1
|
Chen F, Pu S, Tian L, Zhang H, Zhou H, Yan Y, Hu X, Wu Q, Chen X, Cheng SH, Xu S. Radix Rehmanniae Praeparata promoted zebrafish fin regeneration through aryl hydrocarbon receptor-dependent autophagy. J Ethnopharmacol 2024:118272. [PMID: 38710459 DOI: 10.1016/j.jep.2024.118272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/21/2024] [Accepted: 04/28/2024] [Indexed: 05/08/2024]
Abstract
HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE Rehmanniae Radix Praeparata (RRP), a staple in traditional Chinese medicine, is derived from Rehmannia glutinosa Libosch and is renowned for its wound-healing properties. Despite its clinical prevalence, the molecular mechanisms underlying RRP's wound-healing effects have not been fully elucidated. AIM OF THE STUDY This research endeavored to delineate the molecular and cellular mechanisms underlying the beneficial effects of RRP on wound healing, utilizing a zebrafish model. MATERIALS AND METHODS Zebrafish larvae at 3 days post-fertilization were amputated at the fin and subsequently treated with RRP. The pro-wound healing and regenerative effects of RRP were evaluated through morphological analysis, assessment of cell proliferation and apoptosis, Additionally, mechanistic insights were gained through a comprehensive approach encompassing network pharmacology analysis, cell tracing, RNA-sequencing, CRISPR/Cas9 gene editing, and pharmacological inhibition. RESULTS Our findings demonstrate that RRP significantly accelerates caudal fin regeneration in zebrafish following injury by suppressing cell apoptosis, promoting cell proliferation, and upregulating the expression of regenerative-related genes. Furthermore, RRP triggers autophagy signals during the regenerative process, which is attenuated by the autophagy inhibitor chloroquine (CQ). Notably, the administration of RRP enhances the expression of ahr1 and ahr2 in the regenerating fin. Genetic knockout of ahr1a, ahr1b, or ahr2 using CRISPR/Cas9, or pharmacological blockade of AHR signals with the antagonist CH-223191, diminishes the regenerative potential of RRP. Remarkably, zebrafish lacking ahr2 completely lose their fin regeneration ability. Additionally, inhibition of AHR signaling suppresses autophagy signaling during fin regeneration. CONCLUSIONS This study uncovers that RRP stimulates fin regeneration in zebrafish by inducing AHR signals and, at least partially, activating the autophagy process. These findings provide novel insights into the molecular mechanisms underlying the wound-healing effects of RRP and may pave the way for the development of novel therapeutic strategies.
Collapse
Affiliation(s)
- Fengyan Chen
- Guangxi Universities Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; Research Center for Biomedical Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; College of Life Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China
| | - Shiming Pu
- Guangxi Universities Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; Research Center for Biomedical Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; College of Life Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China
| | - Li Tian
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Science, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Huan Zhang
- Department of Food Science and Nutrition, The Hong Kong Polytechnic University, Hong Kong SAR, People's Republic of China
| | - Huixian Zhou
- Guangxi Universities Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; Research Center for Biomedical Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; College of Life Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China
| | - Yijing Yan
- Guangxi Universities Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; Research Center for Biomedical Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; College of Life Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China
| | - Xiaolin Hu
- School of Economics and Management, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China
| | - Qiong Wu
- Guangxi Universities Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; Research Center for Biomedical Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; College of Life Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China
| | - Xueping Chen
- Vitargent (International) Biotechnology Limited, Unit 516, 5/F. Biotech Centre 2, No. 11 Science Park West Avenue, Hong Kong Science Park, Shatin, Hong Kong SAR, People's Republic of China
| | - Shuk Han Cheng
- Department of Biomedical Sciences, College of Veterinary Medicine and Life Science, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Shisan Xu
- Guangxi Universities Key Laboratory of Stem Cell and Biopharmaceutical Technology, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; Research Center for Biomedical Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China; College of Life Sciences, Guangxi Normal University, Guangxi Zhuang Autonomous Region, Guilin, China.
| |
Collapse
|
2
|
Chen H, Diolaiti ME, O’Leary PC, Rojc A, Krogan NJ, Kim M, Ashworth A. A Whole-Genome CRISPR Screen Identifies AHR Loss as a Mechanism of Resistance to a PARP7 Inhibitor. Mol Cancer Ther 2022; 21:1076-1089. [PMID: 35439318 PMCID: PMC9769698 DOI: 10.1158/1535-7163.mct-21-0841] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 02/09/2022] [Accepted: 04/12/2022] [Indexed: 01/07/2023]
Abstract
Inhibitors directed toward PARP1 and PARP2 are approved agents for the treatment of BRCA1 and BRCA2-related cancers. Other members of the PARP family have also been implicated in cancer and are being assessed as therapeutic targets in cancer and other diseases. Recently, an inhibitor of PARP7 (RBN-2397) has reached early-stage human clinical trials. Here, we performed a genome-wide CRISPR screen for genes that modify the response of cells to RBN-2397. We identify the polycyclic aromatic hydrocarbon receptor AHR and multiple components of the cohesin complex as determinants of resistance to this agent. Activators and inhibitors of AHR modulate the cellular response to PARP7 inhibition, suggesting potential combination therapy approaches.
Collapse
Affiliation(s)
- Huadong Chen
- Helen Diller Family Comprehensive Cancer Center, San Francisco, CA, USA 94158
| | - Morgan E. Diolaiti
- Helen Diller Family Comprehensive Cancer Center, San Francisco, CA, USA 94158
- The Cancer Cell Map Initiative, San Francisco and La Jolla, CA, USA
| | - Patrick C. O’Leary
- Helen Diller Family Comprehensive Cancer Center, San Francisco, CA, USA 94158
- The Cancer Cell Map Initiative, San Francisco and La Jolla, CA, USA
| | - Ajda Rojc
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA 94158
- The J. David Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, USA 94158
- Quantitative Biosciences Institute, University of California, San Francisco, CA, USA 94158
- The Cancer Cell Map Initiative, San Francisco and La Jolla, CA, USA
| | - Nevan J. Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA 94158
- The J. David Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, USA 94158
- Quantitative Biosciences Institute, University of California, San Francisco, CA, USA 94158
- The Cancer Cell Map Initiative, San Francisco and La Jolla, CA, USA
| | - Minkyu Kim
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA 94158
- The J. David Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, USA 94158
- Quantitative Biosciences Institute, University of California, San Francisco, CA, USA 94158
- The Cancer Cell Map Initiative, San Francisco and La Jolla, CA, USA
| | - Alan Ashworth
- Helen Diller Family Comprehensive Cancer Center, San Francisco, CA, USA 94158
- The Cancer Cell Map Initiative, San Francisco and La Jolla, CA, USA
| |
Collapse
|
3
|
Meynier M, Baudu E, Rolhion N, Defaye M, Straube M, Daugey V, Modoux M, Wawrzyniak I, Delbac F, Villéger R, Méleine M, Borras Nogues E, Godfraind C, Barnich N, Ardid D, Poirier P, Sokol H, Chatel JM, Langella P, Livrelli V, Bonnet M, Carvalho FA. AhR/IL-22 pathway as new target for the treatment of post-infectious irritable bowel syndrome symptoms. Gut Microbes 2022; 14:2022997. [PMID: 35090380 PMCID: PMC8803069 DOI: 10.1080/19490976.2021.2022997] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 12/10/2021] [Indexed: 02/04/2023] Open
Abstract
Alterations in brain/gut/microbiota axis are linked to Irritable Bowel Syndrome (IBS) physiopathology. Upon gastrointestinal infection, chronic abdominal pain and anxio-depressive comorbidities may persist despite pathogen clearance leading to Post-Infectious IBS (PI-IBS). This study assesses the influence of tryptophan metabolism, and particularly the microbiota-induced AhR expression, on intestinal homeostasis disturbance following gastroenteritis resolution, and evaluates the efficacy of IL-22 cytokine vectorization on PI-IBS symptoms. The Citrobacter rodentium infection model in C57BL6/J mice was used to mimic Enterobacteria gastroenteritis. Intestinal homeostasis was evaluated as low-grade inflammation, permeability, mucosa-associated microbiota composition, and colonic sensitivity. Cognitive performances and emotional state of animals were assessed using several tests. Tryptophan metabolism was analyzed by targeted metabolomics. AhR activity was evaluated using a luciferase reporter assay method. One Lactococcus lactis strain carrying an eukaryotic expression plasmid for murine IL-22 (L. lactisIL-22) was used to induce IL-22 production in mouse colonic mucosa. C. rodentium-infected mice exhibited persistent colonic hypersensitivity and cognitive impairments and anxiety-like behaviors after pathogen clearance. These post-infectious disorders were associated with low-grade inflammation, increased intestinal permeability, decrease of Lactobacillaceae abundance associated with the colonic layer, and increase of short-chain fatty acids (SCFAs). During post-infection period, the indole pathway and AhR activity were decreased due to a reduction of tryptophol production. Treatment with L. lactisIL-22 restored gut permeability and normalized colonic sensitivity, restored cognitive performances and decreased anxiety-like behaviors. Data from the video-tracking system suggested an upgrade of welfare for mice receiving the L.lactisIL-22 strain. Our findings revealed that AhR/IL-22 signaling pathway is altered in a preclinical PI-IBS model. IL-22 delivering alleviate PI-IBS symptoms as colonic hypersensitivity, cognitive impairments, and anxiety-like behaviors by acting on intestinal mucosa integrity. Thus, therapeutic strategies targeting this pathway could be developed to treat IBS patients suffering from chronic abdominal pain and associated well-being disorders.
Collapse
Affiliation(s)
- Maëva Meynier
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
- NeuroDol, UMR 1107 INSERM, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Elodie Baudu
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
- NeuroDol, UMR 1107 INSERM, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Nathalie Rolhion
- Sorbonne University, INSERM, Centre de Recherche Saint-Antoine, CRSA, AP-HP, Saint Antoine Hospital, Gastroenterology Department, F-75012Paris, France
- Paris Centre for Microbiome Medicine FHU, Paris, France
| | - Manon Defaye
- NeuroDol, UMR 1107 INSERM, University of Clermont Auvergne, Clermont-Ferrand63001, France
- Department of Physiology and Pharmacology, Inflammation Research Network, Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada
- LMGE, CNRS 6023, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Marjolène Straube
- Sorbonne University, INSERM, Centre de Recherche Saint-Antoine, CRSA, AP-HP, Saint Antoine Hospital, Gastroenterology Department, F-75012Paris, France
| | - Valentine Daugey
- NeuroDol, UMR 1107 INSERM, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Morgane Modoux
- Sorbonne University, INSERM, Centre de Recherche Saint-Antoine, CRSA, AP-HP, Saint Antoine Hospital, Gastroenterology Department, F-75012Paris, France
| | - Ivan Wawrzyniak
- LMGE, CNRS 6023, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Frédéric Delbac
- LMGE, CNRS 6023, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Romain Villéger
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
| | - Mathieu Méleine
- NeuroDol, UMR 1107 INSERM, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Esther Borras Nogues
- Université Paris-Saclay, Institut National de la Recherche Agronomique et Environnementale (INRAE), AgroParisTech UMR 1319 MICALIS, Jouy-en-Josas, France
| | - Catherine Godfraind
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
- CHU Clermont-Ferrand, Neuropathology Unit, Clermont-Ferrand, France
| | - Nicolas Barnich
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
| | - Denis Ardid
- NeuroDol, UMR 1107 INSERM, University of Clermont Auvergne, Clermont-Ferrand63001, France
| | - Philippe Poirier
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
- CHU Clermont-Ferrand, Laboratoire de Parasitologie et de Mycologie, Clermont-Ferrand, France
| | - Harry Sokol
- Sorbonne University, INSERM, Centre de Recherche Saint-Antoine, CRSA, AP-HP, Saint Antoine Hospital, Gastroenterology Department, F-75012Paris, France
- Paris Centre for Microbiome Medicine FHU, Paris, France
- Université Paris-Saclay, Institut National de la Recherche Agronomique et Environnementale (INRAE), AgroParisTech UMR 1319 MICALIS, Jouy-en-Josas, France
| | - Jean-Marc Chatel
- Université Paris-Saclay, Institut National de la Recherche Agronomique et Environnementale (INRAE), AgroParisTech UMR 1319 MICALIS, Jouy-en-Josas, France
| | - Philippe Langella
- Université Paris-Saclay, Institut National de la Recherche Agronomique et Environnementale (INRAE), AgroParisTech UMR 1319 MICALIS, Jouy-en-Josas, France
| | - Valérie Livrelli
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
- CHU Clermont-Ferrand, Laboratoire de Parasitologie et de Mycologie, Clermont-Ferrand, France
| | - Mathilde Bonnet
- M2iSH, UMR 1071 INSERM, University of Clermont Auvergne, INRAE USC 2018, Clermont-Ferrand63001, France
| | | |
Collapse
|
4
|
Lordo MR, Wu KG, Altynova E, Shilo N, Kronen P, Nalin AP, Weigel C, Zhang X, Yu J, Oakes CC, Caligiuri MA, Freud AG, Mundy-Bosse BL. Acute Myeloid Leukemia Alters Group 1 Innate Lymphoid Cell Differentiation from a Common Precursor. J Immunol 2021; 207:1672-1682. [PMID: 34417259 PMCID: PMC8429221 DOI: 10.4049/jimmunol.2100023] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 07/20/2021] [Indexed: 11/19/2022]
Abstract
NK cells are known to be developmentally blocked and functionally inhibited in patients with acute myeloid leukemia (AML), resulting in poor clinical outcomes. In this study, we demonstrate that whereas NK cells are inhibited, closely related type 1 innate lymphoid cells (ILC1s) are enriched in the bone marrow of leukemic mice and in patients with AML. Because NK cells and ILC1s share a common precursor (ILCP), we asked if AML acts on the ILCP to alter developmental potential. A combination of ex vivo and in vivo studies revealed that AML skewing of the ILCP toward ILC1s and away from NK cells represented a major mechanism of ILC1 generation. This process was driven by AML-mediated activation of the aryl hydrocarbon receptor (AHR), a key transcription factor in ILCs, as inhibition of AHR led to decreased numbers of ILC1s and increased NK cells in the presence of AML. These results demonstrate a mechanism of ILC developmental skewing in AML and support further preclinical study of AHR inhibition in restoring normal NK cell development and function in the setting of AML.
Collapse
MESH Headings
- Animals
- Azo Compounds/pharmacology
- Basic Helix-Loop-Helix Transcription Factors/agonists
- Basic Helix-Loop-Helix Transcription Factors/antagonists & inhibitors
- Basic Helix-Loop-Helix Transcription Factors/metabolism
- Bone Marrow/immunology
- Carbazoles/pharmacology
- Cell Differentiation/drug effects
- Cell Differentiation/immunology
- Cells, Cultured
- Disease Models, Animal
- Female
- Humans
- Immunity, Innate
- Killer Cells, Natural/immunology
- Leukemia, Myeloid, Acute/blood
- Leukemia, Myeloid, Acute/immunology
- Lymphocyte Count
- Male
- Mice
- Mice, Inbred C57BL
- Pyrazoles/pharmacology
- Receptors, Aryl Hydrocarbon/agonists
- Receptors, Aryl Hydrocarbon/antagonists & inhibitors
- Receptors, Aryl Hydrocarbon/metabolism
- Signal Transduction/drug effects
Collapse
Affiliation(s)
- Matthew R Lordo
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Medical Scientist Training Program, Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH
| | - Kevin G Wu
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | | | - Nikolas Shilo
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Parker Kronen
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Ansel P Nalin
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Medical Scientist Training Program, Biomedical Sciences Graduate Program, The Ohio State University, Columbus, OH
| | - Christoph Weigel
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
| | - Xiaoli Zhang
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Center for Biostatistics/Department of Biomedical Informatics, The Ohio State University, Columbus, OH
| | - Jianhua Yu
- City of Hope National Medical Center, Los Angeles, CA
| | - Christopher C Oakes
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH
- Division of Hematology, Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH; and
| | | | - Aharon G Freud
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH;
- Department of Pathology, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Bethany L Mundy-Bosse
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH;
- Division of Hematology, Department of Internal Medicine, The Ohio State University Wexner Medical Center, Columbus, OH; and
| |
Collapse
|
5
|
Muku GE, Kusnadi A, Kuzu G, Tanos R, Murray IA, Gowda K, Amin S, Perdew GH. Selective Ah receptor modulators attenuate NPC1L1-mediated cholesterol uptake through repression of SREBP-2 transcriptional activity. J Transl Med 2020; 100:250-64. [PMID: 31417158 DOI: 10.1038/s41374-019-0306-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [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.
Collapse
|
6
|
Zhu K, Meng Q, Zhang Z, Yi T, He Y, Zheng J, Lei W. Aryl hydrocarbon receptor pathway: Role, regulation and intervention in atherosclerosis therapy (Review). Mol Med Rep 2019; 20:4763-4773. [PMID: 31638212 PMCID: PMC6854528 DOI: 10.3892/mmr.2019.10748] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/05/2019] [Indexed: 12/20/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand‑activated transcription factor originally isolated and characterized as the dioxin or xenobiotic receptor. With the discovery of endogenous ligands and studies of AhR knockout mice, AhR has been found to serve an important role in several biological processes, including immune responses and developmental and pathological regulation. In particular, it has been considered as a new major player in cardiovascular diseases. Recent studies have revealed that the development of atherosclerosis is closely associated with AhR function. However, the roles of the AhR in the pathological development of atherosclerosis and atherosclerosis‑associated diseases remain unclear. The current review presents the molecular mechanisms involved in the regulation of AhR expression during inflammation, oxidative stress and lipid deposition. Additionally, the role of the AhR in atherosclerosis and atherosclerosis‑associated diseases is reviewed.
Collapse
Affiliation(s)
- Kaixi Zhu
- Cardiovascular Medicine Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
- Laboratory of Cardiovascular Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
| | - Qingqi Meng
- Department of Orthopedics, Guangzhou Red Cross Hospital, Guangzhou, Guangdong 510000, P.R. China
| | - Zhi Zhang
- Department of Vascular, Thyroid and Breast Surgery, Affiliated Hospital of Guangdong Medical College, Zhanjiang, Guangdong 524001, P.R. China
| | - Tao Yi
- Cardiovascular Medicine Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
- Laboratory of Cardiovascular Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
| | - Yuan He
- Laboratory of Cardiovascular Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
| | - Jing Zheng
- Department of Obstetrics and Gynecology, University of Wisconsin, Madison, WI 53715, USA
| | - Wei Lei
- Cardiovascular Medicine Center, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
- Laboratory of Cardiovascular Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524001, P.R. China
| |
Collapse
|
7
|
Ulin A, Henderson J, Pham MT, Meyo J, Chen Y, Karchner SI, Goldstone JV, Hahn ME, Williams LM. Developmental Regulation of Nuclear Factor Erythroid-2 Related Factors (nrfs) by AHR1b in Zebrafish (Danio rerio). Toxicol Sci 2019; 167:536-545. [PMID: 30321412 PMCID: PMC6358246 DOI: 10.1093/toxsci/kfy257] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Interactions between regulatory pathways allow organisms to adapt to their environment and respond to stress. One interaction that has been recently identified occurs between the aryl hydrocarbon receptor (AHR) and the nuclear factor erythroid-2 related factor (NRF) family. Each transcription factor regulates numerous downstream genes involved in the cellular response to toxicants and oxidative stress; they are also implicated in normal developmental pathways. The zebrafish model was used to explore the role of AHR regulation of nrf genes during development and in response to toxicant exposure. To determine if AHR1b is responsible for transcriptional regulation of 6 nrf genes during development, a loss-of-function experiment using morpholino-modified oligonucleotides was conducted followed by a chromatin immunoprecipitation study at the beginning of the pharyngula period (24 h postfertilization). The expression of nrf1a was AHR1b dependent and its expression was directly regulated through specific XREs in its cis-promoter. However, nrf1a expression was not altered by exposure to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), a toxicant and prototypic AHR agonist. The expression of nrf1b, nrf2a, and nfe2 was induced by TCDD, and AHR1b directly regulated their expression by binding to cis-XRE promoter elements. Last, nrf2b and nrf3 were neither induced by TCDD nor regulated by AHR1b. These results show that AHR1b transcriptionally regulates nrf genes under toxicant modulation via binding to specific XREs. These data provide a better understanding of how combinatorial molecular signaling potentially protects embryos from embryotoxic events following toxicant exposure.
Collapse
Affiliation(s)
- Alexandra Ulin
- Department of biology, Bates College, Lewiston, Maine 04240
| | - Jake Henderson
- Department of biology, Bates College, Lewiston, Maine 04240
| | - Minh-Tam Pham
- Department of biology, Bates College, Lewiston, Maine 04240
| | - James Meyo
- Department of biology, Bates College, Lewiston, Maine 04240
| | - Yuying Chen
- Department of biology, Bates College, Lewiston, Maine 04240
| | - Sibel I Karchner
- Department of biology, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
| | - Jared V Goldstone
- Department of biology, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
| | - Mark E Hahn
- Department of biology, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
| | - Larissa M Williams
- Department of biology, Bates College, Lewiston, Maine 04240
- Department of biology, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
| |
Collapse
|
8
|
Miller M, Vuong C, Garcia MF, Rosenthal P, Das S, Weng N, Pham A, Kim YJ, Broide DH. Does reduced zona pellucida binding protein 2 (ZPBP2) expression on chromosome 17q21 protect against asthma? J Allergy Clin Immunol 2018; 142:706-709.e4. [PMID: 29709669 PMCID: PMC6078789 DOI: 10.1016/j.jaci.2018.04.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 04/09/2018] [Accepted: 04/20/2018] [Indexed: 10/17/2022]
Affiliation(s)
- Marina Miller
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | - Christine Vuong
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | | | - Peter Rosenthal
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | - Sudipta Das
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | - Ning Weng
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | - Alexa Pham
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | - Yu Jin Kim
- Department of Medicine, University of California San Diego, La Jolla, Calif
| | - David H Broide
- Department of Medicine, University of California San Diego, La Jolla, Calif.
| |
Collapse
|
9
|
Gabriely G, Wheeler MA, Takenaka MC, Quintana FJ. Role of AHR and HIF-1α in Glioblastoma Metabolism. Trends Endocrinol Metab 2017; 28:428-436. [PMID: 28318896 PMCID: PMC5438779 DOI: 10.1016/j.tem.2017.02.009] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 02/10/2017] [Accepted: 02/16/2017] [Indexed: 01/01/2023]
Abstract
Glioblastoma (GBM) progression is associated with metabolic remodeling in both glioma and immune cells, resulting in the use of aerobic glycolysis as the main source of energy and biosynthetic molecules. The transcription factor hypoxia-inducible factor (HIF)-1α drives this metabolic reorganization. Oxygen levels, as well as other factors, control the activity of HIF-1α. In addition, the ligand-activated transcription factor aryl hydrocarbon receptor (AHR) modulates tumor-specific immunity and can also participate in metabolic remodeling. AHR activity is regulated by tryptophan derivatives present in the tumor microenvironment. Thus, the tumor microenvironment and signaling via HIF-1α and AHR regulate the metabolism of gliomas and immune cells, modulating tumor-specific immunity and, consequently, tumor growth. Here, we review the roles of HIF-1α and AHR in cancer and immune cell metabolism in GBM.
Collapse
Affiliation(s)
- Galina Gabriely
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Michael A Wheeler
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Maisa C Takenaka
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Francisco J Quintana
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; The Broad Institute of MIT and Harvard, Cambridge, MA, USA.
| |
Collapse
|
10
|
Zhang L, Hatzakis E, Nichols RG, Hao R, Correll J, Smith PB, Chiaro CR, Perdew GH, Patterson AD. Metabolomics Reveals that Aryl Hydrocarbon Receptor Activation by Environmental Chemicals Induces Systemic Metabolic Dysfunction in Mice. Environ Sci Technol 2015; 49:8067-77. [PMID: 26023891 PMCID: PMC4890155 DOI: 10.1021/acs.est.5b01389] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Environmental exposure to dioxins and dioxin-like compounds poses a significant health risk for human health. Developing a better understanding of the mechanisms of toxicity through activation of the aryl hydrocarbon receptor (AHR) is likely to improve the reliability of risk assessment. In this study, the AHR-dependent metabolic response of mice exposed to 2,3,7,8-tetrachlorodibenzofuran (TCDF) was assessed using global (1)H nuclear magnetic resonance (NMR)-based metabolomics and targeted metabolite profiling of extracts obtained from serum and liver. (1)H NMR analyses revealed that TCDF exposure suppressed gluconeogenesis and glycogenolysis, stimulated lipogenesis, and triggered inflammatory gene expression in an Ahr-dependent manner. Targeted analyses using gas chromatography coupled with mass spectrometry showed TCDF treatment altered the ratio of unsaturated/saturated fatty acids. Consistent with this observation, an increase in hepatic expression of stearoyl coenzyme A desaturase 1 was observed. In addition, TCDF exposure resulted in inhibition of de novo fatty acid biosynthesis manifested by down-regulation of acetyl-CoA, malonyl-CoA, and palmitoyl-CoA metabolites and related mRNA levels. In contrast, no significant changes in the levels of glucose and lipid were observed in serum and liver obtained from Ahr-null mice following TCDF treatment, thus strongly supporting the important role of the AHR in mediating the metabolic effects seen following TCDF exposure.
Collapse
Affiliation(s)
- Limin Zhang
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
- CAS Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Centre for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences (CAS), Wuhan 430071, China
| | - Emmanuel Hatzakis
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Robert G. Nichols
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Ruixin Hao
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Jared Correll
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Philip B. Smith
- Metabolomics Facility, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Christopher R. Chiaro
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Gary H. Perdew
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
| | - Andrew D. Patterson
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania, 16802, USA
- To whom correspondence should be addressed. Address: 322 Life Sciences Building, Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, PA 16802; USA, Phone: 8148674565; Fax:
| |
Collapse
|
11
|
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates the toxic and biological effects of structurally diverse chemicals, including the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). As part of a larger effort to identify the full spectrum of chemicals that can bind to and activate the AhR, we have examined the ability of several naturally occurring marine-derived brominated indoles and brominated (methylthio)indoles (collectively referred to as brominated indoles) to bind to the AhR and stimulate AhR-dependent gene expression. Incubation of mouse, rat, and guinea pig recombinant cell lines containing a stably transfected AhR-responsive luciferase reporter gene with eight brominated indoles revealed that all compounds stimulated luciferase reporter gene activity, although some species-specific differences were observed. All compounds induced significantly more luciferase activity when incubated with cells for 4 h as compared to 24 h, demonstrating that these compounds are transient activators of the AhR signaling pathway. Three of the brominated indoles induced CYP1A1 mRNA in human HepG2 cells in vitro and Cyp1a mRNA in zebrafish embryos in vivo. The identification of the brominated indoles as direct ligands and activators/agonists of the AhR was confirmed by their ability to compete with [(3)H]TCDD for binding to the AhR and to stimulate AhR transformation and DNA binding in vitro. Taken together, these results indicate that marine-derived brominated indoles are members of a new class of naturally occurring AhR agonists.
Collapse
Affiliation(s)
- Danica E. DeGroot
- Department of Environmental Toxicology, University of California, Davis, CA USA
| | - Diana G. Franks
- Department of Biology and the Woods Hole Center for Oceans and Human Health, Woods Hole Oceanographic Institution, Woods Hole, MA USA
| | - Tatsuo Higa
- Department of Chemistry, Biology and Marine Sciences, University of the Ryukyus, Nishihara, Okinawa, JAPAN
| | - Junichi Tanaka
- Department of Chemistry, Biology and Marine Sciences, University of the Ryukyus, Nishihara, Okinawa, JAPAN
| | - Mark E. Hahn
- Department of Biology and the Woods Hole Center for Oceans and Human Health, Woods Hole Oceanographic Institution, Woods Hole, MA USA
| | - Michael S. Denison
- Department of Environmental Toxicology, University of California, Davis, CA USA
| |
Collapse
|
12
|
Vogel CFA, Wu D, Goth SR, Baek J, Lollies A, Domhardt R, Grindel A, Pessah IN. Aryl hydrocarbon receptor signaling regulates NF-κB RelB activation during dendritic-cell differentiation. Immunol Cell Biol 2013; 91:568-75. [PMID: 23999131 PMCID: PMC3806313 DOI: 10.1038/icb.2013.43] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 07/26/2013] [Accepted: 07/27/2013] [Indexed: 12/26/2022]
Abstract
How the aryl hydrocarbon receptor (AhR) regulates dendritic-cell (DC) differentiation is unknown. We show that activation of AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) caused enhanced differentiation from immature DCs (IDCs) to mature DCs (MDCs) in the bone-marrow-derived DCs (BMDC) from B6 wild-type mice but not in the BMDCs from AhR-null mice as indicated by the expression of CD11c and class II major histocompatibility complex (MHC). Enhanced maturation of BMDCs was associated with elevated levels of CD86 and an increased AhR-dependent nuclear accumulation of nuclear factor-kappa-light-chain enhancer of activated B cell (NF-κB) member RelB in BMDCs. The expression of interleukin (IL) 10 and chemokine DC-CK1 was suppressed, whereas that of CXCL2, CXCL3 and IL-22 was significantly increased in AhR-activated BMDCs. Furthermore, TCDD induced expression of the regulatory enzymes indoleamine 2,3-dioxygenase (IDO1) and indoleamine 2,3-dioxygenase-like 1 (IDO2). Increased expression of IDO2 was associated with coexpression of the cell-surface marker CCR6. Interestingly, mRNA expression of the chemokine receptor CCR6 was drastically decreased in AhR-null IDCs and MDCs. Overall, these data demonstrate that AhR modifies the maturation of BMDCs associated with the induction of the regulatory enzyme IDO and altered expression of cytokine, chemokines and DC-specific surface markers and receptors.
Collapse
Affiliation(s)
- Christoph F A Vogel
- Department of Environmental Toxicology, University of California at Davis, Davis, CA, USA
- Center for Health and the Environment, University of California at Davis, Davis, CA, USA
| | - Dalei Wu
- Center for Health and the Environment, University of California at Davis, Davis, CA, USA
| | - Samuel R Goth
- School of Veterinary Medicine: Molecular Biosciences, University of California at Davis, Davis, CA, USA
| | - Jaeeun Baek
- Center for Health and the Environment, University of California at Davis, Davis, CA, USA
| | - Anna Lollies
- Center for Health and the Environment, University of California at Davis, Davis, CA, USA
| | - Rowena Domhardt
- Center for Health and the Environment, University of California at Davis, Davis, CA, USA
| | - Annemarie Grindel
- Center for Health and the Environment, University of California at Davis, Davis, CA, USA
| | - Isaac N Pessah
- School of Veterinary Medicine: Molecular Biosciences, University of California at Davis, Davis, CA, USA
| |
Collapse
|
13
|
Zanette J, Jenny MJ, Goldstone JV, Parente T, Woodin BR, Bainy ACD, Stegeman JJ. Identification and expression of multiple CYP1-like and CYP3-like genes in the bivalve mollusk Mytilus edulis. Aquat Toxicol 2013; 128-129:101-12. [PMID: 23277104 PMCID: PMC3846546 DOI: 10.1016/j.aquatox.2012.11.017] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/16/2012] [Accepted: 11/22/2012] [Indexed: 05/06/2023]
Abstract
Various sequencing projects over the last several years have aided the discovery of previously uncharacterized invertebrate sequences, including new cytochrome P450 genes (CYPs). Here we present data on the identification and characterization of two CYP1-like and three CYP3-like genes from the bivalve mollusk Mytilus edulis, and assess their potential as biomarkers based on their responses to several known vertebrate aryl hydrocarbon receptor (AHR) agonists. Quantitative real-time PCR was used to measure CYP transcript levels in digestive gland, labial palps, adductor muscle, gill, foot, and different regions of the mantle. Levels of both CYP1-like genes were highest in digestive gland, whereas labial palps had the highest expression levels of the three CYP3-like genes followed by digestive gland and outer margin of the mantle. Mussels were exposed by injection to the AHR agonists, β-naphthoflavone (BNF; 25 μg g(-1)), 3,3',4,4',5-polychlorinated biphenyl (PCB126; 2 μg g(-1)), or 6-formylindolo[3,2-b]carbazole (FICZ; 0.1 μg g(-1)), or to Aroclor 1254 (a mixture of PCBs; 50 μg g(-1)) for 24 h, followed by CYP expression analysis. There was no statistically significant change in expression of either of the CYP1-like genes after exposure to the various AHR agonists. The CYP3-like-1 gene was significantly up-regulated by BNF in gill tissues and the CYP3-like-2 gene was up-regulated in digestive gland by PCB126 and in gill tissue by BNF. These results suggest that distinct mechanisms of CYP gene activation could be present in M. edulis, although the importance of the CYP1-like and CYP3-like genes for xenobiotic and endogenous lipids biotransformation requires additional investigation.
Collapse
Affiliation(s)
- Juliano Zanette
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543
- Biochemistry Department, Federal University of Santa Catarina, Florianopolis SC, Brazil
| | - Matthew J. Jenny
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543
- Department of Biological Sciences, University of Alabama, Tuscaloosa AL 35487
| | - Jared V. Goldstone
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543
| | - Thiago Parente
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543
- Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Bruce R. Woodin
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543
| | - Afonso C. D. Bainy
- Biochemistry Department, Federal University of Santa Catarina, Florianopolis SC, Brazil
| | - John J. Stegeman
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543
- Correspondence to: John J. Stegeman, Biology Department, MS 32, Woods Hole Oceanographic Institution, Woods Hole MA USA 02543,
| |
Collapse
|
14
|
Chang HYS, Mitzner W, Watson J. Variation in airway responsiveness of male C57BL/6 mice from 5 vendors. J Am Assoc Lab Anim Sci 2012; 51:401-406. [PMID: 23043804 PMCID: PMC3400687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 10/11/2011] [Accepted: 12/12/2011] [Indexed: 06/01/2023]
Abstract
Mice are now the most commonly used animal model for the study of asthma. The mouse asthma model has many characteristics of the human pathology, including allergic sensitization and airway hyperresponsiveness. Inbred strains are commonly used to avoid variations due to genetic background, but variations due to rearing environment are not as well recognized. After a change in mouse vendors and a switch from C57BL/6J mice to C57BL/6N mice, we noted significant differences in airway responsiveness between the substrains. To further investigate the effect of vendor, we tested C57BL/6N mice from 3 other vendors and found significant differences between several of the substrains. To test whether this difference was due to genetic drift or rearing environment, we purchased new groups of mice from all 5 vendors, bred them in separate vendor-specific groups under uniform environmental conditions, and tested male first generation (F1) offspring at 8 to 10 wk of age. These F1 mice showed no significant differences in airway responsiveness, indicating that the rearing environment rather than genetic differences was responsible for the initial variation in pulmonary phenotype. The environmental factors that caused the phenotypic variation are unknown. However, differences between vendor in feed components, bedding type, or microbiome could have contributed. Whatever the basis, investigators using mouse models of asthma should be cautious in comparing data from mice obtained from different vendors.
Collapse
Affiliation(s)
| | | | - Julie Watson
- Departments of Molecular and Comparative Pathobiology, Johns Hopkins University, Baltimore, Maryland
| |
Collapse
|
15
|
Tanos R, Patel RD, Murray IA, Smith PB, Perdew GH, Perdew GH. Aryl hydrocarbon receptor regulates the cholesterol biosynthetic pathway in a dioxin response element-independent manner. Hepatology 2012; 55:1994-2004. [PMID: 22234961 PMCID: PMC3340481 DOI: 10.1002/hep.25571] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
UNLABELLED The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor. Activation of AhR mediates the expression of target genes (e.g., CYP1A1) by binding to dioxin response element (DRE) sequences in their promoter region. To understand the multiple mechanisms of AhR-mediated gene regulation, a microarray analysis on liver isolated from ligand-treated transgenic mice expressing a wild-type (WT) Ahr or a DRE-binding mutant Ahr (A78D) on an ahr-null background was performed. Results revealed that AhR DRE binding is not required for the suppression of genes involved in cholesterol synthesis. Quantitative reverse-transcription polymerase chain reaction performed on both mouse liver and primary human hepatocyte RNA demonstrated a coordinated repression of genes involved in cholesterol biosynthesis, namely, HMGCR, FDFT1, SQLE, and LSS after receptor activation. An additional transgenic mouse line was established expressing a liver-specific Ahr-A78D on a Cre(Alb)/Ahr(flox/flox) background. These mice displayed a similar repression of cholesterol biosynthetic genes, compared to Ahr(flox/flox) mice, further indicating that the observed modulation is AhR specific and occurs in a DRE-independent manner. Elevated hepatic transcriptional levels of the genes of interest were noted in congenic C57BL/6J-Ah(d) allele mice, when compared to the WT C57BL/6J mice, which carry the Ah(b) allele. Down-regulation of AhR nuclear translocator levels using short interfering RNA in a human cell line revealed no effect on the expression of cholesterol biosynthetic genes. Finally, cholesterol secretion was shown to be significantly decreased in human cells after AhR activation. CONCLUSION These data firmly establish an endogenous role for AhR as a regulator of the cholesterol biosynthesis pathway independent of its DRE-binding ability, and suggest that AhR may be a previously unrecognized therapeutic target.
Collapse
Affiliation(s)
| | | | | | | | - Gary H. Perdew
- To whom correspondence should be addressed. Telephone: (814) 865-0400. Fax: 814-863-1696.
| | | |
Collapse
|
16
|
Vaynshteyn D, Jeong H. Caffeine induces CYP1A2 expression in rat hepatocytes but not in human hepatocytes. Drug Metab Lett 2012; 6:116-119. [PMID: 23167901 PMCID: PMC3715142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 05/29/2012] [Accepted: 05/30/2012] [Indexed: 06/01/2023]
Abstract
Caffeine is the active constituent in coffee. Continual consumption of caffeine can lead to an attenuated response also known as tolerance. Results from rat studies have shown that caffeine is an inducer of CYP1A2, the enzyme responsible for caffeine's metabolism. This suggests that CYP1A2 induction by caffeine may be in part responsible for caffeine tolerance. However, whether caffeine induces CYP1A2 expression in humans remains unknown. Our results from luciferase assays performed in HepG2 cells showed that caffeine is not an activator of the aromatic hydrocarbon receptor (AhR), a major transcription factor involved in upregulation of CYP1A2. Furthermore, caffeine did not induce CYP1A2 expression in primary human hepatocytes at a concentration attained by ordinary coffee drinking. On the other hand, caffeine enhanced CYP1A2 expression by 9-fold in rat hepatocytes. Our results suggest that caffeine from ordinary coffee drinking does not induce CYP1A2 expression in humans and that factors other than CYP1A2 induction by caffeine likely contribute to development of caffeine tolerance in humans.
Collapse
Affiliation(s)
- David Vaynshteyn
- Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL
| | - Hyunyoung Jeong
- Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL
| |
Collapse
|
17
|
King-Heiden TC, Mehta V, Xiong KM, Lanham KA, Antkiewicz DS, Ganser A, Heideman W, Peterson RE. Reproductive and developmental toxicity of dioxin in fish. Mol Cell Endocrinol 2012; 354:121-38. [PMID: 21958697 PMCID: PMC3306500 DOI: 10.1016/j.mce.2011.09.027] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 09/12/2011] [Accepted: 09/13/2011] [Indexed: 10/17/2022]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin) is a global environmental contaminant and the prototypical ligand for investigating aryl hydrocarbon receptor (AHR)-mediated toxicity. Environmental exposure to TCDD results in developmental and reproductive toxicity in fish, birds and mammals. To resolve the ecotoxicological relevance and human health risks posed by exposure to dioxin-like AHR agonists, a vertebrate model is needed that allows for toxicity studies at various levels of biological organization, assesses adverse reproductive and developmental effects and establishes appropriate integrative correlations between different levels of effects. Here we describe the reproductive and developmental toxicity of TCDD in feral fish species and summarize how using the zebrafish model to investigate TCDD toxicity has enabled us to characterize the AHR signaling in fish and to better understand how dioxin-like chemicals induce toxicity. We propose that such studies can be used to predict the risks that AHR ligands pose to feral fish populations and provide a platform for integrating risk assessments for both ecologically relevant organisms and humans.
Collapse
Affiliation(s)
- Tisha C. King-Heiden
- Department of Biology and River Studies Center, University of Wisconsin, La Crosse, WI
| | - Vatsal Mehta
- Molecular and Environmental Toxicology Center, University of Wisconsin, Madison, WI
| | - Kong M. Xiong
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI
| | - Kevin A. Lanham
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI
| | | | - Alissa Ganser
- Department of Biology and River Studies Center, University of Wisconsin, La Crosse, WI
| | - Warren Heideman
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison, WI
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI
- Molecular and Environmental Toxicology Center, University of Wisconsin, Madison, WI
| | - Richard E. Peterson
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin, Madison, WI
- Molecular and Environmental Toxicology Center, University of Wisconsin, Madison, WI
| |
Collapse
|
18
|
Vogel CFA, Garcia J, Wu D, Mitchell DC, Zhang Y, Kado NY, Wong P, Trujillo DA, Lollies A, Bennet D, Schenker MB, Mitloehner FM. Activation of inflammatory responses in human U937 macrophages by particulate matter collected from dairy farms: an in vitro expression analysis of pro-inflammatory markers. Environ Health 2012; 11:17. [PMID: 22452745 PMCID: PMC3342144 DOI: 10.1186/1476-069x-11-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 03/28/2012] [Indexed: 05/22/2023]
Abstract
BACKGROUND The purpose of the present study was to investigate activation of inflammatory markers in human macrophages derived from the U937 cell line after exposure to particulate matter (PM) collected on dairy farms in California and to identify the most potent components of the PM. METHODS PM from different dairies were collected and tested to induce an inflammatory response determined by the expression of various pro-inflammatory genes, such as Interleukin (IL)-8, in U937 derived macrophages. Gel shift and luciferase reporter assays were performed to examine the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Toll-like-receptor 4 (TLR4). RESULTS Macrophage exposure to PM derived from dairy farms significantly activated expression of pro-inflammatory genes, including IL-8, cyclooxygenase 2 and Tumor necrosis factor-alpha, which are hallmarks of inflammation. Acute phase proteins, such as serum amyloid A and IL-6, were also significantly upregulated in macrophages treated with PM from dairies. Coarse PM fractions demonstrated more pro-inflammatory activity on an equal-dose basis than fine PM. Urban PM collected from the same region as the dairy farms was associated with a lower concentration of endotoxin and produced significantly less IL-8 expression compared to PM collected on the dairy farms. CONCLUSION The present study provides evidence that the endotoxin components of the particles collected on dairies play a major role in mediating an inflammatory response through activation of TLR4 and NF-κB signaling.
Collapse
Affiliation(s)
- Christoph FA Vogel
- Department of Environmental Toxicology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
- Center for Health and The Environment, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Johnny Garcia
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Dalei Wu
- Center for Health and The Environment, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Diane C Mitchell
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Yanhong Zhang
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Norman Y Kado
- Department of Environmental Toxicology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
- California Environmental Protection Agency, Air Resources Board, Sacramento, CA 95814, USA
| | - Patrick Wong
- California Environmental Protection Agency, Air Resources Board, Sacramento, CA 95814, USA
| | - Danitza Alvizar Trujillo
- Center for Health and The Environment, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Anna Lollies
- Center for Health and The Environment, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Deborah Bennet
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Marc B Schenker
- Department of Public Health Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Frank M Mitloehner
- Department of Animal Science, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| |
Collapse
|
19
|
Qiu J, Heller JJ, Guo X, Chen ZME, Fish K, Fu YX, Zhou L. The aryl hydrocarbon receptor regulates gut immunity through modulation of innate lymphoid cells. Immunity 2012; 36:92-104. [PMID: 22177117 PMCID: PMC3268875 DOI: 10.1016/j.immuni.2011.11.011] [Citation(s) in RCA: 638] [Impact Index Per Article: 53.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 09/05/2011] [Accepted: 11/29/2011] [Indexed: 02/08/2023]
Abstract
Innate lymphoid cells (ILCs) expressing the nuclear receptor RORγt are essential for gut immunity presumably through production of interleukin-22 (IL-22). The molecular mechanism underlying the development of RORγt(+) ILCs is poorly understood. Here, we have shown that the aryl hydrocarbon receptor (Ahr) plays an essential role in RORγt(+) ILC maintenance and function. Expression of Ahr in the hematopoietic compartment was important for accumulation of adult but not fetal intestinal RORγt(+) ILCs. Without Ahr, RORγt(+) ILCs had increased apoptosis and less production of IL-22. RORγt interacted with Ahr and promoted Ahr binding at the Il22 locus. Upon IL-23 stimulation, Ahr-deficient RORγt(+) ILCs had reduced IL-22 expression, consistent with downregulation of IL-23R in those cells. Ahr-deficient mice succumbed to Citrobacter rodentium infection, whereas ectopic expression of IL-22 protected animals from early mortality. Our data uncover a previously unrecognized physiological role for Ahr in promoting innate gut immunity by regulating RORγt(+) ILCs.
Collapse
Affiliation(s)
- Ju Qiu
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Jennifer J. Heller
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Xiaohuan Guo
- Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
| | - Zong-ming E Chen
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Kamonwan Fish
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Yang-Xin Fu
- Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
| | - Liang Zhou
- Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| |
Collapse
|
20
|
Sutter CH, Bodreddigari S, Campion C, Wible RS, Sutter TR. 2,3,7,8-Tetrachlorodibenzo-p-dioxin increases the expression of genes in the human epidermal differentiation complex and accelerates epidermal barrier formation. Toxicol Sci 2011; 124:128-37. [PMID: 21835898 PMCID: PMC3196651 DOI: 10.1093/toxsci/kfr205] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Chloracne is commonly observed in people exposed to dioxins, yet the mechanism of toxicity is not well understood. The pathology of chloracne is characterized by hyperkeratinization of the interfollicular squamous epithelium, hyperproliferation and hyperkeratinization of hair follicle cells as well as a metaplastic response of the ductular sebum secreting sebaceous glands. In vitro studies using normal human epidermal keratinocytes to model interfollicular human epidermis demonstrate a 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-mediated acceleration of differentiation and increase in gene expression of several prodifferentiation genes, including filaggrin (FLG). Here, we demonstrated that the TCDD-activated aryl hydrocarbon receptor (AHR) bound a small fragment of DNA upstream of the transcriptional start sites of the FLG gene, containing one of two candidate xenobiotic response elements (XREs). Reporter assays using the promoter region of FLG containing the two putative XREs indicated that the increase in this messenger RNA (mRNA) was due to TCDD-mediated enhanced transcription, which was lost when both XREs were mutated. As FLG is part of the human epidermal differentiation complex (EDC) found on chromosome 1, we measured mRNAs from an additional 18 EDC genes for their regulation by TCDD. Of these genes, 14 were increased by TCDD. Immunoblot assays demonstrated that the proteins of FLG as well as that of another prodifferentiation gene, small proline rich protein 2, were increased by TCDD. In utero exposure to TCDD accelerated the formation of the epidermal barrier in the developing mouse fetus by approximately 1 day. These results indicate that the epidermal permeability barrier is a functional target of the TCDD-activated AHR.
Collapse
Affiliation(s)
- Carrie Hayes Sutter
- W. Harry Feinstone Center for Genomic Research, Department of Biological Sciences, University of Memphis, 201 Life Sciences Building, Memphis, TN 38152-3560, USA.
| | | | | | | | | |
Collapse
|
21
|
Jacobs H, Dennefeld C, Féret B, Viluksela M, Håkansson H, Mark M, Ghyselinck NB. Retinoic acid drives aryl hydrocarbon receptor expression and is instrumental to dioxin-induced toxicity during palate development. Environ Health Perspect 2011; 119:1590-5. [PMID: 21807577 PMCID: PMC3226489 DOI: 10.1289/ehp.1003075] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 08/01/2011] [Indexed: 05/07/2023]
Abstract
BACKGROUND Palate development depends on complex events and is very sensitive to disruption. Accordingly, clefts are the most common congenital malformations worldwide, and a connection is proposed with fetal exposure to toxic factors or environmental contaminants, such as dioxins. There is increasing evidence that dioxin interferes with all-trans-retinoic acid (atRA), a hormone-like signal derived from vitamin A, which plays an essential role during embryonic development. Although similarities have been described between dioxin-induced toxicity and the outcome of altered atRA signaling during palate development, their relationship needs to be clarified. OBJECTIVES We used a genetic approach to understand the interaction between atRA and dioxin and to identify the cell type targeted by dioxin toxicity during secondary palate formation in mice. METHODS We analyzed the phenotype of mouse embryos harboring an atRA-sensitive reporter transgene or bearing null mutations for atRA-synthesizing enzymes (RALDH) or atRA receptors (RAR) and maternally exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at gestation day 10.5. RESULTS We found that an intact atRA signal was required to enable TCDD to induce cleft palate. This mandatory atRA signal was generated through the activity of RALDH3 in the nasal epithelium and was transduced by RARγ (RARG) in the nasal mesenchyme, where it notably controlled aryl hydrocarbon receptor (Ahr) transcript levels. TCDD also did not alter the developmental pattern of atRA signaling during palate formation. CONCLUSIONS TCDD-induced alteration of secondary palate development in the mouse appears to depend on atRA signaling, which controls AHR expression. This mechanism is likely conserved throughout vertebrate evolution and may therefore be relevant in humans.
Collapse
Affiliation(s)
- Hugues Jacobs
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Centre National de la Recherche Scientifique (CNRS UMR7104), Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Université de Strasbourg, Illkirch, France
| | | | | | | | | | | | | |
Collapse
|
22
|
Wu D, Nishimura N, Kuo V, Fiehn O, Shahbaz S, Winkle LV, Matsumura F, Vogel C. Activation of aryl hydrocarbon receptor induces vascular inflammation and promotes atherosclerosis in apolipoprotein E-/- mice. Arterioscler Thromb Vasc Biol 2011; 31:1260-7. [PMID: 21441140 PMCID: PMC3098318 DOI: 10.1161/atvbaha.110.220202] [Citation(s) in RCA: 136] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Exposure to dioxins has been shown to contribute to the development of inflammatory diseases, such as atherosclerosis. Macrophage-mediated inflammation is a critical event in the initiation of atherosclerosis. Previously, we showed that treatment of macrophages with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to aryl hydrocarbon receptor (AhR)-dependent activation of inflammatory mediators and the formation of cholesterol-laden foam cells. However, the mechanisms responsible for the formation of atherosclerotic lesions mediated through AhR have not been identified. METHODS AND RESULTS An in vitro macrophage and an apolipoprotein E (ApoE)-/- mouse model were used to determine whether chemokines and their receptors are responsible for the AhR-mediated atherogenesis. Exposure of ApoE-/- mice to TCDD caused a time-dependent progression of atherosclerosis, which was associated with induction of inflammatory genes, including interleukin-8, as well as F4/80 and matrix metalloproteinase-12. A high-fat diet enhanced the TCDD-mediated inflammatory response and aggravated the formation of complex atheromas. Treatment with a CXCR2 inhibitor and an AhR antagonist reduced the TCDD-induced progression of early atherosclerotic lesions in ApoE-/- mice. CONCLUSION The results suggest that CXCR2 mediates the atherogenic activity of environmental pollutants, such as dioxins, and contributes to the development of atherosclerosis through the induction of a vascular inflammatory response by activating the AhR-signaling pathway.
Collapse
Affiliation(s)
- Dalei Wu
- Department of Environmental Toxicology, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
- Center for Health and the Environment, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Noriko Nishimura
- Endocrine Disruptors and Dioxin Research Project, National Institute for Environmental Studies, Tsukuba 305-8506, Japan
| | - Victoria Kuo
- Center for Health and the Environment, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Oliver Fiehn
- Department of Molecular and Cellular Biology & Genome Center, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Sevini Shahbaz
- Department of Molecular and Cellular Biology & Genome Center, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Laura Van Winkle
- Center for Health and the Environment, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Fumio Matsumura
- Department of Environmental Toxicology, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
- Center for Health and the Environment, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Christoph Vogel
- Department of Environmental Toxicology, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
- Center for Health and the Environment, University of California Davis, One Shields Avenue, Davis, CA 95616, USA
| |
Collapse
|
23
|
Kearley J, Erjefalt JS, Andersson C, Benjamin E, Jones CP, Robichaud A, Pegorier S, Brewah Y, Burwell TJ, Bjermer L, Kiener PA, Kolbeck R, Lloyd CM, Coyle AJ, Humbles AA. IL-9 governs allergen-induced mast cell numbers in the lung and chronic remodeling of the airways. Am J Respir Crit Care Med 2011; 183:865-75. [PMID: 20971830 PMCID: PMC3385369 DOI: 10.1164/rccm.200909-1462oc] [Citation(s) in RCA: 165] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
RATIONALE IL-9 is a pleiotropic cytokine that has multiple effects on structural as well as numerous hematopoietic cells, which are central to the pathogenesis of asthma. OBJECTIVES The contribution of IL-9 to asthma pathogenesis has thus far been unclear, due to conflicting reports in the literature. These earlier studies focused on the role of IL-9 in acute inflammatory models; here we have investigated the effects of IL-9 blockade during chronic allergic inflammation. METHODS Mice were exposed to either prolonged ovalbumin or house dust mite allergen challenge to induce chronic inflammation and airway remodeling. MEASUREMENTS AND MAIN RESULTS We found that IL-9 governs allergen-induced mast cell (MC) numbers in the lung and has pronounced effects on chronic allergic inflammation. Anti-IL-9 antibody-treated mice were protected from airway remodeling with a concomitant reduction in mature MC numbers and activation, in addition to decreased expression of the profibrotic mediators transforming growth factor-β1, vascular endothelial growth factor, and fibroblast growth factor-2 in the lung. Airway remodeling was associated with impaired lung function in the peripheral airways and this was reversed by IL-9 neutralization. In human asthmatic lung tissue, we identified MCs as the main IL-9 receptor expressing population and found them to be sources of vascular endothelial growth factor and fibroblast growth factor-2. CONCLUSIONS Our data suggest an important role for an IL-9-MC axis in the pathology associated with chronic asthma and demonstrate that an impact on this axis could lead to a reduction in chronic inflammation and improved lung function in patients with asthma.
Collapse
Affiliation(s)
- Jennifer Kearley
- Department of Respiratory, Inflammation, and Autoimmunity, MedImmune LLC, Gaithersburg, MD 20878, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Tischkau SA, Jaeger CD, Krager SL. Circadian clock disruption in the mouse ovary in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Lett 2011; 201:116-22. [PMID: 21182907 PMCID: PMC3039055 DOI: 10.1016/j.toxlet.2010.12.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 12/13/2010] [Accepted: 12/14/2010] [Indexed: 12/29/2022]
Abstract
Activation of the aryl hydrocarbon receptor (AhR) by the highly toxic, prototypical ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or other dioxin-like compounds compromises ovarian function by altering follicle maturation and steroid synthesis. Although alteration of transcription after nuclear translocation and heterodimerization of AhR with its binding partner, aryl hydrocarbon nuclear transporter (ARNT), is often cited as a primary mechanism for mediating the toxic effects of dioxins, recent evidence indicates that crosstalk between AhR and several other signaling pathways also occurs. Like the circadian clock genes, AhR is a member of the basic helix-loop-helix, Per-ARNT-SIM (bHLH-PAS) domain family of proteins. Thus, these studies tested the hypothesis that TCDD can act to alter circadian clock regulation in the ovary. Adult female c57bl6/J mice entrained to a typical 12h light/12h dark cycle were exposed to a single 1 μg/kg dose of TCDD by gavage. Six days after exposure, animals were released into constant darkness and ovaries were collected every 4h over a 24h period. Quantitative real-time PCR and immunoblot analysis demonstrated that TCDD exposure alters expression of the canonical clock genes, Bmal1 and Per2 in the ovary. AhR transcript and protein, which displayed a circadian pattern of expression in the ovaries of control mice, were also altered after TCDD treatment. Immunohistochemistry studies revealed co-localization of AhR with BMAL1 in various ovarian cell types. Furthermore, co-immunoprecipitation demonstrated time-of-day dependent interactions of AhR with BMAL1 that were enhanced after TCDD treatment. Collectively these studies suggest that crosstalk between classical AhR signaling and the molecular circadian clockworks may be responsible for altered ovarian function after TCDD exposure.
Collapse
Affiliation(s)
- Shelley A Tischkau
- Department of Pharmacology, Southern Illinois University, School of Medicine, 801N. Rutledge, Springfield, IL 62794-9629, USA.
| | | | | |
Collapse
|
25
|
Cao J, Patisaul HB, Petersen SL. Aryl hydrocarbon receptor activation in lactotropes and gonadotropes interferes with estradiol-dependent and -independent preprolactin, glycoprotein alpha and luteinizing hormone beta gene expression. Mol Cell Endocrinol 2011; 333:151-9. [PMID: 21187122 PMCID: PMC3059512 DOI: 10.1016/j.mce.2010.12.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 01/13/2023]
Abstract
Arylhydrocarbon receptor (Ahr) activation by 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) interferes with female reproductive functions, but there is little information on the specific targets of TCDD in the hypothalamic-pituitary-gonadal (HPG) axis. In these studies, we found that TCDD upregulated known AhR target genes, cytochrome p450 1a1 (Cyp1a1), Cyp1a2 and Cyp1b1 in the rat pituitary gland. Moreover, 75% of pituitary lactotropes and 45% of gonadotropes contained Ahr mRNA, and most Ahr-containing cells were estrogen receptor 1 (Esr1)-positive. TCDD abrogated estradiol (E(2))-induced prolactin (Prl) expression in vivo and in vitro; conversely, E(2) blocked TCDD upregulation of luteinizing hormone beta (Lhb) and glycoprotein hormone alpha polypeptide (Cga) expression. TCDD had no effect on levels of Ahr mRNA, but upregulated Esr1 mRNA. E(2) independently repressed Ahr and Esr1 expression and blocked TCDD upregulation of Esr1. Thus, complex interactions between Ahr and Esr alter Prl and luteinizing hormone (LH) synthesis by direct actions in lactotropes and gonadotropes. These findings provide important insights into how TCDD disrupts female reproductive functions.
Collapse
Affiliation(s)
- JinYan Cao
- Molecular and Cellular Biology Graduate Program, 435 Morrill I North, University of Massachusetts Amherst, 637 North Pleasant Street, Amherst, MA 01003-9298
- Department of Biology, 127 David Clark Labs, North Carolina State University, Raleigh, NC 27695
| | - Heather B. Patisaul
- Department of Biology, 127 David Clark Labs, North Carolina State University, Raleigh, NC 27695
| | - Sandra L. Petersen
- Molecular and Cellular Biology Graduate Program, 435 Morrill I North, University of Massachusetts Amherst, 637 North Pleasant Street, Amherst, MA 01003-9298
- Department of Veterinary and Animal Sciences, 661 North Pleasant Street, University of Massachusetts, Amherst MA 01003
| |
Collapse
|
26
|
Gassmann K, Abel J, Bothe H, Haarmann-Stemmann T, Merk HF, Quasthoff KN, Rockel TD, Schreiber T, Fritsche E. Species-specific differential AhR expression protects human neural progenitor cells against developmental neurotoxicity of PAHs. Environ Health Perspect 2010; 118:1571-7. [PMID: 20570779 PMCID: PMC2974695 DOI: 10.1289/ehp.0901545] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Revised: 05/21/2010] [Accepted: 06/22/2010] [Indexed: 05/07/2023]
Abstract
BACKGROUND Because of their lipophilicity, persistent organic pollutants (POPs) cross the human placenta, possibly affecting central nervous system development. Most POPs are known aryl hydrocarbon receptor (AhR) ligands and activators of AhR signaling. Therefore, AhR activation has been suggested to cause developmental neurotoxicity (DNT). OBJECTIVE We studied the effects of AhR ligands on basic processes of brain development in two comparative in vitro systems to determine whether AhR-activation is the underlying mechanism for reported DNT of POPs in humans. METHODS We employed neurosphere cultures based on human neural progenitor cells (hNPCs) and wild-type and AhR-deficient mouse NPCs (mNPCs) and studied the effects of different AhR agonists [3-methylcholanthrene (3-MC), benzo(a)pyrene [B(a)P], and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)] and an antagonist [3'-methoxy-4'-nitroflavone (MNF)] on neurosphere development. Moreover, we analyzed expression of AhR and genes involved in AhR signaling. RESULTS In contrast to wild-type mNPCs, hNPCs and AhR-deficient mNPCs were insensitive to AhR agonism or antagonism. Although AhR modulation attenuated wild-type mNPC proliferation and migration, hNPCs and AhR-deficient mNPCs remained unaffected. Results also suggest that species-specific differences resulted from nonfunctional AhR signaling in hNPCs. CONCLUSION Our findings suggest that in contrast to wild-type mNPCs, hNPCs were protected against polycyclic aromatic hydrocarbon-induced DNT because of an absence of AhR This difference may contribute to species-specific differences in sensitivity to POPs.
Collapse
Affiliation(s)
- Kathrin Gassmann
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Josef Abel
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Hanno Bothe
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Thomas Haarmann-Stemmann
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Hans F. Merk
- Department of Dermatology, University Hospital, RWTH Aachen, Aachen, Germany
| | - Kim N. Quasthoff
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Thomas Dino Rockel
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Timm Schreiber
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
| | - Ellen Fritsche
- Department of Molecular Toxicology, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Düsseldorf, Germany
- Department of Dermatology, University Hospital, RWTH Aachen, Aachen, Germany
- Address correspondence to E. Fritsche, Institut für umweltmedizinische Forschung gGmbH, Heinrich Heine University, Department of Molecular Toxicology, Auf’m Hennekamp 50, 40225 Dusseldorf, Germany. Telephone: 00492113389217. Fax: 00492113190910. E-mail:
| |
Collapse
|
27
|
Choi YJ, Arzuaga X, Kluemper CT, Caraballo A, Toborek M, Hennig B. Quercetin blocks caveolae-dependent pro-inflammatory responses induced by co-planar PCBs. Environ Int 2010; 36:931-934. [PMID: 19608276 PMCID: PMC2889233 DOI: 10.1016/j.envint.2009.06.009] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 01/13/2009] [Accepted: 06/07/2009] [Indexed: 05/28/2023]
Abstract
Polychlorinated biphenyls (PCBs) are widespread environmental contaminants, and co-planar PCBs can induce oxidative stress and activation of pro-inflammatory signaling cascades which are associated with atherosclerosis. The majority of the toxicological effects elicited by the co-planar PCB exposure are associated to the activation of the aryl hydrocarbon receptor (AHR) and subsequent induction of responsive genes. Previous studies from our group have shown that quercetin, a nutritionally relevant flavonoid can significantly reduce PCB77 induction of oxidative stress and expression of the AHR responsive gene cytochrome P450 1A1 (CYP1A1). We also have evidence that membrane domains called caveolae may regulate PCB-induced inflammatory parameters. Thus, we hypothesized that quercetin can modulate PCB-induced endothelial inflammation associated with caveolae. To test this hypothesis, endothelial cells were exposed to co-planar PCBs in combination with quercetin, and the expression of pro-inflammatory genes was analyzed by real-time PCR. Quercetin co-treatment significantly blocked both PCB77 and PCB126 induction of CYP1A1, vascular cell adhesion molecule 1 (VCAM-1), E-selectin and P-selectin. Exposure to PCB77 also induced caveolin-1 protein expression, which was reduced by co-treatment with quercetin. Our results suggest that inflammatory pathways induced by co-planar PCBs can be down-regulated by the dietary flavonoid quercetin through mechanisms associated with functional caveolae.
Collapse
Affiliation(s)
- Yean Jung Choi
- Molecular and Cell Nutrition Laboratory, College of Agriculture, University of Kentucky, Lexington, USA
| | - Xabier Arzuaga
- Molecular and Cell Nutrition Laboratory, College of Agriculture, University of Kentucky, Lexington, USA
| | | | - Adelka Caraballo
- Department of Biology, University of Puerto Rico, Rio Piedras, Puerto Rico
| | - Michal Toborek
- Department of Neurosurgery, University of Kentucky, Lexington, USA
| | - Bernhard Hennig
- Molecular and Cell Nutrition Laboratory, College of Agriculture, University of Kentucky, Lexington, USA
- Graduate Center for Toxicology, University of Kentucky, Lexington, USA
| |
Collapse
|
28
|
Jensen BA, Reddy CM, Nelson RK, Hahn ME. Developing tools for risk assessment in protected species: Relative potencies inferred from competitive binding of halogenated aromatic hydrocarbons to aryl hydrocarbon receptors from beluga (Delphinapterus leucas) and mouse. Aquat Toxicol 2010; 100:238-245. [PMID: 20728228 PMCID: PMC3175004 DOI: 10.1016/j.aquatox.2010.07.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 07/09/2010] [Accepted: 07/17/2010] [Indexed: 05/29/2023]
Abstract
Persistent organic pollutants such as halogenated aromatic hydrocarbons (HAHs) biomagnify in food webs and accumulate to high concentrations in top predators like odontocete cetaceans (toothed whales). The most toxic HAHs are the 2,3,7,8-substituted halogenated dibenzo-p-dioxins and furans, and non-ortho-substituted polychlorinated biphenyls (PCBs), which exert their effects via the aryl hydrocarbon receptor (AHR). Understanding the impact of HAHs in wildlife is limited by the lack of taxon-specific information about the relative potencies of toxicologically important congeners. To assess whether Toxic Equivalency Factors (TEFs) determined in rodents are predictive of HAH relative potencies in a cetacean, we used beluga and mouse AHRs expressed in vitro from cloned cDNAs to measure the relative AHR-binding affinities of ten HAHs from five different structural classes. The rank order of mean IC(50)s for competitive binding to beluga AHR was: TCDD<TCDF<PCB-126<PCB-169<PCB-77<PCB-81⋘PCB-156∼PCB-128<PCB-105<PCB-118. The rank order of mean IC(50)s for binding to the mouse AHR was TCDD<TCDF<PCB-126<PCB-169<PCB-81<PCB-77<PCB-156≪PCB-128∼PCB-105∼PCB-118. K(i) values for binding of HAHs to beluga and mouse AHRs were highly correlated (r(2)=0.96). Comparison of K(i) values suggested that the beluga AHR had a higher affinity than the mouse AHR for most of the HAHs tested, consistent with the ∼2-fold higher [(3)H]TCDD binding affinity determined previously. These results are consistent with the World Health Organization mammalian TEFs for non- and mono-ortho PCB congeners. The comparatively high HAH binding affinities of the beluga AHR relative to those of an AHR from a dioxin-responsive mouse suggests that beluga, and perhaps cetaceans in general, may be particularly sensitive to the toxic effects of AHR agonists. Further study is warranted in order to more fully address this important question affecting protected and endangered species.
Collapse
Affiliation(s)
- Brenda A Jensen
- Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
| | | | | | | |
Collapse
|
29
|
Safe S. 3-methylcholanthrene induces differential recruitment of aryl hydrocarbon receptor to human promoters. Toxicol Sci 2010; 117:1-3. [PMID: 20651249 PMCID: PMC2923292 DOI: 10.1093/toxsci/kfq193] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 06/19/2010] [Indexed: 11/14/2022] Open
Abstract
The paper by Pansoy and coworkers investigates the effects of the aryl hydrocarbon receptor (AHR) ligand 3-methylcholanthrene (3MC) on recruitment of the AHR complex to human promoters in T47D breast cancer cells. The results are particularly important because they can be compared with a prior study using the potent AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the same cell line. The chromatin immunoprecipitation and promoter-focused microarrays (ChIP-chip) demonstrated that after treatment of T47D cells with 1microM 3MC, there were 241 AHR-3MC bound regions and many of these contained AHR-responsive elements. However, they also observed interactions with regions that do not contain these responsive elements, and subsequent analysis of selected target genes show that 3MC-dependent AHR binding did not necessarily predict Ah-responsiveness because induction, repression, and no effects were observed. A prior study with TCDD demonstrated that both 3MC and TCDD induced AHR binding to 127 common regions; however, there were significant differences in ligand (3MC vs. TCDD)-dependent AHR bound regions. The results illustrate the complexity of AHR signaling and also demonstrate that compared with TCDD as a reference ligand, 3MC is a selective AHR modulator.
Collapse
Affiliation(s)
- Stephen Safe
- Department of Veterinary Physiology & Physiology, Texas A&M University, College Station, Texas 77843-4466, USA.
| |
Collapse
|
30
|
Apetoh L, Quintana FJ, Pot C, Joller N, Xiao S, Kumar D, Burns EJ, Sherr DH, Weiner HL, Kuchroo VK. The aryl hydrocarbon receptor interacts with c-Maf to promote the differentiation of type 1 regulatory T cells induced by IL-27. Nat Immunol 2010; 11:854-61. [PMID: 20676095 PMCID: PMC2940320 DOI: 10.1038/ni.1912] [Citation(s) in RCA: 566] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 07/01/2010] [Indexed: 02/07/2023]
Abstract
Type 1 regulatory T cells (Tr1 cells ) that produce interleukin 10 (IL-10) are instrumental in the prevention of tissue inflammation, autoimmunity and graft-versus-host disease. The transcription factor c-Maf is essential for the induction of IL-10 by Tr1 cells, but the molecular mechanisms that lead to the development of these cells remain unclear. Here we show that the ligand-activated transcription factor aryl hydrocarbon receptor (AhR), which was induced by IL-27, acted in synergy with c-Maf to promote the development of Tr1 cells. After T cell activation under Tr1-skewing conditions, the AhR bound to c-Maf and promoted transactivation of the Il10 and Il21 promoters, which resulted in the generation of Tr1 cells and the amelioration of experimental autoimmune encephalomyelitis. Manipulating AhR signaling could therefore be beneficial in the resolution of excessive inflammatory responses.
Collapse
Affiliation(s)
- Lionel Apetoh
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Francisco J. Quintana
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Caroline Pot
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Nicole Joller
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Sheng Xiao
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Deepak Kumar
- Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston 02115, MA, USA
| | - Evan J. Burns
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - David H. Sherr
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, United States
| | - Howard L. Weiner
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| | - Vijay K. Kuchroo
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, United States
| |
Collapse
|
31
|
Howard GJ, Schlezinger JJ, Hahn ME, Webster TF. Generalized concentration addition predicts joint effects of aryl hydrocarbon receptor agonists with partial agonists and competitive antagonists. Environ Health Perspect 2010; 118:666-72. [PMID: 20435555 PMCID: PMC2866683 DOI: 10.1289/ehp.0901312] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 12/22/2009] [Indexed: 05/18/2023]
Abstract
BACKGROUND Predicting the expected outcome of a combination exposure is critical to risk -assessment. The toxic equivalency factor (TEF) approach used for analyzing joint effects of dioxin-like chemicals is a special case of the method of concentration addition. However, the TEF method assumes that individual agents are full aryl hydrocarbon receptor (AhR) agonists with parallel dose-response curves, whereas many mixtures include partial agonists. OBJECTIVES We assessed the ability of generalized concentration addition (GCA) to predict effects of combinations of full AhR agonists with partial agonists or competitive antagonists. METHODS We measured activation of AhR-dependent gene expression in H1G1.1c3 cells after application of binary combinations of AhR ligands. A full agonist (2,3,7,8-tetrachlorodibenzo-p--dioxin or 2,3,7,8-tetrachlorodibenzofuran) was combined with either a full agonist (3,3 ,4,4 ,5-penta-chloro-biphenyl), a partial agonist (2,3,3 ,4,4 -pentachlorobiphenyl or galangin), or an antagonist (3,3 -diindolylmethane). Combination effects were modeled by the TEF and GCA approaches, and goodness of fit of the modeled response surface to the experimental data was assessed using a nonparametric statistical test. RESULTS The GCA and TEF models fit the experimental data equally well for a mixture of two full agonists. In all other cases, GCA fit the experimental data significantly better than the TEF model. CONCLUSIONS The TEF model overpredicts effects of AhR ligands at the highest concentration combinations. At lower concentrations, the difference between GCA and TEF approaches depends on the efficacy of the partial agonist. GCA represents a more accurate definition of additivity for mixtures that include partial agonist or competitive antagonist ligands.
Collapse
Affiliation(s)
- Gregory J. Howard
- Environmental Health Department, Boston University School of Public Health, Boston, Massachusetts, USA
- Environmental Studies Department, Dickinson College, Carlisle, Pennsylvania, USA
| | - Jennifer J. Schlezinger
- Environmental Health Department, Boston University School of Public Health, Boston, Massachusetts, USA
- Address correspondence to J. Schlezinger, Boston University School of Public Health, Department of Environmental Health, 715 Albany St., R405, Boston, MA 02118 USA. Telephone: (617) 638-6497. Fax: (617) 638-6463. E-mail:
| | - Mark E. Hahn
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
| | - Thomas F. Webster
- Environmental Health Department, Boston University School of Public Health, Boston, Massachusetts, USA
| |
Collapse
|
32
|
Merson RR, Karchner SI, Hahn ME. Interaction of fish aryl hydrocarbon receptor paralogs ( AHR1 and AHR2) with the retinoblastoma protein. Aquat Toxicol 2009; 94:47-55. [PMID: 19539383 PMCID: PMC2833323 DOI: 10.1016/j.aquatox.2009.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 05/20/2009] [Accepted: 05/27/2009] [Indexed: 05/10/2023]
Abstract
The aryl hydrocarbon receptor (AHR) mediates the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. In some mammalian cell lines, TCDD induces G1 cell cycle arrest, which depends on an interaction between the AHR and the retinoblastoma tumor suppressor (RB). Mammals possess one AHR, whereas fishes possess two or more AHR paralogs that differ in the domains important for AHR-RB interactions in mammals. To test the hypothesis that fish AHR paralogs differ in their ability to interact with RB, we cloned RB cDNA from Atlantic killifish, Fundulus heteroclitus, and studied the interactions of killifish RB protein with killifish AHR1 and AHR2. In coimmunoprecipitation experiments, in vitro-expressed killifish RB coprecipitated with both AHR1 and AHR2. Consistent with these results, both killifish AHR1 and AHR2 interacted with RB in mammalian two-hybrid assays. These results suggest that both fish AHR1 and AHR2 paralogs may have the potential to influence cell proliferation through interactions with RB.
Collapse
Affiliation(s)
- Rebeka R Merson
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
| | | | | |
Collapse
|
33
|
Abstract
Corneal allografts transplanted into hosts with allergic conjunctivitis experience an increased incidence and swifter tempo of immune rejection compared to corneal allografts transplanted to nonallergic hosts. Previous findings suggested that increased risk for rejection was not a local effect produced by an inflamed eye, but was due to perturbation of the systemic immune responses to alloantigens on the corneal allograft. We tested the hypothesis that another allergic disease, airway hyperreactivity (AHR), would also increase the risk for corneal allograft rejection. Induction of AHR with either ovalbumin (OVA) or short ragweed (SRW) extract prior to keratoplasty resulted in a steep increase in the speed and incidence of corneal allograft rejection. Delayed-type hypersensitivity (DTH) responses to corneal alloantigens were closely associated with corneal allograft rejection. However, the deleterious effect of AHR on corneal allograft survival was not reflected in a heightened magnitude of allospecific DTH, cytotoxic T lymphocyte and lymphoproliferative responses to the alloantigens on the corneal allograft. Unlike Th2-based immediate hypersensitivity, CD8+ T-cell-based contact hypersensitivity to oxazolone did not increase the risk for corneal allograft rejection. Thus, Th2-based allergic diseases significantly reduce the immune privilege of the corneal allograft and represent important risk factors for consideration in the atopic patient.
Collapse
|
34
|
Sciullo EM, Dong B, Vogel CFA, Matsumura F. Characterization of the pattern of the nongenomic signaling pathway through which TCDD-induces early inflammatory responses in U937 human macrophages. Chemosphere 2009; 74:1531-1537. [PMID: 19162293 PMCID: PMC2879335 DOI: 10.1016/j.chemosphere.2008.11.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2008] [Revised: 10/17/2008] [Accepted: 11/06/2008] [Indexed: 05/27/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo(p)dioxin (TCDD) has been known to induce inflammatory signaling in a number of cell types and tissues. We found that in U937 macrophages TCDD causes rapid activation of cytosolic phospholipase A2 (cPLA2) within 30min as judged by the increase in the serine 505 phosphorylated form of cPLA2 protein and the increased cellular release of free arachidonic acid. This initial action of TCDD is accompanied with the up-regulation of an important inflammation marker, COX-2 mRNA expression within 1h, and by 3h, several other markers become up-regulated. These effects appear to be dependent on the initial increase in the intracellular concentration of Ca(2+), and activation of cPLA2 and COX-2. A comparative study among three different human cell lines showed that activation of COX-2 within 1h of action of TCDD is a common feature exhibited by all cell lines. On the other hand, the U937 macrophage line appears to be unique among them with respect to its ability to activate TNF-alpha and IL-8 mRNA expressions, and not requiring Src kinase in propagating the initial signaling of cPLA2. Based on the rapidity of activation of cPLA2 and COX-2, which occurs within 1h of cell exposure to TCDD, when no change in mRNA expression of CYP1A1 has been observed, it is apparent that this unique action of TCDD is carried out through a distinct "nongenomic" pathway which, is clearly discernable from the classical, "genomic" action pathway of the AhR by not requiring the participation of ARNT.
Collapse
Affiliation(s)
- Eric M Sciullo
- Department of Environmental Toxicology, University of California Davis, Center for Health and the Environment, One Shields Ave., Old Davis Rd., Davis, CA 95616, USA
| | | | | | | |
Collapse
|
35
|
Luu TC, Bhattacharya P, Chan WK. Cyclophilin-40 has a cellular role in the aryl hydrocarbon receptor signaling. FEBS Lett 2008; 582:3167-73. [PMID: 18708059 PMCID: PMC2630774 DOI: 10.1016/j.febslet.2008.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/28/2008] [Accepted: 08/05/2008] [Indexed: 11/16/2022]
Abstract
Cyclophilin-40 (CyP40) promotes the formation of the gel shift complex that contains the aryl hydrocarbon receptor (AhR), AhR nuclear translocator (Arnt) and dioxin response element (DRE) using baculovirus expressed proteins. Here we reported that CyP40 plays a role in the AhR signaling. When the CyP40 content in MCF-7 cells is reduced, up-regulation of cyp1a1 and cyp1b1 by 3-methylchloranthrene (3MC) is also reduced, suggesting that CyP40 is essential for maximal AhR function. The CyP40 region containing amino acids 186-215, but not the peptidyl-prolyl cis-trans isomerase and tetratricopeptide repeat domains, is essential for forming the AhR/Arnt/DRE complex. CyP40 is found in the cell nucleus after 3MC treatment and appears to promote the DRE binding form of the AhR/Arnt heterodimer.
Collapse
Affiliation(s)
- Tony C. Luu
- Department of Pharmaceutics and Medicinal Chemistry, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211
| | - Pompeya Bhattacharya
- Department of Pharmaceutics and Medicinal Chemistry, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211
| | - William K. Chan
- Department of Pharmaceutics and Medicinal Chemistry, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211
| |
Collapse
|
36
|
Goldstone J, Hamdoun A, Cole B, Howard-Ashby M, Nebert D, Scally M, Dean M, Epel D, Hahn M, Stegeman J. The chemical defensome: environmental sensing and response genes in the Strongylocentrotus purpuratus genome. Dev Biol 2006; 300:366-84. [PMID: 17097629 PMCID: PMC3166225 DOI: 10.1016/j.ydbio.2006.08.066] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2006] [Revised: 08/18/2006] [Accepted: 08/28/2006] [Indexed: 01/08/2023]
Abstract
Metazoan genomes contain large numbers of genes that participate in responses to environmental stressors. We surveyed the sea urchin Strongylocentrotus purpuratus genome for homologs of gene families thought to protect against chemical stressors; these genes collectively comprise the 'chemical defensome.' Chemical defense genes include cytochromes P450 and other oxidases, various conjugating enzymes, ATP-dependent efflux transporters, oxidative detoxification proteins, and transcription factors that regulate these genes. Together such genes account for more than 400 genes in the sea urchin genome. The transcription factors include homologs of the aryl hydrocarbon receptor, hypoxia-inducible factor, nuclear factor erythroid-derived 2, heat shock factor, and nuclear hormone receptors, which regulate stress-response genes in vertebrates. Some defense gene families, including the ABCC, the UGT, and the CYP families, have undergone expansion in the urchin relative to other deuterostome genomes, whereas the stress sensor gene families do not show such expansion. More than half of the defense genes are expressed during embryonic or larval life stages, indicating their importance during development. This genome-wide survey of chemical defense genes in the sea urchin reveals evolutionary conservation of this network combined with lineage-specific diversification that together suggest the importance of these chemical stress sensing and response mechanisms in early deuterostomes. These results should facilitate future studies on the evolution of chemical defense gene networks and the role of these networks in protecting embryos from chemical stress during development.
Collapse
Affiliation(s)
- J.V. Goldstone
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - A. Hamdoun
- Hopkins Marine Station, Stanford University, Oceanview Blvd. Pacific Grove, CA 93950, USA
| | - B.J. Cole
- Hopkins Marine Station, Stanford University, Oceanview Blvd. Pacific Grove, CA 93950, USA
| | - M. Howard-Ashby
- Department of Biology, California Institute of Technology, CA, USA
| | - D.W. Nebert
- Department of Environmental Health, University Cincinnati Medical Center, Cincinnati, OH 45267-0056, USA
| | - M. Scally
- Human Genetics Section, Laboratory of Genomic Diversity, NCI-Frederick, Frederick, MD 21702, USA
| | - M. Dean
- Human Genetics Section, Laboratory of Genomic Diversity, NCI-Frederick, Frederick, MD 21702, USA
| | - D. Epel
- Hopkins Marine Station, Stanford University, Oceanview Blvd. Pacific Grove, CA 93950, USA
| | - M.E. Hahn
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - J.J. Stegeman
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| |
Collapse
|
37
|
Emond C, Birnbaum LS, DeVito MJ. Use of a physiologically based pharmacokinetic model for rats to study the influence of body fat mass and induction of CYP1A2 on the pharmacokinetics of TCDD. Environ Health Perspect 2006; 114:1394-400. [PMID: 16966094 PMCID: PMC1570044 DOI: 10.1289/ehp.8805] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly lipophilic chemical that distributes into adipose tissue, especially at low doses. However, at high doses TCDD sequesters in liver because it induces cytochrome P450 1A2 (CYP1A2) that binds TCDD. A physiologically based pharmacokinetic (PBPK) model was developed that included an inducible elimination rate of TCDD in the Sprague-Dawley rat. Objectives of this work were to characterize the influence of induction of CYP1A2 and adipose tissue mass fraction on the terminal elimination half-life (t1/2) of TCDD using this PBPK model. When the model assumes a fixed elimination of TCDD, t1/2 increases with dose, due to hepatic sequestration. Because experimental data indicate that the t1/2 of TCDD decreases with dose, the model was modified to include an inducible elimination rate. The PBPK model was then used to compare the t1/2 after an increase of adipose tissue mass fraction from 6.9 to 70%. The model suggests that at low exposures, increasing adipose tissue mass increases the terminal t1/2. However, at higher exposures, as CYP1A2 is induced, the relationship between adipose tissue mass and t1/2 reaches a plateau. This demonstrates that an inducible elimination rate is needed in a PBPK model in order to describe the pharmacokinetics of TCDD. At low exposures these models are more sensitive to parameters related to partitioning into adipose tissue.
Collapse
Affiliation(s)
- Claude Emond
- National Research Council, National Academy of Sciences, Washington, DC, USA
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
- Environmental and Occupational Health Department, Medicine Faculty, University of Montreal, Montreal, Quebec, Canada
| | - Linda S. Birnbaum
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
| | - Michael J. DeVito
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
- Address correspondence to M.J. DeVito, U.S. EPA, National Health and Environmental Effects Research Laboratory, Environmental Toxicology Division, Pharmacokinetics Branch, Mail Drop B143-05, Research Triangle Park, NC 27711 USA. Telephone: (919) 541-0061. Fax: (919) 541-4284. E-mail:
| |
Collapse
|
38
|
Klein GP, Hodge EM, Diamond ML, Yip A, Dann T, Stern G, Denison MS, Harper PA. Gas-phase ambient air contaminants exhibit significant dioxin-like and estrogen-like activity in vitro. Environ Health Perspect 2006; 114:697-703. [PMID: 16675423 PMCID: PMC1459922 DOI: 10.1289/ehp.8496] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2005] [Accepted: 12/29/2005] [Indexed: 05/09/2023]
Abstract
Several adverse health effects, such as respiratory and cardiovascular morbidity, have been linked to exposure to particulate matter in ambient air; however, the biologic activity of gas-phase ambient organic air contaminants has not been examined as thoroughly. Using aryl hydrocarbon receptor (AHR)-based and estrogen receptor (ER)-based cell bioassay systems, we assessed the dioxin-like and estrogenic activities of gas-phase organic ambient air contaminants compared with those of particulate-phase contaminants using samples collected between seasons over 2 years from an urban and a rural location in the Greater Toronto Area, Canada. The concentration of the sum (Sigma) of polycyclic aromatic hydrocarbons, which was highest in the gas phase, was 10-100 times more abundant than that of Sigmapolychlorinated biphenyls, Sigmanitro-polycyclic aromatic hydrocarbons, and Sigmaorganochlorine pesticides, and 10(3) to 10(4) times more abundant than Sigmapolychlorinated dibenzo-p-dioxins/dibenzofurans. Gas-phase samples induced significant AHR- and ER-dependent gene expression. The activity of the gas-phase samples was greater than that of the particulate-phase samples in the estrogen assay and, in one case, in the AHR assay. We found no strong associations between either summer or winter seasons or urban or rural locations in the relative efficacy of the extracts in either the ER or AHR assay despite differences in chemical composition, concentrations, and abundance. Our results suggest that mechanistic studies of the health effects of ambient air must consider gas and particulate phases because chemicals present in both phases can affect AHR and ER signaling pathways.
Collapse
Affiliation(s)
- Gail P Klein
- Department of Pharmacology, Centre for Urban Health Initiatives, University of Toronto, and Program in Developmental Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | | | | | | | | | | | | | | |
Collapse
|
39
|
Yuan Z, Courtenay S, Chambers RC, Wirgin I. Evidence of spatially extensive resistance to PCBs in an anadromous fish of the Hudson River. Environ Health Perspect 2006; 114:77-84. [PMID: 16393662 PMCID: PMC1332660 DOI: 10.1289/ehp.8255] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Populations of organisms that are chronically exposed to high levels of chemical contaminants may not suffer the same sublethal or lethal effects as naive populations, a phenomenon called resistance. Atlantic tomcod (Microgadus tomcod) from the Hudson River, New York, are exposed to high concentrations of polycyclic aromatic hydrocarbons (PAHs) and bioaccumulate polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). They have developed resistance to PCBs and PCDDs but not to PAHs. Resistance is largely heritable and manifests at early-life-stage toxic end points and in inducibility of cytochrome P4501A (CYP1A) mRNA expression. Because CYP1A induction is activated by the aryl hydrocarbon receptor (AHR) pathway, as are most toxic responses to these compounds, we sought to determine the geographic extent of resistance to CYP1A mRNA induction by PCBs in the Hudson River tomcod population. Samples of young-of-the-year tomcod were collected from seven locales in the Hudson River, extending from the Battery at river mile 1 (RM 1) to RM 90, and from the Miramichi River, New Brunswick, Canada. Laboratory-reared offspring of tomcod adults from Newark Bay, in the western portion of the Hudson River estuary, were also used in this study. Fish were partially depurated in clean water and intraperitoneally injected with 10 ppm coplanar PCB-77, 10 ppm benzo[a]pyrene (BaP), or corn oil vehicle, and levels of CYP1A mRNA were determined. CYP1A was significantly inducible by treatment with BaP in tomcod from the Miramichi River, from laboratory-spawned offspring of Newark Bay origin, and from all Hudson River sites spanning 90 miles of river. In contrast, only tomcod from the Miramichi River displayed significantly induced CYP1A mRNA expression when treated with PCB-77. Our results suggest that the population of tomcod from throughout the Hudson River estuary has developed resistance to CYP1A inducibility and probably other toxicities mediated by the AHR pathway. Tomcod from the Hudson River may represent the most geographically expansive population of vertebrates with resistance to chemical pollutants that has been characterized.
Collapse
Affiliation(s)
- Zhanpeng Yuan
- Department of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987, USA
| | | | | | | |
Collapse
|
40
|
Vezina CM, Walker NJ, Olson JR. Subchronic exposure to TCDD, PeCDF, PCB126, and PCB153: effect on hepatic gene expression. Environ Health Perspect 2004; 112:1636-44. [PMID: 15598615 PMCID: PMC1247661 DOI: 10.1289/txg.7253] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We employed DNA microarray to identify unique hepatic gene expression patterns associated with subchronic exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other halogenated aromatic hydrocarbons (HAHs). Female Harlan Sprague-Dawley rats were exposed for 13 weeks to toxicologically equivalent doses of four different HAHs based on the toxic equivalency factor of each chemical: TCDD (100 ng/kg/day), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF; 200 ng/kg/day), 3,3',4,4',5-pentachlorobiphenyl (PCB126; 1,000 ng/kg/day), or 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153; 1,000 microg/kg/day). Global gene expression profiles for each exposure, which account for 8,799 gene probe sets contained on Affymetrix RGU34A GeneChips, were compared by principal components analysis. The aryl hydrocarbon receptor (AhR) ligands TCDD, PeCDF, and PCB126 produced very similar global gene expression profiles that were unique from the nonAhR ligand PCB153, underscoring the extensive impact of AhR activation and/or the resulting hepatic injury on global gene expression in female rat liver. Many genes were co-expressed during the 13-week TCDD, PeCDF, or PCB126 exposures, including classical AhR-regulated genes and some genes not previously characterized as being AhR regulated, such as carcinoembryonic-cell adhesion molecule 4 (C-CAM4) and adenylate cyclase-associated protein 2 (CAP2). Real-time reverse-transcriptase polymerase chain reaction confirmed the increased expression of these genes in TCDD-, PeCDF-, and PCB126-exposed rats as well as the up- or down-regulation of several other novel dioxin-responsive genes. In summary, DNA microarray successfully identified dioxin-responsive genes expressed after exposure to AhR ligands (TCDD, PeCDF, PCB126) but not after exposure to the non-AhR ligand PCB153. Together, these findings may help to elucidate some of the fundamental features of dioxin toxicity and may further clarify the biologic role of the AhR signaling pathway.
Collapse
Affiliation(s)
- Chad M Vezina
- University of Wisconsin-Madison, School of Pharmacy, Madison, Wisconsin, USA
| | | | | |
Collapse
|
41
|
Abstract
Ah receptor (AhR) is a ligand-activated transcription factor that mediates pleiotropic effects of environmental pollutants such as 2,3, 7,8-tetrachlorodibenzo-p-dioxin on host animals. In addition to induction of drug-metabolizing enzymes, the liganded AhR complex was found to activate gene expression of a factor designated AhR repressor (AhRR), which inhibits AhR function by competing with AhR for dimerizing with Arnt and binding to the XRE sequence. Thus, AhR and AhRR form a regulatory circuit in the xenobiotic signal transduction pathway and provide a novel mechanism of regulation of AhR function that may determine tissue-specific sensitivity to environmental pollutants.
Collapse
Affiliation(s)
- J Mimura
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
| | | | | | | |
Collapse
|