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Cultured chicken embryonic hepatocytes (CEH) exposed to linear PFOS (L-PFOS), technical-grade PFOS (T-PFOS), or linear PFUdA

ABSTRACT: This series was used for two studies: Study 1: Recently it was discovered that the perfluorooctane sulfonate (PFOS) detected in wildlife, such as fish-eating birds, had a greater proportion of linear PFOS (L-PFOS) than the manufactured technical product (T-PFOS), which contains linear and branched isomers. This suggests toxicological studies based on T-PFOS data may inaccurately assess exposure risk to wildlife. To determine if PFOS effects were influenced by isomer content we compared the transcriptional profiles of cultured chicken embryonic hepatocytes (CEH) exposed to either L-PFOS or T-PFOS using Agilent microarrays. At equal concentrations (10 ?M), T-PFOS altered the expression of more transcripts (340, >1.5 fold change, p<0.05) compared to L-PFOS (130 transcripts). Higher concentrations of L-PFOS (40 ?M) were also less transcriptionally disruptive (217 transcripts) than T-PFOS at 10 ?M. Functional analysis showed that L-PFOS and T-PFOS affected genes involved in lipid metabolism, hepatic system development and cellular growth and proliferation. Pathway and interactome analysis suggested that genes may be affected through the RXR receptor, oxidative stress response, TP53 signaling, MYC signaling, Wnt/?-catenin signaling and PPAR? and SREBP receptors. In all functional categories and pathways examined, the response elicited by T-PFOS was greater than L-PFOS. These data show that T-PFOS elicits a greater transcriptional response in CEH than L-PFOS alone and demonstrates the importance of considering the isomer-specific toxicological properties of PFOS when assessing exposure risk. Study 2: In many bird populations, concentrations of perfluoroundanoic acid (PFUdA) are second only to perfluorooctane sulfonate (PFOS) among perfluoroalkyl compounds. Here, we used microarrays to characterize the transcriptional response of cultured chicken embryonic hepatocytes (CEH) to PFUdA and compared it to the response induced by PFOS. At non-cytotoxic doses, PFUdA (1 or 10 ?M) disrupted the expression of more genes (854) than PFOS (447, at 10 or 40 ?M) in CEH. Using functional, pathway and interactome analysis we identified several potentially important modes-of-action (MoAs) for PFUdA and some associated key events, including the suppression of the acute-phase response (APR) through peroxisome proliferator activated receptor activation. We then measured the expression of five APR genes, fibrinogen alpha (fga), fibrinogen gamma (fgg), thrombin (f2), plasminogen (plg), and protein C (proC), in the liver of chicken embryos exposed in ovo to PFUdA. The expression of fga, f2, and proC were down-regulated in embryo livers (100 or 1000 ng/g, p<0.1) as predicted from microarray analysis, whereas fibrinogen gamma (fgg) was up-regulated and plg was not significantly affected. Our results demonstrate PFUdA is more transcriptionally disruptive than PFOS in CEH. Additionally, we identified APR suppression as a potentially important and environmentally relevant MoA. These findings suggest in ovo exposure of birds to PFUdA could lead to post-hatch developmental deficiencies, such as impaired immune response.

ORGANISM(S): Gallus gallus

PROVIDER: GSE33291 | GEO | 2011/10/29

SECONDARY ACCESSION(S): PRJNA149281

REPOSITORIES: GEO

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Project description:Perfluorooctane sulfonate (PFOS) has been manufactured for over 50 years in increasing quantities and has been used for several industrial and commercial aims. Due to the persistence and the bioaccumulation of this pollutant, it can be found worldwide in wildlife and humans. Biochemical effects of PFOS exposure are mainly studied in mammalian model species and information about effects on fish species remain largely scarce. This lack of toxicity data points out that there is an urgent need for the mechanistic molecular understanding of the mode of action of this pollutant. In the present study, common carp (Cyprinus carpio) was exposed through water for 14 days at concentrations of 0.1; 0.5 and 1 mg/l PFOS. Liver was selected as target tissue. Custom microarrays were constructed from cDNA libraries obtained with Suppression Subtractive Hybridization-Polymerase chain reaction (SSH-PCR) experiments. Microarray data revealed that the expression of several genes in the liver was influenced by PFOS exposure and real-time PCR was used to confirm these gene expression changes. The affected genes were mainly involved in energy metabolism, reproduction and stress response. Furthermore, the relative condition factor and the hepatosomatic index of the exposed fish were significantly lower after 14 days of exposure as well as the available glycogen reserves. At all levels of biological organization, indications of a trade-off between the metabolic cost of toxicant exposure on one hand and processes vital to the survival of the organism on the other hand were seen. Our results support the prediction that increases in energy expenditure negatively affects processes vital to the survival of an organism, such as growth. Keywords: PFOS, common carp, microarray, condition factor, energy reserves, metabolic cost There were 3 biological replicates for each exposure concentration. For each biological replicate control versus exposed hybridizations were carried out. The mean of the biological replicates was calculated for the differentially expressed genes.

Project description:Perfluorooctane sulfonate (PFOS) is a perfluoroalkyl acid (PFAA) and a persistent environmental contaminant found in the tissues of humans and wildlife. Although blood levels of PFOS have begun to decline, health concerns remain because of the long half-life of PFOS in humans. Like other PFAAs, such as perfluorooctanoic acid (PFOA), PFOS is an activator of peroxisome proliferator-activated receptor-alpha (PPARα) and exhibits hepatocarcinogenic potential in rodents. PFOS is also a developmental toxicant in rodents where, unlike PFOA, it’s mode of action is independent of PPARα. Wild-type (WT) and PPARα-null (Null) mice were dosed with 0, 3, or 10 mg/kg/day PFOS for 7 days. Animals were euthanized, livers weighed, and liver samples collected for histology and preparation of total RNA. Gene profiling was conducted using Affymetrix 430_2 microarrays. In WT mice, PFOS induced changes that were characteristic of PPARα transactivation including regulation of genes associated with lipid metabolism, peroxisome biogenesis, proteasome activation, and inflammation. PPARα-independent changes were indicated in both WT and Null mice by altered expression of genes related to lipid metabolism, inflammation, and xenobiotic metabolism. Such results are similar to prior studies done with PFOA and are consistent with modest activation of the constitutive androstane receptor (CAR) and possibly PPARγ and/or PPARβ/δ. Unique treatment-related effects were also found in Null mice including altered expression of genes associated with ribosome biogenesis, oxidative phosphorylation and cholesterol biosynthesis. Of interest was up-regulation of Cyp7a1, a gene which is under the control of various transcription regulators. Hence, in addition to its ability to modestly activate PPARα, PFOS induces a variety of “off-target” effects as well. PPARalpha-null and wild-type male mice at 6-9 months of age were dosed by gavage for 7 consecutive days with either 0, 3, or 10 mg/kg PFOS (potassium salt) in 0.5% Tween 20. Five biological replicates consisting of individual animals were included in each dosage group. Data were compared to results previously published by our group for PFOA and Wy-14,643, a commonly used agonist of PPARalpha (Rosen et al., Toxicol Pathol. 36:592-607, 2008; GSE9796)

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Cultured chicken embryonic hepatocytes (CEH) exposed to linear PFOS (L-PFOS), technical-grade PFOS (T-PFOS), or linear PFUdA

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