Deletion of TIPARP increases sensitivity to dioxin-induced hepatosteatosis and lethality
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE61534 | GEO | 2015/05/14
SECONDARY ACCESSION(S): PRJNA261417
REPOSITORIES: GEO
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Project description:The aryl hydrocarbon receptor (AHR) is a ligand activated transcription factor that mediates the toxic effects of the environmental contaminant, dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD). Dioxin causes a diverse range of toxic responses, including hepatic damage and lethal wasting syndrome; however, the mechanisms of dioxin-induced toxicity are still unknown. Here we show that the loss of TCDD-inducible poly(ADP-ribose) polymerase (TIPARP; ARTD14), an ADP-ribosyltransferase and AHR repressor, increases sensitivity to dioxin-induced toxicity and lethality. Tiparp-/- mice treated with a single injection of 100 mg/kg dioxin display an accelerated lethal wasting syndrome with no Tiparp-/- mice surviving beyond day 5; all Tiparp+/+ mice survived up to 30 days post treatment. Tiparp-/- mice displayed dramatic increases in liver steatosis and hepatotoxicity. At the molecular level, TIPARP selectively ADP-ribosylates AHR, but not AHR nuclear translocator (ARNT) and the Tiparp-dependent repression of AHR is reversed by the ADP-ribosylase and macrodomain containing protein MacroD1, but not MacroD2. These results describe previously unidentified roles for Tiparp, MacroD1, and ADP-ribosylation in AHR signaling, dioxin toxicity and lethality. 12 samples were analyzed. There were 4 treatment groups and each treatment group was done in triplicate. Gene expression changes were determine in hepatic RNA isolated from (1) corn oil treated C57BL/6;129Sv mice; (2) 30 ug/kg/bw 2,3,7,8-Tetrachlorodibenzo-p-dioxin C57BL/6;129Sv mice; (3) corn oil treated C57BL/6;129Sv Tiparp-/- mice; and (4) 30 ug/kg/bw 2,3,7,8-Tetrachlorodibenzo-p-dioxin C57BL/6;129Sv Tiparp-/- mice
2015-05-14 | E-GEOD-61534 | biostudies-arrayexpress
Project description:We previously reported that TCDD-inducible poly-ADP-ribose polymerase (TIPARP), an aryl hydrocarbon receptor (AHR) target gene and mono-ADP-ribosyltransferase, acts as part of a negative feedback loop to repress AHR signalling, a process that prevented by a single H532A mutation that destroys TIPARP catalytic activity. Moreover, whole body or hepatocyte specific-deletion of, increases the sensitivity of mice to dioxin-induced toxicities. Based on these findings, we hypothesized that the loss of TIPARP catalytic activity would increase sensitivity to TCDD-induced toxicity in vivo. To test the hypothesis, we created a catalytically deficient mouse line (TiparpH532A) by introducing a single H532A mutation in Tiparp. Treatment of mouse embryonic fibroblasts (MEFs) or hepatocytes isolated from TiparpH532A mice confirmed the increased TCDD-induced expression of the AHR target genes, Cyp1a1, Cyp1b1 and Tiparp. We also confirmed TCDD-dependent increases in Tiparp protein levels, as well as increased protein stabilization of TiparpH532A compared Tiparp+/+ protein. TiparpH532A mice given a single injection of 10 ug/kg dioxin, a non-lethal dose in Tiparp+/+ mice, did not survive beyond day 10. All Tiparp+/+ mice survived the 30-day treatment. Dioxin treated TiparpH532A mice displayed increased expression of Ahr target genes, increased steatohepatitis and hepatotoxicity as indicated by increased alanine aminotransferase activity compared with wildtypes. Taken together, these data further support TIPARP as a key negative regulator of AHR activity and its specific loss of its catalytic activity is sufficient to increase the sensitivity to dioxin-induced hepatosteatosis and lethality. TIPARP has recently emerged as a potential anti-cancer therapeutic; however, AHR signalling and toxicity will need to be carefully considered in determining the consequences of TIPARP inhibition.
2021-09-08 | GSE167205 | GEO
Project description:Major toxicities of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) result from dysregulation of gene expression mediated by the aryl hydrocarbon receptor (AHR). Dioxin-like chemicals alter expression of numerous genes in liver but the specific genes whose dysregulation leads to toxicities such as wasting, hepatotoxicity and lethality have not been identified. We searched for genes that are most likely to be key to dioxin toxicity by using gene expression arrays to contrast hepatic gene expression after TCDD treatment in dioxin-sensitive rats (that carry wildtype AHR) with gene expression in H/W(Kuopio) rats which are highly resistant to dioxin toxicity due to a major deletion in the AHR's transactivation domain (TAD). The total number of TCDD-responsive genes was smaller in rats with the AHRH/W genotype than in rats with wildtype AHR. However, genes in the classic AH gene battery such as CYP1A1, CYP1A2 and CYP1B1 remained fully responsive to TCDD in AHRH/W rats; thus the TAD deletion selectively interferes with expression of a subset of hepatic genes rather than abolishing global AHR-mediated responses. Genes in the following functional categories differ in response to TCDD between dioxin-sensitive rats and dioxin-resistant rats: fatty acid oxidation, metabolism (xenobiotic, alcohol, amino acid, and fatty acid), phosphate transport, regulation of steroid biosynthesis, nitrogen compound catabolism, and generation of precursor metabolites and energy. Many of these differentially-responsive genes are integral parts of pathways such as: protein degradation and synthesis, fatty acid metabolism and synthesis, cytokinesis, cell growth, and apoptosis which may be part of mechanisms which lead to TCDD-induced wasting, hepatotoxicity, tumors, and death. These differentially-responsive genes are worthy candidates for further mechanistic studies to test their role in mediating or protecting from major dioxin toxicities. Experiment Overall Design: Four strains of rats were either treated with 100 ug/kg TCDD or cornoil vehicle and profiled at 19 hours, each with four replicates. Two strains were also analyzed at 3 hours, each with four replicates.
2009-12-02 | E-GEOD-10083 | biostudies-arrayexpress
Project description:The dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a wide range of toxic effects in rodent species, all of which are mediated by a ligand-dependent transcription-factor, the aryl hydrocarbon receptor (AHR). The Han/Wistar (Kuopio) (H/W) strain shows exceptional resistance to many TCDD-induced toxicities; the LD50 of >9600 µg/kg for H/W rats is higher than for any other wild-type mammal known. We have previously shown that this resistance primarily results from H/W rats expressing a variant AHR isoform that has a substantial portion of the AHR transactivation domain deleted. Despite this large deletion, H/W rats are not entirely refractory to the effects of TCDD; the variant AHR in these animals remains fully competent to up-regulate well-known dioxin-inducible genes. TCDD-sensitive (Long-Evans, L-E) and resistant (H/W) rats were treated with either corn-oil (with or without feed-restriction) or 100 µg/kg TCDD for either four or ten days. Hepatic transcriptional profiling was done using microarrays, and was validated by RT-PCR analysis of 41 genes. . A core set of genes was altered in both strains at all time points tested, including CYP1A1, CYP1A2, CYP1B1, Nqo1, Aldh3a1, Tiparp, Exoc3, and Inmt. Outside this core, the strains differed significantly in the breadth of response: three-fold more genes were altered in L-E than H/W rats. At ten days almost all expressed genes were dysregulated in L-E rats, likely reflecting emerging toxic responses. Far fewer genes were affected by feed-restriction, suggesting that only a minority of the TCDD-induced changes are secondary to the wasting syndrome. Rats from sensitive (Long-Evans, LE) and resistant (Han/Wistar, HW) strains were treated with 100 ug/kg TCDD or corn oil vehicle and sacrificed either 4 or 10 days after treatment. LE control rats were either fed normally or feed-restricted to control for the wasting effects of TCDD treatment. Each treatment group contains four or five animals (biological replicates), each of which was assayed on an individual microarray.
2011-11-14 | E-GEOD-13513 | biostudies-arrayexpress
Project description:Major toxicities of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) result from dysregulation of gene expression mediated by the aryl hydrocarbon receptor (AHR). Dioxin-like chemicals alter expression of numerous genes in liver but the specific genes whose dysregulation leads to toxicities such as wasting, hepatotoxicity and lethality have not been identified. We searched for genes that are most likely to be key to dioxin toxicity by using gene expression arrays to contrast hepatic gene expression after TCDD treatment in dioxin-sensitive rats (that carry wildtype AHR) with gene expression in H/W(Kuopio) rats which are highly resistant to dioxin toxicity due to a major deletion in the AHR's transactivation domain (TAD). The total number of TCDD-responsive genes was smaller in rats with the AHRH/W genotype than in rats with wildtype AHR. However, genes in the classic AH gene battery such as CYP1A1, CYP1A2 and CYP1B1 remained fully responsive to TCDD in AHRH/W rats; thus the TAD deletion selectively interferes with expression of a subset of hepatic genes rather than abolishing global AHR-mediated responses. Genes in the following functional categories differ in response to TCDD between dioxin-sensitive rats and dioxin-resistant rats: fatty acid oxidation, metabolism (xenobiotic, alcohol, amino acid, and fatty acid), phosphate transport, regulation of steroid biosynthesis, nitrogen compound catabolism, and generation of precursor metabolites and energy. Many of these differentially-responsive genes are integral parts of pathways such as: protein degradation and synthesis, fatty acid metabolism and synthesis, cytokinesis, cell growth, and apoptosis which may be part of mechanisms which lead to TCDD-induced wasting, hepatotoxicity, tumors, and death. These differentially-responsive genes are worthy candidates for further mechanistic studies to test their role in mediating or protecting from major dioxin toxicities. Keywords: Treatment-Control, Inter-Strain, Time-Course
2009-11-24 | GSE10083 | GEO
Project description:The dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a wide range of toxic effects in rodent species, all of which are mediated by a ligand-dependent transcription-factor, the aryl hydrocarbon receptor (AHR). The Han/Wistar (Kuopio) (H/W) strain shows exceptional resistance to many TCDD-induced toxicities; the LD50 of >9600 µg/kg for H/W rats is higher than for any other wild-type mammal known. We have previously shown that this resistance primarily results from H/W rats expressing a variant AHR isoform that has a substantial portion of the AHR transactivation domain deleted. Despite this large deletion, H/W rats are not entirely refractory to the effects of TCDD; the variant AHR in these animals remains fully competent to up-regulate well-known dioxin-inducible genes. TCDD-sensitive (Long-Evans, L-E) and resistant (H/W) rats were treated with either corn-oil (with or without feed-restriction) or 100 µg/kg TCDD for either four or ten days. Hepatic transcriptional profiling was done using microarrays, and was validated by RT-PCR analysis of 41 genes. . A core set of genes was altered in both strains at all time points tested, including CYP1A1, CYP1A2, CYP1B1, Nqo1, Aldh3a1, Tiparp, Exoc3, and Inmt. Outside this core, the strains differed significantly in the breadth of response: three-fold more genes were altered in L-E than H/W rats. At ten days almost all expressed genes were dysregulated in L-E rats, likely reflecting emerging toxic responses. Far fewer genes were affected by feed-restriction, suggesting that only a minority of the TCDD-induced changes are secondary to the wasting syndrome.
2011-11-14 | GSE13513 | GEO
Project description:In many mammals, halogenated aromatic hydrocarbon (HAH) exposure causes wasting syndrome, defined as lethal weight loss as a result of severe and persistent hypophagia. The most potent HAH in causing wasting is 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD), which exerts its toxic effects through the aryl hydrocarbon receptor (AHR) – a transcription factor. Because TCDD toxicity is thought to predominantly arise from dysregulation of AHR-transcribed genes, we hypothesized that wasting syndrome is due to TCDD-induced dysregulation of genes involved in regulation of food-intake. We therefore focused on the hypothalamus, as it is the regulatory center of food-intake and energy balance in the central nervous system. We profiled mRNA abundance in hypothalamic tissue from two rat strains with widely differing sensitivities to wasting syndrome: TCDD-sensitive Long-Evans rats and TCDD-resistant Han/Wistar rats, 23 hours after exposure to TCDD (100 μg/kg) or corn oil vehicle. We found that TCDD exposure caused minimal transcriptional dysregulation effects in the hypothalamus, with only 6 genes changed in Long-Evans rats and 15 genes in Han/Wistar rats. Two of the most dysregulated genes were Cyp1a1 and Nqo1, which are induced by TCDD across a wide range of tissues and are considered sensitive markers of TCDD exposure. The minimal response of the hypothalamic transcriptome to a lethal dose of TCDD at an early time-point suggests that the hypothalamus is not the predominant site of initial events leading to hypophagia and associated wasting. TCDD may affect feeding behaviour via events upstream or downstream of the hypothalamus, and further work is required to evaluate this at the level of individual hypothalamic nuclei and subregions. Two strains, each with drug-treated vs vehicle-control
2014-12-23 | E-GEOD-61039 | biostudies-arrayexpress
Project description:Dioxin-like chemicals are well-known for their ability to upregulate expression of numerous genes via the AH receptor (AHR). However, recent transcriptomic analyses in several laboratories indicate that dioxin-like chemicals or AHR genotype itself also can downregulate levels of mRNAs encoded by numerous genes. The mechanism responsible for such downregulation is unknown. We hypothesized that microRNAs (miRNAs), which have emerged as powerful negative regulators of mRNA levels in several systems, might be responsible for mRNA downregulation in dioxin/AHR pathways. We conducted a thorough investigation to address the following questions: (1) does AHR genotype itself affect constitutive expression of microRNAs? (2) does TCDD affect microRNA levels and, if so, is this response dependent on the AHR? (3) does TCDD affect microRNA levels differently in animals that are sensitive to dioxin toxicity versus those that are dioxin-resistant? We used the Exiqon miRNA array platform as well as quantitative RT-PCR to measure miRNA levels in wildtype vs. Ahr-null mice. Treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vivo caused few changes in miRNA levels in mouse livers and those changes that were statistically significant were of modest magnitude. AHR genotype had little effect on hepatic miRNA levels, either in constitutive expression or in response to TCDD M-bM-^@M-^S only a few miRNAs differed in expression between Ahr-null mice compared to mice with wildtype AHR. It is unlikely that mRNA downregulation by dioxins is mediated by miRNAs, nor are miRNAs likely to play a significant role in dioxin toxicity in adult mouse liver. Manuscript Submitted: Moffat ID, Boutros PC, Celius T, Pohjanvirta R & Okey AB. Micro-RNAs in rodent liver are refractory to dioxin treatment. Toxicological Sciences May, 2007. Keywords: miRNA expression, gene knockout, response to xenobiotics, genetic modification This was a two-factor, two-level design, the factors being genotype Ahr+/+ (WT) or Ahr-/- (KO) and treatment TCDD-treated (T) or vehicle control (C). Each total-RNA sample was separately labeled either with a Hy3- or a Hy5-fluorophore (Exiqon). Hy3- and Hy5-labeled samples were co-hybridized to an array. Dye-reversal was performed to eliminate dye bias. We tested 3 TCDD-treated and 3 control mice in the Ahr-/- groups and 4 TCDD-treated and 4 control mice in the Ahr+/+ groups. Technical replication of 1 TCDD-treated and 1 control mice in the Ahr-/- groups was performed. A loop design was used.
2007-08-14 | E-GEOD-8468 | biostudies-arrayexpress
Project description:The aryl hydrocarbon receptor (AHR) mediates most of the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, TCDD toxicity phenotypes vary widely between species, strains and even between sexes within a strain. While the exact reasons for this variation remain unclear, it is thought to be related to differences in the structure of the AHR. Previous studies comparing the downstream effects of TCDD exposure between animals with different AHR isoforms have been confounded by the genetic differences between these model systems. To address this issue conclusively, we evaluated three transgenic mouse lines, each of which express a different rat AHR isoform (rWT, DEL, and INS) from two strains of rat with highly divergent TCDD-susceptibilities, within identical genetic backgrounds. Here we profile hepatic transcriptomic responses following exposure to TCDD, and use these to identify transcripts associated with toxicity. We have confirmed that the variation in toxicity is inherent to the AHR isoform. Additionally, we note the enhanced activity of the modified transactivation domain of the DEL isoform, relative to the INS isoform, and provide further evidence that the INS isoform is responsible for the high resistance to TCDD observed in H/W rats. We also uncover several candidate genes that were consistently differentially expressed in TCDD-sensitive mice and rats. Adult male transgenic mice were treated by gavage with 0, 125, 250, 500, or 1000 µg/kg TCDD dissolved in corn oil vehicle. Mice were euthanized 4 days following treatment and liver tissue was harvested for analysis. RNA was isolated and the transcriptome for each animal assayed on separate microarrays.
2016-07-03 | E-GEOD-72270 | biostudies-arrayexpress
Project description:The aryl hydrocarbon receptor (AHR) mediates the toxic effects of environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Frogs are very insensitive to the toxic effects of TCDD.
2009-06-24 | GSE16670 | GEO