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Grishanova AY, Perepechaeva ML. Aryl Hydrocarbon Receptor in Oxidative Stress as a Double Agent and Its Biological and Therapeutic Significance. Int J Mol Sci 2022; 23:ijms23126719. [PMID: 35743162 PMCID: PMC9224361 DOI: 10.3390/ijms23126719] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 06/14/2022] [Accepted: 06/14/2022] [Indexed: 12/02/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) has long been implicated in the induction of a battery of genes involved in the metabolism of xenobiotics and endogenous compounds. AhR is a ligand-activated transcription factor necessary for the launch of transcriptional responses important in health and disease. In past decades, evidence has accumulated that AhR is associated with the cellular response to oxidative stress, and this property of AhR must be taken into account during investigations into a mechanism of action of xenobiotics that is able to activate AhR or that is susceptible to metabolic activation by enzymes encoded by the genes that are under the control of AhR. In this review, we examine various mechanisms by which AhR takes part in the oxidative-stress response, including antioxidant and prooxidant enzymes and cytochrome P450. We also show that AhR, as a participant in the redox balance and as a modulator of redox signals, is being increasingly studied as a target for a new class of therapeutic compounds and as an explanation for the pathogenesis of some disorders.
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Rejano-Gordillo C, Ordiales-Talavero A, Nacarino-Palma A, Merino JM, González-Rico FJ, Fernández-Salguero PM. Aryl Hydrocarbon Receptor: From Homeostasis to Tumor Progression. Front Cell Dev Biol 2022; 10:884004. [PMID: 35465323 PMCID: PMC9022225 DOI: 10.3389/fcell.2022.884004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 03/15/2022] [Indexed: 12/19/2022] Open
Abstract
Transcription factor aryl hydrocarbon receptor (AHR) has emerged as one of the main regulators involved both in different homeostatic cell functions and tumor progression. Being a member of the family of basic-helix-loop-helix (bHLH) transcriptional regulators, this intracellular receptor has become a key member in differentiation, pluripotency, chromatin dynamics and cell reprogramming processes, with plenty of new targets identified in the last decade. Besides this role in tissue homeostasis, one enthralling feature of AHR is its capacity of acting as an oncogene or tumor suppressor depending on the specific organ, tissue and cell type. Together with its well-known modulation of cell adhesion and migration in a cell-type specific manner in epithelial-mesenchymal transition (EMT), this duality has also contributed to the arise of its clinical interest, highlighting a new potential as therapeutic tool, diagnosis and prognosis marker. Therefore, a deregulation of AHR-controlled pathways may have a causal role in contributing to physiological and homeostatic failures, tumor progression and dissemination. With that firmly in mind, this review will address the remarkable capability of AHR to exert a different function influenced by the phenotype of the target cell and its potential consequences.
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Affiliation(s)
- Claudia Rejano-Gordillo
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | - Ana Ordiales-Talavero
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | - Ana Nacarino-Palma
- Chronic Diseases Research Centre (CEDOC), Rua Do Instituto Bacteriológico, Lisboa, Portugal
| | - Jaime M. Merino
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | - Francisco J. González-Rico
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
- *Correspondence: Francisco J. González-Rico, ; Pedro M. Fernández-Salguero,
| | - Pedro M. Fernández-Salguero
- Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
- *Correspondence: Francisco J. González-Rico, ; Pedro M. Fernández-Salguero,
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3
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The Aryl Hydrocarbon Receptor (AHR): A Novel Therapeutic Target for Pulmonary Diseases? Int J Mol Sci 2022; 23:ijms23031516. [PMID: 35163440 PMCID: PMC8836075 DOI: 10.3390/ijms23031516] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 12/30/2021] [Accepted: 01/13/2022] [Indexed: 01/08/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a cytoplasmic transcription factor that is well-known for regulating xenobiotic metabolism. Studies in knockout and transgenic mice indicate that the AHR plays a vital role in the development of liver and regulation of reproductive, cardiovascular, hematopoietic, and immune homeostasis. In this focused review on lung diseases associated with acute injury and alveolar development, we reviewed and summarized the current literature on the mechanistic role(s) and therapeutic potential of the AHR in acute lung injury, chronic obstructive pulmonary disease, and bronchopulmonary dysplasia (BPD). Pre-clinical studies indicate that endogenous AHR activation is necessary to protect neonatal and adult lungs against hyperoxia- and cigarette smoke-induced injury. Our goal is to provide insight into the high translational potential of the AHR in the meaningful management of infants and adults with these lung disorders that lack curative therapies.
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Nuclear expression of VDR and AHR is mutually exclusive in glandular cells in endometriosis. Histochem Cell Biol 2021; 156:391-399. [PMID: 34155552 PMCID: PMC8550147 DOI: 10.1007/s00418-021-02005-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2021] [Indexed: 11/03/2022]
Abstract
The vitamin D receptor (VDR) and aryl hydrocarbon receptor (AHR) are two nuclear receptors that exert their effects by binding with ligands and forming a molecular complex. These complexes translocate to the nucleus and activate the expression of a series of genes which have a response element to VDR or AHR. Both receptors have been identified in the pathogenesis of endometriosis, a common disease characterized by the formation of endometrium-like tissue in ectopic zones. Despite numerous therapies, there is no definitive cure for endometriosis at the pharmacological level. Our study aims to describe the location and the expression of VDR and AHR at the protein level. For this purpose, an evaluation was performed using tissue from the three normal phases of the endometrium (proliferative, early, and late secretory) and in endometriosis by immunohistochemistry, using anti-VDR and anti-AHR antibodies. We demonstrate that in the nuclei of glandular cells in endometriosis, the expression of VDR and AHR is mutually exclusive—when the expression of one receptor is high, the other one is low—suggesting a possible target in the treatment of endometriosis. We also identify a significant change in the expression of glandular cytoplasmic AHR between the proliferative and late secretory endometrium.
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A New Insight into the Potential Role of Tryptophan-Derived AhR Ligands in Skin Physiological and Pathological Processes. Int J Mol Sci 2021; 22:ijms22031104. [PMID: 33499346 PMCID: PMC7865493 DOI: 10.3390/ijms22031104] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 01/15/2021] [Accepted: 01/19/2021] [Indexed: 12/31/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) plays a crucial role in environmental responses and xenobiotic metabolism, as it controls the transcription profiles of several genes in a ligand-specific and cell-type-specific manner. Various barrier tissues, including skin, display the expression of AhR. Recent studies revealed multiple roles of AhR in skin physiology and disease, including melanogenesis, inflammation and cancer. Tryptophan metabolites are distinguished among the groups of natural and synthetic AhR ligands, and these include kynurenine, kynurenic acid and 6-formylindolo[3,2-b]carbazole (FICZ). Tryptophan derivatives can affect and regulate a variety of signaling pathways. Thus, the interest in how these substances influence physiological and pathological processes in the skin is expanding rapidly. The widespread presence of these substances and potential continuous exposure of the skin to their biological effects indicate the important role of AhR and its ligands in the prevention, pathogenesis and progression of skin diseases. In this review, we summarize the current knowledge of AhR in skin physiology. Moreover, we discuss the role of AhR in skin pathological processes, including inflammatory skin diseases, pigmentation disorders and cancer. Finally, the impact of FICZ, kynurenic acid, and kynurenine on physiological and pathological processes in the skin is considered. However, the mechanisms of how AhR regulates skin function require further investigation.
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6
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Wang Z, Snyder M, Kenison JE, Yang K, Lara B, Lydell E, Bennani K, Novikov O, Federico A, Monti S, Sherr DH. How the AHR Became Important in Cancer: The Role of Chronically Active AHR in Cancer Aggression. Int J Mol Sci 2020; 22:ijms22010387. [PMID: 33396563 PMCID: PMC7795223 DOI: 10.3390/ijms22010387] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 12/25/2020] [Accepted: 12/28/2020] [Indexed: 12/13/2022] Open
Abstract
For decades, the aryl hydrocarbon receptor (AHR) was studied for its role in environmental chemical toxicity i.e., as a quirk of nature and a mediator of unintended consequences of human pollution. During that period, it was not certain that the AHR had a “normal” physiological function. However, the ongoing accumulation of data from an ever-expanding variety of studies on cancer, cancer immunity, autoimmunity, organ development, and other areas bears witness to a staggering array of AHR-controlled normal and pathological activities. The objective of this review is to discuss how the AHR has gone from a likely contributor to genotoxic environmental carcinogen-induced cancer to a master regulator of malignant cell progression and cancer aggression. Particular focus is placed on the association between AHR activity and poor cancer outcomes, feedback loops that control chronic AHR activity in cancer, and the role of chronically active AHR in driving cancer cell invasion, migration, cancer stem cell characteristics, and survival.
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Affiliation(s)
- Zhongyan Wang
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA; (Z.W.); (K.Y.); (E.L.)
| | - Megan Snyder
- Graduate Program in Genetics and Genomics, Division of Graduate Medical Sciences, Boston University School of Medicine, Boston, MA 02118, USA;
| | - Jessica E. Kenison
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA 02118, USA;
| | - Kangkang Yang
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA; (Z.W.); (K.Y.); (E.L.)
| | - Brian Lara
- Department of Environmental Health, Boston University, Boston, MA 02118, USA; (B.L.); (K.B.)
| | - Emily Lydell
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA; (Z.W.); (K.Y.); (E.L.)
| | - Kawtar Bennani
- Department of Environmental Health, Boston University, Boston, MA 02118, USA; (B.L.); (K.B.)
| | | | - Anthony Federico
- Division of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA; (A.F.); (S.M.)
| | - Stefano Monti
- Division of Computational Biomedicine, Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA; (A.F.); (S.M.)
| | - David H. Sherr
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA; (Z.W.); (K.Y.); (E.L.)
- Correspondence: ; Tel.: +1-617-358-1707
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7
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Phelan-Dickinson SJ, Palmer BC, Chen Y, DeLouise LA. The UVR Filter Octinoxate Modulates Aryl Hydrocarbon Receptor Signaling in Keratinocytes via Inhibition of CYP1A1 and CYP1B1. Toxicol Sci 2020; 177:188-201. [PMID: 32603427 DOI: 10.1093/toxsci/kfaa091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ultraviolet radiation (UVR) is a consistent part of the environment that has both beneficial and harmful effects on human health. UVR filters in the form of commercial sunscreens have been widely used to reduce the negative health effects of UVR exposure. Despite their benefit, literature suggests that some filters can penetrate skin and have off-target biological effects. We noted that many organic filters are hydrophobic and contain aromatic rings, making them potential modulators of Aryl hydrocarbon Receptor (AhR) signaling. We hypothesized that some filters may be able to act as agonists or antagonists on the AhR. Using a luciferase reporter cell line, we observed that the UVR filter octinoxate potentiated the ability of the known AhR ligand, 6-formylindolo[3,2-b]carbazole (FICZ), to activate the AhR. Cotreatments of keratinocytes with octinoxate and FICZ lead to increased levels of cytochrome P4501A1 (CYP1A1) and P4501B1 (CYP1B1) mRNA transcripts, in an AhR-dependent fashion. Mechanistic studies revealed that octinoxate is an inhibitor of CYP1A1 and CYP1B1, with IC50 values at approximately 1 µM and 586 nM, respectively. In vivo topical application of octinoxate and FICZ also elevated CYP1A1 and CYP1B1 mRNA levels in mouse skin. Our results show that octinoxate is able to indirectly modulate AhR signaling by inhibiting CYP1A1 and CYP1B1 enzyme function, which may have important downstream consequences for the metabolism of various compounds and skin integrity. It is important to continue studying the off-target effects of octinoxate and other UVR filters, because they are used on skin on a daily basis world-wide.
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Affiliation(s)
| | - Brian C Palmer
- Department of Environmental Medicine, University of Rochester Medical Center, New York 14642
| | - Yue Chen
- Department of Biomedical Engineering, University of Rochester, Rochester, New York 14627
| | - Lisa A DeLouise
- Department of Environmental Medicine, University of Rochester Medical Center, New York 14642.,Department of Biomedical Engineering, University of Rochester, Rochester, New York 14627.,Department of Dermatology, University of Rochester Medical Center, Rochester, New York 14642
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8
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New mechanistic insights of clear cell renal cell carcinoma from integrated miRNA and mRNA expression profiling studies. Biomed Pharmacother 2019; 111:821-834. [DOI: 10.1016/j.biopha.2018.12.099] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 12/12/2018] [Accepted: 12/23/2018] [Indexed: 12/20/2022] Open
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9
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Inducible Loss of the Aryl Hydrocarbon Receptor Activates Perigonadal White Fat Respiration and Brown Fat Thermogenesis via Fibroblast Growth Factor 21. Int J Mol Sci 2019; 20:ijms20040950. [PMID: 30813227 PMCID: PMC6412252 DOI: 10.3390/ijms20040950] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 02/14/2019] [Accepted: 02/19/2019] [Indexed: 02/06/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor highly expressed in hepatocytes. Researchers have employed global and liver-specific conditional Ahr knockout mouse models to characterize the physiological roles of the AHR; however, the gestational timing of AHR loss in these models can complicate efforts to distinguish the direct and indirect effects of post-gestational AHR deficiency. Utilizing a novel tamoxifen-inducible AHR knockout mouse model, we analyzed the effects of hepatocyte-targeted AHR loss in adult mice. The data demonstrate that AHR deficiency significantly reduces weight gain and adiposity, and increases multilocular lipid droplet formation within perigonadal white adipose tissue (gWAT). Protein and mRNA expression of fibroblast growth factor 21 (FGF21), an important hepatokine that activates thermogenesis in brown adipose tissue (BAT) and gWAT, significantly increases upon AHR loss and correlates with a significant increase of BAT and gWAT respiratory capacity. Confirming the role of FGF21 in mediating these effects, this phenotype is reversed in mice concomitantly lacking AHR and FGF21 expression. Chromatin immunoprecipitation analyses suggest that the AHR may constitutively suppress Fgf21 transcription through binding to a newly identified xenobiotic response element within the Fgf21 promoter. The data demonstrate an important AHR-FGF21 regulatory axis that influences adipose biology and may represent a “druggable” therapeutic target for obesity and its related metabolic disorders.
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10
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Aryl Hydrocarbon Receptor: A New Player of Pathogenesis and Therapy in Cardiovascular Diseases. BIOMED RESEARCH INTERNATIONAL 2018; 2018:6058784. [PMID: 29984241 PMCID: PMC6015699 DOI: 10.1155/2018/6058784] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Revised: 03/14/2018] [Accepted: 04/05/2018] [Indexed: 01/04/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is a DNA binding protein that acts as a nuclear receptor mediating xenobiotic metabolism and environmental responses. Owing to the evolutionary conservation of this gene and its widespread expression in the immune and circulatory systems, AhR has for many years been almost exclusively studied by the pharmacological/toxicological field for its role in contaminant toxicity. More recently, the functions of AhR in environmental adaption have been examined in the context of the occurrence, development, and therapy of cardiovascular diseases. Increasing evidence suggests that AhR is involved in maintaining homeostasis or in triggering pathogenesis by modulating the biological responses of critical cell types in the cardiovascular system. Here, we describe the structure, distribution, and ligands of AhR and the AhR signaling pathway and review the impact of AhR on cardiovascular physiology. We also discuss the potential contribution of AhR as a new potential factor in the targeted treatment of cardiovascular diseases.
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Abstract
Pituitary adenomas (PA) represent the largest group of intracranial neoplasms and yet the molecular mechanisms driving this disease remain largely unknown. The aim of this study was to use a high-throughput screening method to identify molecular pathways that may be playing a significant and consistent role in PA. RNA profiling using microarrays on eight local PAs identified the aryl hydrocarbon receptor (AHR) signalling pathway as a key canonical pathway downregulated in all PA types. This was confirmed by real-time PCR in 31 tumours. The AHR has been shown to regulate cell cycle progression in various cell types; however, its role in pituitary tissue has never been investigated. In order to validate the role of AHR in PA behaviour, further functional studies were undertaken. Over-expression of AHR in GH3 cells revealed a tumour suppressor potential independent of exogenous ligand activation by benzo α-pyrene (BαP). Cell cycle analysis and quantitative PCR of cell cycle regulator genes revealed that both unstimulated and BαP-stimulated AHR reduced E2F-driven transcription and altered expression of cell cycle regulator genes, thus increasing the percentage of cells in G0/G1 phase and slowing the proliferation rate of GH3 cells. Co-immunoprecipitation confirmed the interaction between AHR and retinoblastoma (Rb1) protein supporting this as a functional mechanism for the observed reduction. Endogenous Ahr reduction using silencing RNA confirmed the tumour suppressive function of the Ahr. These data support a mechanistic pathway for the putative tumour suppressive role of AHR specifically in PA, possibly through its role as a cell cycle co-regulator, even in the absence of exogenous ligands.
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Affiliation(s)
- R Formosa
- Department of MedicineFaculty of Medicine and Surgery, University of Malta, Msida, Malta
| | - J Borg
- Department of Applied Biomedical ScienceFaculty of Health Sciences, University of Malta, Msida, Malta
| | - J Vassallo
- Department of MedicineFaculty of Medicine and Surgery, University of Malta, Msida, Malta
- Department of MedicineNeuroendocrine Clinic, Mater Dei Hospital, Msida, Malta
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Formosa R, Vassallo J. The Complex Biology of the Aryl Hydrocarbon Receptor and Its Role in the Pituitary Gland. Discov Oncol 2017. [PMID: 28634910 DOI: 10.1007/s12672-017-0300-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor best known for its ability to mediate the effects of environmental toxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin), polycyclic aromatic hydrocarbons (PAHs), benzene, and polychlorinated biphenyls (PCBs) through the initiation of transcription of a number of metabolically active enzymes. Therefore, the AHR has been studied mostly in the context of xenobiotic signaling. However, several studies have shown that the AHR is constitutively active and plays an important role in general cell physiology, independently of its activity as a xenobiotic receptor and in the absence of exogenous ligands. Within the pituitary, activation of the AHR by environmental toxins has been implicated in disruption of gonadal development and fertility. Studies carried out predominantly in mouse models have revealed the detrimental influence of several environmental toxins on specific cell lineages of the pituitary tissue mediated by activation of AHR and its downstream effectors. Activation of AHR during fetal development adversely affected pituitary development while adult models exposed to AHR ligands demonstrated varying degrees of pituitary dysfunction. Such dysfunction may arise as a result of direct effects on pituitary cells or indirect effects on the hypothalamic-pituitary-gonadal axis. This review offers in-depth analysis of all aspects of AHR biology, with a particular focus on its role and activity within the adenohypophysis and specifically in pituitary tumorigenesis. A novel mechanism by which the AHR may play a direct role in pituitary cell proliferation and tumor formation is postulated. This review therefore attempts to cover all aspects of the AHR's role in the pituitary tissue, from fetal development to adult physiology and the pathophysiology underlying endocrine disruption and pituitary tumorigenesis.
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Affiliation(s)
- Robert Formosa
- Department of Medicine, Faculty of Medicine and Surgery, University of Malta, MSD 2080, Msida, Malta
| | - Josanne Vassallo
- Department of Medicine, Faculty of Medicine and Surgery, University of Malta, MSD 2080, Msida, Malta. .,Neuroendocrine Clinic, Department of Medicine, Mater Dei Hospital, Msida, Malta.
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Role of the aryl hydrocarbon receptor in carcinogenesis and potential as an anti-cancer drug target. Arch Toxicol 2017; 91:2497-2513. [PMID: 28508231 DOI: 10.1007/s00204-017-1981-2] [Citation(s) in RCA: 109] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 05/08/2017] [Indexed: 12/31/2022]
Abstract
The aryl hydrocarbon receptor (AhR) was initially identified as the receptor that binds and mediates the toxic effects induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and structurally related halogenated aromatics. Other toxic compounds including some polynuclear aromatic hydrocarbons act through the AhR; however, during the last 25 years, it has become apparent that the AhR plays an essential role in maintaining cellular homeostasis. Moreover, the scope of ligands that bind the AhR includes endogenous compounds such as multiple tryptophan metabolites, other endogenous biochemicals, pharmaceuticals and health-promoting phytochemicals including flavonoids, indole-3-carbinol and its metabolites. It has also been shown that like other receptors, the AhR is a drug target for multiple diseases including cancer, where both AhR agonists and antagonists effectively block many of the critical hallmarks of cancer in multiple tumor types. This review describes the anti-cancer activities of AhR ligands and demonstrates that it is time to separate the AhR from TCDD and exploit the potential of the AhR as a novel target for cancer chemotherapy.
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Wang Z, Monti S, Sherr DH. The diverse and important contributions of the AHR to cancer and cancer immunity. CURRENT OPINION IN TOXICOLOGY 2017. [DOI: 10.1016/j.cotox.2017.01.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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15
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Villa M, Gialitakis M, Tolaini M, Ahlfors H, Henderson CJ, Wolf CR, Brink R, Stockinger B. Aryl hydrocarbon receptor is required for optimal B-cell proliferation. EMBO J 2017; 36:116-128. [PMID: 27875245 PMCID: PMC5210087 DOI: 10.15252/embj.201695027] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 10/05/2016] [Accepted: 10/11/2016] [Indexed: 12/18/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR), a transcription factor known for mediating xenobiotic toxicity, is expressed in B cells, which are known targets for environmental pollutants. However, it is unclear what the physiological functions of AhR in B cells are. We show here that expression of Ahr in B cells is up-regulated upon B-cell receptor (BCR) engagement and IL-4 treatment. Addition of a natural ligand of AhR, FICZ, induces AhR translocation to the nucleus and transcription of the AhR target gene Cyp1a1, showing that the AhR pathway is functional in B cells. AhR-deficient (Ahr-/-) B cells proliferate less than AhR-sufficient (Ahr+/+) cells following in vitro BCR stimulation and in vivo adoptive transfer models confirmed that Ahr-/- B cells are outcompeted by Ahr+/+ cells. Transcriptome comparison of AhR-deficient and AhR-sufficient B cells identified cyclin O (Ccno), a direct target of AhR, as a top candidate affected by AhR deficiency.
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Affiliation(s)
- Matteo Villa
- The Francis Crick Institute, Mill Hill Laboratory, London, UK
| | | | - Mauro Tolaini
- The Francis Crick Institute, Mill Hill Laboratory, London, UK
| | - Helena Ahlfors
- The Francis Crick Institute, Mill Hill Laboratory, London, UK
| | - Colin J Henderson
- Division of Cancer Research, University of Dundee Ninewells Hospital and Medical School, Dundee, UK
| | - C Roland Wolf
- Division of Cancer Research, University of Dundee Ninewells Hospital and Medical School, Dundee, UK
| | - Robert Brink
- Garvan Institute of Medical Research, Sydney, NSW, Australia
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Zaragoza-Ojeda M, Eguía-Aguilar P, Perezpeña-Díazconti M, Arenas-Huertero F. Benzo[ghi]perylene activates the AHR pathway to exert biological effects on the NL-20 human bronchial cell line. Toxicol Lett 2016; 256:64-76. [DOI: 10.1016/j.toxlet.2016.05.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 05/17/2016] [Accepted: 05/24/2016] [Indexed: 02/08/2023]
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17
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Yang J, Chen W, Fan Y, Zhang H, Wang W, Zhang H. Ubiquitin Protein Ligase Ring2 Is Involved in S-phase Checkpoint and DNA Damage in Cells Exposed to Benzo[a]pyrene. J Biochem Mol Toxicol 2016; 30:481-488. [PMID: 27095601 DOI: 10.1002/jbt.21811] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 03/11/2016] [Accepted: 03/22/2016] [Indexed: 01/08/2023]
Abstract
Previous studies in our laboratory demonstrated that Ring2 may affect DNA damage and repair through pathways other than through regulating the expression of the nucleotide excision repair protein. In a series of experiments using wild-type cell (16HBE and WI38) and small interfering RNA (siRNA) Ring2 cells exposed to benzo[a]pyrene (BaP), we evaluated the cell cycle and DNA damage. The benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE-DNA) adduct assay demonstrated that in vitro exposure to BaP increased DNA damage in a time- and dose-dependent manner in wild-type and siRNA Ring2 cells. Analysis of covariance showed that a decrease of Ring2 caused DNA hypersensitivity to BaP. Flow cytometry results and proliferating cell nuclear antigen levels indicated that inhibition of Ring2 attenuated the effect of BaP on S-phase arrest. Taken together, these data implied that the lower proportion of cells in the S phase induced by inhibition of Ring2 may play an important role in DNA hypersensitivity to BaP.
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Affiliation(s)
- Jin Yang
- Department of Occupational Health, School of Public Health, Shanxi Medical University, 030001, Taiyuan, People's Republic of China.
| | - Wentao Chen
- Department of Occupational Health, School of Public Health, Shanxi Medical University, 030001, Taiyuan, People's Republic of China
| | - Yanfeng Fan
- Department of Occupational Health, School of Public Health, Shanxi Medical University, 030001, Taiyuan, People's Republic of China
| | - Huitao Zhang
- Department of Occupational Health, School of Public Health, Shanxi Medical University, 030001, Taiyuan, People's Republic of China
| | - Wubin Wang
- Department of Occupational Health, School of Public Health, Shanxi Medical University, 030001, Taiyuan, People's Republic of China
| | - Hongjie Zhang
- Department of Occupational Health, School of Public Health, Shanxi Medical University, 030001, Taiyuan, People's Republic of China
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Esser C, Rannug A. The aryl hydrocarbon receptor in barrier organ physiology, immunology, and toxicology. Pharmacol Rev 2015; 67:259-79. [PMID: 25657351 DOI: 10.1124/pr.114.009001] [Citation(s) in RCA: 351] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) is an evolutionarily old transcription factor belonging to the Per-ARNT-Sim-basic helix-loop-helix protein family. AhR translocates into the nucleus upon binding of various small molecules into the pocket of its single-ligand binding domain. AhR binding to both xenobiotic and endogenous ligands results in highly cell-specific transcriptome changes and in changes in cellular functions. We discuss here the role of AhR for immune cells of the barrier organs: skin, gut, and lung. Both adaptive and innate immune cells require AhR signaling at critical checkpoints. We also discuss the current two prevailing views-namely, 1) AhR as a promiscuous sensor for small chemicals and 2) a role for AhR as a balancing factor for cell differentiation and function, which is controlled by levels of endogenous high-affinity ligands. AhR signaling is considered a promising drug and preventive target, particularly for cancer, inflammatory, and autoimmune diseases. Therefore, understanding its biology is of great importance.
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Affiliation(s)
- Charlotte Esser
- Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany (C.E.); and Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden (A.R.)
| | - Agneta Rannug
- Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany (C.E.); and Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden (A.R.)
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de Tomaso Portaz AC, Caimi GR, Sánchez M, Chiappini F, Randi AS, Kleiman de Pisarev DL, Alvarez L. Hexachlorobenzene induces cell proliferation, and aryl hydrocarbon receptor expression (AhR) in rat liver preneoplastic foci, and in the human hepatoma cell line HepG2. AhR is a mediator of ERK1/2 signaling, and cell cycle regulation in HCB-treated HepG2 cells. Toxicology 2015. [DOI: 10.1016/j.tox.2015.07.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Go RE, Kim CW, Choi KC. Effect of fenhexamid and cyprodinil on the expression of cell cycle- and metastasis-related genes via an estrogen receptor-dependent pathway in cellular and xenografted ovarian cancer models. Toxicol Appl Pharmacol 2015; 289:48-57. [PMID: 26344002 DOI: 10.1016/j.taap.2015.09.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 09/01/2015] [Indexed: 12/22/2022]
Abstract
Fenhexamid and cyprodinil are antifungal agents (pesticides) used for agriculture, and are present at measurable amounts in fruits and vegetables. In the current study, the effects of fenhexamid and cyprodinil on cancer cell proliferation and metastasis were examined. Additionally, the protein expression levels of cyclin D1 and cyclin E as well as cathepsin D were analyzed in BG-1 ovarian cancer cells that express estrogen receptors (ERs). The cells were cultured with 0.1% dimethyl sulfoxide (DMSO; control), 17β-estradiol (E2; 10(-9)M), and fenhexamid or cyprodinil (10(-5)-10(-7)M). Results of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that fenhexamid and cyprodinil increased BG-1 cell proliferation about 1.5 to 2 times similar to E2 (5 times) compared to the control. When the cells were co-treated with ICI 182,780 (10(-8)M), an ER antagonist, the proliferation of pesticide-treated BG-1 cells was decreased to the level of the control. A wound healing assay revealed that the pesticides reduced the disrupted area in the BG-1 cell monolayer similar to E2. Protein levels of cyclin D1 and E as well as cathepsin D were increased by fenhexamid and cyprodinil. This effect was reversed by co-treatment with ICI 182,780. In a xenograft mouse model with transplanted BG-1 cells, cyprodinil significantly increased tumor mass formation about 2 times as did E2 (6 times) compared to the vehicle (0.1% DMSO) over an 80-day period. In contrast, fenhexamid did not promote ovarian tumor formation in this mouse model. Cyprodinil also induced cell proliferation along with the expression of proliferating cell nuclear antigen (PCNA) and cathepsin D in tumor tissues similar to E2. Taken together, these results imply that fenhexamid and cyprodinil may have disruptive effects on ER-expressing cancer by altering the cell cycle- and metastasis-related gene expression via an ER-dependent pathway.
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Affiliation(s)
- Ryeo-Eun Go
- Laboratory of Biochemistry and Immunology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Republic of Korea
| | - Cho-Won Kim
- Laboratory of Biochemistry and Immunology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Republic of Korea
| | - Kyung-Chul Choi
- Laboratory of Biochemistry and Immunology, College of Veterinary Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Republic of Korea.
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Jackson DP, Joshi AD, Elferink CJ. Ah Receptor Pathway Intricacies; Signaling Through Diverse Protein Partners and DNA-Motifs. Toxicol Res (Camb) 2015; 4:1143-1158. [PMID: 26783425 PMCID: PMC4714567 DOI: 10.1039/c4tx00236a] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Ah receptor is a transcription factor that modulates gene expression via interactions with multiple protein partners; these are reviewed, including the novel NC-XRE pathway involving KLF6.
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Ishida M, Mikami S, Shinojima T, Kosaka T, Mizuno R, Kikuchi E, Miyajima A, Okada Y, Oya M. Activation of aryl hydrocarbon receptor promotes invasion of clear cell renal cell carcinoma and is associated with poor prognosis and cigarette smoke. Int J Cancer 2015; 137:299-310. [PMID: 25523818 DOI: 10.1002/ijc.29398] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 12/02/2014] [Indexed: 12/16/2023]
Abstract
Although exposure to environmental pollutants is one of the risk factors for renal cell carcinoma (RCC), its relationship with carcinogenesis and the progression of RCC remains unknown. The present study was designed to elucidate the role of the aryl hydrocarbon receptor (AhR), a major mediator of carcinogenesis caused by environmental pollutants, in the progression of RCC. The expression of AhR was investigated in 120 patients with RCC using immunohistochemistry, and its relationship with clinicopathological parameters and prognoses was statistically analyzed. RCC cell lines were exposed to indirubin or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), AhR ligands, to activate the AhR pathway, or were transfected with small interfering RNA (siRNA) for AhR. The expression of the AhR target genes CYP1A1 and CYP1B1, matrix metalloproteinases (MMPs), and invasion through Matrigel(TM) were then examined. AhR was predominantly expressed in the nuclei of high-grade clear cell RCC (ccRCC) and tumor-infiltrating lymphocytes (TILs), and its expression levels in cancer cells and TILs correlated with the pathological tumor stage and histological grade. A multivariate Cox analysis revealed that the strong expression of AhR in cancer cells was a significant and independent predictor of disease-specific survival. AhR ligands up-regulated the expression of AhR and CYPs and promoted invasion by up-regulating MMPs. Furthermore, siRNA for AhR down-regulated CYPs, and inhibited cancer cell invasion together with the down-regulation of MMPs. These results suggest that AhR regulates the invasion of ccRCC and may be involved in tumor immunity. Therefore, inhibiting the activation of AhR may represent a potentially attractive therapeutic target for ccRCC patients.
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Affiliation(s)
- Masaru Ishida
- Department of Urology, Keio University School of Medicine, Tokyo, Japan
- Department of Urology, Saiseikai Yokohamashi Tobu Hospital, Yokohama, Japan
| | - Shuji Mikami
- Division of Diagnostic Pathology, Keio University Hospital, Tokyo, Japan
| | | | - Takeo Kosaka
- Department of Urology, Keio University School of Medicine, Tokyo, Japan
| | - Ryuichi Mizuno
- Department of Urology, Keio University School of Medicine, Tokyo, Japan
| | - Eiji Kikuchi
- Department of Urology, Keio University School of Medicine, Tokyo, Japan
| | - Akira Miyajima
- Department of Urology, Keio University School of Medicine, Tokyo, Japan
| | - Yasunori Okada
- Department of Pathology, Keio University School of Medicine, Tokyo, Japan
| | - Mototsugu Oya
- Department of Urology, Keio University School of Medicine, Tokyo, Japan
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23
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Medjakovic S, Zoechling A, Gerster P, Ivanova MM, Teng Y, Klinge CM, Schildberger B, Gartner M, Jungbauer A. Effect of nonpersistent pesticides on estrogen receptor, androgen receptor, and aryl hydrocarbon receptor. ENVIRONMENTAL TOXICOLOGY 2014; 29:1201-1216. [PMID: 23436777 DOI: 10.1002/tox.21852] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 01/07/2013] [Accepted: 01/17/2013] [Indexed: 06/01/2023]
Abstract
Nonpersistent pesticides are considered less harmful for the environment, but their impact as endocrine disruptors has not been fully explored. The pesticide Switch was applied to grape vines, and the maximum residue concentration of its active ingredients was quantified. The transactivation potential of the pesticides Acorit, Frupica, Steward, Reldan, Switch, Cantus, Teldor, and Scala and their active compounds (hexythiazox, mepanipyrim, indoxacarb, chlorpyrifos-methyl, cyprodinil, fludioxonil, boscalid, fenhexamid, and pyrimethanil) were tested on human estrogen receptor α (ERα), androgen receptor (AR) and arylhydrocarbon receptor (AhR) in vitro. Relative binding affinities of the pure pesticide constituents for AR and their effect on human breast cancer and prostate cancer cell lines were evaluated. Residue concentrations of Switch's ingredients were below maximum residue limits. Fludioxonil and fenhexamid were ERα agonists (EC50 -values of 3.7 and 9.0 μM, respectively) and had time-dependent effects on endogenous ERα-target gene expression (cyclin D1, progesterone receptor, and nuclear respiratory factor 1) in MCF-7 human breast cancer cells. Fludioxonil, mepanipyrim, cyprodinil, pyrimethanil, and chlorpyrifos-methyl were AhR-agonists (EC50 s of 0.42, 0.77, 1.4, 4.6, and 5.1 μM, respectively). Weak AR binding was shown for chlorpyrifos-methyl, cyprodinil, fenhexamid, and fludioxonil. Assuming a total uptake which does not take metabolism and clearance rates into account, our in vitro evidence suggests that pesticides could activate pathways affecting hormonal balance, even within permitted limits, thus potentially acting as endocrine disruptors.
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Affiliation(s)
- Svjetlana Medjakovic
- Christian Doppler Laboratory for Receptor Biotechnology, A-1190 Vienna, Austria; Department of Biotechnology, University of Natural Resources and Life Sciences Vienna, A-1190 Vienna, Austria
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24
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Lowe MM, Mold JE, Kanwar B, Huang Y, Louie A, Pollastri MP, Wang C, Patel G, Franks DG, Schlezinger J, Sherr DH, Silverstone AE, Hahn ME, McCune JM. Identification of cinnabarinic acid as a novel endogenous aryl hydrocarbon receptor ligand that drives IL-22 production. PLoS One 2014; 9:e87877. [PMID: 24498387 PMCID: PMC3912126 DOI: 10.1371/journal.pone.0087877] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 12/30/2013] [Indexed: 01/17/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) binds to environmental toxicants including synthetic halogenated aromatic hydrocarbons and is involved in a diverse array of biological processes. Recently, the AHR was shown to control host immunity by affecting the balance between inflammatory T cells that produce IL-17 (Th17) and IL-22 versus regulatory T cells (Treg) involved in tolerance. While environmental AHR ligands can mediate this effect, endogenous ligands are likely to be more relevant in host immune responses. We investigated downstream metabolites of tryptophan as potential AHR ligands because (1) tryptophan metabolites have been implicated in regulating the balance between Th17 and Treg cells and (2) many of the AHR ligands identified thus far are derivatives of tryptophan. We characterized the ability of tryptophan metabolites to bind and activate the AHR and to increase IL-22 production in human T cells. We report that the tryptophan metabolite, cinnabarinic acid (CA), is an AHR ligand that stimulates the differentiation of human and mouse T cells producing IL-22. We compare the IL-22-stimulating activity of CA to that of other tryptophan metabolites and define stimulation conditions that lead to CA production from immune cells. Our findings link tryptophan metabolism to AHR activation and define a novel endogenous AHR agonist with potentially broad biological functions.
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MESH Headings
- Animals
- Cell Differentiation
- Cells, Cultured
- Chromatography, Liquid
- Cytochrome P-450 CYP1A1/metabolism
- Humans
- Interleukins/metabolism
- Ligands
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Oxazines/metabolism
- Receptors, Aryl Hydrocarbon/physiology
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- T-Lymphocytes, Regulatory/cytology
- T-Lymphocytes, Regulatory/immunology
- T-Lymphocytes, Regulatory/metabolism
- Th17 Cells
- Tryptophan/metabolism
- Interleukin-22
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Affiliation(s)
- Margaret M. Lowe
- Division of Experimental Medicine, Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
| | - Jeff E. Mold
- Division of Experimental Medicine, Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
| | - Bittoo Kanwar
- Division of Experimental Medicine, Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
- Division of Gastroenterology, Department of Pediatrics, University of California San Francisco, San Francisco, California, United States of America
| | - Yong Huang
- Drug Studies Unit, Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California, United States of America
| | - Alexander Louie
- Drug Studies Unit, Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California, United States of America
| | - Michael P. Pollastri
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Cuihua Wang
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Gautam Patel
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States of America
| | - Diana G. Franks
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States of America
| | - Jennifer Schlezinger
- Department of Environmental Health, School of Public Health, Boston University, Boston, Massachusetts, United States of America
| | - David H. Sherr
- Department of Environmental Health, School of Public Health, Boston University, Boston, Massachusetts, United States of America
| | - Allen E. Silverstone
- Department of Microbiology and Immunology, State University of New York Upstate Medical University, Syracuse, New York, United States of America
| | - Mark E. Hahn
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States of America
| | - Joseph M. McCune
- Division of Experimental Medicine, Department of Medicine, University of California San Francisco, San Francisco, California, United States of America
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25
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Jackson DP, Li H, Mitchell KA, Joshi AD, Elferink CJ. Ah receptor-mediated suppression of liver regeneration through NC-XRE-driven p21Cip1 expression. Mol Pharmacol 2014; 85:533-41. [PMID: 24431146 DOI: 10.1124/mol.113.089730] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies in hepatocyte-derived cell lines and the whole liver established that the aryl hydrocarbon receptor (AhR) can disrupt G1-phase cell cycle progression following exposure to persistent AhR agonists, such as TCDD (dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin). Growth arrest was attributed to inhibition of G1-phase cyclin-dependent kinase 2 (CDK2) activity. The present study examined the effect of TCDD exposure on liver regeneration following 70% partial hepatectomy in mice lacking the Cip/Kip inhibitors p21(Cip1) or p27(Kip1) responsible for regulating CDK2 activity. Assessment of the regenerative process in wild-type, p21(Cip1) knockout, and p27(Kip1) knockout mice confirmed that TCDD-induced inhibition of liver regeneration is entirely dependent on p21(Cip1) expression. Compared with wild-type mice, the absence of p21(Cip1) expression completely abrogated the TCDD inhibition, and accelerated hepatocyte progression through G1 phase during the regenerative process. Analysis of the transcriptional response determined that increased p21(Cip1) expression during liver regeneration involved an AhR-dependent mechanism. Chromatin immunoprecipitation studies revealed that p21(Cip1) induction required AhR binding to the newly characterized nonconsensus xenobiotic response element, in conjunction with the tumor suppressor protein Kruppel-like factor 6 functioning as an AhR binding partner. The evidence also suggests that AhR functionality following partial hepatectomy is dependent on a p21(Cip1)-regulated signaling process, intimately linking AhR biology to the G1-phase cell cycle program.
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Affiliation(s)
- Daniel P Jackson
- Department of Pharmacology and Toxicology (D.P.J., A.D.J., C.J.E.) and Department of Pediatrics (H.L.), University of Texas Medical Branch, Galveston, Texas; and Department of Biological Sciences, Boise State University, Boise, Idaho (K.A.M.)
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26
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Safe S, Lee SO, Jin UH. Role of the aryl hydrocarbon receptor in carcinogenesis and potential as a drug target. Toxicol Sci 2013; 135:1-16. [PMID: 23771949 PMCID: PMC3748760 DOI: 10.1093/toxsci/kft128] [Citation(s) in RCA: 205] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/03/2013] [Indexed: 12/22/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is highly expressed in multiple organs and tissues, and there is increasing evidence that the AHR plays an important role in cellular homeostasis and disease. The AHR is expressed in multiple tumor types, in cancer cell lines, and in tumors from animal models, and the function of the AHR has been determined by RNA interference, overexpression, and inhibition studies. With few exceptions, knockdown of the AHR resulted in decreased proliferation and/or invasion and migration of cancer cell lines, and in vivo studies in mice overexpressing the constitutively active AHR exhibited enhanced stomach and liver cancers, suggesting a pro-oncogenic role for the AHR. In contrast, loss of the AHR in transgenic mice that spontaneously develop colonic tumors and in carcinogen-induced liver tumors resulted in increased carcinogenesis, suggesting that the receptor may exhibit antitumorigenic activity prior to tumor formation. AHR ligands also either enhanced or inhibited tumorigenesis, and these effects were highly tumor specific, demonstrating that selective AHR modulators that exhibit agonist or antagonist activities represent an important new class of anticancer agents that can be directed against multiple tumors.
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Affiliation(s)
- Stephen Safe
- Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, Texas 77843-4466, USA.
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Quintana FJ, Sherr DH. Aryl hydrocarbon receptor control of adaptive immunity. Pharmacol Rev 2013; 65:1148-61. [PMID: 23908379 DOI: 10.1124/pr.113.007823] [Citation(s) in RCA: 244] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that belongs to the family of basic helix-loop-helix transcription factors. Although the AhR was initially recognized as the receptor mediating the pathologic effects of dioxins and other pollutants, the activation of AhR by endogenous and environmental factors has important physiologic effects, including the regulation of the immune response. Thus, the AhR provides a molecular pathway through which environmental factors modulate the immune response in health and disease. In this review, we discuss the role of AhR in the regulation of the immune response, the source and chemical nature of AhR ligands, factors controlling production and degradation of AhR ligands, and the potential to target the AhR for therapeutic immunomodulation.
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Affiliation(s)
- Francisco J Quintana
- Center for Neurologic Diseases, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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28
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Brandner S, Eberhagen C, Lichtmannegger J, Hieber L, Andrae U. TCDD induces the expression of insulin-like growth factor binding protein 4 in 5L rat hepatoma cells: A cautionary tale of the use of this cell line in studies on dioxin toxicity. Toxicology 2013; 309:107-16. [DOI: 10.1016/j.tox.2013.04.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 04/18/2013] [Accepted: 04/19/2013] [Indexed: 11/29/2022]
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Schulz M, Brandner S, Eberhagen C, Eckardt-Schupp F, Larsen MR, Andrae U. Quantitative phosphoproteomic analysis of early alterations in protein phosphorylation by 2,3,7,8-tetrachlorodibenzo-p-dioxin. J Proteome Res 2013; 12:866-82. [PMID: 23298284 DOI: 10.1021/pr3009429] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A comprehensive quantitative analysis of changes in protein phosphorylation preceding or accompanying transcriptional activation by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 5L rat hepatoma cells was performed using the SILAC approach. Following exposure of the cells to DMSO or 1 nM TCDD for 0.5 to 2 h, 5648 phosphorylated peptides corresponding to 2156 phosphoproteins were identified. Eight peptides exhibited a statistically significantly altered phosphorylation because of TCDD exposure and 22 showed a regulation factor of ≥ 1.5 in one of the experiments per time point. The vast majority of the TCCD-induced phosphorylation changes had not been reported before. The transcription factor ARNT, the obligate partner for gene activation by the TCDD-bound Ah receptor, exhibited an up-regulation of its Ser77 phosphorylation, a modification known to control the differential binding of ARNT homodimers and heterodimers to different enhancers suggesting that this phosphorylation represents a novel mechanism contributing to the alteration of gene expression by TCDD. Other proteins with altered phosphorylation included, among others, various transcriptional coregulators previously unknown to participate in TCDD-induced gene activation, regulators of small GTPases of the Ras superfamily, UBX domain-containing proteins and the oncogenic protein LYRIC. The results open up new directions for research on the molecular mechanisms of dioxin action and toxicity.
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Affiliation(s)
- Melanie Schulz
- Institute of Molecular Toxicology and Pharmacology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
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Beijer K, Gao K, Jönsson ME, Larsson DGJ, Brunström B, Brandt I. Effluent from drug manufacturing affects cytochrome P450 1 regulation and function in fish. CHEMOSPHERE 2013; 90:1149-1157. [PMID: 23062946 DOI: 10.1016/j.chemosphere.2012.09.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 07/12/2012] [Accepted: 09/08/2012] [Indexed: 06/01/2023]
Abstract
We have previously reported very high concentrations of pharmaceuticals in the effluent from a treatment plant receiving wastewater from about 90 bulk drug manufacturers near Hyderabad, India. The main objective of the present study was to examine how high dilutions of this effluent affect mRNA expression of cytochrome P450 (CYP) 1 family genes and ethoxyresorufin O-deethylase (EROD) activity in exposed wildlife, using the three-spined stickleback (Gasterosteus aculeatus) as a model. In gill filaments exposed to diluted effluent ex vivo, EROD activity was strongly inhibited in a concentration-dependent manner. In a subsequent in vivo study, groups of fish were exposed (24h) to three concentrations of effluent, 0.8%, 1.6% or 3.2%. In this experiment, EROD in gills was induced 27-, 52- or 60-fold, respectively. Accordingly, CYP1A mRNA was markedly up-regulated in gill, liver and brain of fish exposed to all three effluent concentrations. Expression of mRNA for CYP1B1 and CYP1C1 was induced in gills at all concentrations while effects on these genes in liver and brain were weak or absent. The results of a time course study suggested that most CYP1-inducing substances in the effluent were readily metabolised or excreted, because the induced EROD activity and mRNA expression decreased when the fish were transferred to clean water. Considering that CYP1 enzymes play important roles in biotransformation of endogenous and foreign compounds, the observed dual effect of the effluent on CYP1 catalytic activity and mRNA expression suggests that multiple physiological functions could be affected in exposed wildlife.
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Affiliation(s)
- Kristina Beijer
- Department of Environmental Toxicology, Uppsala University, Sweden.
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31
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Cigarette smoke condensate induces aryl hydrocarbon receptor-dependent changes in gene expression in spermatocytes. Reprod Toxicol 2012; 34:665-76. [DOI: 10.1016/j.reprotox.2012.10.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 09/14/2012] [Accepted: 10/05/2012] [Indexed: 01/08/2023]
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32
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Stolpmann K, Brinkmann J, Salzmann S, Genkinger D, Fritsche E, Hutzler C, Wajant H, Luch A, Henkler F. Activation of the aryl hydrocarbon receptor sensitises human keratinocytes for CD95L- and TRAIL-induced apoptosis. Cell Death Dis 2012; 3:e388. [PMID: 22951985 PMCID: PMC3461363 DOI: 10.1038/cddis.2012.127] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In this study, we have analysed the apoptotic effects of the ubiquitous environmental toxin benzo[a]pyrene (BP) in HaCaT cells and human keratinocytes. Although prolonged exposure to BP was not cytotoxic on its own, a strong enhancement of CD95 (Fas)-mediated apoptosis was observed with BP at concentrations activating the aryl hydrocarbon receptor (AhR). Importantly, the ultimately mutagenic BP-metabolite, that is, (+)-anti-BP-7,8-diol-9,10-epoxide (BPDE), failed to enhance CD95-mediated cell death, suggesting that the observed pro-apoptotic effect of BP is neither associated with DNA adducts nor DNA-damage related signalling. CD95-induced apoptosis was also enhanced by β-naphtoflavone, a well-known agonist of the AhR that does not induce DNA damage, thus suggesting a crucial role for AhR activation. Consistently, BP failed to sensitise for CD95L-induced apoptosis in AhR knockdown HaCaT cells. Furthermore, inhibition of CYP1A1 and/or 1B1 expression did not affect the pro-apoptotic crosstalk. Exposure to BP did not increase expression of CD95, but led to augmented activation of caspase-8. Enhancement of apoptosis was also observed with the TRAIL death receptors that activate caspase-8 and apoptosis by similar mechanisms as CD95. Together, these observations indicate an interference of AhR signalling with the activity of receptor-associated signalling intermediates that are shared by CD95 and TRAIL receptors. Our data thus suggest that AhR agonists can enhance cytokine-mediated adversity upon dermal exposure.
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Affiliation(s)
- K Stolpmann
- German Federal Institute for Risk Assessment, Department of Product Safety, Berlin, Germany
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33
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Volkov MS, Bolotina NA, Evteev VA, Koblyakov VA. Ah-receptor-independent stimulation of hepatoma 27 culture cell proliferation by polycyclic aromatic hydrocarbons. BIOCHEMISTRY (MOSCOW) 2012; 77:201-7. [DOI: 10.1134/s0006297912020125] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Black MB, Budinsky RA, Dombkowski A, Cukovic D, LeCluyse EL, Ferguson SS, Thomas RS, Rowlands JC. Cross-species comparisons of transcriptomic alterations in human and rat primary hepatocytes exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Sci 2012; 127:199-215. [PMID: 22298810 DOI: 10.1093/toxsci/kfs069] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A toxicogenomics approach was used to qualitatively and quantitatively compare the gene expression changes in human and rat primary hepatocytes exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Hepatocytes from five individual rats and five individual humans were exposed for 24 h to 11 concentrations of TCDD ranging from 0.00001 to 100nM and a vehicle control. Gene expression changes were analyzed using whole-genome microarrays containing 13,002 orthologs. Significant changes in expression of individual orthologs at any concentration (fold change [FC] ± 1.5 and false discovery rate < 0.05) were higher in the rat (1547) compared with human hepatocytes (475). Only 158 differentially expressed orthologs were common between rats and humans. Enrichment analysis was performed on the differentially expressed orthologs in each species with 49 and 34 enriched human and rat pathways, respectively. Only 12 enriched pathways were shared between the two species. The results demonstrate significant cross-species differences in expression at both the gene and pathway level. Benchmark dose analysis of gene expression changes showed an average 18-fold cross-species difference in potency among differentially expressed orthologs with the rat more sensitive than the human. Similar cross-species differences in potency were observed for signaling pathways. Using the maximum FC in gene expression as a measure of efficacy, the human hepatocytes showed on average a 20% lower efficacy among the individual orthologs showing differential expression. The results provide evidence for divergent cross-species gene expression changes in response to TCDD and are consistent with epidemiological and clinical evidence showing humans to be less sensitive to TCDD-induced hepatotoxicity.
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Affiliation(s)
- Michael B Black
- The Hamner Institutes for Health Sciences, Research Triangle Park, North Carolina 27709, USA
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Huang G, Elferink CJ. A novel nonconsensus xenobiotic response element capable of mediating aryl hydrocarbon receptor-dependent gene expression. Mol Pharmacol 2011; 81:338-47. [PMID: 22113079 DOI: 10.1124/mol.111.075952] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) is a mediator of xenobiotic toxicity, best recognized for conveying the deleterious effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. The AhR functions as a ligand-activated transcription factor that binds to a canonical xenobiotic response element (XRE) in association with the heterodimerization partner, the AhR nuclear translocator (Arnt) protein. However, within the repertoire of AhR target genes identified in recent years, many lack a clearly defined XRE highlighting the growing realization that AhR-mediated gene expression seems to involve additional mechanisms distinct from the well characterized process involving the XRE. The present study characterized a novel nonconsensus XRE (NC-XRE) in the promoter of the plasminogen activator inhibitor-1 (PAI-1) gene that recruits a novel protein-DNA complex responsible for TCDD-inducible expression. DNA binding studies and reporter assays identified key residues in the NC-XRE necessary for protein-DNA binding and function, respectively. Functional studies with AhR expression constructs confirm that TCDD-inducibility is AhR-dependent and requires direct AhR-DNA binding to the NC-XRE. Chromatin immunoprecipitation and RNA interference studies reveal that the Arnt protein is not a component of the NC-XRE-bound AhR complex, suggesting that in contrast to the XRE, AhR-dependent gene expression mediated through the NC-XRE may involve a new DNA binding partner.
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Affiliation(s)
- Gengming Huang
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX 77555-0654, USA
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Hamouchene H, Arlt VM, Giddings I, Phillips DH. Influence of cell cycle on responses of MCF-7 cells to benzo[a]pyrene. BMC Genomics 2011; 12:333. [PMID: 21714911 PMCID: PMC3145607 DOI: 10.1186/1471-2164-12-333] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2011] [Accepted: 06/29/2011] [Indexed: 01/26/2023] Open
Abstract
Background Benzo[a]pyrene (BaP) is a widespread environmental genotoxic carcinogen that damages DNA by forming adducts. This damage along with activation of the aryl hydrocarbon receptor (AHR) induces complex transcriptional responses in cells. To investigate whether human cells are more susceptible to BaP in a particular phase of the cell cycle, synchronised breast carcinoma MCF-7 cells were exposed to BaP. Cell cycle progression was analysed by flow cytometry, DNA adduct formation was assessed by 32P-postlabeling analysis, microarrays of 44K human genome-wide oligos and RT-PCR were used to detect gene expression (mRNA) changes and Western blotting was performed to determine the expression of some proteins, including cytochrome P450 (CYP) 1A1 and CYP1B1, which are involved in BaP metabolism. Results Following BaP exposure, cells evaded G1 arrest and accumulated in S-phase. Higher levels of DNA damage occurred in S- and G2/M- compared with G0/G1-enriched cultures. Genes that were found to have altered expression included those involved in xenobiotic metabolism, apoptosis, cell cycle regulation and DNA repair. Gene ontology and pathway analysis showed the involvement of various signalling pathways in response to BaP exposure, such as the Catenin/Wnt pathway in G1, the ERK pathway in G1 and S, the Nrf2 pathway in S and G2/M and the Akt pathway in G2/M. An important finding was that higher levels of DNA damage in S- and G2/M-enriched cultures correlated with higher levels of CYP1A1 and CYP1B1 mRNA and proteins. Moreover, exposure of synchronised MCF-7 cells to BaP-7,8-diol-9,10-epoxide (BPDE), the ultimate carcinogenic metabolite of BaP, did not result in significant changes in DNA adduct levels at different phases of the cell cycle. Conclusions This study characterised the complex gene response to BaP in MCF-7 cells and revealed a strong correlation between the varying efficiency of BaP metabolism and DNA damage in different phases of the cell cycle. Our results suggest that growth kinetics within a target-cell population may be important determinants of susceptibility and response to a genotoxic agent.
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Affiliation(s)
- Hamza Hamouchene
- Section of Molecular Carcinogenesis, Institute of Cancer Research, Brookes Lawley Building, Cotswold Road, Sutton, Surrey SM2 5NG, UK.
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Kalmes M, Hennen J, Clemens J, Blömeke B. Impact of aryl hydrocarbon receptor (AhR) knockdown on cell cycle progression in human HaCaT keratinocytes. Biol Chem 2011; 392:643-51. [PMID: 21627536 DOI: 10.1515/bc.2011.067] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Abstract While activation of the aryl hydrocarbon receptor (AhR) by exogenous ligands is well investigated, its physiological function is less understood. By extending research in AhR biology, evidence appeared that the receptor generally plays an important role in cell physiology. In keratinocytes, little is known about endogenous functions of the AhR. In order to expand this knowledge, we analyzed the impact of AhR knockdown on cell cycle progression in HaCaT cells and showed that proliferation of siAhR HaCaT cells was significantly decreased. In line with that result, western blot analysis revealed that protein level of the cyclin dependent kinase inhibitor p27(KIP1) was increased, whereas protein level of the cyclin dependent kinase (CDK) 2 was reduced. CDK4 and CDK6 protein levels remained unchanged, whereas protein level of the retinoblastoma protein (pRB) was reduced. By measuring ethoxyresorufin-O-deethylase (EROD) activity we showed that endogenous cytochrome P450 1 (CYP1), especially CYP1A1 is required for normal cell cycle in HaCaT cells, as well. To the best of our knowledge, we provide evidence for the first time in human skin cells, that in the absence of exogenous ligands, the AhR promotes cell cycle progression in HaCaT cells and one can speculate that this is the physiological function of this receptor in keratinocytes.
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Affiliation(s)
- Michaela Kalmes
- Department of Environmental Toxicology, University of Trier, Germany
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Gaitanis G, Velegraki A, Magiatis P, Pappas P, Bassukas ID. Could Malassezia yeasts be implicated in skin carcinogenesis through the production of aryl-hydrocarbon receptor ligands? Med Hypotheses 2011; 77:47-51. [PMID: 21444158 DOI: 10.1016/j.mehy.2011.03.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 03/07/2011] [Indexed: 01/09/2023]
Abstract
UNLABELLED Malassezia yeasts are found on the skin of all humans and many warm-blooded animals. In vitro they have the ability to synthesize potent ligands (indolo[3,2-b]carbazole, malassezin and indirubin) of the aryl-hydrocarbon receptor (AhR; synonym: dioxin receptor) when the sweat contained L-tryptophan is used as the single nitrogen source. The production of these AhR-ligands has been associated with pathogenic strains of a certain Malassezia species (Malassezia furfur) but recent evidence shows that this property is widely distributed in almost all currently known Malassezia species. AhR is associated with carcinogenesis and the potential connection of these ubiquitous skin symbionts, and putative pathogens, with skin neoplasia should be evaluated mainly focusing on mechanisms related to the distinctive ability of the yeast to produce potent AhR ligands. HYPOTHESIS Synthesis of available pertinent data show a possible link between Malassezia produced AhR ligands and skin carcinogenesis, particularly of basal cell carcinoma (BCC). BCCs are almost exclusively observed in animal species colonized by Malassezia. In humans and animals there is overlapping in the skin regions colonized by this yeast and affected by BCC. The potent AhR ligands synthesized by pathogenic Malassezia strains could contribute to tumor promotion by: modification of the UV radiation carcinogenesis, alterations in the salvage/survival of initiated tumor cells, inhibition of cell senescence, interaction with vitamin D metabolism, promotion of immune tolerance and finally pro-carcinogenic modulation of cell cycle progression and apoptosis.
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Affiliation(s)
- G Gaitanis
- Department of Skin and Venereal Diseases, Medical School, University of Ioannina, S. Niarchou Av., University Campus, 45110 Ioannina, Greece.
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External influences on the immune system via activation of the aryl hydrocarbon receptor. Semin Immunol 2011; 23:99-105. [PMID: 21288737 DOI: 10.1016/j.smim.2011.01.008] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 01/10/2011] [Indexed: 02/06/2023]
Abstract
The aryl hydrocarbon receptor (AhR), subject of intensive research over three decades by the pharmacology/toxicology field has recently made its entry into mainstream immunology research and is set to continue to intrigue with ever more complex modes of modulating immune responses. The discovery of high and selective AhR expression on Th17 cells and its role in induction of the cytokine IL-22 attributed new immunological functions to this transcription factor and stimulated further research into physiological functions of the AhR in the immune system. A number of recent reviews have highlighted potential new avenues of research. This review addresses recent new insight into physiological roles of AhR in the immune system.
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Mitchell KA, Wilson SR, Elferink CJ. The activated aryl hydrocarbon receptor synergizes mitogen-induced murine liver hyperplasia. Toxicology 2010; 276:103-9. [PMID: 20637255 DOI: 10.1016/j.tox.2010.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 07/01/2010] [Accepted: 07/06/2010] [Indexed: 11/18/2022]
Abstract
Mechanisms of hepatocyte proliferation triggered by tissue loss are distinguishable from those that promote proliferation in the intact liver in response to mitogens. Previous studies demonstrate that exogenous activation of the aryl hydrocarbon receptor (AhR), a soluble ligand-activated transcription factor in the basic helix-loop-helix family of proteins, suppresses compensatory liver regeneration elicited by surgical partial hepatectomy. The goal of the present study was to determine how AhR activation modulates hepatocyte cell cycle progression in the intact liver following treatment with the hepatomitogen, 1,4-bis[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP). Mice were pretreated with the exogenous AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) 24h prior to treatment with TCPOBOP (3 mg/kg).). In contrast to the suppressive effects of AhR activation observed during compensatory regeneration, TCDD pretreatment resulted in a 30-50% increase in hepatocyte proliferation in the intact liver of TCPOBOP-treated mice. Although pretreatment with TCDD suppressed CDK2 kinase activity and increased the association of CDK2 with negative regulatory proteins p21Cip1 and p27Kip1, a corresponding increase in CDK4/cyclin D1 association and CDK4 activity which culminated in enhanced phosphorylation of retinoblastoma protein, consistent with the increased proliferative response. These findings are in stark contrast to previous observations that the activated AhR can suppress hepatocyte proliferation in vivo and reveal a new complexity to AhR-mediated cell cycle control.
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Affiliation(s)
- Kristen A Mitchell
- Department of Pharmacology and Toxicology, School of Medicine, University of Texas Medical Branch, Galveston, TX 77555-1031, USA
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41
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Bonifas J, Hennen J, Dierolf D, Kalmes M, Blömeke B. Evaluation of cytochrome P450 1 (CYP1) and N-acetyltransferase 1 (NAT1) activities in HaCaT cells: Implications for the development of in vitro techniques for predictive testing of contact sensitizers. Toxicol In Vitro 2010; 24:973-80. [DOI: 10.1016/j.tiv.2009.12.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 11/27/2009] [Accepted: 12/22/2009] [Indexed: 10/20/2022]
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Fan Y, Boivin GP, Knudsen ES, Nebert DW, Xia Y, Puga A. The aryl hydrocarbon receptor functions as a tumor suppressor of liver carcinogenesis. Cancer Res 2009; 70:212-20. [PMID: 19996281 DOI: 10.1158/0008-5472.can-09-3090] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the biological and toxic effects of its xenobiotic ligands. Previous cell culture studies have shown that, in addition to controlling the xenobiotic detoxification response, AHR activation leads to G0-G1 arrest, diminished capacity for DNA replication, and inhibition of cell proliferation. In fact, recent work from our own and from other laboratories suggests that AHR may function as a tumor suppressor gene that becomes silenced during the process of tumor formation. To test this hypothesis and determine whether the mouse Ahr gene acts as a tumor suppressor gene in vivo, we have examined the role of Ahr ablation in liver tumorigenesis induced by the genotoxic chemical diethylnitrosamine (DEN), a hepatic carcinogen that is not an AHR ligand. In mice given a single i.p. injection of DEN, AHR antagonized liver tumor formation and growth by regulating cell proliferation, inflammatory cytokine expression, and DNA damage, parameters which were significantly elevated in the livers of control and, more so, of DEN-exposed Ahr-/- mice. Ahr-/- hepatocytes also showed significantly higher numbers of 4N cells, increased expression of proliferative markers, and repression of tumor suppressor genes. These data support the concept that in its basal state in the absence of a xenobiotic ligand, the Ahr gene functions as a tumor suppressor gene, and that its silencing may be associated with cancer progression.
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Affiliation(s)
- Yunxia Fan
- Department of Environmental Health, University of Cincinnati Medical Center, College of Medicine, Cincinnati, Ohio 45267-0056, USA
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Methylation of dietary flavones increases their metabolic stability and chemopreventive effects. Int J Mol Sci 2009; 10:5002-5019. [PMID: 20087474 PMCID: PMC2808020 DOI: 10.3390/ijms10115002] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Accepted: 11/16/2009] [Indexed: 12/27/2022] Open
Abstract
Dietary flavones have promising chemoprotective properties, in particular with regard to cancer, but problems with low oral bioavailability and sometimes unacceptable toxicity have made their use as protective additives to normal diets questionable. However, methylation of free phenolic hydroxyl groups leads to derivatives not susceptible to glucuronic acid or sulfate conjugation, resulting in increased metabolic stability. Methylation also leads to greatly improved transport through biological membranes, such as in intestinal absorption, and much increased oral bioavailability. Recent studies also indicate that methylation results in derivatives with increasing potency to kill cancer cells. They also show high potency towards inhibition of hormone-regulating enzymes, e.g., aromatase, important in the causation of breast cancer. Methylation of the flavones may also result in derivatives with diminished toxic side-effects and improved aqueous solubility. In conclusion, it appears that methylation of dietary flavones as well as of other food products may produce derivatives with much improved health effects.
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Androutsopoulos VP, Tsatsakis AM, Spandidos DA. Cytochrome P450 CYP1A1: wider roles in cancer progression and prevention. BMC Cancer 2009; 9:187. [PMID: 19531241 PMCID: PMC2703651 DOI: 10.1186/1471-2407-9-187] [Citation(s) in RCA: 287] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 06/16/2009] [Indexed: 02/08/2023] Open
Abstract
CYP1A1 is one of the main cytochrome P450 enzymes, examined extensively for its capacity to activate compounds with carcinogenic properties. Continuous exposure to inhalation chemicals and environmental carcinogens is thought to increase the level of CYP1A1 expression in extrahepatic tissues, through the aryl hydrocarbon receptor (AhR). Although the latter has long been recognized as a ligand-induced transcription factor, which is responsible for the xenobiotic activating pathway of several phase I and phase II metabolizing enzymes, recent evidence suggests that the AhR is involved in various cell signaling pathways critical to cell cycle regulation and normal homeostasis. Disregulation of these pathways is implicated in tumor progression. In addition, it is becoming increasingly evident that CYP1A1 plays an important role in the detoxication of environmental carcinogens, as well as in the metabolic activation of dietary compounds with cancer preventative activity. Ultimately the contribution of CYP1A1 to cancer progression or prevention may depend on the balance of procarcinogen activation/detoxication and dietary natural product extrahepatic metabolism.
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Affiliation(s)
- Vasilis P Androutsopoulos
- Department of Medicine, Division of Forensic Sciences and Toxicology, University of Crete, Crete, Greece.
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Mitchell KA, Elferink CJ. Timing is everything: consequences of transient and sustained AhR activity. Biochem Pharmacol 2008; 77:947-56. [PMID: 19027718 DOI: 10.1016/j.bcp.2008.10.028] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 10/18/2008] [Accepted: 10/24/2008] [Indexed: 01/08/2023]
Abstract
The aryl hydrocarbon receptor (AhR) was implicated as a mediator of xenobiotic toxicity over three decades ago. Although a complete picture continues to elude us, investigations by many laboratories during the ensuing period have revealed much about AhR biology in normal physiological processes, as well as the toxicities induced by the dioxins and related polychlorinated aromatic hydrocarbons. The findings are captured in numerous excellent reviews. This commentary attempts to inject a new perspective on some new as well as frequently overlooked observations in the context of established receptor properties. Specifically, we examine the impact of transient versus sustained receptor activation on AhR biology, and explore the potential role for cytochrome P450 expression in regulating AhR activity amongst various tissues. The growing recognition that AhR action functions through multiple mechanisms serves to further highlight the importance of limiting prolonged receptor activation.
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Affiliation(s)
- Kristen A Mitchell
- Department of Pharmacology and Toxicology, and Sealy Center for Cancer Cell Biology, School of Medicine, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1031, USA
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Hahn ME, Allan LL, Sherr DH. Regulation of constitutive and inducible AHR signaling: complex interactions involving the AHR repressor. Biochem Pharmacol 2008; 77:485-97. [PMID: 18848529 DOI: 10.1016/j.bcp.2008.09.016] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 09/10/2008] [Accepted: 09/11/2008] [Indexed: 01/13/2023]
Abstract
The AHR is well known for regulating responses to an array of environmental chemicals. A growing body of evidence supports the hypothesis that the AHR also plays perhaps an even more important role in modulating critical aspects of cell function including cell growth, death, and migration. As these and other important AHR activities continue to be elucidated, it becomes apparent that attention now must be directed towards the mechanisms through which the AHR itself is regulated. Here, we review what is known of and what biological outcomes have been attributed to the AHR repressor (AHRR), an evolutionarily conserved bHLH-PAS protein that inhibits both xenobiotic-induced and constitutively active AHR transcriptional activity in multiple species. We discuss the structure and evolution of the AHRR and the dominant paradigm of a xenobiotic-inducible negative feedback loop comprised of AHR-mediated transcriptional up-regulation of AHRR and the subsequent AHRR-mediated suppression of AHR activity. We highlight the role of the AHRR in limiting AHR activity in the absence of xenobiotic AHR ligands and the important contribution of constitutively repressive AHRR to cancer biology. In this context, we also suggest a new hypothesis proposing that, under some circumstances, constitutively active AHR may repress AHRR transcription, resulting in unbridled AHR activity. We also review the predominant hypotheses on the molecular mechanisms through which AHRR inhibits AHR as well as novel mechanisms through which the AHRR may exert AHR-independent effects. Collectively, this discussion emphasizes the importance of this understudied bHLH-PAS protein in tissue development, normal cell biology, xenobiotic responsiveness, and AHR-regulated malignancy.
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Affiliation(s)
- Mark E Hahn
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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Plöttner S, Degen GH, Roos PH, Föllmann W. Analysis of CYP1A1 induction in single cells of urothelial cell populations by flow cytometry. Anal Bioanal Chem 2008; 392:1149-58. [DOI: 10.1007/s00216-008-2363-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Revised: 08/14/2008] [Accepted: 08/19/2008] [Indexed: 11/29/2022]
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Yang X, Solomon S, Fraser LR, Trombino AF, Liu D, Sonenshein GE, Hestermann EV, Sherr DH. Constitutive regulation of CYP1B1 by the aryl hydrocarbon receptor (AhR) in pre-malignant and malignant mammary tissue. J Cell Biochem 2008; 104:402-17. [PMID: 18059014 DOI: 10.1002/jcb.21630] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is a receptor/transcription factor which regulates cytochrome P450 (CYP) gene transcription and which is activated by environmental carcinogens, some of which are associated with increased breast cancer risk. Here, we show that the AhR is over-expressed and constitutively active in human and rodent mammary tumors, suggesting its ongoing contribution to tumorigenesis regardless of tumor etiology. AhR regulation of CYP1A1 and CYP1B1 was studied to determine if constitutively active AhR effects the same transcriptional outcomes as environmental chemical-activated AhR. Elevated AhR and CYP1B1 but not CYP1A1 before tumor formation in a rat model of mammary tumorigenesis suggested differential CYP1B1 regulation by a constitutively active AhR. This hypothesis was tested with human mammary gland cell lines which hyper-express AhR and CYP1B1 but which express little or no CYP1A1. CYP1B1 expression was diminished by repression of AhR activity or by AhR knockdown, demonstrating AhR control of basal CYP1B1 levels. ChIP assays demonstrated constitutive AhR binding to both CYP1A1 and CYP1B1 promoters, demonstrating that differential CYP1A1 and CYP1B1 regulation by constitutively active AhR does not result from different amounts of promoter-bound AhR. While increasing AhR binding to both CYP1A1 and CYP1B1, 2,3,7,8-tetrachlorodibenzo-p-dioxin induced CYP1A1 mRNA in both a malignant and non-malignant line but increased only CYP1B1 mRNA in the malignant line, again demonstrating that the level of promoter binding does not necessarily correlate with gene mRNA levels. These studies suggest that constitutively active AhR mediates different molecular outcomes than environmental chemical-activated AhR, and further implicate the AhR in mammary tumorigenesis.
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Affiliation(s)
- Xinhai Yang
- Department of Environmental Health, Boston University School of Public Health, Boston, Massachusetts 02118, USA
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Repression of Ah receptor and induction of transforming growth factor-beta genes in DEN-induced mouse liver tumors. Toxicology 2008; 246:242-7. [PMID: 18282651 DOI: 10.1016/j.tox.2008.01.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 12/22/2007] [Accepted: 01/07/2008] [Indexed: 01/20/2023]
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the biologic and toxic effects of its xenobiotic ligands. In recent years it has become evident that in the absence of ligand the AHR promotes cell cycle progression and that its activation by high-affinity ligands results in interactions with the retinoblastoma protein (RB) that lead to perturbation of the cell cycle, G0/G1 arrest, diminished capacity for DNA replication and inhibition of cell proliferation. Hence, the AHR has diametrically opposed pro-proliferative and anti-proliferative functions that have yet to be reconciled at the molecular level. Work from our own and from other laboratories suggests that the AHR may function as a tumor suppressor gene that becomes silenced in the process of tumor formation. To develop preliminary support for a more thorough examination of this hypothesis we characterized the expression levels of various tumor suppressor genes, transforming growth factor-beta (Tgfb) genes and the Ahr gene in liver tumor samples from mice with a liver-specific RB ablation and their wild-type littermates. In tumors arising in RB-positive livers, Cdkn2d and Tgfb1 were repressed and Cdkn2c, Tgfb2, Tgfb3 and Pai1 were induced, whereas in RB-negative tumors, only Cdkn2c and Tgfb3 were induced. Ahr was significantly repressed in tumors from both sets of mice, supporting the concept that Ahr silencing may be associated with cancer progression.
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Schlezinger JJ, Liu D, Farago M, Seldin DC, Belguise K, Sonenshein GE, Sherr DH. A role for the aryl hydrocarbon receptor in mammary gland tumorigenesis. Biol Chem 2008; 387:1175-87. [PMID: 16972784 DOI: 10.1515/bc.2006.145] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is an evolutionarily conserved transcription factor bound and activated by ubiquitous environmental pollutants. Historically, the AhR has been studied for its transcriptional regulation of genes encoding cytochrome P450 enzymes, which metabolize many of these chemicals into mutagenic and toxic intermediates. However, recent studies demonstrate that the AhR plays an important role in the biology of several cell types in the absence of environmental chemicals. Here, this paradigm shift is discussed in the context of a putative role for the AhR in mammary gland tumorigenesis. Data demonstrating high levels of constitutively active AhR in mammary tumors are summarized. Particular focus is placed on the likelihood that the AhR contributes to ongoing mammary tumor cell growth and on the possibility that the AhR inhibits apoptosis while promoting transition to an invasive, metastatic phenotype. A working model is proposed that may help explain the sometimes contradictory outcomes observed after AhR manipulation and that serves as a blueprint for the design of therapeutics which target the AhR in breast cancer. The theme that malignant cells reveal the functions for which the AhR has been evolutionarily conserved is presented throughout this discussion.
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Affiliation(s)
- Jennifer J Schlezinger
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA
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