scholarly journals Activation of the aryl hydrocarbon receptor by clozapine induces preadipocyte differentiation and contributes to endothelial dysfunction

2022 ◽  
pp. 026988112110558
Author(s):  
K Fehsel ◽  
K Schwanke ◽  
BA Kappel ◽  
E Fahimi ◽  
E Meisenzahl-Lechner ◽  
...  
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Hepg2 Cells ◽  
Physiological Role ◽  
Structural Similarity ◽  
Therapeutic Benefit ◽  
Luciferase Reporter ◽  
Pcr Analysis ◽  
Wild Type ◽  
Preadipocyte Differentiation ◽  
Aryl Hydrocarbon

Background: The superior therapeutic benefit of clozapine is often associated with metabolic disruptions as obesity, insulin resistance, tachycardia, higher blood pressure, and even hypertension. Aims: These adverse vascular/ metabolic events under clozapine are similar to those caused by polycyclic aromatic hydrocarbons (PAHs), and clozapine shows structural similarity to well-known ligands of the aryl hydrocarbon receptor (AhR). Therefore, we speculated that the side effects caused by clozapine might rely on AhR signaling. Methods: We examined clozapine-induced AhR activation by luciferase reporter assays in hepatoma HepG2 cells and we proved upregulation of the prototypical AhR target gene Cyp1A1 by realtime-PCR (RT-PCR) analysis and enzyme activity. Next we studied the physiological role of AhR in clozapine’s effects on human preadipocyte differentiation and on vasodilatation by myography in wild-type and AhR-/- mice. Results: In contrast to other antipsychotic drugs (APDs), clozapine triggered AhR activation and Cyp1A1 expression in HepG2 cells and adipocytes. Clozapine induced adipogenesis via AhR signaling. After PGF2α-induced constriction of mouse aortic rings, clozapine strongly reduced the maximal vasorelaxation under acetylcholine in rings from wild-type mice, but only slightly in rings from AhR-/- mice. The reduction was also prevented by pretreatment with the AhR antagonist CH-223191. Conclusion: Identification of clozapine as a ligand for the AhR opens new perspectives to explain common clozapine therapy-associated adverse effects at the molecular level.

scholarly journals Aryl hydrocarbon receptor and NF-E2-related factor 2 are key regulators of human MRP4 expression

2010 ◽  
Vol 299 (1) ◽  
pp. G126-G135 ◽  
Author(s):  
Shuhua Xu ◽  
Jittima Weerachayaphorn ◽  
Shi-Ying Cai ◽  
Carol J. Soroka ◽  
James L. Boyer
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Program Analysis ◽  
Promoter Activity ◽  
Therapeutic Benefit ◽  
Proximal Promoter ◽  
Luciferase Reporter ◽  
Related Factor ◽  
Response Element ◽  
Aryl Hydrocarbon ◽  
Reporter Assays

Multidrug resistance protein 4 (MRP4; ABCC4) is an ATP binding cassette transporter that facilitates the excretion of bile salt conjugates and other conjugated steroids in hepatocytes and renal proximal tubule epithelium. MRP4/Mrp4 undergoes adaptive upregulation in response to oxidative and cholestatic liver injury in human and animal models of cholestasis. However, the molecular mechanism of this regulation remains to be determined. The aryl hydrocarbon receptor (AhR) and NF-E2-related factor 2 (Nrf2) play important roles in protecting cells from oxidative stress. Here we examine the role of these two nuclear factors in the regulation of the expression of human MRP4. HepG2 cells and human hepatocytes were treated with the AhR and Nrf2 activators, 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), 3-methylcholanthrene (3-MC), or oltipraz and other nuclear receptor agonists. TCDD, 3-MC, and oltipraz significantly increased MRP4 expression at mRNA and protein levels. Computer program analysis revealed three Xenobiotic response element (XRE) and one Maf response element sites within the first 500 bp of the MRP4 proximal promoter. Luciferase reporter assay detected strong promoter activity (53-fold higher than vector control) in this region. TCDD and 3-MC also induced promoter activity in the reporter assays. Mutation of any of these XRE sites significantly decreased MRP4 promoter activity in reporter assays, although XRE2 demonstrated the strongest effects on both basal and TCDD-inducible activity. EMSA and chromatin immunoprecipitation assays further confirmed that both AhR and Nrf2 bind to the proximal promoter of MRP4. Our findings indicate that AhR and Nrf2 play important roles in regulating MRP4 expression and suggest that agents that activate their activity may be of therapeutic benefit for cholestasis.

Constitutive Effects of Lead on Aryl Hydrocarbon Receptor Gene Battery and Protection by β-carotene and Ascorbic Acid in Human HepG2 Cells

2015 ◽  
Vol 81 (1) ◽  
pp. T275-T281 ◽  
Author(s):  
Wageh S. Darwish ◽  
Yoshinori Ikenaka ◽  
Shouta M. M. Nakayama ◽  
Hazuki Mizukawa ◽  
Mayumi Ishizuka
Keyword(s):  
Ascorbic Acid ◽  
Aryl Hydrocarbon Receptor ◽  
Hepg2 Cells ◽  
Receptor Gene ◽  
Aryl Hydrocarbon ◽  
Β Carotene

scholarly journals Immunotoxicity of Xenobiotics in Fish: A Role for the Aryl Hydrocarbon Receptor (AhR)?

2021 ◽  
Vol 22 (17) ◽  
pp. 9460
Author(s):  
Helmut Segner ◽  
Christyn Bailey ◽  
Carolina Tafalla ◽  
Jun Bo
Keyword(s):  
Immune System ◽  
Aryl Hydrocarbon Receptor ◽  
Disease Susceptibility ◽  
Immune Cell ◽  
Physiological Role ◽  
Immune Gene ◽  
Immune Systems ◽  
Aryl Hydrocarbon ◽  
The Impact

The impact of anthropogenic contaminants on the immune system of fishes is an issue of growing concern. An important xenobiotic receptor that mediates effects of chemicals, such as halogenated aromatic hydrocarbons (HAHs) and polyaromatic hydrocarbons (PAHs), is the aryl hydrocarbon receptor (AhR). Fish toxicological research has focused on the role of this receptor in xenobiotic biotransformation as well as in causing developmental, cardiac, and reproductive toxicity. However, biomedical research has unraveled an important physiological role of the AhR in the immune system, what suggests that this receptor could be involved in immunotoxic effects of environmental contaminants. The aims of the present review are to critically discuss the available knowledge on (i) the expression and possible function of the AhR in the immune systems of teleost fishes; and (ii) the impact of AhR-activating xenobiotics on the immune systems of fish at the levels of immune gene expression, immune cell proliferation and immune cell function, immune pathology, and resistance to infectious disease. The existing information indicates that the AhR is expressed in the fish immune system, but currently, we have little understanding of its physiological role. Exposure to AhR-activating contaminants results in the modulation of numerous immune structural and functional parameters of fish. Despite the diversity of fish species studied and the experimental conditions investigated, the published findings rather uniformly point to immunosuppressive actions of xenobiotic AhR ligands in fish. These effects are often associated with increased disease susceptibility. The fact that fish populations from HAH- and PAH-contaminated environments suffer immune disturbances and elevated disease susceptibility highlights that the immunotoxic effects of AhR-activating xenobiotics bear environmental relevance.

scholarly journals Hepatitis B Virus X-Associated Protein 2 Is a Subunit of the Unliganded Aryl Hydrocarbon Receptor Core Complex and Exhibits Transcriptional Enhancer Activity

1998 ◽  
Vol 18 (2) ◽  
pp. 978-988 ◽  
Author(s):  
Brian K. Meyer ◽  
Marilyn G. Pray-Grant ◽  
John P. Vanden Heuvel ◽  
Gary H. Perdew
Keyword(s):  
Amino Acid ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Aryl Hydrocarbon Receptor ◽  
In Vitro Translation ◽  
Luciferase Reporter ◽  
Core Complex ◽  
Aryl Hydrocarbon ◽  
B Virus

ABSTRACT Prior to ligand activation, the unactivated aryl hydrocarbon receptor (AhR) exists in a heterotetrameric 9S core complex consisting of the AhR ligand-binding subunit, a dimer of hsp90, and an unknown subunit. Here we report the purification of an ∼38-kDa protein (p38) from COS-1 cell cytosol that is a member of this complex by coprecipitation with a FLAG-tagged AhR. Internal amino acid sequence information was obtained, and p38 was identified as the hepatitis B virus X-associated protein 2 (XAP2). The simian ortholog of XAP2 was cloned from a COS-1 cDNA library; it codes for a 330-amino-acid protein containing regions of homology to the immunophilins FKBP12 and FKBP52. A tetratricopeptide repeat (TPR) domain in the carboxy-terminal region of XAP2 was similar to the third and fourth TPR domains of human FKBP52 and the Saccharomyces cerevisiae transcriptional modulator SSN6, respectively. Polyclonal antibodies raised against XAP2 recognized p38 in the unliganded AhR complex in COS-1 and Hepa 1c1c7 cells. It was ubiquitously expressed in murine tissues at the protein and mRNA levels. It was not required for the assembly of an AhR-hsp90 complex in vitro. Additionally, XAP2 did not directly associate with hsp90 upon in vitro translation, but was present in a 9S form when cotranslated in vitro with murine AhR. XAP2 enhanced the ability of endogenous murine and human AhR complexes to activate a dioxin-responsive element–luciferase reporter twofold, following transient expression of XAP2 in Hepa 1c1c7 and HeLa cells.

scholarly journals Increase Paclitaxel Sensitivity to Better Suppress Serous Epithelial Ovarian Cancer via Ablating Androgen Receptor/Aryl Hydrocarbon Receptor-ABCG2 Axis

Cancers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 463 ◽  
Author(s):  
Wei-Min Chung ◽  
Yen-Ping Ho ◽  
Wei-Chun Chang ◽  
Yuan-Chang Dai ◽  
Lumin Chen ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Androgen Receptor ◽  
Epithelial Ovarian Cancer ◽  
Aryl Hydrocarbon Receptor ◽  
Proximal Promoter ◽  
Luciferase Reporter ◽  
Aryl Hydrocarbon ◽  
Paclitaxel Treatment

Background: Epithelial ovarian cancer (EOC) is one of the most lethal gynecological malignancies and presents chemoresistance after chemotherapy treatment. Androgen receptor (AR) has been known to participate in proliferation. Yet the mechanisms of the resistance of this drug and its linkage to the AR remains unclear. Methods: To elucidate AR-related paclitaxel sensitivity, co-IP, luciferase reporter assay and ChIP assay were performed to identify that AR direct-regulated ABCG2 expression under paclitaxel treatment. IHC staining by AR antibody presented higher AR expression in serous-type patients than other types. AR degradation enhancer (ASC-J9) was used to examine paclitaxel-associated and paclitaxel-resistant cytotoxicity in vitro and in vivo. Results: We found AR/aryl hydrocarbon receptor (AhR)-mediates ABCG2 expression and leads to a change in paclitaxel cytotoxicity/sensitivity in EOC serous subtype cell lines. Molecular mechanism study showed that paclitaxel activated AR transactivity and bound to alternative ARE in the ABCG2 proximal promoter region. To identify AR as a potential therapeutic target, the ASC-J9 was used to re-sensitize paclitaxel-resistant EOC tumors upon paclitaxel treatment in vitro and in vivo. Conclusion: The results demonstrated that activation of AR transactivity beyond the androgen-associated biological effect. This novel AR mechanism explains that degradation of AR is the most effective therapeutic strategy for treating AR-positive EOC serous subtype.

scholarly journals Transcriptional Regulation of gga-miR-451 by AhR:Arnt in Mycoplasma gallisepticum (HS Strain) Infection

2019 ◽  
Vol 20 (12) ◽  
pp. 3087 ◽  
Author(s):  
Yabo Zhao ◽  
Yali Fu ◽  
Yingfei Sun ◽  
Mengyun Zou ◽  
Xiuli Peng
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Chromatin Immunoprecipitation ◽  
Regulatory Region ◽  
Mycoplasma Gallisepticum ◽  
Luciferase Reporter ◽  
Binding Motif ◽  
Aryl Hydrocarbon ◽  
Transcriptional Regulatory ◽  
Reporter Assays ◽  
Transcriptional Regulatory Region

MicroRNAs (miRNAs) have been determined to be important regulators for pathogenic microorganism infection. However, it is largely unclear how miRNAs are triggered during pathogen infection. We previously reported that the up-regulation of gga-miR-451 negatively regulates the Mycoplasma gallisepticum (MG)-induced production of inflammatory cytokines via targeting tyrosine3-monooxygenase/tryptophan5-monooxygenase activation protein zeta (YWHAZ). The aim of this study was to investigate the mechanism regulating gga-miR-451 in MG infection in chickens. Analysis of gga-miR-451 precursor, pri-miR-451, and pre-miR-451 indicated that the regulation occurred transcriptionally. We also identified the transcriptional regulatory region of gga-miR-451 that contained consensus-binding motif for aryl hydrocarbon receptor (AhR) and aryl hydrocarbon receptor nuclear translocator (Arnt) complex, which is known as the transcription factor that regulates gene expression. Luciferase reporter assays combined with chromatin immunoprecipitation (ChIP) demonstrated that AhR:Arnt bound directly to the promoter elements of gga-miR-451, which were responsible for gga-miR-451 transcription in the context of MG infection. Furthermore, upregulation of AhR:Arnt significantly induced gga-miR-451 and inhibited YWHAZ expression, suggesting that AhR:Arnt may play an anti-inflammatory role in MG infection. This discovery suggests that induced gga-miR-451 expression is modulated by AhR:Arnt in response to MG infection.

scholarly journals The UVR Filter Octinoxate Modulates Aryl Hydrocarbon Receptor Signaling in Keratinocytes via Inhibition of CYP1A1 and CYP1B1

2020 ◽  
Vol 177 (1) ◽  
pp. 188-201
Author(s):  
Sarah J Phelan-Dickinson ◽  
Brian C Palmer ◽  
Yue Chen ◽  
Lisa A DeLouise
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Biological Effects ◽  
Mouse Skin ◽  
Daily Basis ◽  
Luciferase Reporter ◽  
Mrna Levels ◽  
Aryl Hydrocarbon ◽  
Ic50 Values ◽  
Cyp1b1 Mrna

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.

scholarly journals AHR1B, a new functional aryl hydrocarbon receptor in zebrafish: tandem arrangement of ahr1b and ahr2 genes

2005 ◽  
Vol 392 (1) ◽  
pp. 153-161 ◽  
Author(s):  
Sibel I. Karchner ◽  
Diana G. Franks ◽  
Mark E. Hahn
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Amino Acid Sequence Identity ◽  
Developmental Toxicity ◽  
Physiological Role ◽  
Vertebrate Development ◽  
Chromosome 16 ◽  
Model Species ◽  
High Affinity ◽  
Aryl Hydrocarbon

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates gene expression following activation by TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) or a variety of other synthetic and natural compounds. Previous studies have identified two AHR genes, AHR1 and AHR2, in zebrafish (Danio rerio), a widely used model species for studying vertebrate development and an emerging model in developmental toxicology. Zebrafish AHR2 binds TCDD with high affinity, is transcriptionally active and has a major role in mediating the developmental toxicity of TCDD. Zebrafish AHR1 lacks the ability to bind TCDD and activate transcription, and has no known function. In the present study, we report a new zebrafish AHR, designated AHR1B, which shares 34% amino acid sequence identity with AHR1 (AHR1A). The ahr1b gene resides on chromosome 22, adjacent to ahr2, whereas the ahr1a gene is located on chromosome 16. AHR1B is expressed in embryos as early as 24 hours post-fertilization and increases through the next 2 days, but expression is not inducible by TCDD. In contrast with the previously identified AHR1A, in vitro-expressed AHR1B protein exhibits specific, high-affinity binding of [3H]TCDD. Furthermore, AHR1B is able to activate the transcription of a reporter gene under the control of AHR response elements with an efficacy comparable with that of AHR2, but with a higher EC50. We speculate that AHR1B may have a physiological role, such as in embryonic development, whereas AHR2 mediates the response to xenobiotics.

scholarly journals A42 MICROBIAL METABOLISM OF DIETARY TRYPTOPHAN ENHANCES ARYL HYDROCARBON RECEPTOR ACTIVATION: IMPLICATIONS FOR IBD

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. 50-51
Author(s):  
L Rondeau ◽  
A V Clarizio ◽  
J Jury ◽  
D L Gibson ◽  
P Bercik ◽  
...  
Keyword(s):  
16S Rrna ◽  
Gut Microbiota ◽  
Aryl Hydrocarbon Receptor ◽  
Healthy Subjects ◽  
Tryptophan Metabolism ◽  
Luciferase Reporter ◽  
Reporter Assay ◽  
Aryl Hydrocarbon ◽  
Deficient Mice ◽  
Activation Capacity

Abstract Background Intestinal immune homeostasis is maintained by the interplay between microbiota and the mucosal immune system. Changes in gut microbiota have been associated with chronic intestinal conditions, such as inflammatory bowel disease (IBD). The aryl hydrocarbon receptor (AhR) is a transcription factor that is activated by dietary and environmental stimuli to control immune responses in the gut and homeostatic mechanisms at mucosal surfaces. In IBD, AhR expression is downregulated. Major agonists of AhR in the gut include microbial tryptophan metabolites such as indole derivatives, which are decreased in IBD patients. The mechanisms involved in tryptophan metabolism by bacteria and their implications in AhR activation and thus IBD pathogenesis are not well understood. Aims To investigate whether tryptophan metabolism by intestinal bacteria participates in AhR activation and IBD pathogenesis. Methods Microbiota profiles (16S rRNA Illumina) and activation of AhR (luciferase reporter assay) were determined in fecal samples from IBD patients (n=10) and healthy volunteers (n=10). Germ-free C57BL/6 mice were colonized with fecal slurries of 2 healthy subjects and 4 IBD patients (n=4 mice/donor) by oral gavage (humanized-mice). All mice were fed irradiated tryptophan diets with 0.1% or 1% tryptophan content for 14 days. Simultaneously, SPF Mucin 2 (Muc2) deficient mice (C57BL/6 background), which develop colitis spontaneously, were fed tryptophan diets (0.1%, 0.3% and 1% content). Activation of AhR was measured in feces using an AhR luciferase reporter assay. Inflammation was determined by immunohistochemistry and the characterization of immune infiltrate in colon cross-sections. Bacteria from human and mouse fecal samples were isolated and screened for their ability to produce indoles using biochemical reagents. Positive bacteria were identified by colony PCR and 16S rRNA Sanger sequencing. Results IBD patients had an altered fecal microbiota with a lower capacity to activate AhR compared to healthy subjects. Colonization of mice with microbiota from healthy subjects induced greater activation of AhR compared to mice colonized with microbiota from patients with IBD. Furthermore, increasing dietary tryptophan composition rescued the capacity to activate AhR. In Muc2 deficient mice, dietary tryptophan treatment enhanced AhR activation capacity and reduced infiltration of innate immune cells before the onset of colitis. Several AhR agonist producing bacterial species were identified and will be used in future experiments. Conclusions Activation of AhR is dependent on the gut microbiota and disease status of the donor. Dietary intervention with tryptophan enhances AhR activation capacity and may be a potential therapeutic avenue in IBD individuals with intestinal dysbiosis. Funding Agencies Farncombe Family Digestive Health Research Institute, Biocodex Microbiota Foundation

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