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Title: Disruption of period gene expression alters the inductive effects of dioxin on the AhR signaling pathway in the mouse liver

Abstract

The aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) are transcription factors that express Per-Arnt-Sim (PAS) DNA-binding motifs and mediate the metabolism of drugs and environmental toxins in the liver. Because these transcription factors interact with other PAS genes in molecular feedback loops forming the mammalian circadian clockworks, we determined whether targeted disruption or siRNA inhibition of Per1 and Per2 expression alters toxin-mediated regulation of the AhR signaling pathway in the mouse liver and Hepa1c1c7 hepatoma cells in vitro. Treatment with the prototypical Ahr ligand, 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), had inductive effects on the primary targets of AhR signaling, Cyp1A1 and Cyp1B1, in the liver of all animals, but genotype-based differences were evident such that the toxin-mediated induction of Cyp1A1 expression was significantly greater (2-fold) in mice with targeted disruption of Per1 (Per1{sup ldc} and Per1{sup ldc}/Per2{sup ldc}). In vitro experiments yielded similar results demonstrating that siRNA inhibition of Per1 significantly increases the TCDD-induced expression of Cyp1A1 and Cyp1B1 in Hepa1c1c7 cells. Per2 inhibition in siRNA-infected Hepa1c1c7 cells had the opposite effect and significantly decreased both the induction of these p450 genes as well as AhR and Arnt expression in response to TCDD treatment. These findings suggest that Per1 may playmore » a distinctive role in modulating AhR-regulated responses to TCDD in the liver.« less

Authors:
 [1];  [2]; ;  [3];  [1];  [2];  [1];  [2];  [4]
  1. Department of Biology, College Station, Texas 77843-3258 (United States)
  2. (United States)
  3. Department of Integrative Biosciences, College of Veterinary Medicine, Texas A and M University, College Station, TX 77843-4458 (United States)
  4. (United States), E-mail: dearnest@tamu.edu
Publication Date:
OSTI Identifier:
21182723
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 234; Journal Issue: 3; Other Information: DOI: 10.1016/j.taap.2008.10.016; PII: S0041-008X(08)00457-2; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; AMINO ACIDS; DIOXIN; DNA; ENZYMES; GENE REGULATION; GENES; GENOTYPE; HEPATOMAS; IN VITRO; INHIBITION; LIGANDS; LIVER; METABOLISM; MICE; POLYCYCLIC AROMATIC HYDROCARBONS; RECEPTORS; TOXINS; TRANSCRIPTION FACTORS; XENOBIOTICS

Citation Formats

Qu Xiaoyu, Center for Research on Biological Clocks, College Station, Texas 77843-3258, Metz, Richard P., Porter, Weston W., Cassone, Vincent M., Center for Research on Biological Clocks, College Station, Texas 77843-3258, Earnest, David J., Center for Research on Biological Clocks, College Station, Texas 77843-3258, and Department of Neuroscience and Experimental Therapeutics, Texas A and M University Health Science Center, College of Medicine, College Station, Texas 77843-1114. Disruption of period gene expression alters the inductive effects of dioxin on the AhR signaling pathway in the mouse liver. United States: N. p., 2009. Web.
Qu Xiaoyu, Center for Research on Biological Clocks, College Station, Texas 77843-3258, Metz, Richard P., Porter, Weston W., Cassone, Vincent M., Center for Research on Biological Clocks, College Station, Texas 77843-3258, Earnest, David J., Center for Research on Biological Clocks, College Station, Texas 77843-3258, & Department of Neuroscience and Experimental Therapeutics, Texas A and M University Health Science Center, College of Medicine, College Station, Texas 77843-1114. Disruption of period gene expression alters the inductive effects of dioxin on the AhR signaling pathway in the mouse liver. United States.
Qu Xiaoyu, Center for Research on Biological Clocks, College Station, Texas 77843-3258, Metz, Richard P., Porter, Weston W., Cassone, Vincent M., Center for Research on Biological Clocks, College Station, Texas 77843-3258, Earnest, David J., Center for Research on Biological Clocks, College Station, Texas 77843-3258, and Department of Neuroscience and Experimental Therapeutics, Texas A and M University Health Science Center, College of Medicine, College Station, Texas 77843-1114. 2009. "Disruption of period gene expression alters the inductive effects of dioxin on the AhR signaling pathway in the mouse liver". United States. doi:.
@article{osti_21182723,
title = {Disruption of period gene expression alters the inductive effects of dioxin on the AhR signaling pathway in the mouse liver},
author = {Qu Xiaoyu and Center for Research on Biological Clocks, College Station, Texas 77843-3258 and Metz, Richard P. and Porter, Weston W. and Cassone, Vincent M. and Center for Research on Biological Clocks, College Station, Texas 77843-3258 and Earnest, David J. and Center for Research on Biological Clocks, College Station, Texas 77843-3258 and Department of Neuroscience and Experimental Therapeutics, Texas A and M University Health Science Center, College of Medicine, College Station, Texas 77843-1114},
abstractNote = {The aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (ARNT) are transcription factors that express Per-Arnt-Sim (PAS) DNA-binding motifs and mediate the metabolism of drugs and environmental toxins in the liver. Because these transcription factors interact with other PAS genes in molecular feedback loops forming the mammalian circadian clockworks, we determined whether targeted disruption or siRNA inhibition of Per1 and Per2 expression alters toxin-mediated regulation of the AhR signaling pathway in the mouse liver and Hepa1c1c7 hepatoma cells in vitro. Treatment with the prototypical Ahr ligand, 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), had inductive effects on the primary targets of AhR signaling, Cyp1A1 and Cyp1B1, in the liver of all animals, but genotype-based differences were evident such that the toxin-mediated induction of Cyp1A1 expression was significantly greater (2-fold) in mice with targeted disruption of Per1 (Per1{sup ldc} and Per1{sup ldc}/Per2{sup ldc}). In vitro experiments yielded similar results demonstrating that siRNA inhibition of Per1 significantly increases the TCDD-induced expression of Cyp1A1 and Cyp1B1 in Hepa1c1c7 cells. Per2 inhibition in siRNA-infected Hepa1c1c7 cells had the opposite effect and significantly decreased both the induction of these p450 genes as well as AhR and Arnt expression in response to TCDD treatment. These findings suggest that Per1 may play a distinctive role in modulating AhR-regulated responses to TCDD in the liver.},
doi = {},
journal = {Toxicology and Applied Pharmacology},
number = 3,
volume = 234,
place = {United States},
year = 2009,
month = 2
}
  • 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a common environmental contaminant. TCDD binds and activates the transcription factor aryl hydrocarbon receptor (AHR), leading to adverse biological responses via the alteration of the expression of various AHR target genes. Although small amounts of TCDD are consumed via contaminated daily foodstuffs and environmental exposures, the effects of low-dose TCDD on gene expression in animal tissues have not been clarified, while a number of genes affected by high-dose TCDD were reported. In this study, we comprehensively analyzed gene expression profiles in livers of C57BL/6N mice that were orally administered relatively low doses of TCDD (5, 50, ormore » 500 ng/kg body weight (bw) day{sup -1}) for 18 days. The hepatic TCDD concentrations, measured by gas chromatography-mass spectrometry, were 1.2, 17, and 1063 pg toxicity equivalent quantity (TEQ)/g, respectively. The mRNA level of the cytochrome P450 CYP1A1 was significantly increased by treatment with only TCDD 500 ng/kg bw day{sup -1}. DNA microarray and quantitative RT-PCR analyses revealed changes in the expression of genes involved in the circadian rhythm, cholesterol biosynthesis, fatty acid synthesis, and glucose metabolism in the liver with at all doses of TCDD employed. However, repression of expression of genes involved in energy metabolism was not observed in the livers of Ahr-null mice that were administered the same dose of TCDD. These results indicate that changes in gene expression by TCDD are mediated by AHR and that exposure to low-dose TCDD could affect energy metabolism via alterations of gene expression.« less
  • Administration of peroxisome proliferators to rodents causes proliferation of peroxisomes, induction of {beta}-oxidation enzymes, hepatocellular hypertrophy and hyperplasia, with chronic exposure ultimately leading to hepatocellular carcinomas. Many responses associated with peroxisome proliferators are nuclear receptor-mediated events involving peroxisome proliferators-activated receptor alpha (PPAR{alpha}). A role for nuclear receptor-independent events has also been shown, with evidence of Kupffer cell-mediated free radical production, presumably through NAPDH oxidase, induction of redox-sensitive transcription factors involved in cytokine production and cytokine-mediated cell replication following acute treatment with peroxisome proliferators in rodents. Recent studies have demonstrated, by using p47{sup phox}-null mice which are deficient in NADPH oxidase,more » that this enzyme is not related to the phenotypic events caused by prolonged administration of peroxisome proliferators. In an effort to determine the timing of the transition from Kupffer cell-to PPAR{alpha}-dependent modulation of peroxisome proliferator effects, gene expression was assessed in liver from Ppar{alpha}-null, p47{sup phox}-null and corresponding wild-type mice following treatment with 4-chloro-6-(2,3-xylidino)-pyrimidynylthioacetic acid (WY-14,643) for 8 h, 24 h, 72 h, 1 week or 4 weeks. WY-14,643-induced gene expression in p47{sup phox}-null mouse liver differed substantially from wild-type mice at acute doses and striking differences in baseline expression of immune related genes were evident. Pathway mapping of genes that respond to WY-14,643 in a time- and dose-dependent manner demonstrates suppression of immune response, cell death and signal transduction and promotion of lipid metabolism, cell cycle and DNA repair. Furthermore, these pathways were largely dependent on PPAR{alpha}, not NADPH oxidase demonstrating a temporal shift in response to peroxisome proliferators. Overall, this study shows that NADPH oxidase-dependent events, while detectable following acute treatment, are transient. To the contrary, a strong PPAR{alpha}-specific gene signature was evident in mice that were continually exposed to WY-14,643.« less
  • Valproic acid (VPA) is used clinically to treat epilepsy, however it induces hepatotoxicity such as microvesicular steatosis. Acute hepatotoxicity of VPA has been well documented by biochemical studies and microarray analysis, but little is known about the chronic effects of VPA in the liver. In the present investigation, we profiled gene expression patterns in the mouse liver after subchronic treatment with VPA. VPA was administered orally at a dose of 100 mg/kg/day or 500 mg/kg/day to ICR mice, and the livers were obtained after 1, 2, or 4 weeks. The activities of serum liver enzymes did not change, whereas triglyceridemore » concentration increased significantly. Microarray analysis revealed that 1325 genes of a set of 32,996 individual genes were VPA responsive when examined by two-way ANOVA (P < 0.05) and fold change (> 1.5). Consistent with our previous results obtained using an acute VPA exposure model (Lee et al., Toxicol Appl Pharmacol. 220:45-59, 2007), the most significantly over-represented biological terms for these genes included lipid, fatty acid, and steroid metabolism. Biological pathway analysis suggests that the genes responsible for increased biosynthesis of cholesterol and triglyceride, and for decreased fatty acid {beta}-oxidation contribute to the abnormalities in lipid metabolism induced by subchronic VPA treatment. A comparison of the VPA-responsive genes in the acute and subchronic models extracted 15 commonly altered genes, such as Cyp4a14 and Adpn, which may have predictive power to distinguish the mode of action of hepatotoxicants. Our data provide a better understanding of the molecular mechanisms of VPA-induced hepatotoxicity and useful information to predict steatogenic hepatotoxicity.« less
  • Research highlights: {yields} AG490, a member of tyrosine kinase inhibitors, could inhibit the JAK2V617F/STAT5 signaling pathway in HEL cell which harbor JAK2V617F mutation. {yields} Inhibition of the JAK2V617F/STAT5 signaling pathway inhibited the growth of HEL cells. {yields} JAK2V617F mutation promotes cell proliferation through activation of PTTG1 expression. {yields} JAK2V617F/STAT5 signaling pathway regulate PTTG1 expression at transcriptional level. -- Abstract: Gain-of-function mutations of JAK2 play crucial roles in the development of myeloproliferative neoplasms; however, the underlying downstream events of this activated signaling pathway are not fully understood. Our experiment was designed and performed to address one aspect of this issue. Heremore » we report that AG490, a potent JAK2V617F kinase inhibitor, effectively inhibits the proliferation of HEL cells. Interestingly, AG490 also decreases the expression of PTTG1, a possible target gene of the aberrant signaling pathway, in a dose- and time-dependent manner. Furthermore, the promoter activity analyses reveal that the inhibition of the PTTG1 expression is affected at the transcriptional level. Thus, our results suggest that the JAK2V617F/STAT5 signaling pathway promotes cell proliferation through the transcriptional activation of PTTG1.« less