Unknown,Transcriptomics,Genomics,Proteomics

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Hepatic miRNA profiles and thyroid hormone homeostasis in rats exposed to dietary potassium perfluorooctanesulfonate (PFOS) [miRNA]

ABSTRACT: Perfluorooctanesulfonate (PFOS) has been widely used in a variety of industrial and commercial applications as a surfactant and stain repellent. PFOS causes liver damage (including liver tumors) in experimental animals, primarily via interaction with PPARa and CAR/PXR. We investigated the involvement of microRNAs (miRNAs) in PFOS-induced hepatotoxicity, and mechanisms involved in abnormal TH homeostasis, in the livers of adult male rats exposed in feed to 50 mg PFOS/kg diet for 28 days. PFOS-treated rats exhibited expected histopathological and clinical chemistry changes. Global gene expression changes were consistent with the involvement of PPARα and CAR/PXR in PFOS-induced effects. Thirty-eight miRNAs were significantly altered. Three members of the miR-200 family were the most increased, while miR-122 and miR-21 were the most decreased, in PFOS-treated relative to control rats. Expression of the miR-23b/27b/24 cluster also decreased in PFOS-treated animals. Pathway analysis of miRNAs and associated gene expression changes demonstrated enrichment of transcripts involved in epithelial to mesenchymal transition (EMT), which is a primary process involved in tumor cell motility and cancer metastasis. Liver expression analysis revealed transcripts that may mediate PFOS effects on thyroid hormone (TH) homeostasis including: activation of the CAR/PXR pathway, phase II/III enzymes, and deiodinase. These changes are consistent with low serum TH due to enhanced metabolic clearance of TH. However, most TH hepatic target genes were not altered in a manner consistent with reduced TH signalling; suggesting that PFOS exposure did not induce functional hypothyroidism. Collectively, PFOS-induced miRNA perturbations were strongly associated with EMT suggesting an important role for miRNAs in PFOS-induced hepatotoxicity. The work also provides novel insights into the effects of PFOS on TH homeostasis. Total RNAs from liver samples (4 animals from each group) were labelled using the miRNA Complete Labelling and Hybridization kit (Agilent Technologies). Labelled RNA was hybridized on 8 X 15K Agilent rat miRNA microarray slides. Arrays were scanned using an Agilent G2505B scanner (5 μm resolution). Agilent Feature Extraction (version 10.7.3.1) was used to acquire the fluorescence intensity of each probe. The quality of the microarray data was evaluated using Agilent Feature Extraction quality control metrics. Data were normalized in R using cyclic-lowess (Bolstad et al., 2003). Ratio-intensity plots, boxplots and cluster analyses were used to identify potential outliers. One control sample failed the quality control tests and was eliminated for subsequent analyses. Statistically significantly altered miRNAs were identified using the methods described above for gene expression.

ORGANISM(S): Rattus norvegicus

SUBMITTER: hongyan dong

PROVIDER: E-GEOD-69521 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Perfluorooctanesulfonate (PFOS) has been widely used in a variety of industrial and commercial applications as a surfactant and stain repellent. PFOS causes liver damage (including liver tumors) in experimental animals, primarily via interaction with PPARa and CAR/PXR. We investigated the involvement of microRNAs (miRNAs) in PFOS-induced hepatotoxicity, and mechanisms involved in abnormal TH homeostasis, in the livers of adult male rats exposed in feed to 50 mg PFOS/kg diet for 28 days. PFOS-treated rats exhibited expected histopathological and clinical chemistry changes. Global gene expression changes were consistent with the involvement of PPARα and CAR/PXR in PFOS-induced effects. Thirty-eight miRNAs were significantly altered. Three members of the miR-200 family were the most increased, while miR-122 and miR-21 were the most decreased, in PFOS-treated relative to control rats. Expression of the miR-23b/27b/24 cluster also decreased in PFOS-treated animals. Pathway analysis of miRNAs and associated gene expression changes demonstrated enrichment of transcripts involved in epithelial to mesenchymal transition (EMT), which is a primary process involved in tumor cell motility and cancer metastasis. Liver expression analysis revealed transcripts that may mediate PFOS effects on thyroid hormone (TH) homeostasis including: activation of the CAR/PXR pathway, phase II/III enzymes, and deiodinase. These changes are consistent with low serum TH due to enhanced metabolic clearance of TH. However, most TH hepatic target genes were not altered in a manner consistent with reduced TH signalling; suggesting that PFOS exposure did not induce functional hypothyroidism. Collectively, PFOS-induced miRNA perturbations were strongly associated with EMT suggesting an important role for miRNAs in PFOS-induced hepatotoxicity. The work also provides novel insights into the effects of PFOS on TH homeostasis. Four RNA samples from control and four from PFOS treated rats were labelled with Cyanine 5-CTP (Cy5) using Low Input Quick Amp Labelling kits (Agilent Technologies Inc.) following the manufacturer’s instruction. Universal rat reference total RNA (Agilent Technologies Inc.) was labelled with Cyanine 3-CTP (Cy3). Cy5-sample cRNA and Cy3-reference cRNA were hybridized to Agilent G4853A SurePrint G3 Rat GE 8 X 60K microarrays (Agilent Technologies Inc.) at 65°C overnight with Agilent hybridization solution. Slides were washed and scanned on an Agilent G2505B microarray scanner at 5 μm resolution, and the data were acquired with Agilent Feature Extraction software version 10.7.3.1. Microarray data quality was confirmed using Agilent Feature Extraction quality control metrics and in-house metrics (boxplots, cluster analyses, and MA plots to identify poor quality outlier arrays). All samples passed the quality control tests and were used for subsequent analyses.

Project description:The constitutive androstane receptor (CAR) and the pregnane X receptor (PXR) are closely related nuclear receptors involved in drug metabolism and play important roles in the mechanism of phenobarbital (PB)-induced rodent nongenotoxic hepatocarcino- genesis. Here, we have used a humanized CAR/PXR mouse model to examine potential species differences in receptor-dependent mechanisms underlying liver tissue molecular responses to PB. Early and late transcriptomic responses to sustained PB exposure were investigated in liver tissue from double knock-out CAR and PXR (CARKO -PXRKO ), double humanized CAR and PXR (CARh - PXRh), and wild-type C57BL/6 mice. Wild-type and CARh-PXRh mouse livers exhibited temporally and quantitatively similar tran- scriptional responses during 91 days of PB exposure including the sustained induction of the xenobiotic response gene Cyp2b10, the Wnt signaling inhibitor Wisp1, and noncoding RNA biomarkers from the Dlk1-Dio3 locus. Transient induction of DNA replication (Hells, Mcm6, and Esco2) and mitotic genes (Ccnb2, Cdc20, and Cdk1) and the proliferation-related nuclear antigen Mki67 were ob- served with peak expression occurring between 1 and 7 days PB ex- posure. All these transcriptional responses were absent in CARKO- PXRKO mouse livers and largely reversible in wild-type and CARh - PXRh mouse livers following 91 days of PB exposure and a subse- quent 4-week recovery period. Furthermore, PB-mediated upregu- lation of the noncoding RNA Meg3, which has recently been associ- ated with cellular pluripotency, exhibited a similar dose response and perivenous hepatocyte-specific localization in both wild-type and CARh-PXRh mice. Thus, mouse livers coexpressing human CAR and PXR support both the xenobiotic metabolizing and the proliferative transcriptional responses following exposure to PB. 13-week oral (drinking water) investigative phenobarbital study in male C57BL/6 wild type, CAR/PXR knockout and humanized CAR/PXR mice with a 4 week recovery period

Project description:MicroRNAs (miRNAs) are extensively in diverse biological processes. However, very little is known about the role of miRNAs in mediating thyroid hormones (TH) action. Maintenance of appropriate TH levels is known to be critically important for development, differentiation and maintenance of metabolic balance in mammals. We induced transient hypothyroidism in juvenile mice by short term exposure to methimazole and perchlorate from post natal day (PND) 12 to 15. The expression of miRNAs in the liver was analyzed with the Taqman Low Density Array (containing up to 600 rodent microRNAs). We found the expression of 40 miRNAs was significantly altered in the liver of hypothyroid mice compared to euthyroid controls. Among the miRNAs, miR-1/206/133 exhibited a massive increase in expression (50 – 500 folds). To further explore TH effect on miR-1/206/133, we treated mouse hepatocyte AML 12 cells with 10 nm T3 for 1 hr and 24 hrs. TH treatment induced the down-regulation of miR-1/206/133b at both time points, reaching statistical significance at 24 hrs. To identify the genes targeted by these miRNAs, DNA microarrays were used to examine hepatic mRNA levels in the hypothyroid mouse model alongside controls. We found transcripts from 92 known genes were significantly altered in hypothyroid mice. Web-based target predication softwares (TargetScan and Microcosm) identified 14 of these transcripts as targets of miR-1/106/133. The vast majority of these mRNA targets were significantly down-regulated in hypothyroid mice, corresponding well with the up-regulation of miR-1/206/133 in hypothyroid mouse liver. The results suggest that TH regulation of these genes may occur secondarily via the reduced repression consequent to TH-induced down-regulation of miR-1/206/133. These studies provide novel insight into the role of miRNAs in mediating TH regulation of gene expression. Agilent two-color microarray were used to perform gene expression profile in euthyroid and hypothyroid male mouse livers, 5 biological replicates. TLDA (Taqman microRNA Array) was used to explore the miRNA expression profile in euthyroid and hypothyroid male mouse livers, 4 biological replicates.

Project description:Liver tumors in rodents are frequently induced by non-genotoxic carcinogens. These hepatocarcinogens generally activate hepatic nuclear receptors (e.g., CAR and PXR), resulting in a cascade of signals causing modifications in the expression of genes responsible for several processes involved in carcinogenesis. Evaluation of the carcinogenic potential of chemicals is a regulatory requirement but is time-consuming and expensive. Consequently, several short-term in vivo and in vitro approaches, using molecular tools, have been proposed as predictive models for non-genotoxic hepatocarcinogens. The objective of our study was to discriminate between chemicals that are either non-genotoxic hepatocarcinogens or merely hepatotoxicants and also between CAR and PXR modulators on the basis of their gene expression profiles. Thus, we treated rats for seven days with the hepatoxicants, diclofenac and diazepam, or with several CAR and PXR modulators, which were mainly hepatocarcinogens. Different hepatic gene expression profiles were obtained not only between the hepatotoxicants and the non-genotoxic hepatocarcinogens but also between the CAR activators phenobarbital, phenytoin and 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene which were grouped together, and the two PXR activators pregnenolone 16Î±-carbonitrile and clotrimazole. Diethylstilbestrol had an expression profile that was quite distinct from the other PXR activators, suggesting that this compound is certainly not a classic PXR modulator. Moreover, some differences were observed between phenytoin (not considered as a hepatocarcinogen), and the other two CAR activators. Our data therefore indicate that discrimination is possible between hepatocarcinogens and hepatotoxicants, between CAR and PXR modulators and also between compounds within the same class of modulators using a short-term transcriptomic approach. CAR or PXR inducers were administered in suspension to rats (7 weeks old at start of treatment) by oral gavage at a daily dose for 7 consecutive days. Treatment-related changes in gene expression were determined in the liver using whole genome oligonucleotide microarrays.

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Hepatic miRNA profiles and thyroid hormone homeostasis in rats exposed to dietary potassium perfluorooctanesulfonate (PFOS) [miRNA]

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