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Hsieh CW, Chang LH, Wang YH, Li WT, Chang JK, Chen CH, Ho ML. Indoxyl Sulfate Inhibits Osteogenesis in Bone Marrow Mesenchymal Stem Cells through the AhR/Hes1 Pathway. Int J Mol Sci 2024; 25:8770. [PMID: 39201457 PMCID: PMC11354967 DOI: 10.3390/ijms25168770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2024] [Revised: 08/05/2024] [Accepted: 08/09/2024] [Indexed: 09/02/2024] Open
Abstract
Uremic toxins cause bone disorders in patients with chronic kidney disease (CKD). These disorders are characterized by low turnover osteodystrophy and impaired bone formation in the early stages of CKD. Evidence indicates that the aryl hydrocarbon receptor (AhR) mediates signals that suppress early osteogenic differentiation in bone marrow mesenchymal stem cells (BMSCs). However, whether the AhR mediates the effects of indoxyl sulfate (IS), a uremic toxin, on BMSC osteogenesis remains unclear. We investigated whether IS affects osteogenesis through the AhR/Hes1 pathway. Expression levels of osteogenesis genes (Runx2, Bmp2, Alp, and Oc), AhR, and Hes1 were measured in mouse BMSCs (D1 cells). At concentrations of 2-50 μM, IS significantly reduced mineralization, particularly in the early stages of BMSC osteogenesis. Furthermore, IS significantly downregulated the expression of Runx2, Bmp2, Oc, and Alp. Notably, this downregulation could be prevented using an AhR antagonist and through Ahr knockdown. Mechanistically, IS induced the expression of Hes1 through AhR signaling, thereby suppressing the transcription of Runx2 and Bmp2. Our findings suggest that IS inhibits early osteogenesis of BMSCs through the AhR/Hes1 pathway, thus suppressing the transcription of Runx2 and Bmp2. Our findings may guide new therapeutic strategies against CKD-related bone disorders.
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Affiliation(s)
- Chin-Wen Hsieh
- Division of Nephrology, Department of Internal Medicine, Pingtung Christian Hospital, Pingtung 900, Taiwan;
- Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Ling-Hua Chang
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan; (L.-H.C.); (Y.-H.W.); (W.-T.L.); (J.-K.C.)
- Regenerative Medicine and Cell Therapy Research Center, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Yan-Hsiung Wang
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan; (L.-H.C.); (Y.-H.W.); (W.-T.L.); (J.-K.C.)
- Regenerative Medicine and Cell Therapy Research Center, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Wei-Ting Li
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan; (L.-H.C.); (Y.-H.W.); (W.-T.L.); (J.-K.C.)
| | - Je-Ken Chang
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan; (L.-H.C.); (Y.-H.W.); (W.-T.L.); (J.-K.C.)
- Regenerative Medicine and Cell Therapy Research Center, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Orthopedics, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung 801, Taiwan
| | - Chung-Hwan Chen
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan; (L.-H.C.); (Y.-H.W.); (W.-T.L.); (J.-K.C.)
- Regenerative Medicine and Cell Therapy Research Center, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Orthopedics, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung 801, Taiwan
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Ph.D. Program in Biomedical Engineering, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Graduate Institute of Materials Engineering, College of Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
| | - Mei-Ling Ho
- Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan; (L.-H.C.); (Y.-H.W.); (W.-T.L.); (J.-K.C.)
- Regenerative Medicine and Cell Therapy Research Center, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Ph.D. Program in Biomedical Engineering, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Graduate Institute of Materials Engineering, College of Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
- Department of Physiology, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan
- Department of Marine Biotechnology and Resources, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
- College of Professional Studies, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
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2
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Stanic B, Sukur N, Milošević N, Markovic Filipovic J, Pogrmic-Majkic K, Andric N. Differential eigengene network analysis reveals benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin consensus regulatory network in human liver cell line HepG2. Toxicology 2024; 502:153737. [PMID: 38311099 DOI: 10.1016/j.tox.2024.153737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 01/17/2024] [Accepted: 01/24/2024] [Indexed: 02/06/2024]
Abstract
Aryl hydrocarbon receptor (AHR) is one of the main mediators of the toxic effects of benzo[a]pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, a vast number of BaP- and TCDD-affected genes may suggest a more complex transcriptional regulatory network driving common adverse effects of these two chemicals. Unlike TCDD, BaP is rapidly metabolized in the liver, yielding products with a questionable ability to bind and activate AHR. In this study, we used transcriptomics data from the BaP- and TCCD-exposed human liver cell line HepG2, and performed differential eigengene network analysis to understand the correlation among genes and to untangle the common regulatory mechanism in the action of BaP and TCDD. The genes were grouped into 11 meta-modules with an overall preservation of 0.72 and were also segregated into three consensus time clusters: 12, 24, and 48 h. The analysis showed that the consensus genes in each time cluster were either directly regulated by the AHR or the AHR-TF interactions. Some TFs form a direct physical interaction with AHR such as ESR1, FOXA1, and E2F1, whereas others, including CTCF, RXRA, FOXO1, CEBPA, CEBPB, and TP53 show an indirect interaction with AHR. The analysis of biological processes (BPs) identified unique and common BPs in BaP and TCDD samples, with DNA damage response detected in all three time points. In summary, we identified a consensus transcriptional regulatory network common for BaP and TCDD consisting of direct AHR targets and AHR-TF targets. This analysis sheds new light on the common mechanism of action of a genotoxic (BaP) and non-genotoxic (TCDD) chemical in liver cells.
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Affiliation(s)
- Bojana Stanic
- Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad, Serbia
| | - Nataša Sukur
- Department of Mathematics and Informatics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 4, 21000 Novi Sad, Serbia
| | - Nemanja Milošević
- Department of Mathematics and Informatics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 4, 21000 Novi Sad, Serbia
| | - Jelena Markovic Filipovic
- Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad, Serbia
| | - Kristina Pogrmic-Majkic
- Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad, Serbia
| | - Nebojsa Andric
- Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 2, 21000 Novi Sad, Serbia.
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3
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Teino I, Matvere A, Pook M, Varik I, Pajusaar L, Uudeküll K, Vaher H, Trei A, Kristjuhan A, Org T, Maimets T. Impact of AHR Ligand TCDD on Human Embryonic Stem Cells and Early Differentiation. Int J Mol Sci 2020; 21:E9052. [PMID: 33260776 PMCID: PMC7731104 DOI: 10.3390/ijms21239052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 11/20/2020] [Accepted: 11/26/2020] [Indexed: 12/17/2022] Open
Abstract
Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor, which mediates the effects of a variety of environmental stimuli in multiple tissues. Recent advances in AHR biology have underlined its importance in cells with high developmental potency, including pluripotent stem cells. Nonetheless, there is little data on AHR expression and its role during the initial stages of stem cell differentiation. The purpose of this study was to investigate the temporal pattern of AHR expression during directed differentiation of human embryonic stem cells (hESC) into neural progenitor, early mesoderm and definitive endoderm cells. Additionally, we investigated the effect of the AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the gene expression profile in hESCs and differentiated cells by RNA-seq, accompanied by identification of AHR binding sites by ChIP-seq and epigenetic landscape analysis by ATAC-seq. We showed that AHR is differentially regulated in distinct lineages. We provided evidence that TCDD alters gene expression patterns in hESCs and during early differentiation. Additionally, we identified novel potential AHR target genes, which expand our understanding on the role of this protein in different cell types.
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Affiliation(s)
- Indrek Teino
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Antti Matvere
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Martin Pook
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Inge Varik
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Laura Pajusaar
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Keyt Uudeküll
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Helen Vaher
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Annika Trei
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Arnold Kristjuhan
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
| | - Tõnis Org
- Chair of Biotechnology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia;
- Institute of Genomics, University of Tartu, Riia 23b, 51010 Tartu, Estonia
| | - Toivo Maimets
- Chair of Cell Biology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu, Estonia; (A.M.); (M.P.); (I.V.); (L.P.); (K.U.); (H.V.); (A.T.); (A.K.); (T.M.)
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Selective Ah receptor modulators attenuate NPC1L1-mediated cholesterol uptake through repression of SREBP-2 transcriptional activity. J Transl Med 2020; 100:250-264. [PMID: 31417158 PMCID: PMC6989381 DOI: 10.1038/s41374-019-0306-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 06/26/2019] [Accepted: 07/02/2019] [Indexed: 02/07/2023] Open
Abstract
The ability of the aryl hydrocarbon receptor (AHR) to alter hepatic expression of cholesterol synthesis genes in a DRE-independent manner in mice and humans has been reported. We have examined the influence of functionally distinct classes of AHR ligands on the levels of Niemann-Pick C1-like intracellular cholesterol transporter (NPC1L1) and enzymes involved in the cholesterol synthesis pathway. NPC1L1 is known to mediate the intestinal absorption of dietary cholesterol and is clinically targeted. AHR ligands were capable of attenuating cholesterol uptake through repression of NPC1L1 expression. Through mutagenesis experiments targeting the two DRE sequences present in the promoter region of the NPC1L1 gene, we provide evidence that the repression does not require functional DRE sequences; while knockdown experiments demonstrated that this regulation is dependent on AHR and sterol-regulatory element-binding protein-2 (SREBP-2). Furthermore, upon ligand activation of AHR, the human intestinal Caco-2 cell line revealed coordinate repression of both mRNA and protein levels for a number of the cholesterol biosynthetic enzymes. Transcription of NPC1L1 and genes of the cholesterol synthesis pathway is predominantly regulated by SREBP-2, especially after treatment with a statin. Immunoblot analyses revealed a significant decrease in transcriptionally active SREBP-2 levels upon ligand treatment, whereas the precursor form of SREBP-2 was modestly increased by AHR activation. Mechanistic insights indicate that AHR induces proteolytic degradation of mature SREBP-2 in a calcium-dependent manner, which correlates with the AHR ligand-mediated upregulation of the transient receptor potential cation channel subfamily V member 6 (TRPV6) gene encoding for a membrane calcium channel. These observations emphasize a role for AHR in the systemic homeostatic regulation of cholesterol synthesis and absorption, indicating the potential use of this receptor as a target for the treatment of hyperlipidosis-associated metabolic diseases.
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5
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Akishina AA, Vorontsova JE, Cherezov RO, Slezinger MS, Simonova OB, Kuzin BA. NAP Family CG5017 Chaperone Pleiotropically Regulates Human AHR Target Genes Expression in Drosophila Testis. Int J Mol Sci 2018; 20:ijms20010118. [PMID: 30597983 PMCID: PMC6337364 DOI: 10.3390/ijms20010118] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/11/2018] [Accepted: 12/13/2018] [Indexed: 12/13/2022] Open
Abstract
To study the regulatory mechanism of the Aryl hydrocarbon receptor (AHR), target genes of transcription are necessary for understanding the normal developmental and pathological processes. Here, we examined the effects of human AHR ligands on male fecundity. To induce ectopic human AhR gene expression, we used Drosophilamelanogaster transformed with human AhR under the control of a yeast UAS promoter element capable of activation in the two-component UAS-GAL4 system. We found that exogenous AHR ligands decrease the number of Drosophila gonadal Tj-positive cells. We also found both an increase and decrease of AHR target gene expression, including in genes that control homeostasis and testis development. This suggests that gonadal AHR activation may affect the expression of gene networks that control sperm production and could be critical for fertility not just in Drosophila but also in humans. Finally, we found that the activation of the expression for some AHR target genes depends on the expression of testis-specific chaperone CG5017 in gonadal cells. Since CG5017 belongs to the nucleosome assembly protein (NAP) family and may participate in epigenetic regulation, we propose that this nucleotropic chaperone is essential to provide the human AHR with access to only the defined set of its target genes during spermatogenesis.
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Affiliation(s)
- Angelina A Akishina
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119991, Russia.
| | - Julia E Vorontsova
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119991, Russia.
| | - Roman O Cherezov
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119991, Russia.
| | - Mikhail S Slezinger
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119991, Russia.
| | - Olga B Simonova
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119991, Russia.
| | - Boris A Kuzin
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova str. 26, Moscow 119991, Russia.
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6
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Safe S, Han H, Goldsby J, Mohankumar K, Chapkin RS. Aryl Hydrocarbon Receptor (AhR) Ligands as Selective AhR Modulators: Genomic Studies. CURRENT OPINION IN TOXICOLOGY 2018; 11-12:10-20. [PMID: 31453421 DOI: 10.1016/j.cotox.2018.11.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The aryl hydrocarbon receptor (AhR) binds structurally diverse ligands that vary from the environmental toxicant 2,3,7,8-tetrachlorodibenzo-B-dioxin (TCDD) to AhR- active pharmaceuticals and health-promoting phytochemicals. There are remarkable differences in the toxicity of TCDD and related halogenated aromatics (HAs) vs. health promoting AhR ligands, and genomic analysis shows that even among the toxic HAs, there are differences in their regulation of genes and pathways. Thus, like ligands for other receptors, AhR ligands are selective AhR modulators (SAhRMs) which exhibit variable tissue-, organ- and species-specific genomic and functional activities.
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Affiliation(s)
- Stephen Safe
- Department of Veterinary Physiology and Pharmacology
| | - Huajun Han
- Department of Biochemistry & Biophysics
- Department of Nutrition & Food Science
- Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, TX, USA
| | - Jennifer Goldsby
- Department of Nutrition & Food Science
- Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, TX, USA
| | | | - Robert S Chapkin
- Department of Biochemistry & Biophysics
- Department of Nutrition & Food Science
- Program in Integrative Nutrition & Complex Diseases, Texas A&M University, College Station, TX, USA
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Hutin D, Tamblyn L, Gomez A, Grimaldi G, Soedling H, Cho T, Ahmed S, Lucas C, Kanduri C, Grant DM, Matthews J. Hepatocyte-Specific Deletion of TIPARP, a Negative Regulator of the Aryl Hydrocarbon Receptor, Is Sufficient to Increase Sensitivity to Dioxin-Induced Wasting Syndrome. Toxicol Sci 2018; 165:347-360. [PMID: 29873790 PMCID: PMC6154274 DOI: 10.1093/toxsci/kfy136] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) mediates the toxic effects of dioxin (2, 3, 7, 8-tetrachlorodibenzo-p-dioxin; TCDD), which includes thymic atrophy, steatohepatitis, and a lethal wasting syndrome in laboratory rodents. Although the mechanisms of dioxin toxicity remain unknown, AHR signaling in hepatocytes is necessary for dioxin-induced liver toxicity. We previously reported that loss of TCDD-inducible poly(adenosine diphosphate [ADP]-ribose) polymerase (TIPARP/PARP7/ARTD14), an AHR target gene and mono-ADP-ribosyltransferase, increases the sensitivity of mice to dioxin-induced toxicities. To test the hypothesis that TIPARP is a negative regulator of AHR signaling in hepatocytes, we generated Tiparpfl/fl mice in which exon 3 of Tiparp is flanked by loxP sites, followed by Cre-lox technology to create hepatocyte-specific (Tiparpfl/flCreAlb) and whole-body (Tiparpfl/flCreCMV; TiparpEx3-/-) Tiparp null mice. Tiparpfl/flCreAlb and TiparpEx3-/- mice given a single injection of 10 μg/kg dioxin did not survive beyond days 7 and 9, respectively, while all Tiparp+/+ mice survived the 30-day treatment. Dioxin-exposed Tiparpfl/flCreAlb and TiparpEx3-/- mice had increased steatohepatitis and hepatotoxicity as indicated by greater staining of neutral lipids and serum alanine aminotransferase activity than similarly treated wild-type mice. Tiparpfl/flCreAlb and TiparpEx3-/- mice exhibited augmented AHR signaling, denoted by increased dioxin-induced gene expression. Metabolomic studies revealed alterations in lipid and amino acid metabolism in liver extracts from Tiparpfl/flCreAlb mice compared with wild-type mice. Taken together, these data illustrate that TIPARP is an important negative regulator of AHR activity, and that its specific loss in hepatocytes is sufficient to increase sensitivity to dioxin-induced steatohepatitis and lethality.
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Affiliation(s)
- David Hutin
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Laura Tamblyn
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Alvin Gomez
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Giulia Grimaldi
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Helen Soedling
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Tiffany Cho
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Shaimaa Ahmed
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Christin Lucas
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Chakravarthi Kanduri
- Department of Informatics, Jebsen Centre of Excellence for Celiac Disease Research, University of Oslo, Oslo, Norway
| | - Denis M Grant
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Jason Matthews
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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8
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Gadupudi GS, Elser BA, Sandgruber FA, Li X, Gibson-Corley KN, Robertson LW. PCB126 Inhibits the Activation of AMPK-CREB Signal Transduction Required for Energy Sensing in Liver. Toxicol Sci 2018; 163:440-453. [PMID: 29474705 PMCID: PMC5974782 DOI: 10.1093/toxsci/kfy041] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
3,3',4,4',5-pentachlorobiphenyl (PCB126), a dioxin-like PCB, elicits toxicity through a wide array of noncarcinogenic effects, including metabolic syndrome, wasting, and nonalcoholic fatty-liver disease. Previously, we reported decreases in the transcription of several enzymes involved in gluconeogenesis, before the early onset of lipid accumulation. Hence, this study was aimed at understanding the impact of resultant decreases gluconeogenic enzymes on growth, weight, and metabolism in the liver, upon extended exposure. Male Sprague Dawley rats (75-100 g), fed a defined AIN-93G diet, were injected (ip) with single dose of soy oil (5 ml/kg body weight; n = 14) or PCB126 (5 µmol/kg; n = 15), 28 days, prior euthanasia. A subset of rats from each group were fasted for 12 h (vehicle [n = 6] and PCB126 [n = 4]). Rats only showed significant weight loss between days 14 and 28 (p < .05) and some mortality (p = .0413). As in our previous studies, the expression levels of enzymes involved in gluconeogenesis (Pepck-c, G6Pase, Sds, Pc, and Ldh-A) and glycogenolysis (Pygl) were strongly downregulated. The decreased expression of these enzymes in PCB126-treated rats after a 12 h fast decreased hepatic glucose production from glycogen and gluconeogenic substrates, exacerbating the hypoglycemia. Additionally, PCB126 caused hepatic steatosis and decreased the expression of the transcription factor Pparα and its targets, necessary for fatty-acid oxidation. The observed metabolic disruption across multiple branches of fasting metabolism resulted from inhibition in the activation of enzyme AMPK and transcription factor CREB signaling, necessary for "sensing" energy-deprivation and the induction of enzymes that respond to the PCB126 triggered fuel crisis in liver.
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Affiliation(s)
- Gopi S Gadupudi
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, Iowa
- Department of Occupational and Environmental Health, College of Public Health
| | - Benjamin A Elser
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, Iowa
- Department of Occupational and Environmental Health, College of Public Health
| | - Fabian A Sandgruber
- Department of Occupational and Environmental Health, College of Public Health
| | - Xueshu Li
- Department of Occupational and Environmental Health, College of Public Health
| | | | - Larry W Robertson
- Interdisciplinary Graduate Program in Human Toxicology, Graduate College, The University of Iowa, Iowa City, Iowa
- Department of Occupational and Environmental Health, College of Public Health
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9
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Akishina AA, Vorontsova JE, Cherezov RO, Mertsalov IB, Zatsepina OG, Slezinger MS, Panin VM, Petruk S, Enikolopov GN, Mazo A, Simonova OB, Kuzin BA. Xenobiotic-induced activation of human aryl hydrocarbon receptor target genes in Drosophila is mediated by the epigenetic chromatin modifiers. Oncotarget 2017; 8:102934-102947. [PMID: 29262535 PMCID: PMC5732701 DOI: 10.18632/oncotarget.22173] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 10/13/2017] [Indexed: 01/07/2023] Open
Abstract
Aryl hydrocarbon receptor (AHR) is the key transcription factor that controls animal development and various adaptive processes. The AHR’s target genes are involved in biodegradation of endogenous and exogenous toxins, regulation of immune response, organogenesis, and neurogenesis. Ligand binding is important for the activation of the AHR signaling pathway. Invertebrate AHR homologs are activated by endogenous ligands whereas vertebrate AHR can be activated by both endogenous and exogenous ligands (xenobiotics). Several studies using mammalian cultured cells have demonstrated that transcription of the AHR target genes can be activated by exogenous AHR ligands, but little is known about the effects of AHR in a living organism. Here, we examined the effects of human AHR and its ligands using transgenic Drosophila lines with an inducible human AhR gene. We found that exogenous AHR ligands can increase as well as decrease the transcription levels of the AHR target genes, including genes that control proliferation, motility, polarization, and programmed cell death. This suggests that AHR activation may affect the expression of gene networks that could be critical for cancer progression and metastasis. Importantly, we found that AHR target genes are also controlled by the enzymes that modify chromatin structure, in particular components of the epigenetic Polycomb Repressive complexes 1 and 2. Since exogenous AHR ligands (alternatively – xenobiotics) and small molecule inhibitors of epigenetic modifiers are often used as pharmaceutical anticancer drugs, our findings may have significant implications in designing new combinations of therapeutic treatments for oncological diseases.
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Affiliation(s)
- Angelina A Akishina
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Julia E Vorontsova
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Roman O Cherezov
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Il'ya B Mertsalov
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Olga G Zatsepina
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia
| | - Mikhail S Slezinger
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Vladislav M Panin
- Department of Biochemistry and Biophysics, Texas A and M University, College Station, TX, USA
| | - Svetlana Petruk
- Department of Biochemistry and Molecular Biology and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA
| | - Grigori N Enikolopov
- Center for Developmental Genetics, Department of Anesthesiology, Stony Brook University, Stony Brook, NY, USA
| | - Alexander Mazo
- Department of Biochemistry and Molecular Biology and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, USA
| | - Olga B Simonova
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Boris A Kuzin
- Kol'tsov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
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10
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Yang SY, Ahmed S, Satheesh SV, Matthews J. Genome-wide mapping and analysis of aryl hydrocarbon receptor (AHR)- and aryl hydrocarbon receptor repressor (AHRR)-binding sites in human breast cancer cells. Arch Toxicol 2017; 92:225-240. [PMID: 28681081 PMCID: PMC5773648 DOI: 10.1007/s00204-017-2022-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 06/28/2017] [Indexed: 12/18/2022]
Abstract
The aryl hydrocarbon receptor (AHR) mediates the toxic actions of environmental contaminants, such as 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD), and also plays roles in vascular development, the immune response, and cell cycle regulation. The AHR repressor (AHRR) is an AHR-regulated gene and a negative regulator of AHR; however, the mechanisms of AHRR-dependent repression of AHR are unclear. In this study, we compared the genome-wide binding profiles of AHR and AHRR in MCF-7 human breast cancer cells treated for 24 h with TCDD using chromatin immunoprecipitation followed by next-generation sequencing (ChIP-Seq). We identified 3915 AHR- and 2811 AHRR-bound regions, of which 974 (35%) were common to both datasets. When these 24-h datasets were also compared with AHR-bound regions identified after 45 min of TCDD treatment, 67% (1884) of AHRR-bound regions overlapped with those of AHR. This analysis identified 994 unique AHRR-bound regions. AHRR-bound regions mapped closer to promoter regions when compared with AHR-bound regions. The AHRE was identified and overrepresented in AHR:AHRR-co-bound regions, AHR-only regions, and AHRR-only regions. Candidate unique AHR- and AHRR-bound regions were validated by ChIP–qPCR and their ability to regulate gene expression was confirmed by luciferase reporter gene assays. Overall, this study reveals that AHR and AHRR exhibit similar but also distinct genome-wide binding profiles, supporting the notion that AHRR is a context- and gene-specific repressor of AHR activity.
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Affiliation(s)
- Sunny Y. Yang
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
- Present Address: Department of Pharmaceutical Sciences, University of British Columbia, Wesbrook Mall, Vancouver, V6T 1Z3 Canada
| | - Shaimaa Ahmed
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
| | - Somisetty V. Satheesh
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Blindern, 1046, 0317 Oslo, Norway
| | - Jason Matthews
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Canada
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Blindern, 1046, 0317 Oslo, Norway
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11
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Gadupudi GS, Klaren WD, Olivier AK, Klingelhutz AJ, Robertson LW. PCB126-Induced Disruption in Gluconeogenesis and Fatty Acid Oxidation Precedes Fatty Liver in Male Rats. Toxicol Sci 2015; 149:98-110. [PMID: 26396156 DOI: 10.1093/toxsci/kfv215] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
3,3',4,4',5-Pentachlorobiphenyl (PCB126), a dioxin-like polychlorinated biphenyl (PCB) and a potent aryl hydrocarbon receptor (AhR) agonist, is implicated in the disruption of both carbohydrate and lipid metabolism which ultimately leads to wasting disorders, metabolic disease, and nonalcoholic fatty liver disease. However, the mechanisms are unclear. Because liver is the target organ for PCB toxicity and responsible for metabolic homeostasis, we hypothesized that early disruption of glucose and lipid homeostasis contributes to later manifestations such as hepatic steatosis. To test this hypothesis, groups of male Sprague Dawley rats, fed on AIN-93G diet, were injected (intraperitoneal.) with a single bolus of PCB126 (5 µmol/kg) at various time intervals between 9 h and 12 days prior to euthanasia. An early decrease in serum glucose and a gradual decrease in serum triglycerides were observed over time. Liver lipid accumulation was most severe at 6 and 12 days of exposure. Transcript levels of cytosolic phosphoenol-pyruvate carboxykinase (Pepck-c/Pck1) and glucose transporter (Glut2/Slc2a2) involved in gluconeogenesis and hepatic glucose transport were time-dependently downregulated between 9 h and 12 days of PCB126 exposure. Additionally, transcript levels of Pparα, and its targets acyl-CoA oxidase (Acox1) and hydroxy-3-methylglutaryl-CoA synthase 2 (Hmgcs2), were also downregulated, indicating changes in peroxisomal fatty acid oxidation and ketogenesis. In a separate animal study, we found that the measured changes in the transcript levels of Pepck-c, Glut2, Pparα, Acox1, and Hmgcs2 were also dose dependent. Furthermore, PCB126-induced effects on Pepck-c were demonstrated to be AhR dependent in rat H4IIE hepatocytes. These results indicate that PCB126-induced wasting and steatosis are preceded initially by (1) decreased serum glucose caused by decreased hepatic glucose production, followed by (2) decreased peroxisomal fatty acid oxidation.
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Affiliation(s)
- Gopi S Gadupudi
- *Interdisciplinary Graduate Program in Human Toxicology; Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa
| | - William D Klaren
- *Interdisciplinary Graduate Program in Human Toxicology; Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa
| | - Alicia K Olivier
- Department of Pathobiology and Population Medicine, Mississippi State University, Starkville, Mississippi; and
| | | | - Larry W Robertson
- *Interdisciplinary Graduate Program in Human Toxicology; Department of Occupational and Environmental Health, College of Public Health, University of Iowa, Iowa City, Iowa;
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12
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Jackson DP, Joshi AD, Elferink CJ. Ah Receptor Pathway Intricacies; Signaling Through Diverse Protein Partners and DNA-Motifs. Toxicol Res (Camb) 2015; 4:1143-1158. [PMID: 26783425 PMCID: PMC4714567 DOI: 10.1039/c4tx00236a] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Ah receptor is a transcription factor that modulates gene expression via interactions with multiple protein partners; these are reviewed, including the novel NC-XRE pathway involving KLF6.
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13
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Simon TW, Budinsky RA, Rowlands JC. A model for aryl hydrocarbon receptor-activated gene expression shows potency and efficacy changes and predicts squelching due to competition for transcription co-activators. PLoS One 2015; 10:e0127952. [PMID: 26039703 PMCID: PMC4454675 DOI: 10.1371/journal.pone.0127952] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 04/22/2015] [Indexed: 12/17/2022] Open
Abstract
A stochastic model of nuclear receptor-mediated transcription was developed based on activation of the aryl hydrocarbon receptor (AHR) by 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and subsequent binding the activated AHR to xenobiotic response elements (XREs) on DNA. The model was based on effects observed in cells lines commonly used as in vitro experimental systems. Following ligand binding, the AHR moves into the cell nucleus and forms a heterodimer with the aryl hydrocarbon nuclear translocator (ARNT). In the model, a requirement for binding to DNA is that a generic coregulatory protein is subsequently bound to the AHR-ARNT dimer. Varying the amount of coregulator available within the nucleus altered both the potency and efficacy of TCDD for inducing for transcription of CYP1A1 mRNA, a commonly used marker for activation of the AHR. Lowering the amount of available cofactor slightly increased the EC50 for the transcriptional response without changing the efficacy or maximal response. Further reduction in the amount of cofactor reduced the efficacy and produced non-monotonic dose-response curves (NMDRCs) at higher ligand concentrations. The shapes of these NMDRCs were reminiscent of the phenomenon of squelching. Resource limitations for transcriptional machinery are becoming apparent in eukaryotic cells. Within single cells, nuclear receptor-mediated gene expression appears to be a stochastic process; however, intercellular communication and other aspects of tissue coordination may represent a compensatory process to maintain an organism’s ability to respond on a phenotypic level to various stimuli within an inconstant environment.
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Affiliation(s)
- Ted W. Simon
- Ted Simon LLC, Winston, GA, United States of America
- * E-mail:
| | - Robert A. Budinsky
- The Dow Chemical Company, Toxicology and Environmental Research & Consulting. Midland, MI, United States of America
| | - J. Craig Rowlands
- The Dow Chemical Company, Toxicology and Environmental Research & Consulting. Midland, MI, United States of America
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14
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MacPherson L, Ahmed S, Tamblyn L, Krutmann J, Förster I, Weighardt H, Matthews J. Aryl hydrocarbon receptor repressor and TiPARP (ARTD14) use similar, but also distinct mechanisms to repress aryl hydrocarbon receptor signaling. Int J Mol Sci 2014; 15:7939-57. [PMID: 24806346 PMCID: PMC4057711 DOI: 10.3390/ijms15057939] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 04/23/2014] [Indexed: 12/16/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) regulates the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The AHR repressor (AHRR) is an AHR target gene and functions as a ligand-induced repressor of AHR; however, its mechanism of inhibition is controversial. Recently, we reported that TCDD-inducible poly (ADP-ribose) polymerase (TiPARP; ARTD14) also acts as a repressor of AHR, representing a new player in the mechanism of AHR action. Here we compared the ability of AHRR- and TiPARP-mediated inhibition of AHR activity. TCDD increased AHRR mRNA levels and recruitment of AHRR to cytochrome P450 1A1 (CYP1A1) in MCF7 cells. Knockdown of TiPARP, but not AHRR, increased TCDD-induced CYP1A1 mRNA and AHR protein levels. Similarly, immortalized TiPARP−/− mouse embryonic fibroblasts (MEFs) and AHRR−/− MEFs exhibited enhanced AHR transactivation. However, unlike TiPARP−/− MEFs, AHRR−/− MEFs did not exhibit increased AHR protein levels. Overexpression of TiPARP in AHRR−/− MEFs or AHRRΔ8, the active isoform of AHRR, in TiPARP−/− MEFs reduced TCDD-induced CYP1A1 mRNA levels, suggesting that they independently repress AHR. GFP-AHRRΔ8 and GFP-TiPARP expressed as small diffuse nuclear foci in MCF7 and HuH7 cells. GFP-AHRRΔ8_Δ1-49, which lacks its putative nuclear localization signal, localized to both the nucleus and the cytoplasm, while the GFP-AHRRΔ8_Δ1-100 mutant localized predominantly in large cytoplasmic foci. Neither GFP-AHRRΔ8_Δ1-49 nor GFP-AHRRΔ8_Δ1-100 repressed AHR. Taken together, AHRR and TiPARP repress AHR transactivation by similar, but also different mechanisms.
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Affiliation(s)
- Laura MacPherson
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Shaimaa Ahmed
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Laura Tamblyn
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Jean Krutmann
- IUF-Leibniz Research Institute for Environmental Medicine gGmbH, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany.
| | - Irmgard Förster
- Immunology and Environment, Life and Medical Sciences (LIMES) Institute, University of Bonn, Carl-Troll-Straβe 31, 53115 Bonn, Germany.
| | - Heike Weighardt
- IUF-Leibniz Research Institute for Environmental Medicine gGmbH, Auf'm Hennekamp 50, 40225 Düsseldorf, Germany.
| | - Jason Matthews
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON M5S 1A8, Canada.
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15
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De Tata V. Association of dioxin and other persistent organic pollutants (POPs) with diabetes: epidemiological evidence and new mechanisms of beta cell dysfunction. Int J Mol Sci 2014; 15:7787-811. [PMID: 24802877 PMCID: PMC4057704 DOI: 10.3390/ijms15057787] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 04/16/2014] [Accepted: 04/21/2014] [Indexed: 12/23/2022] Open
Abstract
The worldwide explosion of the rates of diabetes and other metabolic diseases in the last few decades cannot be fully explained only by changes in the prevalence of classical lifestyle-related risk factors, such as physical inactivity and poor diet. For this reason, it has been recently proposed that other "nontraditional" risk factors could contribute to the diabetes epidemics. In particular, an increasing number of reports indicate that chronic exposure to and accumulation of a low concentration of environmental pollutants (especially the so-called persistent organic pollutants (POPs)) within the body might be associated with diabetogenesis. In this review, the epidemiological evidence suggesting a relationship between dioxin and other POPs exposure and diabetes incidence will be summarized, and some recent developments on the possible underlying mechanisms, with particular reference to dioxin, will be presented and discussed.
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Affiliation(s)
- Vincenzo De Tata
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Via Roma, 55, Scuola Medica, 56126 Pisa, Italy.
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16
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The aryl hydrocarbon receptor and estrogen receptor alpha differentially modulate nuclear factor erythroid-2-related factor 2 transactivation in MCF-7 breast cancer cells. Toxicol Appl Pharmacol 2013; 270:139-48. [DOI: 10.1016/j.taap.2013.03.029] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 03/22/2013] [Accepted: 03/23/2013] [Indexed: 12/15/2022]
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17
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MacPherson L, Tamblyn L, Rajendra S, Bralha F, McPherson JP, Matthews J. 2,3,7,8-Tetrachlorodibenzo-p-dioxin poly(ADP-ribose) polymerase (TiPARP, ARTD14) is a mono-ADP-ribosyltransferase and repressor of aryl hydrocarbon receptor transactivation. Nucleic Acids Res 2012; 41:1604-21. [PMID: 23275542 PMCID: PMC3562000 DOI: 10.1093/nar/gks1337] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-inducible poly(ADP-ribose) polymerase (TiPARP/ARTD14) is a member of the PARP family and is regulated by the aryl hydrocarbon receptor (AHR); however, little is known about TiPARP function. In this study, we examined the catalytic function of TiPARP and determined its role in AHR transactivation. We observed that TiPARP exhibited auto-mono-ADP-ribosyltransferase activity and ribosylated core histones. RNAi-mediated knockdown of TiPARP in T-47D breast cancer and HuH-7 hepatoma cells increased TCDD-dependent cytochrome P450 1A1 (CYP1A1) and CYP1B1 messenger RNA (mRNA) expression levels and recruitment of AHR to both genes. Overexpression of TiPARP reduced AHR-dependent increases in CYP1A1-reporter gene activity, which was restored by overexpression of AHR, but not aryl hydrocarbon receptor nuclear translocator. Deletion and mutagenesis studies showed that TiPARP-mediated inhibition of AHR required the zinc-finger and catalytic domains. TiPARP and AHR co-localized in the nucleus, directly interacted and both were recruited to CYP1A1 in response to TCDD. Overexpression of Tiparp enhanced, whereas RNAi-mediated knockdown of TiPARP reduced TCDD-dependent AHR proteolytic degradation. TCDD-dependent induction of AHR target genes was enhanced in Tiparp−/− mouse embryonic fibroblasts compared with wildtype controls. Our findings show that TiPARP is a mono-ADP-ribosyltransferase and a transcriptional repressor of AHR, revealing a novel negative feedback loop in AHR signalling.
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Affiliation(s)
- Laura MacPherson
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
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18
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Harper TA, Joshi AD, Elferink CJ. Identification of stanniocalcin 2 as a novel aryl hydrocarbon receptor target gene. J Pharmacol Exp Ther 2012; 344:579-88. [PMID: 23269473 DOI: 10.1124/jpet.112.201111] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Proper hepatocyte function is vital for survival; thus, unrepaired destruction of the parenchymal tissue leading to liver decompensation is devastating. Therefore, understanding the homeostatic process regulating liver regeneration is clinically important, and evidence that the aryl hydrocarbon receptor (AhR) can promote cell survival after intrinsic apoptotic stimuli is integral to the regenerative process. The current study uses primary hepatocytes to identify survival mechanisms consistent with normal AhR biology. Taking advantage of the Cre-lox system to manipulate AhR status, we designed a comprehensive microarray analysis to identify immediate and direct changes in the transcriptome concomitant with the loss of the AhR. As a result, we identified a unique data set with minimal overlap, compared with previous array studies, culminating in the identification of Stanniocalcin 2 (Stc2) as a novel receptor target gene previously reported to have a cytoprotective role in endoplasmic reticulum stress. The Stc2 promoter contains multiple putative xenobiotic response elements clustered in a 250-bp region that was shown to recruit the AhR by chromatin immunoprecipitation. Of interest, Stc2 gene expression is refractory to classic exogenous AhR agonists, but responds to cellular stress in an AhR-dependent mechanism consistent with a process promoting cell survival.
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Affiliation(s)
- Tod A Harper
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0654, USA
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Lo R, Matthews J. High-resolution genome-wide mapping of AHR and ARNT binding sites by ChIP-Seq. Toxicol Sci 2012; 130:349-61. [PMID: 22903824 DOI: 10.1093/toxsci/kfs253] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) and AHR nuclear translocator (ARNT) activated complex regulates genes in response to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). AHR has also emerged as a potential therapeutic target for the treatment of human diseases and different cancers, including breast cancer. To better understand AHR and ARNT signaling in breast cancer cells, we used chromatin immunoprecipitation linked to high-throughput sequencing to identify AHR- and ARNT-binding sites across the genome in TCDD-treated MCF-7 cells. We identified 2594 AHR-bound, 1352 ARNT-bound, and 882 AHR/ARNT cobound regions. No significant differences in the genomic distribution of AHR and ARNT were observed. Approximately 60% of the cobound regions contained at least one core an aryl hydrocarbon response element (AHRE), 5'-GCGTG-3'. AHR/ARNT peak density was the highest within 1 kb of transcription start sites (TSS); however, a number of AHR/ARNT cobound regions were located as far as 100 kb from TSS. De novo motif discovery identified a symmetrical variation of the AHRE (5'-GTGCGTG-3'), as well as FOXA1 and SP1 binding motifs. Microarray analysis identified 104 TCDD-responsive genes where 98 genes were upregulated by TCDD. Of the 104 regulated genes, 69 (66.3%) were associated with an AHR- or ARNT-bound region within 100 kb of their TSS. Overall our study identified AHR/ARNT cobound regions across the genome, revealed the importance but not absolute requirement for an AHRE in AHR/ARNT interactions with DNA, and identified a modified AHRE motif, thereby increasing our understanding of AHR/ARNT signaling pathway.
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Affiliation(s)
- Raymond Lo
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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Ahmed S, Al-Saigh S, Matthews J. FOXA1 Is Essential for Aryl Hydrocarbon Receptor–Dependent Regulation of Cyclin G2. Mol Cancer Res 2012; 10:636-48. [DOI: 10.1158/1541-7786.mcr-11-0502] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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