJNA156837

REPOSITORIES: GEO

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Project description:Organotin compounds are highly persistent organic pollutants that bioaccumulate in marine biota, behaving as potent endocrine disruptors. Tributyltin (TBT) has been described as an environmental obesogen, as it contributes in mammals to lipid accumulation in a mechanism mediated by PPARÎ³ and RXR. With the aim of studying the molecular mechanisms that elicit TBT-induced pathogenesis in fish, thicklip grey mullets Chelon labrosus were exposed to low (10 ng/L) and high (500 ng/L) TBT concentrations for 1, 7 and 21 days, and gene transcription and metabolome profiles were studied. With this purpose, the multitissue transcriptome of mullet was sequenced by 454 pyrosequencing obtaining 126 Mb of sequence information. Assembly and annotation allowed spotting 8330 gene signatures on an oligonucleotide microarray that was used to identify hepatic gene transcription profiles specific to each TBT exposure set-up. Functional pathway analysis revealed that early profiles were characterized by genes related to response to organic substances and to oxidative stress and glucose metabolic processes. After 21 days of exposure, enriched GO terms in both concentrations were related to lipid homeostasis with a significant regulation of steroid metabolic and cholesterol biosynthetic processes. Also, the androgen receptor signalling pathway was regulated while PPAR signalling appeared as the most significantly regulated KEGG pathway. Neutral lipid accumulation measured by Oil-Red-O histochemistry did not show any treatment-related effect but hepatic and plasma NMR and GC-MS metabolomic analysis revealed distinctive metabolites. Aqueous profiles were characterised by lactate, glucose and alanine while GC-MS revealed a whole set of discriminating polyunsaturated fatty acids. Thus, TBT pathogenesis involves alterations of lipid metabolism through a mechanism that could involve PPARÎ³-regulated processes confirming the obesogen hypothesis for TBT in fish. Thicklip grey mullets were exposed to tributyltin (TBT). 3 treatments: control, TBT low dose (10ng/L), TBT high dose (500ng/L); 3 sampling times: 1 day, 1 week, 3 weeks. 6 mullets were dissected in each sampling point and group.

Project description:Obesogenic compounds are chemicals that might have an influence on obesity development through in utero or chronic lifetime exposure. Tributyltin (TBT) is one of the most studied obesogenic compounds, inducing adipogenesis in vitro and increasing body fat after in utero exposure of mice. This study was designed to unravel the molecular mechanisms of TBT, using microarray analysis, and to evaluate the use of toxicogenomics for obesogen screening. The murine 3T3-L1 cell line was used to study TBT induced adipogenesis. Lipid staining as well as gene expression measurements of an adipocyte specific marker gene were performed to select relevant concentrations (10 nM, 50 nM) and time points (day1, day10) for microarray analysis. Additionally, solvent control and positive control (MDI) treated 3T3-L1 cells were included in the analysis. The microarray results were analysed using GO enrichment and Pathway analysis tools, which revealed enrichment of several GO terms involved in energy and fat metabolism after 10 days of TBT exposure. Pathway analysis unveiled PPAR signalling pathway as the sole pathway significantly enriched after 1 day and the most significantly enriched pathway after 10 days of exposure. By examination of effects on both cell physiological and gene expression level we provide a detailed overview of TBT induced obesogenic mechanisms. To our knowledge, this is the first study delivering an in depth mechanistic outline of the mode of action of TBT as an obesogen. Furthermore, our results show that combining omics with 3T3-L1 cells is promising for screening of potential obesogenic compounds. A separate v+2 A-optimal hybridization design was used for each time-point. Using this design each exposure condition is represented by three biological replicates, with each biological replicate analysed in technical duplicate while applying the dye swap principle to correct for dye bias. Two concentrations of TBT (10 nM, 50 nM), DMSO and MDI (positive control, adipogenic hormone cocktail) were the conditions tested, at two time-points (day 1 and day10).

Project description:The obesogen hypothesis states that exposure to environmental compounds early in life or throughout lifetime might have an influence on obesity development. In this paper a new approach for obesogen screening is proposed, namely the use of transcriptomics in the 3T3-L1 pre-adipocyte cell line. Based on the data from a previous study of our group using a lipid accumulation based adipocyte differentiation assay, several humanly relevant obesogenic compounds were selected: reference obesogens [Rosiglitazone (ROSI), Tributyltin (TBT)], test obesogens [Butylbenzyl phthalate (BBP), butylparaben (BP), propylparaben (PP), Bisphenol A (BPA)] and non-obesogens [Ethylene Brassylate (EB), Bis (2-ethylhexyl)phthalate (DEHP)]. In this paper, the high stability and reproducibility of the 3T3-L1 gene transcription patterns over different experiments and cell batches was shown. Obesogens and non-obesogen gene transcription profiles were clearly distinguished using hierarchical clustering. Furthermore, a gradual distinction corresponding to differences in induction of lipid accumulation could be made between test and reference obesogens based on transcription patterns, indicating the potential use of this strategy for classification of obesogens. Marker genes that are able to distinguish between non, test and reference obesogens were identified. Well known genes involved in adipocyte differentiation, as well as genes with unknown functions were selected, implying a potential adipocyte related function of the latter. Cell physiological lipid accumulation was well predicted based on transcription levels of the marker genes, indicating the biological relevance of omics data. In conclusion, this study shows the high relevance and reproducibility of this 3T3-L1 based in vitro toxicogenomics tool for classification of obesogens and biomarker discovery. The hybridization design was a reference design (reference sample was a mixture of equal aliquots from control and exposed samples), recommended for class discovery purposes (Knapen et al. 2009). The reference sample was labeled with Cy5, and the exposed samples with Cy3. Three biological replicates were measured for every condition.

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Systems biology of tributyltin-induced pathogenesis in thicklip grey mullets (Chelon labrosus)

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