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1.
Cell Physiol Biochem ; 54(1): 126-141, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32017483

RESUMO

BACKGROUND/AIMS: Serotonin (5-hydroxytryptamine, 5-HT) is a neurotransmitter and hormone with important physiological functions in many organs, including the intestine. We have previously shown that 5-HT activates the aryl hydrocarbon receptor (AhR) in intestinal epithelial cells (IECs) via a serotonin transporter (SERT)-dependent mechanism. AhR is a nuclear receptor that binds a variety of molecules including tryptophan (TRP) metabolites to regulate physiological processes in the intestine including xenobiotic detoxification and immune modulation. We hypothesized that 5-HT activates AhR indirectly by interfering with metabolic clearance of AhR ligands by cytochrome P450 1A1 (CYP1A1). METHODS: Inhibition of CYP1A1 activity by 5-HT was assessed in the human intestinal epithelial cell line Caco-2 and recombinant CYP1A1 microsomes using both luciferase and LC-MS/MS. Degradation of 5-HT by recombinant CYP1A1 was measured by LC-MS/MS. For in vitro studies, CYP1A1 and CYP1B1 mRNA expression levels were measured by RT-PCR and CYP1A1 activity was measured by ethoxyresorufin-O-deethylase (EROD) assays. For in vivo studies, AhR ligands were administered to SERT KO mice and WT littermates and intestinal mucosa CYP1A1 mRNA was measured. RESULTS: We show that 5-HT inhibits metabolism of both the pro-luciferin CYP1A1 substrate Luc-CEE as well as the high affinity AhR ligand 6-formylindolo[3,2-b] carbazole (FICZ). Recombinant CYP1A1 assays revealed that 5-HT is metabolized by CYP1A1 in an NADPH dependent manner. Treatment with 5-HT in TRP-free medium, which is devoid of trace AhR ligands, showed that 5-HT requires the presence of AhR ligands to activate AhR. Cotreatment with 5-HT and FICZ confirmed that 5-HT potentiates induction of AhR target genes by AhR ligands. However, this was only true for ligands which are CYP1A1 substrates such as FICZ. Administration of ß-napthoflavone by gavage or indole-3-carbinol via diet to SERT KO mice revealed that lack of SERT impairs intestinal AhR activation. CONCLUSION: Our studies provide novel evidence of crosstalk between serotonergic and AhR signaling where 5-HT can influence the ability of AhR ligands to activate the receptor in the intestine.


Assuntos
Citocromo P-450 CYP1A1/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Serotonina/farmacologia , Transcrição Genética/efeitos dos fármacos , Animais , Células CACO-2 , Carbazóis/farmacologia , Citocromo P-450 CYP1A1/genética , Citocromo P-450 CYP1B1/genética , Citocromo P-450 CYP1B1/metabolismo , Humanos , Ligantes , Masculino , Camundongos , Camundongos Knockout , RNA Mensageiro/metabolismo , Receptores de Hidrocarboneto Arílico/química , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Proteínas da Membrana Plasmática de Transporte de Serotonina/deficiência , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Transdução de Sinais/efeitos dos fármacos , Especificidade por Substrato , beta-Naftoflavona/administração & dosagem
2.
Environ Pollut ; 254(Pt B): 113098, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31479813

RESUMO

While humans are exposed to mixtures of persistent organic pollutants (POPs), their risk assessment is usually based on a chemical-by-chemical approach. To assess the health effects associated with mixed exposures, knowledge on mixture toxicity is required. Several POPs are potential ligands of the Aryl hydrocarbon receptor (AhR), which involves in xenobiotic metabolism and controls many biological pathways. This study assesses AhR agonistic and antagonistic activities of 29 POPs individually and in mixtures by using Chemical-Activated LUciferase gene eXpression bioassays with 3 transgenic cell lines (rat hepatoma DR-H4IIE, human hepatoma DR-Hep G2 and human mammary gland carcinoma DR-T47-D). Among the 29 POPs, which were selected based on their abundance in Scandinavian human blood, only 4 exerted AhR agonistic activities, while 16 were AhR antagonists in DR-H4IIE, 5 in DR-Hep G2 and 7 in DR-T47-D when tested individually. The total POP mixture revealed to be AhR antagonistic. It antagonized EC50 TCDD inducing AhR transactivation at a concentration of 125 and 250 and 500 fold blood levels in DR-H4IIE, DR-T47-D and DR-Hep G2, respectively, although each compound was present at these concentrations lower than their LOEC values. Such values could occur in real-life in food contamination incidents or in exposed populations. In DR-H4IIE, the antagonism of the total POP mixture was due to chlorinated compounds and, in particular, to PCB-118 and PCB-138 which caused 90% of the antagonistic activity in the POP mixture. The 16 active AhR antagonists acted additively. Their mixed effect was predicted successfully by concentration addition or generalized concentration addition models, rather than independent action, with only two-fold IC50 underestimation. We also attained good predictions for the full dose-response curve of the antagonistic activity of the total POP mixture.


Assuntos
Poluentes Ambientais/farmacologia , Bifenilos Policlorados/farmacologia , Receptores de Hidrocarboneto Arílico/química , Ativação Transcricional/efeitos dos fármacos , Animais , Linhagem Celular , Humanos , Bifenilos Policlorados/química , Ratos , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/antagonistas & inibidores
3.
J Exp Clin Cancer Res ; 38(1): 335, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31370872

RESUMO

BACKGROUND: The chemical carcinogen 3-methylcholanthrene (3MC) binds to the aryl hydrocarbon receptor (AHR) that regulates the expression of cytochrome P450 (CYP) enzymes as CYP1B1, which is involved in the oncogenic activation of environmental pollutants as well as in the estrogen biosynthesis and metabolism. 3MC was shown to induce estrogenic responses binding to the estrogen receptor (ER) α and stimulating a functional interaction between AHR and ERα. Recently, the G protein estrogen receptor (GPER) has been reported to mediate certain biological responses induced by endogenous estrogens and environmental compounds eliciting an estrogen-like activity. METHODS: Molecular dynamics and docking simulations were performed to evaluate the potential of 3MC to interact with GPER. SkBr3 breast cancer cells and cancer-associated fibroblasts (CAFs) derived from breast tumor patients were used as model system. Real-time PCR and western blotting analysis were performed in order to evaluate the activation of transduction mediators as well as the mRNA and protein levels of CYP1B1 and cyclin D1. Co-immunoprecipitation studies were performed in order to explore the potential of 3MC to trigger the association of GPER with AHR and EGFR. Luciferase assays were carried out to determine the activity of CYP1B1 promoter deletion constructs upon 3MC exposure, while the nuclear shuttle of AHR induced by 3MC was assessed through confocal microscopy. Cell proliferation stimulated by 3MC was determined as biological counterpart of the aforementioned experimental assays. The statistical analysis was performed by ANOVA. RESULTS: We first ascertained by docking simulations the ability of 3MC to interact with GPER. Thereafter, we established that 3MC activates the EGFR/ERK/c-Fos transduction signaling through both AHR and GPER in SkBr3 cells and CAFs. Then, we found that these receptors are involved in the up-regulation of CYP1B1 and cyclin D1 as well as in the stimulation of growth responses induced by 3MC. CONCLUSIONS: In the present study we have provided novel insights regarding the molecular mechanisms by which 3MC may trigger a physical and functional interaction between AHR and GPER, leading to the stimulation of both SkBr3 breast cancer cells and CAFs. Altogether, our results indicate that 3MC may engage both GPER and AHR transduction pathways toward breast cancer progression.


Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Neoplasias da Mama/metabolismo , Fibroblastos Associados a Câncer/efeitos dos fármacos , Fibroblastos Associados a Câncer/metabolismo , Metilcolantreno/farmacologia , Receptores de Hidrocarboneto Arílico/metabolismo , Receptores Estrogênicos/metabolismo , Receptores Acoplados a Proteínas-G/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/química , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Fibroblastos Associados a Câncer/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Citocromo P-450 CYP1B1/genética , Citocromo P-450 CYP1B1/metabolismo , Receptores ErbB/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Metilcolantreno/química , Conformação Molecular , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Ligação Proteica , Transporte Proteico , Receptores de Hidrocarboneto Arílico/química , Receptores Estrogênicos/química , Receptores Acoplados a Proteínas-G/química , Transdução de Sinais/efeitos dos fármacos , Relação Estrutura-Atividade
4.
Ecotoxicol Environ Saf ; 181: 214-223, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31195230

RESUMO

In the aftermath of the Great East Japan Earthquake of March 11, 2011, marine fish in Kesennuma Bay, Japan, have been contaminated with heavy oil containing polycyclic aromatic hydrocarbons (PAHs). To estimate the risk of six PAHs (benzo[α]pyrene, dibenzothiophene, phenanthrene, 2,3,5-trimethylnaphthalene, acenaphthene, and 1-methylphenanthrene), which have been detected at high levels in the tissues of fish from Kesennuma Bay, we attempted to evaluate the effects of these PAHs on the fish aryl hydrocarbon receptor (AHR) signaling pathway. We initially measured PAH concentrations and cytochrome P4501A catalytic activities (EROD: ethoxyresorufin-O-deethylase and MROD: methoxyresorufin-O-demethylase) as markers of AHR activation in greenlings (Hexagrammos otakii) collected from Kesennuma Bay in 2014. The results showed that alkylated PAH concentrations and EROD/MROD activities were higher in sites close to the oil-spilled sites than in the control site, suggesting AHR activation by spilled alkylated PAHs. We then investigated AHR-mediated responses to these PAHs in the in vitro reporter gene assay system where red seabream (Pagrus major) AHR1 (rsAHR1) or rsAHR2 expression plasmids were transiently transfected into COS-7 cells. The in vitro assay showed rsAHR isoform-, PAH-, and dose-dependent transactivation potencies. The relative effective concentrations of benzo[α]pyrene, dibenzothiophene, phenanthrene, 2,3,5-trimethylnaphthalene, acenaphthene, and 1-methylphenanthrene that induce 20% of the maximum benzo[α]pyrene response (REC20-BaP) for rsAHR1 activation were 0.052, 38, 79, 88, 270 nM, and no response, respectively, and those for rsAHR2 activation were 0.0049, 32, 53, 88, 60 nM, and no response, respectively. The results showed that the REC20-BaP values of benzo[α]pyrene for both the rsAHR1 and rsAHR2 isoforms were lower than the concentrations (0.041-0.20 nM) detected in the muscle tissue of fish from Kesennuma Bay, while the REC20-BaP values of other PAHs were higher than their tissue concentrations. In silico rsAHR homology modeling and subsequent ligand docking simulation analyses indicated that the rsAHR activation potencies of PAHs could be predicted from a rsAHR2 model. This study shows that in vitro and in silico rsAHR analyses may be a useful tool for assessing the risks to fish contaminated with PAHs.


Assuntos
Peixes/metabolismo , Poluição por Petróleo , Hidrocarbonetos Policíclicos Aromáticos/análise , Receptores de Hidrocarboneto Arílico/metabolismo , Animais , Células COS , Simulação por Computador , Citocromo P-450 CYP1A1/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Genes Reporter , Japão , Perciformes/metabolismo , Petróleo , Hidrocarbonetos Policíclicos Aromáticos/química , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/genética , Medição de Risco , Dourada/genética
5.
PLoS One ; 14(4): e0215981, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31026283

RESUMO

BACKGROUND: Multiple sclerosis (MS) is a widespread neurological autoimmune disease that includes episodes of demyelination in the central nervous system (CNS). The accumulated evidence has suggested that aryl hydrocarbon receptor (Ahr), a ligand-activated transcription factor, is a promising treatment target for MS. Thus, the current study aimed to identify a novel Ahr ligand with anti-inflammatory potential in experimental autoimmune encephalomyelitis (EAE). METHODS: An in silico analysis was carried out to predict interactions between Ahr and potential natural ligands. The effects of a predicted interaction were examined in vitro using CD4+ T cells under T helper17 (Th17) cell-polarizing conditions and lipopolysaccharide (LPS)-stimulated macrophages. Silencing Ahr and microRNA (miR)-132 was achieved by electroporation. Myelin oligodendrocyte glycoprotein (MOG)35-55 and the adoptive transfer of encephalitogenic CD4+ T cells were used to induce EAE. RESULTS: Molecular docking analysis and in vitro data identified gallic acid (GA) as a novel Ahr ligand with potent activation potential. GA induced the expression of Ahr downstream genes, including cytochrome P450 family 1 subfamily A member 1 (Cyp1a1) and the miR-212/132 cluster, and promoted the formation of the Ahr/Ahr nuclear translocator (Arnt) complex. In vivo, GA-treated mice were resistant to EAE and exhibited reduced levels of proinflammatory cytokines and increased levels of transforming growth factor-ß (TGF-ß). Furthermore, GA reduced infiltration of CD4+CD45+ T cells and monocytes into the CNS. The anti-inflammatory effects of GA were concomitant with miR-132-potentiated cholinergic anti-inflammation and the regulation of the pathogenic potential of astrocytes and microglia. Inducing EAE by adoptive transfer revealed that CD4+ T cells were not entirely responsible for the ameliorative effects of GA. CONCLUSION: Our findings identify GA as a novel Ahr ligand and provide molecular mechanisms elucidating the ameliorative effects of GA on EAE, suggesting that GA is a potential therapeutic agent to control inflammation in autoimmune diseases such as MS.


Assuntos
Encefalomielite Autoimune Experimental/metabolismo , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/metabolismo , Transdução de Sinais , Animais , Astrócitos/patologia , Linfócitos T CD4-Positivos/imunologia , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/imunologia , Feminino , Ácido Gálico/farmacologia , Ácido Gálico/uso terapêutico , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Ligantes , Camundongos Endogâmicos C57BL , MicroRNAs/genética , MicroRNAs/metabolismo , Microglia/patologia , Domínios Proteicos , Receptores de Hidrocarboneto Arílico/química
6.
PLoS One ; 14(3): e0213848, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30870500

RESUMO

The Aryl hydrocarbon receptor (AhR) plays important roles in many normal and pathological physiological processes, including endocrine homeostasis, foetal development, cell cycle regulation, cellular oxidation/antioxidation, immune regulation, metabolism of endogenous and exogenous substances, and carcinogenesis. An experimental data set for human in vitro AhR activation comprising 324,858 substances, of which 1,982 were confirmed actives, was used to test an in-house-developed approach to rationally select Quantitative Structure-Activity Relationship (QSAR) training set substances from an unbalanced data set. In the first iteration, active and inactive substances were selected by random to make QSAR models. Then, more inactive substances were added to the training set in two further iterations based on incorrect or out-of-domain predictions to produce larger models. The resulting 'rational' model, comprising 832 actives and four times as many inactives, i.e. 3,328, was compared to a model with a training set of same size and proportion of inactives chosen entirely by random. Both models underwent robust cross-validation and external validation showing good statistical performance, with the rational model having external validation sensitivity of 85.1% and specificity of 97.1%, compared to the random model with sensitivity 89.1% and specificity 91.3%. Furthermore, we integrated the training sets for both models with the 93 external validation test set actives and 372 randomly selected inactives to make two final models. They also underwent external validations for specificity and cross-validations, which confirmed that good predictivity was maintained. All developed models were applied to predict 80,086 EU REACH substances. The rational and random final models had 63.1% and 56.9% coverage of the REACH set, respectively, and predicted 1,256 and 3,214 substances as actives. The final models as well as predictions for AhR activation for 650,000 substances will be published in the Danish (Q)SAR Database and can, for example, be used for priority setting, in read-across predictions and in weight-of-evidence assessments of chemicals.


Assuntos
Algoritmos , Bases de Dados Factuais , Hidrocarbonetos Aromáticos/química , Hidrocarbonetos Aromáticos/metabolismo , Relação Quantitativa Estrutura-Atividade , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/metabolismo , Humanos , Modelos Moleculares
7.
Ecotoxicol Environ Saf ; 171: 99-111, 2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-30597322

RESUMO

To understand the role of aryl hydrocarbon receptor (AHR) isoforms in avian species, we investigated the functional characteristics of two AHR isoforms (designated as jcAHR1 and jcAHR2) of the jungle crow (Corvus macrorhynchos). Two amino acid residues corresponding to Ile324 and Ser380 (high sensitive type) in chicken AHR1 that are known to determine dioxin sensitivity were Ile325 and Ala381 (moderate sensitive type) in jcAHR1 and Val306 and Ala362 (low sensitive type) in jcAHR2. The quantitative comparison of the two jcAHR mRNA expression levels in a Tokyo jungle crow population showed that jcAHR2 accounted for 92.4% in the liver, while jcAHR1 accounted for only 7.6%. Both in vitro-expressed jcAHR1 and jcAHR2 proteins exhibited a specific binding to [3H]-labeled 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Transactivation potencies for jcAHR1 and jcAHR2 in in vitro reporter gene assays were measured in jcAHR-expressed cells exposed to 16 dioxins and related compounds (DRCs). Both jcAHR1 and jcAHR2 were activated in a congener- and an isoform-specific manner. EC50 value of TCDD for jcAHR2 (0.61 nM) was six-fold higher than that for jcAHR1 (0.098 nM), but jcAHR2 had higher transactivation efficacy than jcAHR1 in terms of the magnitude of response. The high transactivation efficacy of jcAHR2 in DRCs is in contrast to that of AHR2s in other avian species with low transactivation efficacy. Molecular docking simulations of TCDD with in silico jcAHR1 and jcAHR2 homology models showed that the two sensitivity-decisive amino acids indirectly controlled TCDD-binding modes through their surrounding amino acids. Deletion assays of jcAHR2 revealed that 736-805 amino acid residues in the C-terminal region were critical for its transactivation. We suggest that jcAHR2 plays a critical role in regulating the AHR signaling pathway, at least in its highly expressed organs.


Assuntos
Corvos/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Dioxinas/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Animais , Feminino , Genes Reporter , Fígado/metabolismo , Masculino , Simulação de Acoplamento Molecular , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/genética , Transdução de Sinais , Ativação Transcricional
8.
Chem Res Toxicol ; 32(2): 222-233, 2019 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-30608650

RESUMO

Botanical dietary supplements for women's health are increasingly popular. Older women tend to take botanical supplements such as hops as natural alternatives to traditional hormone therapy to relieve menopausal symptoms. Especially extracts from spent hops, the plant material remaining after beer brewing, are enriched in bioactive prenylated flavonoids that correlate with the health benefits of the plant. The chalcone xanthohumol (XH) is the major prenylated flavonoid in spent hops. Other less abundant but important bioactive prenylated flavonoids are isoxanthohumol (IX), 8-prenylnaringenin (8-PN), and 6-prenylnaringenin (6-PN). Pharmacokinetic studies revealed that these flavonoids are conjugated rapidly with glucuronic acid. XH also undergoes phase I metabolism in vivo to form IX, 8-PN, and 6-PN. Several hop constituents are responsible for distinct effects linked to multiple biological targets, including hormonal, metabolic, inflammatory, and epigenetic pathways. 8-PN is one of the most potent phytoestrogens and is responsible for hops' estrogenic activities. Hops also inhibit aromatase activity, which is linked to 8-PN. The weak electrophile, XH, can activate the Keap1-Nrf2 pathway and turn on the synthesis of detoxification enzymes such as NAD(P)H-quinone oxidoreductase 1 and glutathione S-transferase. XH also alkylates IKK and NF-κB, resulting in anti-inflammatory activity. Antiobesity activities have been described for XH and XH-rich hop extracts likely through activation of AMP-activated protein kinase signaling pathways. Hop extracts modulate the estrogen chemical carcinogenesis pathway by enhancing P450 1A1 detoxification. The mechanism appears to involve activation of the aryl hydrocarbon receptor (AhR) by the AhR agonist, 6-PN, leading to degradation of the estrogen receptor. Finally, prenylated phenols from hops are known inhibitors of P450 1A1/2; P450 1B1; and P450 2C8, 2C9, and 2C19. Understanding the biological targets of hop dietary supplements and their phytoconstituents will ultimately lead to standardized botanical products with higher efficacy, safety, and chemopreventive properties.


Assuntos
Flavonoides/química , Humulus/química , Proteínas Quinases Ativadas por AMP/metabolismo , Citocromo P-450 CYP1A1/metabolismo , Feminino , Flavonoides/metabolismo , Flavonoides/farmacologia , Humanos , Humulus/metabolismo , Extratos Vegetais/química , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/metabolismo , Receptores Estrogênicos/química , Receptores Estrogênicos/metabolismo , Transdução de Sinais/efeitos dos fármacos
9.
Int J Mol Sci ; 19(12)2018 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-30567322

RESUMO

Dioxins are highly toxic and persistent halogenated organic pollutants belonging to two families i.e., Polychlorinated Dibenzo-p-Dioxins (PCDDs) and Polychlorinated Dibenzo Furans (PCDFs). They can cause cancer, reproductive and developmental issues, damage to the immune system, and can deeply interfere with the endocrine system. Dioxins toxicity is mediated by the Aryl-hydrocarbon Receptor (AhR) which mediates the cellular metabolic adaptation to these planar aromatic xenobiotics through the classical transcriptional regulation pathway, including AhR binding of ligand in the cytosol, translocation of the receptor to the nucleus, dimerization with the AhR nuclear translocator, and the binding of this heterodimeric transcription factor to dioxin-responsive elements which regulate the expression of genes involved in xenobiotic metabolism. 2,3,7,8-TCDD is the most toxic among dioxins showing the highest affinity toward the AhR receptor. Beside this classical and well-studied pathway, a number of papers are dealing with the role of epigenetic mechanisms in the response to environmental xenobiotics. In this review, we report on the potential role of epigenetic mechanisms in dioxins-induced cellular response by inspecting recent literature and focusing our attention on epigenetic mechanisms induced by the most toxic 2,3,7,8-TCDD.


Assuntos
Poluentes Ambientais/toxicidade , Epigênese Genética/efeitos dos fármacos , Dibenzodioxinas Policloradas/toxicidade , Receptores de Hidrocarboneto Arílico/química , Dibenzofuranos Policlorados/química , Dibenzofuranos Policlorados/toxicidade , Poluentes Ambientais/química , Humanos , Ligantes , Dibenzodioxinas Policloradas/química , Ligação Proteica , Receptores de Hidrocarboneto Arílico/metabolismo , Xenobióticos/toxicidade
10.
BMC Struct Biol ; 18(1): 15, 2018 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-30522477

RESUMO

BACKGROUND: Aryl hydrocarbon receptor (AhR) ligands may act as potential carcinogens or anti-tumor agents. Understanding how some of the residues in AhR ligand binding domain (AhRLBD) modulate their interactions with ligands would be useful in assessing their divergent roles including toxic and beneficial effects. To this end, we have analysed the nature of AhRLBD interactions with 2,3,7,8-tetrachlorodibenzo-ρ-dioxin (TCDD), 6-formylindolo[3,2-b]carbazole (FICZ), indole-3-carbinol (I3C) and its degradation product, 3,3'-diindolylmethane (DIM), Resveratrol (RES) and its analogue, Piceatannol (PTL) using molecular modeling approach followed by molecular dynamic simulations. RESULTS: Results showed that each of the AhR ligands, TCDD, FICZ, I3C, DIM, RES and PTL affect the local and global conformations of AhRLBD. CONCLUSION: The data presented in this study provide a structural understanding of AhR with its ligands and set the basis for its functions in several pathways and their related diseases.


Assuntos
Ligantes , Receptores de Hidrocarboneto Arílico/metabolismo , Animais , Sítios de Ligação , Carbazóis/química , Carbazóis/metabolismo , Indóis/química , Indóis/metabolismo , Camundongos , Simulação de Dinâmica Molecular , Dibenzodioxinas Policloradas/química , Dibenzodioxinas Policloradas/metabolismo , Estrutura Terciária de Proteína , Receptores de Hidrocarboneto Arílico/química , Resveratrol/química , Resveratrol/metabolismo
11.
Int J Mol Sci ; 19(10)2018 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-30297679

RESUMO

A novel pathway of vitamin D activation by CYP11A has previously been elucidated. To define the mechanism of action of its major dihydroxy-products, we tested the divergence and overlap between the gene expression profiles of human epidermal keratinocytes treated with either CYP11A1-derived 20,23(OH)2D3 or classical 1,25(OH)2D3. Both secosteroids have significant chemical similarity with the only differences being the positions of the hydroxyl groups. mRNA was isolated and examined by microarray analysis using Illumina's HumanWG-6 chip/arrays and subsequent bioinformatics analyses. Marked differences in the up- and downregulated genes were observed between 1,25(OH)2D3- and 20,23(OH)2D3-treated cells. Hierarchical clustering identified both distinct, opposite and common (overlapping) gene expression patterns. CYP24A1 was a common gene strongly activated by both compounds, a finding confirmed by qPCR. Ingenuity pathway analysis identified VDR/RXR signaling as the top canonical pathway induced by 1,25(OH)2D3. In contrast, the top canonical pathway induced by 20,23(OH)2D3 was AhR, with VDR/RXR being the second nuclear receptor signaling pathway identified. QPCR analyses validated the former finding by revealing that 20,23(OH)2D3 stimulated CYP1A1 and CYP1B1 gene expression, effects located downstream of AhR. Similar stimulation was observed with 20(OH)D3, the precursor to 20,23(OH)2D3, as well as with its downstream metabolite, 17,20,23(OH)3D3. Using a Human AhR Reporter Assay System we showed marked activation of AhR activity by 20,23(OH)2D3, with weaker stimulation by 20(OH)D3. Finally, molecular modeling using an AhR LBD model predicted vitamin D3 hydroxyderivatives to be good ligands for this receptor. Thus, our microarray, qPCR, functional studies and molecular modeling indicate that AhR is the major receptor target for 20,23(OH)2D3, opening an exciting area of investigation on the interaction of different vitamin D3-hydroxyderivatives with AhR and the subsequent downstream activation of signal transduction pathways in a cell-type-dependent manner.


Assuntos
Calcitriol/farmacologia , Di-Hidroxicolecalciferóis/farmacologia , Queratinócitos/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Hidrocarboneto de Aril Hidroxilases/genética , Hidrocarboneto de Aril Hidroxilases/metabolismo , Sítios de Ligação , Células Cultivadas , Humanos , Queratinócitos/efeitos dos fármacos , Simulação de Acoplamento Molecular , Ligação Proteica , Receptores de Hidrocarboneto Arílico/química
12.
Biochem Pharmacol ; 158: 1-12, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30248327

RESUMO

In its classical genomic mode of action, the aryl hydrocarbon receptor (AhR) acts as a ligand activated transcription factor regulating expression of target genes such as CYP1A1 and CYP1B1. Some ligands may also trigger more rapid nongenomic responses through AhR, including calcium signaling (Ca2+). In the present study we observed that pyrene induced a relatively rapid increase in intracellular Ca2+-concentrations ([Ca2+]i) in human microvascular endothelial cells (HMEC-1) and human embryonic kidney cells (HEK293) that was attenuated by AhR-inhibitor treatment and/or transient AhR knockdown by RNAi. In silico molecular docking based on homology models, suggested that pyrene is not able to bind to the human AhR in the agonist conformation. Instead, pyrene docked in the antagonist conformation of the AhR PAS-B binding pocket, although the interaction differed from antagonists such as GNF-351 and CH223191. Accordingly, pyrene did not induce CYP1A1 or CYP1B1, but suppressed CYP1-expression by benzo[a]pyrene (B[a]P) in HMEC-1 cells, confirming that pyrene act as an antagonist of AhR-induced gene expression. Use of pharmacological inhibitors and Ca2+-free medium indicated that the pyrene-induced AhR nongenomic [Ca2+]i increase was initiated by Ca2+-release from intracellular stores followed by a later phase of extracellular Ca2+-influx, consistent with store operated calcium entry (SOCE). These effects was accompanied by an AhR-dependent reduction in ordered membrane lipid domains, as determined by di-4-ANEPPDHQ staining. Addition of cholesterol inhibited both the pyrene-induced [Ca2+]i-increase and alterations in membrane lipid order. In conclusion, we propose that pyrene binds to AhR, act as an antagonist of the canonical genomic AhR/Arnt/CYP1-pathway, reduces ordered membrane lipid domains, and activates AhR nongenomic Ca2+-signaling from intracellular stores.


Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Sinalização do Cálcio/fisiologia , Pirenos/metabolismo , Pirenos/farmacologia , Receptores de Hidrocarboneto Arílico/metabolismo , Compostos Azo/química , Compostos Azo/metabolismo , Compostos Azo/farmacologia , Fatores de Transcrição Hélice-Alça-Hélice Básicos/agonistas , Fatores de Transcrição Hélice-Alça-Hélice Básicos/antagonistas & inibidores , Fatores de Transcrição Hélice-Alça-Hélice Básicos/química , Sítios de Ligação , Sinalização do Cálcio/efeitos dos fármacos , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Células HEK293 , Humanos , Indóis/química , Indóis/metabolismo , Indóis/farmacologia , Simulação de Acoplamento Molecular/métodos , Estrutura Secundária de Proteína , Purinas/química , Purinas/metabolismo , Purinas/farmacologia , Pirazóis/química , Pirazóis/metabolismo , Pirazóis/farmacologia , Pirenos/química , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/antagonistas & inibidores , Receptores de Hidrocarboneto Arílico/química
13.
Int J Mol Sci ; 19(9)2018 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-30201897

RESUMO

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that modulates gene expression following its binding and activation by structurally diverse chemicals. Species differences in AhR functionality have been observed, with the mouse AhR (mAhR) and human AhR (hAhR) exhibiting significant differences in ligand binding, coactivator recruitment, gene expression and response. While the AhR agonist indirubin (IR) is a more potent activator of hAhR-dependent gene expression than the prototypical ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), it is a significantly less potent activator of the mAhR. DNA binding analysis confirmed the greater potency/efficacy of IR in stimulating transformation/DNA binding of the hAhR in vitro and domain-swapping experiments demonstrated that the enhanced response to IR was primarily due to the hAhR ligand binding domain (LBD). Site-directed mutagenesis and functional analysis studies revealed that mutation of H326 and A349 in the mAhR LBD to the corresponding residues in the hAhR LBD significantly increased the potency of IR. Since these mutations had no significant effect on ligand binding, these residues likely contribute to an enhanced efficiency of transformation/DNA binding by IR-bound hAhR. Molecular docking to mAhR LBD homology models further elucidated the different roles of the A375V mutation in TCDD and IR binding, as revealed by [³H]TCDD competitive binding results. These results demonstrate the differential binding of structurally diverse ligands within the LBD of a given AhR and confirm that amino acid differences within the LBD of AhRs contribute to significant species differences in ligand response.


Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/agonistas , Fatores de Transcrição Hélice-Alça-Hélice Básicos/química , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Sítios de Ligação , Simulação por Computador , Humanos , Técnicas In Vitro , Indóis/farmacologia , Camundongos , Modelos Moleculares , Simulação de Acoplamento Molecular , Mutagênese Sítio-Dirigida , Dibenzodioxinas Policloradas/farmacologia , Ligação Proteica/efeitos dos fármacos , Estrutura Secundária de Proteína , Receptores de Hidrocarboneto Arílico/genética , Especificidade da Espécie
14.
Chemosphere ; 211: 640-647, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30098559

RESUMO

An increasing number of studies have indicated that environmental contamination with chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) has been underestimated. However, insufficient available toxicological information on Cl-PAHs makes evaluating their risks to health challenging. Two in vitro bioassays were used in the present study to characterize the aryl hydrocarbon receptor (AhR) activity and DNA-damaging effects of 22 low-molecular-weight PAHs and their Cl-PAHs by using the EROD assay in rat hepatoma (H4IIE) cells and the SOS/umu test (S. typhimurium TA1535/pSK1002). Compared with their parent PAHs, most of the Cl-PAHs enhanced AhR-mediated activity in the EROD assay. 1,3,6,8-Tetrachloro-pyrene (1,3,6,8-Tetracl-Py) induced the greatest potency of EROD activity (83.1%-TCDD-max) and its single point ReP was 6.64 × 10-6. Compared with their parent PAHs, several Cl-PAHs showed significant DNA-damaging effects in the SOS/umu test with the addition of S9, and the toxic equivalency of benzo[a]pyrene (TEQBaP) was calculated for them. 9-Chloroanthracene (9-Ant) and 5,6-Dichloroacenaphthene (5,6-Dicl-Ace) had relatively high TEQBaP (0.62 and 0.54, respectively). However, only 1,3,6,8-Tetracl-Py elicited strong DNA-damaging effects in the absence of S9. The degree of chlorination, the position of chlorine substitutions, and the structure of parent PAHs influenced the potency of low-molecular-weight PAHs with regard to their AhR activity and DNA-damaging effects. More concern should be raised for these environmentally relevant pollutants.


Assuntos
Dano ao DNA/genética , Poluentes Ambientais/química , Hidrocarbonetos Policíclicos Aromáticos/química , Receptores de Hidrocarboneto Arílico/química
15.
Int J Mol Sci ; 19(5)2018 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-29748474

RESUMO

Exposure to diesel exhaust particles (DEPs) affects endothelial function and may contribute to the development of atherosclerosis and vasomotor dysfunction. As intracellular calcium concentration [Ca2+]i is considered important in myoendothelial signalling, we explored the effects of extractable organic matter from DEPs (DEP-EOM) on [Ca2+]i and membrane microstructure in endothelial cells. DEP-EOM of increasing polarity was obtained by pressurized sequential extraction of DEPs with n-hexane (n-Hex-EOM), dichloromethane (DCM-EOM), methanol, and water. Chemical analysis revealed that the majority of organic matter was extracted by the n-Hex- and DCM-EOM, with polycyclic aromatic hydrocarbons primarily occurring in n-Hex-EOM. The concentration of calcium was measured in human microvascular endothelial cells (HMEC-1) using micro-spectrofluorometry. The lipophilic n-Hex-EOM and DCM-EOM, but not the more polar methanol- and water-soluble extracts, induced rapid [Ca2+]i increases in HMEC-1. n-Hex-EOM triggered [Ca2+]i increase from intracellular stores, followed by extracellular calcium influx consistent with store operated calcium entry (SOCE). By contrast, the less lipophilic DCM-EOM triggered [Ca2+]i increase via extracellular influx alone, resembling receptor operated calcium entry (ROCE). Both extracts increased [Ca2+]i via aryl hydrocarbon receptor (AhR) non-genomic signalling, verified by pharmacological inhibition and RNA-interference. Moreover, DCM-EOM appeared to induce an AhR-dependent reduction in the global plasma membrane order, as visualized by confocal fluorescence microscopy. DCM-EOM-triggered [Ca2+]i increase and membrane alterations were attenuated by the membrane stabilizing lipid cholesterol. In conclusion, lipophilic constituents of DEPs extracted by n-hexane and DCM seem to induce rapid AhR-dependent [Ca2+]i increase in HMEC-1 endothelial cells, possibly involving both ROCE and SOCE-mediated mechanisms. The semi-lipophilic fraction extracted by DCM also caused an AhR-dependent reduction in global membrane order, which appeared to be connected to the [Ca2+]i increase.


Assuntos
Células Endoteliais/efeitos dos fármacos , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Receptores de Hidrocarboneto Arílico/química , Emissões de Veículos/toxicidade , Poluentes Atmosféricos/química , Poluentes Atmosféricos/toxicidade , Aterosclerose/induzido quimicamente , Aterosclerose/fisiopatologia , Cálcio/química , Cálcio/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Células Endoteliais/patologia , Humanos
16.
Hum Mol Genet ; 27(14): 2563-2572, 2018 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-29726989

RESUMO

Retinitis pigmentosa (RP) refers to a group of retinal degenerative diseases, which often lead to vision loss. Although 70 genes have been identified in RP patients, the genetic cause of approximately 30% of RP cases remains unknown. We aimed to identify the cause of the disease in a cohort of RP families by whole exome sequencing. A rare homozygous splicing variant, c.1160 + 1G>A, which introduced skipping of exon 9 of the aryl hydrocarbon receptor (AHR), was identified in family RD-134. This variant is very rare in several exome databases and leads to skipping of exon 9 in the transcript. AHR is expressed in the human retina and is a ligand-activated transcription factor with multiple functions. Mutant AHR failed to promote 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD)-induced xenobiotic responsive element (XRE) luciferase activity. In parallel, mutation in AHR abolished activation of its downstream target gene, such as CYP1A1 and CYP1A2. To investigate the in vivo roles of Ahr in the retina, we generated a retina-specific conditional knockout mouse model of Ahr. Comparing with wild-type mouse, Ahr knockout mice exhibited reduced electroretinogram responses at 9 months of age. Retinal histology revealed retinal histology showed the degeneration of photoreceptors with a thinner outer nuclear layer. Thus, our data demonstrate that AHR is associated with RP.


Assuntos
Receptores de Hidrocarboneto Arílico/genética , Retina/patologia , Retinite Pigmentosa/genética , Sequenciamento Completo do Exoma , Processamento Alternativo/genética , Animais , Citocromo P-450 CYP1A1/genética , Citocromo P-450 CYP1A2/genética , Modelos Animais de Doenças , Feminino , Regulação da Expressão Gênica/genética , Homozigoto , Humanos , Camundongos , Camundongos Knockout , Mutação , Dibenzodioxinas Policloradas/administração & dosagem , Regiões Promotoras Genéticas , Receptores de Hidrocarboneto Arílico/química , Retina/efeitos dos fármacos , Retina/metabolismo , Retinite Pigmentosa/fisiopatologia
17.
Aquat Toxicol ; 197: 19-31, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29427830

RESUMO

Atlantic sturgeon and shortnose sturgeon co-occur in many estuaries along the Atlantic Coast of North America. Both species are protected under the U.S. Endangered Species Act and internationally on the IUCN Red list and by CITES. Early life-stages of both sturgeons may be exposed to persistent aromatic hydrocarbon contaminants such as PCBs and PCDD/Fs which are at high levels in the sediments of impacted spawning rivers. Our objective was to compare the PCBs and TCDD sensitivities of both species with those of other fishes and to determine if environmental concentrations of these contaminants approach those that induce toxicity to their young life-stages under controlled laboratory conditions. Because our previous studies suggested that young life-stages of North American sturgeons are among the more sensitive of fishes to coplanar PCB and TCDD-induced toxicities, we were interested in identifying the molecular bases of this vulnerability. It is known that activation of the aryl hydrocarbon receptor 2 (AHR2) in fishes mediates most toxicities to these contaminants and transcriptional activation of xenobiotic metabolizing enzymes such as cytochrome P4501A (CYP1A). Previous studies demonstrated that structural and functional variations in AHRs are the bases for differing sensitivities of several vertebrate taxa to aromatic hydrocarbons. Therefore, in this study we characterized AHR2 and its expression in both sturgeons as an initial step in understanding the mechanistic bases of their sensitivities to these contaminants. We also used CYP1A expression as an endpoint to develop Toxicity Equivalency Factors (TEFs) for these sturgeons. We found that critical amino acid residues in the ligand binding domain of AHR2 in both sturgeons were identical to those of the aromatic hydrocarbon-sensitive white sturgeon, and differed from the less sensitive lake sturgeon. AHR2 expression was induced by TCDD (up to 6-fold) and by three of four tested coplanar PCB congeners (3-5-fold) in Atlantic sturgeon, but less so in shortnose sturgeon. We found that expression of AHR2 and CYP1A mRNA significantly covaried after exposure to TCDD and PCB77, PCB81, PCB126, but not PCB169 in both sturgeons. We also determined TEFs for the four coplanar PCBs in shortnose sturgeon based on comparison of CYP1A mRNA expression across all doses. Surprisingly, the TEFs for all four coplanar PCBs in shortnose sturgeon were much higher (6.4-162 times) than previously adopted for fishes by the WHO.


Assuntos
Citocromo P-450 CYP1A1/metabolismo , Peixes/metabolismo , Bifenilos Policlorados/toxicidade , Dibenzodioxinas Policloradas/toxicidade , Receptores de Hidrocarboneto Arílico/metabolismo , Sequência de Aminoácidos , Animais , Arocloros/toxicidade , Citocromo P-450 CYP1A1/genética , Peixes/genética , Peixes/crescimento & desenvolvimento , Regulação da Expressão Gênica/efeitos dos fármacos , Filogenia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/genética , Poluentes Químicos da Água/toxicidade
18.
Biochim Biophys Acta Proteins Proteom ; 1866(1): 155-165, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28694077

RESUMO

Limited knowledge of the molecular evolution of deep-sea fish proteomes so far suggests that a few widespread residue substitutions in cytosolic proteins binding hydrophilic ligands contribute to resistance to the effects of high hydrostatic pressure (HP). Structure-function studies with additional protein systems, including membrane bound proteins, are essential to provide a more general picture of adaptation in these extremophiles. We explored molecular features of HP adaptation in proteins binding hydrophobic ligands, either in lipid bilayers (cytochrome P450 1A - CYP1A) or in the cytosol (the aryl hydrocarbon receptor - AHR), and their partners P450 oxidoreductase (POR) and AHR nuclear translocator (ARNT), respectively. Cloning studies identified the full-length coding sequence of AHR, CYP1A and POR, and a partial sequence of ARNT from Coryphaenoides armatus, an abyssal gadiform fish thriving down to 5000m depth. Inferred protein sequences were aligned with many non-deep-sea homologs to identify unique amino acid substitutions of possible relevance in HP adaptation. Positionally unique substitutions of various physicochemical properties were found in all four proteins, usually at sites of strong-to-absolute residue conservation. Some were in domains deemed important for protein-protein interaction or ligand binding. In addition, some involved removal or addition of beta-branched residues; local modifications of beta-branched residue patterns could be important to HP adaptation. In silico predictions further suggested that some unique substitutions might substantially modulate the flexibility of the polypeptide segment in which they are found. Repetitive motifs unique to the abyssal fish AHR were predicted to be rich in glycosylation sites, suggesting that post-translational changes could be involved in adaptation as well. Recombinant CYP1A and AHR showed functional properties (spectral characteristics, catalytic activity and ligand binding) that demonstrate proper folding at 1atm, indicating that they could be used as deep-sea fish protein models to further evaluate protein function under pressure. This article is part of a Special Issue entitled: Cytochrome P450 biodiversity and biotechnology, edited by Erika Plettner, Gianfranco Gilardi, Luet Wong, Vlada Urlacher, Jared Goldstone".


Assuntos
Adaptação Fisiológica , Translocador Nuclear Receptor Aril Hidrocarboneto/química , Sistema Enzimático do Citocromo P-450/química , Proteínas de Peixes/química , Gadiformes/metabolismo , Receptores de Hidrocarboneto Arílico/química , Sequência de Aminoácidos , Anfíbios , Animais , Translocador Nuclear Receptor Aril Hidrocarboneto/genética , Translocador Nuclear Receptor Aril Hidrocarboneto/metabolismo , Sítios de Ligação , Aves , Cristalografia por Raios X , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Peixes/genética , Proteínas de Peixes/metabolismo , Gadiformes/genética , Expressão Gênica , Pressão Hidrostática , Mamíferos , Modelos Moleculares , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Estrutura Secundária de Proteína , Receptores de Hidrocarboneto Arílico/genética , Receptores de Hidrocarboneto Arílico/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Répteis , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade por Substrato
19.
Environ Sci Pollut Res Int ; 25(17): 16481-16492, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28699004

RESUMO

Inflammation in adipose tissue is recognized as a causative factor in the development of type II diabetes. Adipocyte hypertrophy as well as bacterial and environmental factors have been implicated in causing inflammation in mature adipocytes. Exposure to persistent organic pollutants such as polychlorinated biphenyls (PCBs) has been associated with the development of type II diabetes. We show here that PCB126, a dioxin-like PCB, activates a robust proinflammatory state in fat cell precursors (preadipocytes). The response was found to be dependent on aryl hydrocarbon receptor (AhR) activation, although induction of the response was delayed compared to upregulation of CYP1A1, a classic AhR-responsive gene. Treatment of preadipocytes with a nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) inhibitor partially attenuated the PCB126-induced inflammatory response and partly, but not completely, ameliorated disruption of adipogenesis caused by PCB126. Our results indicate a role for PCB126 in mediating an inflammatory response through AhR in preadipocytes that interferes with adipogenesis.


Assuntos
Adipócitos/química , Diabetes Mellitus Tipo 2/metabolismo , Dioxinas/química , NF-kappa B/química , Bifenilos Policlorados/química , Dibenzodioxinas Policloradas/química , Receptores de Hidrocarboneto Arílico/química , Poluentes Ambientais/efeitos adversos , Poluentes Ambientais/química , Humanos , Inflamação/induzido quimicamente , Bifenilos Policlorados/farmacologia , Receptores de Hidrocarboneto Arílico/metabolismo
20.
J Biol Chem ; 293(6): 1994-2005, 2018 02 09.
Artigo em Inglês | MEDLINE | ID: mdl-29279331

RESUMO

Cellular metabolites act as important signaling cues, but are subject to complex unknown chemistry. Kynurenine is a tryptophan metabolite that plays a crucial role in cancer and the immune system. Despite its atypical, non-ligand-like, highly polar structure, kynurenine activates the aryl hydrocarbon receptor (AHR), a PER, ARNT, SIM (PAS) family transcription factor that responds to diverse environmental and cellular ligands. The activity of kynurenine is increased 100-1000-fold by incubation or long-term storage and relies on the hydrophobic ligand-binding pocket of AHR, with identical structural signatures for AHR induction before and after activation. We purified trace-active derivatives of kynurenine and identified two novel, closely related condensation products, named trace-extended aromatic condensation products (TEACOPs), which are active at low picomolar levels. The synthesized compound for one of the predicted structures matched the purified compound in both chemical structure and AHR pharmacology. Our study provides evidence that kynurenine acts as an AHR pro-ligand, which requires novel chemical conversions to act as a receptor agonist.


Assuntos
Cinurenina/química , Cinurenina/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Animais , Sítios de Ligação , Cinética , Ligantes , Camundongos , Estrutura Molecular , Receptores de Hidrocarboneto Arílico/química , Receptores de Hidrocarboneto Arílico/genética
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