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Sample records for aryl hydrocarbon monooxygenase

  1. Aryl hydrocarbon mono-oxygenase activity in human lymphocytes

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, G.D.; Schuresko, D.D.

    1981-06-01

    Aryl hydrocarbon mono-oxygenase (AHM), an enzyme of key importance in metabolism of xenobiotic chemicals such as polynuclear aromatic hydrocarbons (PNA), is present in human lymphocytes. Studies investing the relation of activity of AHM in human lymphocytes to parameters such as disease state, PNA exposure, in vitro mitogen stimulation, etc. have been summarized in this report. Some studies have demonstrated increased AHM activity in lymphocytes from cigarette smokers (compared to nonsmokers), and in lung cancer patients when compared to appropriate control groups. These observations are confused by extreme variability in human lymphocyte AHM activities, such variability arising from factors such as genetic variation in AHM activity, variation in in vitro culture conditions which affect AHM activity, and the problematical relationship of common AHM assays to actual PNA metabolism taking place in lymphocytes. If some of the foregoing problems can be adequately addressed, lymphocyte AHM activity could hold the promise of being a useful biomarker system for human PNA exposure.

  2. Kynurenine 3-monooxygenase mediates inhibition of Th17 differentiation via catabolism of endogenous aryl hydrocarbon receptor ligands.

    Science.gov (United States)

    Stephens, Geoffrey L; Wang, Qun; Swerdlow, Bonnie; Bhat, Geetha; Kolbeck, Roland; Fung, Michael

    2013-07-01

    The aryl hydrocarbon receptor (AhR) is a key transcriptional regulator of Th17-cell differentiation. Although endogenous ligands have yet to be identified, evidence suggests that tryptophan metabolites can act as agonists for the AhR. Tryptophan metabolites are abundant in circulation, so we hypothesized that cell intrinsic factors might exist to regulate the exposure of Th17 cells to AhR-dependent activities. Here, we find that Th17 cells preferentially express kynurenine 3-monooxygenase (KMO), which is an enzyme involved in catabolism of the tryptophan metabolite kynurenine. KMO inhibition, either with a specific inhibitor or via siRNA-mediated silencing, markedly increased IL-17 production in vitro, whereas IFN-γ production by Th1 cells was unaffected. Inhibition of KMO significantly exacerbated disease in a Th17-driven model of autoimmune gastritis, suggesting that expression of KMO by Th17 cells serves to limit their continuous exposure to physiological levels of endogenous AhR ligands in vivo. PMID:23568529

  3. A New Biocatalyst for Production of Optically Pure Aryl Epoxides by Styrene Monooxygenase from Pseudomonas fluorescens ST

    Science.gov (United States)

    Di Gennaro, Patrizia; Colmegna, Andrea; Galli, Enrica; Sello, Guido; Pelizzoni, Francesca; Bestetti, Giuseppina

    1999-01-01

    We developed a biocatalyst by cloning the styrene monooxygenase genes (styA and styB) from Pseudomonas fluorescens ST responsible for the oxidation of styrene to its corresponding epoxide. Recombinant Escherichia coli was able to oxidize different aryl vinyl and aryl ethenyl compounds to their corresponding optically pure epoxides. The results of bioconversions indicate the broad substrate preference of styrene monooxygenase and its potential for the production of several fine chemicals. PMID:10347083

  4. Recombinant expression of the Aryl Hydrocarbon Receptor

    OpenAIRE

    Shaikh-Omar, Osama

    2007-01-01

    Aryl Hydrocarbon Receptor (AhR) mediates drug and toxin action. The AhR proteins have been characterised in several mammalian species, and are soluble proteins found in various tissues. The AhR is normally found in the cytoplasm in a complex with 90 KDa heat shock protein (hsp90) and cellular chaperones such as ARA9 (AIP or XAP2) and p23. However, there has not been a systematic analysis of the proteins which chaperone the AhR ligand-binding domain (LBD). This work investigates the interactio...

  5. Coupling Oxygen Consumption with Hydrocarbon Oxidation in Bacterial Multicomponent Monooxygenases.

    Science.gov (United States)

    Wang, Weixue; Liang, Alexandria D; Lippard, Stephen J

    2015-09-15

    A fundamental goal in catalysis is the coupling of multiple reactions to yield a desired product. Enzymes have evolved elegant approaches to address this grand challenge. A salient example is the biological conversion of methane to methanol catalyzed by soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily. sMMO is a dynamic protein complex of three components: a hydroxylase, a reductase, and a regulatory protein. The active site, a carboxylate-rich non-heme diiron center, is buried inside the 251 kDa hydroxylase component. The enzyme processes four substrates: O2, protons, electrons, and methane. To couple O2 activation to methane oxidation, timely control of substrate access to the active site is critical. Recent studies of sMMO, as well as its homologues in the BMM superfamily, have begun to unravel the mechanism. The emerging and unifying picture reveals that each substrate gains access to the active site along a specific pathway through the hydroxylase. Electrons and protons are delivered via a three-amino-acid pore located adjacent to the diiron center; O2 migrates via a series of hydrophobic cavities; and hydrocarbon substrates reach the active site through a channel or linked set of cavities. The gating of these pathways mediates entry of each substrate to the diiron active site in a timed sequence and is coordinated by dynamic interactions with the other component proteins. The result is coupling of dioxygen consumption with hydrocarbon oxidation, avoiding unproductive oxidation of the reductant rather than the desired hydrocarbon. To initiate catalysis, the reductase delivers two electrons to the diiron(III) center by binding over the pore of the hydroxylase. The regulatory component then displaces the reductase, docking onto the same surface of the hydroxylase. Formation of the hydroxylase-regulatory component complex (i) induces conformational changes of pore residues that may bring protons to the

  6. New Trends in Aryl Hydrocarbon Receptor Biology

    Science.gov (United States)

    Mulero-Navarro, Sonia; Fernandez-Salguero, Pedro M.

    2016-01-01

    Traditionally considered as a critical intermediate in the toxic and carcinogenic response to dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD), the Aryl hydrocarbon/Dioxin receptor (AhR) has proven to be also an important regulator of cell physiology and organ homeostasis. AhR has become an interesting and actual area of research mainly boosted by a significant number of recent studies analyzing its contribution to the proper functioning of the immune, hepatic, cardiovascular, vascular and reproductive systems. At the cellular level, AhR establishes functional interactions with signaling pathways governing cell proliferation and cell cycle, cell morphology, cell adhesion and cell migration. Two exciting new aspects in AhR biology deal with its implication in the control of cell differentiation and its more than likely involvement in cell pluripotency and stemness. In fact, it is possible that AhR could help modulate the balance between differentiation and pluripotency in normal and transformed tumor cells. At the molecular level, AhR regulates an increasingly large array of physiologically relevant genes either by traditional transcription-dependent mechanisms or by unforeseen processes involving genomic insulators, chromatin dynamics and the transcription of mobile genetic elements. AhR is also closely related to epigenetics, not only from the point of view of target gene expression but also with respect to its own regulation by promoter methylation. It is reasonable to consider that deregulation of these many functions could have a causative role, or at least contribute to, human disease. Consequently, several laboratories have proposed that AhR could be a valuable tool as diagnostic marker and/or therapeutic target in human pathologies. An additional point of interest is the possibility of regulating AhR activity by endogenous non-toxic low weight molecules agonist or antagonist molecules that could be present or included in the diet. In this review, we will

  7. Coupling oxygen consumption with hydrocarbon oxidation in bacterial multicomponent monooxygenases

    OpenAIRE

    Wang, Weixue; Liang, Alexandria D.; Lippard, Stephen J.

    2015-01-01

    A fundamental goal in catalysis is the coupling of multiple reactions to yield a desired product. Enzymes have evolved elegant approaches to address this grand challenge. A salient example is the biological conversion of methane to methanol catalyzed by soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily.

  8. Binding of polychlorinated biphenyls to the aryl hydrocarbon receptor.

    OpenAIRE

    Kafafi, S A; Afeefy, H Y; A. H. Ali; Said, H K; Kafafi, A G

    1993-01-01

    A new thermodynamic model for calculating the dissociation constants of complexes formed between the aryl hydrocarbon receptor (AhR) and polychlorinated biphenyls (PCBs) is reported. The free energies of binding of PCBs to AhR are controlled by their lipophilicities, electron affinities, and entropies. The corresponding physicochemical properties of polychlorinated dibenzo-p-dioxins and dibenzofurans also control their interactions with AhR. We present evidence supporting the hypothesis that ...

  9. Novel hydrocarbon monooxygenase genes in the metatranscriptome of a natural deep-sea hydrocarbon plume.

    Science.gov (United States)

    Li, Meng; Jain, Sunit; Baker, Brett J; Taylor, Chris; Dick, Gregory J

    2014-01-01

    Particulate membrane-associated hydrocarbon monooxygenases (pHMOs) are critical components of the aerobic degradation pathway for low molecular weight hydrocarbons, including the potent greenhouse gas methane. Here, we analysed pHMO gene diversity in metagenomes and metatranscriptomes of hydrocarbon-rich hydrothermal plumes in the Guaymas Basin (GB) and nearby background waters in the deep Gulf of California. Seven distinct phylogenetic groups of pHMO were present and transcriptionally active in both plume and background waters, including several that are undetectable with currently available polymerase chain reaction (PCR) primers. The seven groups of pHMOs included those related to a putative ethane oxidizing Methylococcaceae-like group, a group of the SAR324 Deltaproteobacteria, three deep-sea clades (Deep sea-1/symbiont-like, Deep sea-2/PS-80 and Deep sea-3/OPU3) within gammaproteobacterial methanotrophs, one clade related to Group Z and one unknown group. Differential abundance of pHMO gene transcripts in plume and background suggests niche differentiation between groups. Corresponding 16S rRNA genes reflected similar phylogenetic and transcriptomic abundance trends. The novelty of transcriptionally active pHMOs we recovered from a hydrocarbon-rich hydrothermal plume suggests there are significant gaps in our knowledge of the diversity and function of these enzymes in the environment. PMID:23826624

  10. Role of the Aryl Hydrocarbon Receptor in Colon Neoplasia

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Guofeng, E-mail: gxie@medicine.umaryland.edu; Raufman, Jean-Pierre [Division of Gastroenterology and Hepatology, Veterans Administration Maryland Health Care System, University of Maryland School of Medicine, Baltimore, MD 21201 (United States)

    2015-07-31

    For both men and women, colorectal cancer (CRC) is the second leading cause of cancer death in the United States, primarily as a consequence of limited therapies for metastatic disease. The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor with diverse functions in detoxification of xenobiotics, inflammatory responses, and tissue homeostasis. Emerging evidence indicates that AhR also plays an important role in regulating intestinal cell proliferation and tumorigenesis. Here, we review both the pro- and anti-carcinogenic properties of AhR signaling and its potential role as a therapeutic target in CRC.

  11. Role of the Aryl Hydrocarbon Receptor in Colon Neoplasia

    Directory of Open Access Journals (Sweden)

    Guofeng Xie

    2015-07-01

    Full Text Available For both men and women, colorectal cancer (CRC is the second leading cause of cancer death in the United States, primarily as a consequence of limited therapies for metastatic disease. The aryl hydrocarbon receptor (AhR is a ligand-dependent transcription factor with diverse functions in detoxification of xenobiotics, inflammatory responses, and tissue homeostasis. Emerging evidence indicates that AhR also plays an important role in regulating intestinal cell proliferation and tumorigenesis. Here, we review both the pro- and anti-carcinogenic properties of AhR signaling and its potential role as a therapeutic target in CRC.

  12. Binding studies using Pichia pastoris expressed human aryl hydrocarbon receptor and aryl hydrocarbon receptor nuclear translocator proteins.

    Science.gov (United States)

    Zheng, Yujuan; Xie, Jinghang; Huang, Xin; Dong, Jin; Park, Miki S; Chan, William K

    2016-06-01

    The aryl hydrocarbon receptor (AHR) is a transcription factor which activates gene transcription by binding to its corresponding enhancer as the heterodimer, which is consisted of AHR and the aryl hydrocarbon receptor nuclear translocator (ARNT). Human AHR can be rather difficult to study, when compared among the AHR of other species, since it is relatively unstable and less sensitive to some ligands in vitro. Overexpression of human AHR has been limited to the baculovirus expression, which is costly and tedious due to the need of repetitive baculovirus production. Here we explored whether we could generate abundant amounts of human AHR and ARNT in a better overexpression system for functional study. We observed that human AHR and ARNT can be expressed in Pichia pastoris with yields that are comparable to the baculovirus system only if their cDNAs are optimized for Pichia expression. Fusion with a c-myc tag at their C-termini seems to increase the expression yield. These Pichia expressed proteins can effectively heterodimerize and form the ternary AHR/ARNT/enhancer complex in the presence of β-naphthoflavone or kynurenine. Limited proteolysis using thermolysin can be used to study the heterodimerization of these human AHR and ARNT proteins. PMID:26923060

  13. Aryl hydrocarbon receptor antagonism and its role in rheumatoid arthritis

    Science.gov (United States)

    Nguyen, Nam Trung; Nakahama, Taisuke; Nguyen, Chi Hung; Tran, Trang Thu; Le, Van Son; Chu, Hoang Ha; Kishimoto, Tadamitsu

    2015-01-01

    Although rheumatoid arthritis (RA) is the most common autoimmune disease, affecting approximately 1% of the population worldwide, its pathogenic mechanisms are poorly understood. Tobacco smoke, an environmental risk factor for RA, contains several ligands of aryl hydrocarbon receptor (Ahr), also known as dioxin receptor. Ahr plays critical roles in the immune system. We previously demonstrated that Ahr in helper T-cells contributes to development of collagen-induced arthritis, a mouse model of RA. Other studies have shown that cigarette smoke condensate and pure Ahr ligands exacerbate RA by altering bone metabolism and inducing proinflammatory responses in fibroblast-like synoviocytes. Consistent with these findings, several Ahr antagonists such as α-naphthoflavone, resveratrol, and GNF351 reverse the effect of Ahr ligands in RA pathogenesis. In this review, we summarize the current knowledge of Ahr function in the immune system and the potential clinical benefits of Ahr antagonism in treating RA.

  14. Aryl hydrocarbon receptor ligands in cancer: friend and foe.

    Science.gov (United States)

    Murray, Iain A; Patterson, Andrew D; Perdew, Gary H

    2014-12-01

    The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that is best known for mediating the toxicity and tumour-promoting properties of the carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin, commonly referred to as ‘dioxin’. AHR influences the major stages of tumorigenesis — initiation, promotion, progression and metastasis — and physiologically relevant AHR ligands are often formed during disease states or during heightened innate and adaptive immune responses. Interestingly, ligand specificity and affinity vary between rodents and humans. Studies of aggressive tumours and tumour cell lines show increased levels of AHR and constitutive localization of this receptor in the nucleus. This suggests that the AHR is chronically activated in tumours, thus facilitating tumour progression. This Review discusses the role of AHR in tumorigenesis and the potential for therapeutic modulation of its activity in tumours. PMID:25568920

  15. Aryl Hydrocarbon Receptor-Dependent Pathways in Immune Regulation.

    Science.gov (United States)

    Gargaro, M; Pirro, M; Romani, R; Zelante, T; Fallarino, F

    2016-08-01

    The idea of possible involvement of the aryl hydrocarbon receptor (AhR) in transplant tolerance can be traced back >30 years, when very low doses of dioxin-the most potent AhR ligand-were found to markedly reduce the generation of cytotoxic T lymphocytes in response to alloantigen challenge in vivo. AhR is a ligand-activated transcription factor that is activated by dioxins and other environmental pollutants. We now know that AhR can bind a broad variety of activating ligands that are disparate in nature, including endogenous molecules and those formed in the gut from food and bacterial products. Consequently, in addition to its classical role as a toxicological signal mediator, AhR is emerging as a transcription factor involved in the regulation of both innate and adaptive immune responses in various immune cell types, including lymphocytes and antigen-presenting cells (APCs). Allograft rejection is mostly a T cell-mediated alloimmune response initiated by the recognition of alloantigens presented by donor and recipient APCs to recipient CD4(+) and CD8(+) T cells. Based on those findings, AhR may function as a critical sensor of outside and inside environments, leading to changes in the immune system that may have relevance in transplantation. PMID:26751261

  16. Evodiamine as a novel antagonist of aryl hydrocarbon receptor

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Hui [State Key Laboratory of Trauma, Burns, and Combined Injury, Department 1, Research Institute of Surgery, Daping Hospital, The Third Military Medical University, Chongqing 400042 (China); Department of Laboratory Medicine, The Affiliated Tenth People' s Hospital, Tongji University, Shanghai 200072 (China); Tu, Yongjiu; Zhang, Chun; Fan, Xia; Wang, Xi [State Key Laboratory of Trauma, Burns, and Combined Injury, Department 1, Research Institute of Surgery, Daping Hospital, The Third Military Medical University, Chongqing 400042 (China); Wang, Zhanli [College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014 (China); Liang, Huaping, E-mail: huaping_liang@yahoo.com.cn [State Key Laboratory of Trauma, Burns, and Combined Injury, Department 1, Research Institute of Surgery, Daping Hospital, The Third Military Medical University, Chongqing 400042 (China)

    2010-11-05

    Research highlights: {yields} Evodiamine interacted with the AhR. {yields} Evodiamine inhibited the specific binding of [{sup 3}H]-TCDD to the AhR. {yields} Evodiamine acts as an antagonist of the AhR. -- Abstract: Evodiamine, the major bioactive alkaloid isolated from Wu-Chu-Yu, has been shown to interact with a wide variety of proteins and modify their expression and activities. In this study, we investigated the interaction between evodiamine and the aryl hydrocarbon receptor (AhR). Molecular modeling results revealed that evodiamine directly interacted with the AhR. Cytosolic receptor binding assay also provided the evidence that evodiamine could interact with the AhR with the K{sub i} value of 28.4 {+-} 4.9 nM. In addition, we observed that evodiamine suppressed the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced nuclear translocation of the AhR and the expression of CYP1A1 dose-dependently. These results suggested that evodiamine was able to bind to the AhR as ligand and exhibit antagonistic effects.

  17. Oculomotor deficits in aryl hydrocarbon receptor null mouse.

    Directory of Open Access Journals (Sweden)

    Aline Chevallier

    Full Text Available The Aryl hydrocarbon Receptor or AhR, a ligand-activated transcription factor, is known to mediate the toxic and carcinogenic effects of various environmental pollutants such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD. Recent studies in Caenorhabditis elegans and Drosophila melanogaster show that the orthologs of the AhR are expressed exclusively in certain types of neurons and are implicated in the development and the homeostasis of the central nervous system. While physiological roles of the AhR were demonstrated in the mammalian heart, liver and gametogenesis, its ontogenic expression and putative neural functions remain elusive. Here, we report that the constitutive absence of the AhR in adult mice (AhR-/- leads to abnormal eye movements in the form of a spontaneous pendular horizontal nystagmus. To determine if the nystagmus is of vestibular, visual, or cerebellar origin, gaze stabilizing reflexes, namely vestibulo-ocular and optokinetic reflexes (VOR and OKR, were investigated. The OKR is less effective in the AhR-/- mice suggesting a deficit in the visuo-motor circuitry, while the VOR is mildly affected. Furthermore, the AhR is expressed in the retinal ganglion cells during the development, however electroretinograms revealed no impairment of retinal cell function. The structure of the cerebellum of the AhR-/- mice is normal which is compatible with the preserved VOR adaptation, a plastic process dependent on cerebellar integrity. Finally, intoxication with TCDD of control adults did not lead to any abnormality of the oculomotor control. These results demonstrate that the absence of the AhR leads to acquired central nervous system deficits in the adults. Given the many common features between both AhR mouse and human infantile nystagmus syndromes, the AhR-/- mice might give insights into the developmental mechanisms which lead to congenital eye disorders.

  18. Hepatic Aryl Hydrocarbon Receptor Attenuates Fibroblast Growth Factor 21 Expression.

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    Girer, Nathaniel G; Murray, Iain A; Omiecinski, Curtis J; Perdew, Gary H

    2016-07-15

    The Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor involved in many physiological processes. Several studies indicate that AHR is also involved in energy homeostasis. Fibroblast growth factor 21 (FGF21) is an important regulator of the fasting and feeding responses. When administered to various genetic and diet-induced mouse models of obesity, FGF21 can attenuate obesity-associated morbidities. Here, we explore the role of AHR in hepatic Fgf21 expression through the use of a conditional, hepatocyte-targeted AHR knock-out mouse model (Cre(Alb)Ahr(Fx/Fx)). Compared with the congenic parental strain (Ahr(Fx/Fx)), non-fasted Cre(Alb)Ahr(Fx/Fx) mice exhibit a 4-fold increase in hepatic Fgf21 expression, as well as elevated expression of the FGF21-target gene Igfbp1 Furthermore, in vivo agonist activation of AHR reduces hepatic Fgf21 expression during a fast. The Fgf21 promoter contains several putative dioxin response elements (DREs). Using EMSA, we demonstrate that the AHR-ARNT heterodimer binds to a specific DRE that overlaps binding sequences for peroxisome proliferator-activated receptor α (PPARα), carbohydrate response element-binding protein (ChREBP), and cAMP response element-binding protein, hepatocyte specific (CREBH). In addition, we reveal that agonist-activated AHR impairs PPARα-, ChREBP-, and CREBH-mediated promoter activity in Hepa-1 cells. Accordingly, agonist treatment in Hepa-1 cells ablates potent ER stress-driven Fgf21 expression, and pre-treatment with AHR antagonist blocks this effect. Finally, we show that pre-treatment of primary human hepatocytes with AHR agonist diminishes PPARα-, glucose-, and ER stress-driven induction of FGF21 expression, indicating the effect is not mouse-specific. Together, our data show that AHR contributes to hepatic energy homeostasis, partly through the regulation of FGF21 expression and signaling. PMID:27226639

  19. Enantiospecific effects of ketoconazole on aryl hydrocarbon receptor.

    Directory of Open Access Journals (Sweden)

    Aneta Novotna

    Full Text Available Azole antifungal ketoconazole (KET was demonstrated to activate aryl hydrocarbon receptor (AhR. Since clinically used KET is a racemic mixture of two cis-enantiomers (2R,4S-(+-KET and (2S,4R-(--KET, we examined the effects of KET enantiomers on AhR signaling pathway. (+-KET dose-dependently activated AhR in human gene reporter cell line AZ-AHR, and displayed 5-20× higher agonist activity (efficacy, as compared to (--KET; both enantiomers were AhR antagonists with equal potency (IC50. Consistently, (+-KET strongly induced CYP1A1 mRNA and protein in human HepG2 cells, while (--KET exerted less than 10% of (+-KET activity. In primary human hepatocytes, both enantiomers preferentially induced CYP1A2 over CYP1A1 mRNA and protein, and the potency of (+-KET was slightly higher as compared to (--KET. Ligand binding assay with guinea pig liver cytosols revealed that both (+-KET and (--KET are weak ligands of AhR that displaced [3H]-TCDD with comparable potency. Similarly, both enantiomers weakly transformed AhR to DNA-binding form with similar potency, as showed by EMSA, in guinea pig liver cytosolic extracts and nuclear extracts from mouse Hepa-1 cells. We also examined effects of KET on glucocorticoid receptor (GR, a regulator of AhR activity. Both KET enantiomers antagonized GR with similar potency, as revealed by gene reporter assay in AZ-GR cell line and down-regulation of tyrosine aminotransferase mRNA in human hepatocytes. Finally, we demonstrate enantiospecific antifungal activities of KET enantiomers in six Candida spp. strains. In conclusion, the significance of current study is providing the first evidence of enatiospecific effects of cis-enantiomers of ketoconazole on AhR-CYP1A pathway.

  20. Chromatin remodeling by curcumin alters endogenous aryl hydrocarbon receptor signaling.

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    Mohammadi-Bardbori, Afshin; Akbarizadeh, Amin Reza; Delju, Fatemeh; Rannug, Agneta

    2016-05-25

    The aim of this study was to gain more information about the mechanisms that regulate expression of the aryl hydrocarbon receptor (AHR) target gene CYP1A1. Human hepatoma cells (HepG2 and Huh7) and human immortalized keratinocytes (HaCaT) were treated with different concentrations of the dietary polyphenolic compound curcumin (CUR) alone or in combination with the natural AHR agonist 6-formylindolo[3,2-b]carbazole (FICZ). In an earlier study, we described that CUR can activate the AHR indirectly by inhibiting metabolic clearance of FICZ. Here, we measured cell viability, activation of AHR signaling, oxidative stress and histone modifying activities in response to CUR at concentrations ranging from 0.1 to 50 μM. We observed apparent non-linear responses on cell viability and activation of AHR signaling. The CYP1A1 expression and the CYP1A1 enzyme activity in the presence of CUR reflected the histone acetylation efficiency observed in nuclear extracts. At the lowest concentration, CUR significantly decreased histone deacetylase activity and increased the FICZ-induced CYP1A1 activity. In contrast, at the highest concentration, CUR increased the formation of reactive oxygen species, significantly inhibited histone acetylation, and temporally decreased FICZ-induced CYP1A1 activity. The results suggest that CUR can both increase and decrease the accessibility of DNA and thereby influence transcriptional responses to the ligand-activated AHR. This suggestion was supported by the fact that chromatin remodeling treatments with trichostatin A, p300, or 5-aza-dC increased CYP1A1 transcription. We conclude that the AHR-dependent transcriptional efficiency is modified by factors that influence the cellular redox status and the chromatin structure. PMID:27041069

  1. CYP63A2, a catalytically versatile fungal P450 monooxygenase capable of oxidizing higher-molecular-weight polycyclic aromatic hydrocarbons, alkylphenols, and alkanes

    Science.gov (United States)

    Cytochrome P450 monooxygenases (P450s) are known to oxidize hydrocarbons albeit with limited substrate specificity across classes of these compounds. Here we report a P450 monooxygenase (CYP63A2) from the model ligninolytic white rot fungus Phanerochaete chrysosporium that was fo...

  2. The impact of cytochrome P4501-inhibitors on aryl hydrocarbon receptor signaling

    OpenAIRE

    Bengtsson, Johanna

    2016-01-01

    The aryl hydrocarbon receptor (AHR) best known as a ligand-activated transcription factor that mediates toxic responses to xenobiotics such as dioxins, is also activated by certain endogenous compounds. Activation of the AHR up-regulates transcription of a large number of genes, including those encoding members of the cytochrome P450 1 family of enzymes (CYP1s). Although the AHR has been shown to be involved in several normal processes, its physiological role remains elusive. The endogenous l...

  3. The Aryl Hydrocarbon Receptor Affects Distinct Tissue Compartments during Ontogeny of the Immune System

    OpenAIRE

    Hogaboam, Jason P.; Moore, Amanda J.; Lawrence, B. Paige

    2007-01-01

    There is growing evidence that prenatal and early postnatal environmental factors influence the development and programming of the immune system, causing long-lasting negative health consequences. The aryl hydrocarbon receptor (AhR) is an important modulator of the development and function of the immune system; however, the mechanism is poorly understood. Exposure to the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin throughout gestation and during lactation yields adult offspring with persi...

  4. Adaptation of the human aryl hydrocarbon receptor to sense microbiota-derived indoles

    OpenAIRE

    Hubbard, Troy D.; Murray, Iain A.; Bisson, William H.; Lahoti, Tejas S.; Krishne Gowda; Amin, Shantu G.; Patterson, Andrew D.; Perdew, Gary H.

    2015-01-01

    Ligand activation of the aryl hydrocarbon (AHR) has profound effects upon the immunological status of the gastrointestinal tract, establishing and maintaining signaling networks, which facilitate host-microbe homeostasis at the mucosal interface. However, the identity of the ligand(s) responsible for such AHR-mediated activation within the gut remains to be firmly established. Here, we combine in vitro ligand binding, quantitative gene expression, protein-DNA interaction and ligand structure ...

  5. Inducibility of aryl hydrocarbon hydroxylase in BALB/c/ki mice exposed to urban air pollution.

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    Mostardi, R A; Ely, D L; Liebelt, A; Grossman, S; Fu, M M

    1981-05-01

    In two separate experiments BALB/c/ki mice were exposed to urban air pollution. Mice exposed to clean air served as controls. In both experiments there were no obvious quantitative or qualitative differences in lung or liver tissue examined by light microscopy. In both experiments higher aryl hydrocarbon hydroxylase activities and higher trace metal concentrations were observed in the mice exposed to polluted urban air. These data are interpreted in terms of health hazards of urban air pollutants. PMID:7265310

  6. Inducibility of aryl hydrocarbon hydroxylase in BALB/c/Ki mice exposed to urban air pollution

    Energy Technology Data Exchange (ETDEWEB)

    Mostardi, R.A. (Univ. of Akron, OH); Ely, D.L.; Liebelt, A.; Grossman, S.; Fu, M.M.

    1981-05-01

    In two separate experiments BALB/c/Kl mice were exposed to urban air pollution. Mice exposed to clean air served as controls. In both experiments there were no obvious quantitative or qualitative differences in lung or liver tissue examined by light microscopy. In both experiments higher aryl hydrocarbon hydroxylase activities and higher trace metal concentrations were observed in the mice exposed to polluted urban air. These data are interpreted in terms of health hazards of urban air pollutants.

  7. AHR2 Mutant Reveals Functional Diversity of Aryl Hydrocarbon Receptors in Zebrafish

    OpenAIRE

    Goodale, Britton C.; La Du, Jane K; Bisson, William H.; Janszen, Derek B.; Waters, Katrina M.; Tanguay, Robert L.

    2012-01-01

    The aryl hydrocarbon receptor (AHR) is well known for mediating the toxic effects of TCDD and has been a subject of intense research for over 30 years. Current investigations continue to uncover its endogenous and regulatory roles in a wide variety of cellular and molecular signaling processes. A zebrafish line with a mutation in ahr2 (ahr2 hu3335), encoding the AHR paralogue responsible for mediating TCDD toxicity in zebrafish, was developed via Targeting Induced Local Lesions IN Genomes (TI...

  8. Short Synthesis of Sulfur Analogues of Polyaromatic Hydrocarbons through Three Palladium-Catalyzed C-H Bond Arylations.

    Science.gov (United States)

    Hagui, Wided; Besbes, Néji; Srasra, Ezzeddine; Roisnel, Thierry; Soulé, Jean-François; Doucet, Henri

    2016-09-01

    An expeditious synthesis of a wide range of phenanthro[9,10-b]thiophene derivatives, which are a class of polyaromatic hydrocarbon (PAH) containing a sulfur atom, is reported. The synthetic scheme involves only two operations from commercially available thiophenes, 2-bromobenzenesulfonyl chlorides and aryl bromides. In the first step, palladium-catalyzed desulfitative arylation using 2-bromobenzenesulfonyl chlorides allows the synthesis of thiophene derivatives, which are substituted at the C4 position by an aryl group containing an ortho-bromo substituent. Then, a palladium-catalyzed one-pot cascade intermolecular C5-arylation of thiophene using aryl bromides followed by intramolecular arylation led to the corresponding phenanthro[9,10-b]thiophenes in a single operation. In addition, PAHs containing two or three sulfur atoms, as well as both sulfur and nitrogen atoms, were also designed by this strategy. PMID:27550151

  9. Quantitative High-Throughput Screening and Confirmation Studies for Identification of Compounds that Activate the Aryl Hydrocarbon Receptor Pathway (SETAC)

    Science.gov (United States)

    The aryl hydrocarbon receptor (AhR) is a transcription factor that mediates adaptive responses to known environmental pollutants, such as aromatic hydrocarbons, through regulation of Phase I and II xenobiotic metabolizing enzymes as well as important growth and differentiation pa...

  10. The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells

    Czech Academy of Sciences Publication Activity Database

    Andrysík, Zdeněk; Vondráček, Jan; Machala, M.; Krčmář, P.; Šindlerová, Lenka; Kranz, A.; Weiss, C.; Faust, D.; Kozubík, Alois; Dietrich, C.

    2007-01-01

    Roč. 615, č. 1-2 (2007), s. 87-97. ISSN 0027-5107 R&D Projects: GA AV ČR(CZ) KJB6004407 Institutional research plan: CEZ:AV0Z50040702 Keywords : aryl hydrocarbon receptor * contact inhibition * polycyclic aromatic hydrocarbons Subject RIV: BO - Biophysics Impact factor: 4.159, year: 2007

  11. Evidence of the aryl hydrocarbon receptor in chemosynthetic mussels from the Gulf of Mexico

    International Nuclear Information System (INIS)

    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that controls expression of various genes including cytochrome P450. Polynuclear aromatic and halogenated aromatic hydrocarbons are agonists for the AhR in fish and mammalian species. Previously, a homologous AhR has not been identified in marine invertebrate species. Chemosynthetic mussels were collected from gas and petroleum seeps in the Gulf of Mexico to investigate the presence of the AhR and the induction of the cytochrome P450 system. Aryl hydrocarbon hydroxylase and glutathione S-transferase activities in the gill and hepatopancreas were elevated in the petroleum seep mussels relative to those from the gas seep. A nuclear AhR in the hepatopancreas was detected in both mussel populations after treatment with [3H]-tetrachlorodibenzo-p-dioxin (tcdd) followed by sucrose density gradient analysis. Gel mobility shift assays using a labeled dioxin responsive element (DRE) oligonucleotide and tcdd-transformed mussel cytosol showed a retarded band which could be competed with excess unlabeled DRE. Results from gel shifts indicated specific binding of the tcdd-mussel AhR complex to its responsible element. Finally, PCR primers designed to amplify a 700 base pair region of the human AhR detected AhR mRNA in both mussel populations. The sequence of this PCR product is being determined. The presence of the AhR in marine invertebrates has important implications in the evolutionary age of the AhR

  12. Anthocyan does not suppress transformation of aryl hydrocarbon receptor induced by dioxin.

    Science.gov (United States)

    Mukai, Rie; Fukuda, Itsuko; Nishiumi, Shin; Hosokawa, Keizo; Kanazawa, Kazuki; Ashida, Hitoshi

    2004-01-01

    Dioxins cause a variety of toxic effects through transformation of a cytosolic aryl hydrocarbon receptor (AhR). We have previously demonstrated that certain natural flavones and flavonols at the dietary levels suppress AhR transformation. In this study, we investigated whether 5 anthocyanidins, 15 anthocyanins, and protocatechuic acid suppress AhR transformation in mouse hepatoma Hepa-1c1c7 cells. All the compounds tested here at 5 microM unexpectedly failed to suppress the transformation induced by 0.1 nM TCDD, indicating that anthocyan does not have a potential to prevent dioxin toxicity. PMID:15630228

  13. Dioxin increases the interaction between aryl hydrocarbon receptor and estrogen receptor alpha at human promoters

    DEFF Research Database (Denmark)

    Ahmed, Shaaima; Valen, Eivind; Sandelin, Albin Gustav;

    2009-01-01

    Recent studies have shown that activated aryl hydrocarbon receptor (AHR) induced the recruitment of estrogen receptor- (ER ) to AHR-regulated genes and that AHR is recruited to ER -regulated genes. However, these findings were limited to a small number of well-characterized AHR- or ER -responsive...... ER to AHR target genes but also that AHR is recruited to estrogen-responsive regions in a gene-specific manner, suggesting that AHR utilizes both of these mechanisms to modulate estrogen-dependent signaling....

  14. The Aryl Hydrocarbon Receptor: Differential Contribution to T Helper 17 and T Cytotoxic 17 Cell Development

    OpenAIRE

    Hayes, Mark D.; Ovcinnikovs, Vitalijs; Smith, Andrew G.; Kimber, Ian; Dearman, Rebecca J

    2014-01-01

    The aryl hydrocarbon receptor (AhR) has been shown to be required for optimal Thelper (Th) 17 cell activation. Th17 cells provide immunity against extracellular pathogens and are implicated in autoimmune diseases. Herein, the role of the AhR in cytokine production by Th17, and by the analogous population of T cytotoxic (Tc)17 cells, has been examined. Lymph node Tc (CD8+) and Th (CD4+) cells were isolated by negative selection from naive AhR+/− and AhR−/− mice and polarised to Tc1/Th1 or Tc17...

  15. Characterization of Natural Aryl Hydrocarbon Receptor Agonists from Cassia Seed and Rosemary

    OpenAIRE

    Yoshiaki Amakura; Morio Yoshimura; Masashi Takaoka; Haruka Toda; Tomoaki Tsutsumi; Rieko Matsuda; Reiko Teshima; Masafumi Nakamura; Hiroshi Handa; Takashi Yoshida

    2014-01-01

    Many recent studies have suggested that activation of the aryl hydrocarbon receptor (AhR) reduces immune responses, thus suppressing allergies and autoimmune diseases. In our continuing study on natural AhR agonists in foods, we examined the influence of 37 health food materials on the AhR using a reporter gene assay, and found that aqueous ethanol extracts of cassia seed and rosemary had particularly high AhR activity. To characterize the AhR-activating substances in these samples, the chemi...

  16. The Aryl Hydrocarbon Receptor: Differential Contribution to T Helper 17 and T Cytotoxic 17 Cell Development

    OpenAIRE

    Mark D Hayes; Vitalijs Ovcinnikovs; Smith, Andrew G.; Ian Kimber; Dearman, Rebecca J.

    2014-01-01

    The aryl hydrocarbon receptor (AhR) has been shown to be required for optimal Thelper (Th) 17 cell activation. Th17 cells provide immunity against extracellular pathogens and are implicated in autoimmune diseases. Herein, the role of the AhR in cytokine production by Th17, and by the analogous population of T cytotoxic (Tc)17 cells, has been examined. Lymph node Tc (CD8(+)) and Th (CD4(+)) cells were isolated by negative selection from naive AhR(+/-) and AhR(-/-) mice and polarised to Tc1/Th1...

  17. Development of a series of aryl pyrimidine kynurenine monooxygenase inhibitors as potential therapeutic agents for the treatment of Huntington's disease.

    Science.gov (United States)

    Toledo-Sherman, Leticia M; Prime, Michael E; Mrzljak, Ladislav; Beconi, Maria G; Beresford, Alan; Brookfield, Frederick A; Brown, Christopher J; Cardaun, Isabell; Courtney, Stephen M; Dijkman, Ulrike; Hamelin-Flegg, Estelle; Johnson, Peter D; Kempf, Valerie; Lyons, Kathy; Matthews, Kimberly; Mitchell, William L; O'Connell, Catherine; Pena, Paula; Powell, Kendall; Rassoulpour, Arash; Reed, Laura; Reindl, Wolfgang; Selvaratnam, Suganathan; Friley, Weslyn Ward; Weddell, Derek A; Went, Naomi E; Wheelan, Patricia; Winkler, Christin; Winkler, Dirk; Wityak, John; Yarnold, Christopher J; Yates, Dawn; Munoz-Sanjuan, Ignacio; Dominguez, Celia

    2015-02-12

    We report on the development of a series of pyrimidine carboxylic acids that are potent and selective inhibitors of kynurenine monooxygenase and competitive for kynurenine. We describe the SAR for this novel series and report on their inhibition of KMO activity in biochemical and cellular assays and their selectivity against other kynurenine pathway enzymes. We describe the optimization process that led to the identification of a program lead compound with a suitable ADME/PK profile for therapeutic development. We demonstrate that systemic inhibition of KMO in vivo with this lead compound provides pharmacodynamic evidence for modulation of kynurenine pathway metabolites both in the periphery and in the central nervous system. PMID:25590515

  18. The aryl hydrocarbon receptor nuclear translocator (Arnt) is required for tumor initiation by benzo[a]pyrene

    OpenAIRE

    Shi, Shengli; Yoon, Diana Y.; Hodge-Bell, Kimberly C.; Bebenek, Ilona G.; Whitekus, Michael J.; Zhang, Ruixue; Cochran, Alistair J.; Huerta-Yepez, Sara; Yim, Sun-Hee; Gonzalez, Frank J; Jaiswal, Anil K.; Hankinson, Oliver

    2009-01-01

    Benzo[a]pyrene (B[a]P) is a ligand for the aryl hydrocarbon receptor (Ahr). After binding ligand, Ahr dimerizes with the aryl hydrocarbon receptor nuclear translocator (Arnt) protein, and the dimer upregulates the transcription of Cyp1a1, Cyp1b1 and other enzymes involved in the metabolic activation of B[a]P. Arnt null mice die in utero. Mice in which Arnt deletion occurs constitutively in the epidermis die perinatally. In the current study, mice were developed in which the Arnt gene could be...

  19. The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A

    International Nuclear Information System (INIS)

    Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction

  20. The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Shoko, E-mail: satosho@rs.tus.ac.jp [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan); Shirakawa, Hitoshi, E-mail: shirakah@m.tohoku.ac.jp [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan); Tomita, Shuhei, E-mail: tomita@med.tottori-u.ac.jp [Division of Molecular Pharmacology, Department of Pathophysiological and Therapeutic Science, Yonago 683-8503 (Japan); Tohkin, Masahiro, E-mail: tohkin@phar.nagoya-cu.ac.jp [Department of Medical Safety Science, Graduate School of Pharmaceutical Science, Nagoya City University, Nagoya 267-8603 (Japan); Gonzalez, Frank J., E-mail: gonzalef@mail.nih.gov [Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 (United States); Komai, Michio, E-mail: mkomai@m.tohoku.ac.jp [Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555 (Japan)

    2013-11-15

    Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction.

  1. Interactions between polymorphisms in the aryl hydrocarbon receptor signalling pathway and exposure to persistent organochlorine pollutants affect human semen quality

    DEFF Research Database (Denmark)

    Brokken, L J S; Lundberg, P J; Spanò, M;

    2014-01-01

    Persistent organic pollutants (POPs) may affect male reproductive function. Many dioxin-like POPs exert their effects by activation of the aryl hydrocarbon receptor (AHR) signalling pathway. We analysed whether gene-environment interactions between polymorphisms in AHR (R554K) and AHR repressor (...

  2. Direct assessment of cumulative aryl hydrocarbon receptor agonist activity in sera from experimentally exposed mice and environmentally exposed humans

    DEFF Research Database (Denmark)

    Schlezinger, Jennifer J; Bernard, Pamela L; Haas, Amelia;

    2010-01-01

    BACKGROUND: Aryl hydrocarbon receptor (AhR) ligands adversely affect many biological processes. However, assessment of the significance of human exposures is hampered by an incomplete understanding of how complex mixtures affect AhR activation/inactivation. OBJECTIVES: These studies used biologic...

  3. Effect of dioxins on regulation of tyrosine hydroxylase gene expression by aryl hydrocarbon receptor: a neurotoxicology study

    OpenAIRE

    Akahoshi Eiichi; Yoshimura Seiko; Uruno Saeko; Ishihara-Sugano Mitsuko

    2009-01-01

    Abstract Background Dioxins and related compounds are suspected of causing neurological disruption. Epidemiological studies indicated that exposure to these compounds caused neurodevelopmental disturbances such as learning disability and attention deficit hyperactivity disorder, which are thought to be closely related to dopaminergic dysfunction. Although the molecular mechanism of their actions has not been fully investigated, a major participant in the process is aryl hydrocarbon receptor (...

  4. Aqueous high-temperature chemistry of carbo- and heterocycles. 29. Reactions of aryl hydrocarbons, aryl N-oxides and aryl carbonyl compounds in supercritical water at 460{degree}C

    Energy Technology Data Exchange (ETDEWEB)

    Katritzky, A.R.; Ignatchenko, E.S.; Allin, S.M.; Barcock, R.A.; Siskin, M.; Hudson, C.W. [University of Florida, Gainesville, FL (United States). Center for Heterocyclic Compounds, Dept. of Chemistry

    1997-01-01

    A series of aryl hydrocarbons, aryl N-oxides, and aryl carbonyl compounds were subjected to thermolysis at 460{degree}C in water alone, in 15% aqueous formic acid, in 15% aqueous sodium formate, and, for comparison of purely thermal reactions, in cyclohexane. The runs were carried out initially for 7 min and, in most cases, also for 1 h. The aryl carbonyl substrates underwent mainly carbonyl reduction mainly under reduction conditions, with ring opening only observed in significant amounts for 1,4-naphthoquinone and 3,4-benzocoumarin. The arenes produced mainly reduction products with only low yields of ring-opened products observed. Aryl oximes underwent significant denitrogenation and subsequent reduction with only very little cleavage to simpler aromatic systems. The N-oxides underwent deoxygenation, and in the case of isoquinoline, ring opening of the heterocyclce was prevalent. 2-Aminobiphenyl was denitrogenated and cleaved to simpler systems in cyclohexane, but in the aqueous systems it underwent mainly cyclization to yield carbazole with only low yields of denitrogenated products. 2-Phenylphenol was unreactive under aqueous conditions with only low yields of deoxygenated products observed. 11 refs., 15 figs., 1 tab.

  5. Potential protective mechanisms of aryl hydrocarbon receptor (AHR) signaling in benign prostatic hyperplasia.

    Science.gov (United States)

    Mehta, Vatsal; Vezina, Chad M

    2011-01-01

    The aryl hydrocarbon receptor (AHR) is an evolutionarily conserved ligand activated transcription factor best known for its role in mediating toxic responses to dioxin-like environmental contaminants. However, AHR signaling has also emerged as an active participant in processes of normal development and disease progression. Here, we review the role of AHR signaling in prostate development and disease processes, with a particular emphasis on benign prostatic hyperplasia (BPH). Inappropriate AHR activation has recently been associated with a decreased risk of symptomatic BPH in humans and has been shown to impair prostate development and disrupt endocrine signaling in rodents. We highlight known physiological responses to AHR activation in prostate and other tissues and discuss potential mechanisms by which it may act in adult human prostate to protect against symptomatic BPH. PMID:21684673

  6. Enzyme induction and histopathology elucidate aryl hydrocarbon receptor-mediated versus non-aryl hydrocarbon receptor-mediated effects of Aroclor 1268 in American mink (Neovison vison).

    Science.gov (United States)

    Folland, William R; Newsted, John L; Fitzgerald, Scott D; Fuchsman, Phyllis C; Bradley, Patrick W; Kern, John; Kannan, Kurunthachalam; Zwiernik, Matthew J

    2016-03-01

    Polychlorinated biphenyl (PCB) concentrations reported in preferred prey and blubber of bottlenose dolphins from the Turtle-Brunswick River estuary (Georgia, USA) suggest the potential for adverse effects. However, PCBs in Turtle-Brunswick River estuary dolphins are primarily derived from Aroclor 1268, and predicting toxic effects of Aroclor 1268 is uncertain because of the mixture's unique composition and associated physiochemical characteristics. These differences suggest that toxicity benchmarks for other PCB mixtures may not be relevant to dolphins exposed to Aroclor 1268. American mink (Neovison vison) were used as a surrogate model for cetaceans to characterize mechanisms of action associated with Aroclor 1268 exposure. Mink share similarities in phylogeny and life history with cetaceans and are characteristically sensitive to PCBs, making them an attractive surrogate species for marine mammals in ecotoxicity studies. Adult female mink and a subsequent F1 generation were exposed to Aroclor 1268 through diet, and effects on enzyme induction, histopathology, thyroid hormone regulation, hematology, organ weights, and body condition index were compared to a negative control and a 3,3',4,4',5-pentachlorobiphenyl (PCB 126)-positive control. Aroclor 1268 dietary exposure concentrations ranged from 1.8 µg/g wet weight to 29 µg/g wet weight. Anemia, hypothyroidism, and hepatomegaly were observed in mink exposed to Aroclor 1268 beyond various dietary thresholds. Cytochrome P450 induction and squamous epithelial proliferation jaw lesions were low in Aroclor 1268 treatments relative to the positive control. Differences in enzyme induction and the development of squamous epithelial proliferation jaw lesions between Aroclor 1268 treatments and the positive control, coupled with effects observed in Aroclor 1268 treatments not observed in the positive control, indicate that mechanisms additional to the aryl hydrocarbon receptor-mediated pathway are associated with

  7. Aryl Hydrocarbon Receptor Repressor and TiPARP (ARTD14 Use Similar, but also Distinct Mechanisms to Repress Aryl Hydrocarbon Receptor Signaling

    Directory of Open Access Journals (Sweden)

    Laura MacPherson

    2014-05-01

    Full Text Available The aryl hydrocarbon receptor (AHR regulates the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD. The AHR repressor (AHRR is an AHR target gene and functions as a ligand-induced repressor of AHR; however, its mechanism of inhibition is controversial. Recently, we reported that TCDD-inducible poly (ADP-ribose polymerase (TiPARP; ARTD14 also acts as a repressor of AHR, representing a new player in the mechanism of AHR action. Here we compared the ability of AHRR- and TiPARP-mediated inhibition of AHR activity. TCDD increased AHRR mRNA levels and recruitment of AHRR to cytochrome P450 1A1 (CYP1A1 in MCF7 cells. Knockdown of TiPARP, but not AHRR, increased TCDD-induced CYP1A1 mRNA and AHR protein levels. Similarly, immortalized TiPARP−/− mouse embryonic fibroblasts (MEFs and AHRR−/− MEFs exhibited enhanced AHR transactivation. However, unlike TiPARP−/− MEFs, AHRR−/− MEFs did not exhibit increased AHR protein levels. Overexpression of TiPARP in AHRR−/− MEFs or AHRRΔ8, the active isoform of AHRR, in TiPARP−/− MEFs reduced TCDD-induced CYP1A1 mRNA levels, suggesting that they independently repress AHR. GFP-AHRRΔ8 and GFP-TiPARP expressed as small diffuse nuclear foci in MCF7 and HuH7 cells. GFP-AHRRΔ8_Δ1-49, which lacks its putative nuclear localization signal, localized to both the nucleus and the cytoplasm, while the GFP-AHRRΔ8_Δ1-100 mutant localized predominantly in large cytoplasmic foci. Neither GFP-AHRRΔ8_Δ1-49 nor GFP-AHRRΔ8_Δ1-100 repressed AHR. Taken together, AHRR and TiPARP repress AHR transactivation by similar, but also different mechanisms.

  8. Polymorphism of the aryl-hydrocarbon receptor gene in intron 10 of human cancers

    Directory of Open Access Journals (Sweden)

    M. Rocas

    2011-11-01

    Full Text Available Polychlorinated dibenzo-p-dioxins (PCDDs and related halogenated aromatic hydrocarbons (e.g., PCDFs, often called "dioxins", are ubiquitously present environmental contaminants. Some of them, notably 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, are among the most toxic synthetic compounds known. The biological effects of dioxins are mediated via the aryl hydrocarbon receptor (AhR. Mutations in the AhR transactivation domain are linked to sensitivity to the acute lethality of TCDD. We present here a study of AhR gene polymorphism in normal and cancer human tissues affecting pre-mRNA splicing in the AhR gene-coding transactivation domain region (exon 10, intron 10, exon 11 region, previously shown to be associated with AhR dysfunction. We tested 126 pairs of normal and cancer tissue samples from liver, lung, stomach, kidney, mucous, breast, and pancreas of 49 males and 77 females (45-70 years of age. We used in vitro splicing assay, RT-PCR and sequencing methods. Our results showed that in an in vitro system it is possible to reconstitute cellular pre-mRNA splicing events. Tested cancer tissues did not contain mutations in the AhR transactivation domain region when the DNA sequences were compared with those from normal tissues. There were also no differences in AhR mRNA splice variants between normal and malignant breast tissues and no polymorphisms in the studied regions or cDNA.

  9. Polymorphism of the aryl-hydrocarbon receptor gene in intron 10 of human cancers.

    Science.gov (United States)

    Rocas, M; Jakubauskiene, E; Kanopka, A

    2011-11-01

    Polychlorinated dibenzo-p-dioxins (PCDDs) and related halogenated aromatic hydrocarbons (e.g., PCDFs), often called "dioxins", are ubiquitously present environmental contaminants. Some of them, notably 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are among the most toxic synthetic compounds known. The biological effects of dioxins are mediated via the aryl hydrocarbon receptor (AhR). Mutations in the AhR transactivation domain are linked to sensitivity to the acute lethality of TCDD. We present here a study of AhR gene polymorphism in normal and cancer human tissues affecting pre-mRNA splicing in the AhR gene-coding transactivation domain region (exon 10, intron 10, exon 11 region), previously shown to be associated with AhR dysfunction. We tested 126 pairs of normal and cancer tissue samples from liver, lung, stomach, kidney, mucous, breast, and pancreas of 49 males and 77 females (45-70 years of age). We used in vitro splicing assay, RT-PCR and sequencing methods. Our results showed that in an in vitro system it is possible to reconstitute cellular pre-mRNA splicing events. Tested cancer tissues did not contain mutations in the AhR transactivation domain region when the DNA sequences were compared with those from normal tissues. There were also no differences in AhR mRNA splice variants between normal and malignant breast tissues and no polymorphisms in the studied regions or cDNA. PMID:22052373

  10. Aryl Hydrocarbon Receptor (AHR)-Active Pharmaceuticals Are Selective AHR Modulators in MDA-MB-468 and BT474 Breast Cancer Cells

    OpenAIRE

    Jin, Un-Ho; Lee, Syng-Ook; Safe, Stephen

    2012-01-01

    Leflunomide, flutamide, nimodipine, mexiletine, sulindac, tranilast, 4-hydroxytamoxifen, and omeprazole are pharmaceuticals previously characterized as aryl hydrocarbon receptor (AHR) agonists in various cell lines and animal models. In this study, the eight AHR-active pharmaceuticals were investigated in highly aggressive aryl hydrocarbon (Ah)-responsive BT474 and MDA-MB-468 breast cancer cell lines, and their effects on AHR protein, CYP1A1 (protein and mRNA), CYP1B1 (mRNA), and cell migrati...

  11. Development of a Selective Modulator of Aryl Hydrocarbon (Ah) Receptor Activity that Exhibits Anti-Inflammatory Properties

    OpenAIRE

    Murray, Iain A.; KRISHNEGOWDA, GOWDAHALLI; DiNatale, Brett C.; Flaveny, Colin; Chiaro, Chris; Lin, Jyh-Ming; Arun K. Sharma; Amin, Shantu; Perdew, Gary H.

    2010-01-01

    The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, the role of the AHR in normal physiology is still an area of intense investigation. For example, this receptor plays an important role in certain immune responses. We have previously determined that the AHR can mediate repression of acute-phase genes in the liver. For this observation to be therapeutically useful, selective activation of th...

  12. Development of basal and induced aryl hydrocarbon (benzo[a]pyrene) hydroxylase activity in the chicken embryo in ovo.

    OpenAIRE

    Hamilton, J. W.; Denison, M. S.; Bloom, S E

    1983-01-01

    The development of the hepatic microsomal mixed-function oxidase system was studied to determine the basal level of embryonic enzyme activity and the inducibility of this system throughout growth and differentiation. Chicken embryo livers were assayed for basal and inducible hepatic aryl hydrocarbon hydroxylase (AHHase; designated elsewhere as AHH) activity from the first appearance of the liver as a discrete organ at 5 days of incubation (DI) through day 10 after hatching. In addition, whole...

  13. Untersuchung zur Wirkung natürlicher Liganden des `aryl hydrocarbon´ - Rezeptors (AhR)

    OpenAIRE

    Baumgart, Annette

    2004-01-01

    Der `aryl hydrocarbon´-Rezeptor (AhR) ist ein Ligand aktivierter Transkriptionsfaktor, der durch Bindung an spezifische DNA-Elemente (`xenobiotic responsive elements´ (XREs)) Einfluss auf die Expression einer Vielzahl von Genen u.a. Cytochrom P450 (CYP) 1A hat. Liganden des AhR sind unter anderem aromatische halogenierte Kohlenwasserstoffe (z.B: 2,3,7,8-Tetrachlordibenzo-p-dioxin (TCDD)), polyzyklische aromatische Kohlenwasserstoffe und Pharmazeutika. Natürliche Liganden wie Indolderivate sin...

  14. The Effects of Exogenous and Endogenous Ligands of the Aryl Hydrocarbon Receptor on the Activation of Autoimmune Diabetes

    OpenAIRE

    Abu-Rizq, Hana'A

    2012-01-01

    The aryl-hydrocarbon receptor (AhR) is an important receptor found in immune cells. Itfunctions as a detector of environmental toxins, naturally occurring dietary products, andendogenous tryptophan derivatives for induction of gene transcription responses. Previousreports have implicated stimulation of AhR by various ligands in promoting T cellactivation or regulatory function, with effects on autoimmune disease models. Also, effectsof Ah toxins or natural products on increasing or suppressin...

  15. Regulation of mouse small heat shock protein αb-crystallin gene by aryl hydrocarbon receptor.

    Directory of Open Access Journals (Sweden)

    Shuang Liu

    Full Text Available The stress-inducible small heat shock protein (shsp/αB-crystallin gene is expressed highly in the lens and moderately in other tissues. Here we provide evidence that it is a target gene of the aryl hydrocarbon receptor (AhR transcription factor. A sequence (-329/-323, CATGCGA similar to the consensus xenobiotic responsive element (XRE, called here XRE-like, is present in the αBE2 region of αB-crystallin enhancer and can bind AhR in vitro and in vivo. αB-crystallin protein levels were reduced in retina, lens, cornea, heart, skeletal muscle and cultured muscle fibroblasts of AhR(-/- mice; αB-crystallin mRNA levels were reduced in the eye, heart and skeletal muscle of AhR(-/- mice. Increased AhR stimulated αB-crystallin expression in transfection experiments conducted in conjunction with the aryl hydrocarbon receptor nuclear translocator (ARNT and decreased AhR reduced αB-crystallin expression. AhR effect on aB-crystallin promoter activity was cell-dependent in transfection experiments. AhR up-regulated αB-crystallin promoter activity in transfected HeLa, NIH3T3 and COS-7 cells in the absence of exogenously added ligand (TCDD, but had no effect on the αB-crystallin promoter in C(2C(12, CV-1 or Hepa-1 cells with or without TCDD. TCDD enhanced AhR-stimulated αB-crystallin promoter activity in transfected αTN4 cells. AhR could bind to an XRE-like site in the αB-crystallin enhancer in vitro and in vivo. Finally, site-specific mutagenesis experiments showed that the XRE-like motif was necessary for both basal and maximal AhR-induction of αB-crystallin promoter activity. Our data strongly suggest that AhR is a regulator of αB-crystallin gene expression and provide new avenues of research for the mechanism of tissue-specific αB-crystallin gene regulation under normal and physiologically stressed conditions.

  16. Molecular evidence for the existence of an aryl hydrocarbon receptor pathway in scallops Chlamys farreri.

    Science.gov (United States)

    Cai, Yuefeng; Pan, Luqing; Miao, Jingjing

    2016-01-01

    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that controls the expression of a diverse set of genes. In this study we cloned full-length cDNAs encoding an AhR homologue (designated CfAhR, Accession number: FJ588640) from scallop Chlamys farreri. The CfAhR sequence was constituted by an open reading frame (ORF) of 2466bp encoding 821 amino acids. The predicted molecular weight was 93.0kDa. The CfAhR showed a high conservation of the residues and domains essential to the function of AhR, including basic helix-loop-helix (bHLH) and Per-ARNT-Sim (PAS) domains. Phylogenetic analysis demonstrated that it was clustered within the invertebrate AhR branch. CfAhR expression was detected in gill, digestive gland, ovary, spermary, mantle and adductor, and the highest transcription level was observed in gill. Recombinant plasmid CfAhR-pET32a (designated rCfAhR) was successfully expressed in Escherichia coli BL21. To investigate the molecular detoxification mechanism of benzo(a)pyrene (BaP) detoxification-related genes (AhR; aryl hydrocarbon receptor nuclear translocator, ARNT; heat shock protein 90, HSP90; cytochrome P450 1A1, CYP1A1; glutathione S-transferase pi, GST-pi and P glycoprotein, Pgp) in C. farreri gill, real-time quantitative PCR analysis revealed that the mRNA expression level of CfAhR, xenobiotic-metabolizing enzymes and efflux transporters was induced by BaP and was sensitive to BaP exposure time and concentration, suggesting that BaP influenced the expression of a putative AhR/ARNT signaling pathway in scallops. Our results support the possibility that CfAhR genes are early molecular indicators of BaP through a putative CYP signaling pathway in marine bivalves. PMID:26927881

  17. Influence of some anti-inflammatory drugs on the activity of aryl hydrocarbon hydroxylase and the cytochrome P450 content

    Energy Technology Data Exchange (ETDEWEB)

    Mostafa, M.H.; Sheweita, S.A.; Abdel-Moneam, N.M. (Alexandria Univ. (Egypt))

    1990-06-01

    The metabolism of benzo({alpha})pyrene is mediated by the mixed function oxidase system including the cytochrome P450-dependent aryl hydrocarbon hydroxylase. The data of the present study revealed the ability of various commonly used anti-inflammatory drugs to alter the activity of this enzyme system, where all the tested drugs, namely phenyl butazone, ketoprofen, piroxicam, and acetaminophen, caused an increase in both the activity of aryl hydrocarbon hydroxylase and the cytochrome P450 content whether administered as a single dose or as a repeated dose for 6 consecutive days. The percentage of change for all drugs except phenyl butazone was proportional to the duration of drug administration. On the other hand, pyrazole which is chemically related to phenyl butazone, had no significant effect when administered as a single dose but caused a decrease in both studied parameters when administered as a repeated dose for 6 consecutive days. The mechanisms by which these commonly used drugs modify the aryl hydrocarbon hydroxylase activity and the cytochrome p450 content are discussed in the text.

  18. Are styrene oligomers in coastal sediments of an industrial area aryl hydrocarbon-receptor agonists?

    Science.gov (United States)

    Hong, Seongjin; Lee, Junghyun; Lee, Changkeun; Yoon, Seo Joon; Jeon, Seungyeon; Kwon, Bong-Oh; Lee, Jong-Hyeon; Giesy, John P; Khim, Jong Seong

    2016-06-01

    Effect-directed analysis (EDA) was performed to identify the major aryl hydrocarbon receptor (AhR) agonists in sediments collected from a highly industrialized area (Lake Shihwa, Korea). Great AhR-mediated potencies were found in fractions containing aromatic compounds with log Kow values of 5-8, and relatively great concentrations of styrene oligomers (SOs) and polycyclic aromatic hydrocarbons (PAHs) were detected in those fractions. Until now, there was little information on occurrences and toxic relative potencies (RePs) of SOs in coastal environments. In the present study; i) distributions and compositions, ii) AhR binding affinities, and iii) contributions of SOs to total AhR-mediated potencies were determined in coastal sediments. Elevated concentrations of 10 SOs were detected in sediments of inland creeks ranging from 61 to 740 ng g(-1) dry mass (dm), while lesser concentrations were found in inner (mean = 33 ng g(-1) dm) and outer regions (mean = 25 ng g(-1) dm) of the lake. Concentrations of PAHs in sediments were comparable to those of SOs. 2,4-diphenyl-1-butene (SD3) was the predominant SO analogue in sediments. SOs and PAHs were accumulated in sediments near sources, and could not be transported to remote regions due to their hydrophobicity. RePs of 3 SOs could be derived, which were 1000- to 10,000-fold less than that of one representative potent AhR active PAH, benzo[a]pyrene. Although concentrations of SOs in sediments were comparable to those of PAHs, the collective contribution of SOs to total AhR-mediated potencies were rather small (plastic in the coastal environment. PMID:27043777

  19. Cell specific effects of PCB 126 on aryl hydrocarbone receptors in follicular cells of porcine ovaries

    Energy Technology Data Exchange (ETDEWEB)

    Wojtowicz, A.; Augustowska, K.; Gregoraszczuk, E. [Lab. of Physiology and Toxicology of Reproduction, Dept. of Animal Physiology, Inst. of Zoology, Jagiellonian Univ., Krakow (Poland)

    2004-09-15

    Polychlorinated biphenyles (PCBs) like other endocrine disrupters could interfere with natural hormones by binding to their receptors and thus mimicking the cellular response to them. They are known to possess either estrogenic or antiestrogenic properties. In our previous papers we demonstrated that PCBs are able to disrupt ovarian steroidogenesis. We found that the coplanar PCB 126 caused the decrease in estradiol secretion in whole cultured pig ovarian follicles. PCB 126 congener is structurally related to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Since TCDD effects are known to be mediated by aryl hydrocarbone receptors (AhRs), we decided to determine if PCB 126 affects signal transduction pathway activated by these receptors. It has been reported that the functional AhR is present in ovary including oocytes, granulosa and theca cells of rat, mouse, rhesus monkey and human ovary. Moreover, the expression of AhR in the rat ovary appeared to be estrous cycle-dependent, thus suggesting that AhR expression may be regulated by fluctuating hormone levels. This study was designed to investigate the effects of the non-ortho-substituted 3,3',4,4',5-pentachlorobiphenyl (PCB126) on the AhR activation, localization and protein level in pig ovarian follicle cells.

  20. Inhibition of the MEK-1/p42 MAP kinase reduces aryl hydrocarbon receptor-DNA interactions

    International Nuclear Information System (INIS)

    2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces expression of the cytochrome P450 1A1 gene, cyp1a1, by binding to its receptor, aryl hydrocarbon receptor (AhR). TCDD-bound AhR translocates to the nucleus and forms a heterodimer with its partner protein, AhR nuclear translocator (Arnt). The AhR/Arnt heterodimer then binds to the dioxin-response elements (DREs) in the cyp1a1 enhancer and stimulates transcription of cyp1a1. We tested whether kinase pathways are involved in this process by treating Hepa1c1c7 cells with kinase inhibitors. The MEK-1 inhibitor PD98059 reduced TCDD-induced transcription of cyp1a1. TCDD treatment results in phosphorylation of p44/p42 mitogen-activated protein kinase (MAPK), a substrate of MEK-1. Overexpression of dominant negative form of p42 MAPK suppressed TCDD-dependent transcription of a reporter gene controlled by dioxin-response elements (DREs), and pretreatment with PD98059 also blocked this transcription. PD98059 pretreatment also inhibited TCDD-induced DRE binding of the AhR/Arnt heterodimer. Together these results indicate that TCDD activates the MEK-1/p44/p42 MAPK pathway, which in turn activates AhR and so facilitates binding of AhR to the cyp1a1 DRE

  1. Anthocyans fail to suppress transformation of aryl hydrocarbon receptor induced by dioxin.

    Science.gov (United States)

    Mukai, Rie; Fukuda, Itsuko; Hosokawa, Keizo; Nishiumi, Shin; Kaneko, Atsushi; Ashida, Hitoshi

    2005-05-01

    Dioxins induce adverse effects through transformation of the cytosolic aryl hydrocarbon receptor (AhR). Our previous study found that flavones and flavonols at dietary levels suppress AhR transformation. In the present study, we investigated whether 20 anthocyans dissolved in trifluoroacetic acid (TFA)-MeOH suppressed AhR transformation in a cell-free system and in Hepa-1c1c7 cells. Although four compounds at 50 muM suppressed 0.1 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced AhR transformation and their effects were dose-dependent in the cell-free system, they were ineffective at 0.5 muM, which is close to physiological concentration. Moreover, no anthocyan at 50 muM tested here suppressed 0.1 nM TCDD-induced AhR transformation in Hepa-1c1c7 cells. We also confirmed that protocatechuic acid and related compounds, which are possible metabolites of anthocyans, did not affect the transformation in the cell-free system. It is concluded that anthocyans are not suitable candidates for protection from dioxin toxicity. PMID:15914907

  2. Ligand independent aryl hydrocarbon receptor inhibits lung cancer cell invasion by degradation of Smad4.

    Science.gov (United States)

    Lee, Chen-Chen; Yang, Wen-Hao; Li, Ching-Hao; Cheng, Yu-Wen; Tsai, Chi-Hao; Kang, Jaw-Jou

    2016-07-01

    The aryl hydrocarbon receptor (AhR) is a ligand-dependent-activated transcriptional factor that regulates the metabolism of xenobiotic and endogenous compounds. Although AhR plays a crucial role in air toxicant-induced carcinogenesis, AhR expression was shown to negatively regulate tumorigenesis. Therefore, in the present study, we investigated the effect of AhR without ligand treatment on cancer invasion in lung cancer cell lines. Lung cancer cells expressing lower levels of AhR showed higher invasion ability (H1299 cells) compared with cells expressing higher levels of AhR (A549 cells). Overexpression of AhR in H1299 cells inhibited the invasion ability. We found that vimentin expression was inhibited in AhR-overexpressing H1299 cells. Additionally, the expression of EMT-related transcriptional factors Snail and ID-1 decreased. Interestingly, we found that Smad4 degradation was induced in AhR-overexpressing H1299 cells. Our data showed that AhR could interact with Jun-activation domain binding protein (Jab1) and Smad4, which may cause degradation of Smad4 by the proteasome. Our data suggest that AhR affects the transforming growth factor-β signaling pathway by inducing Smad4 degradation by the proteasome and suppressing tumor metastasis via epithelial to mesenchymal transition reduction in lung cancer cells. PMID:27060206

  3. Activation of aryl hydrocarbon receptor signaling by extracts of teak and other wood dusts.

    Science.gov (United States)

    Wilson, Mark J; Sabbioni, Gabriele; Rando, Roy; Miller, Charles A

    2015-12-01

    Wood dusts, as a group, are categorized as known human carcinogens, but the risks of exposure to specific types of wood dusts and the carcinogenic chemicals they contain are not well studied. Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is linked to the carcinogenic action of specific classes of chemicals. Here we examined whether chemicals in various wood dusts had the potential to activate AhR signaling as a potential toxic mechanism of action. We found that methanol extracts of teak, walnut, mahogany, and poplar dusts contained a wide range of AhR ligand activity, whereas extracts of oak, pine, and other softwoods did not contain appreciable activity. Teak dust extract, being particularly potent, was subjected to chemical analysis. The 2-methylanthraquinone (2-MAQ) accounted for the AhR ligand activity and was present at an average concentration of 0.27 parts per hundred in teak dust. Pure 2-MAQ potently induced AhR signaling (EC50 115 nM), confirming that this was the active ligand. Aqueous extracts of teak dust made using yeast or mammalian cell culture medium also contained robust AhR activity, suggesting the 2-MAQ ligand is soluble at bioactive concentrations in physiologically relevant fluids. The high concentration and potency of 2-MAQ in teak wood suggest it may mediate toxic effects through activation of AhR signaling in exposed wood workers. PMID:24898320

  4. Characterization of natural aryl hydrocarbon receptor agonists from cassia seed and rosemary.

    Science.gov (United States)

    Amakura, Yoshiaki; Yoshimura, Morio; Takaoka, Masashi; Toda, Haruka; Tsutsumi, Tomoaki; Matsuda, Rieko; Teshima, Reiko; Nakamura, Masafumi; Handa, Hiroshi; Yoshida, Takashi

    2014-01-01

    Many recent studies have suggested that activation of the aryl hydrocarbon receptor (AhR) reduces immune responses, thus suppressing allergies and autoimmune diseases. In our continuing study on natural AhR agonists in foods, we examined the influence of 37 health food materials on the AhR using a reporter gene assay, and found that aqueous ethanol extracts of cassia seed and rosemary had particularly high AhR activity. To characterize the AhR-activating substances in these samples, the chemical constituents of the respective extracts were identified. From an active ethyl acetate fraction of the cassia seed extract, eight aromatic compounds were isolated. Among these compounds, aurantio-obtusin, an anthraquinone, elicited marked AhR activation. Chromatographic separation of an active ethyl acetate fraction of the rosemary extract gave nine compounds. Among these compounds, cirsimaritin induced AhR activity at 10-10² μM, and nepitrin and homoplantagenin, which are flavone glucosides, showed marked AhR activation at 10-10³ μM. PMID:24747651

  5. Characterization of Natural Aryl Hydrocarbon Receptor Agonists from Cassia Seed and Rosemary

    Directory of Open Access Journals (Sweden)

    Yoshiaki Amakura

    2014-04-01

    Full Text Available Many recent studies have suggested that activation of the aryl hydrocarbon receptor (AhR reduces immune responses, thus suppressing allergies and autoimmune diseases. In our continuing study on natural AhR agonists in foods, we examined the influence of 37 health food materials on the AhR using a reporter gene assay, and found that aqueous ethanol extracts of cassia seed and rosemary had particularly high AhR activity. To characterize the AhR-activating substances in these samples, the chemical constituents of the respective extracts were identified. From an active ethyl acetate fraction of the cassia seed extract, eight aromatic compounds were isolated. Among these compounds, aurantio-obtusin, an anthraquinone, elicited marked AhR activation. Chromatographic separation of an active ethyl acetate fraction of the rosemary extract gave nine compounds. Among these compounds, cirsimaritin induced AhR activity at 10–102 μM, and nepitrin and homoplantagenin, which are flavone glucosides, showed marked AhR activation at 10–103 μM.

  6. Interaction of fish aryl hydrocarbon receptor paralogs (AHR1 and AHR2) with the retinoblastoma protein

    Energy Technology Data Exchange (ETDEWEB)

    Merson, Rebeka R., E-mail: rmerson@ric.edu [Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 (United States); Biology Department, Rhode Island College, 500 Mt. Pleasant Ave., Providence, RI 02908 (United States); Karchner, Sibel I.; Hahn, Mark E. [Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 (United States)

    2009-08-13

    The aryl hydrocarbon receptor (AHR) mediates the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. In some mammalian cell lines, TCDD induces G1 cell cycle arrest, which depends on an interaction between the AHR and the retinoblastoma tumor suppressor (RB). Mammals possess one AHR, whereas fishes possess two or more AHR paralogs that differ in the domains important for AHR-RB interactions in mammals. To test the hypothesis that fish AHR paralogs differ in their ability to interact with RB, we cloned RB cDNA from Atlantic killifish, Fundulus heteroclitus, and studied the interactions of killifish RB protein with killifish AHR1 and AHR2. In coimmunoprecipitation experiments, in vitro-expressed killifish RB coprecipitated with both AHR1 and AHR2. Consistent with these results, both killifish AHR1 and AHR2 interacted with RB in mammalian two-hybrid assays. These results suggest that both fish AHR1 and AHR2 paralogs may have the potential to influence cell proliferation through interactions with RB.

  7. The Unexpected Role for the Aryl Hydrocarbon Receptor on Susceptibility to Experimental Toxoplasmosis

    Directory of Open Access Journals (Sweden)

    Yuriko Sanchez

    2010-01-01

    Full Text Available The aryl hydrocarbon receptor (AhR is part of a signaling system that is mainly triggered by xenobiotic agents. Increasing evidence suggests that AhR may regulate immunity to infections. To determine the role of AhR in the outcome of toxoplasmosis, we used AhR-/- and wild-type (WT mice. Following an intraperitoneal infection with Toxoplasma gondii (T. gondii, AhR-/- mice succumbed significantly faster than WT mice and displayed greater liver damage as well as higher serum levels of tumor necrosis factor (TNF-α, nitric oxide (NO, and IgE but lower IL-10 secretion. Interestingly, lower numbers of cysts were found in their brains. Increased mortality was associated with reduced expression of GATA-3, IL-10, and 5-LOX mRNA in spleen cells but higher expression of IFN-γ mRNA. Additionally, peritoneal exudate cells from AhR-/- mice produced higher levels of IL-12 and IFN-γ but lower TLR2 expression than WT mice. These findings suggest a role for AhR in limiting the inflammatory response during toxoplasmosis.

  8. RelB, a new partner of aryl hydrocarbon receptor-mediated transcription

    Science.gov (United States)

    Vogel, Christoph F. A.; Sciullo, Eric; Li, Wen; Wong, Pat; Lazennec, Gwendal; Matsumura, Fumio

    2007-01-01

    The NF-κB transcription factor family has a crucial role in rapid responses to stress and pathogens. We show that the NF-κB subunit RelB is functionally associated with the aryl hydrocarbon receptor (AhR) and mediates transcription of chemokines such as Interleukin-8 (IL-8) via activation of AhR and protein kinase A (PKA). RelB physically interacts with AhR and binds to an unrecognized RelB/AhR responsive element (RelBAhRE) of the IL-8 promoter linking two signaling pathways to activate gene transcription. We found a time-dependent recruitment of AhR to the RelBAhRE site of IL-8 mediated by the AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and via activation of PKA. Furthermore, NF-κB-binding sites that are preferentially recognized by RelB/p52 are a target for RelB/AhR complexes without addition of any stimuli implicating the endogenous function of the AhR. RelB/AhR complexes are also found to bind on Xenobiotic Responsive Elements (XRE), and RelB drastically increases the TCDD-induced XRE reporter activity. The interaction of RelB with AhR signaling, and AhR with NF-κB RelB signaling pathways represent a new mechanism of cross talk between the two nuclear receptor paradigms. PMID:17823304

  9. Aryl hydrocarbon receptor-driven signals inhibit collagen synthesis in the gut.

    Science.gov (United States)

    Monteleone, Ivan; Zorzi, Francesca; Marafini, Irene; Di Fusco, Davide; Dinallo, Vincenzo; Caruso, Roberta; Izzo, Roberta; Franzè, Eleonora; Colantoni, Alfredo; Pallone, Francesco; Monteleone, Giovanni

    2016-04-01

    Fibrostrictures (FS) are a major complication of Crohn's disease (CD). Pathogenesis of FS is not fully understood, but activation of fibroblasts and excessive collagen deposition are crucial in the development of FS. Here, we investigated the role of aryl hydrocarbon receptor (AhR) in intestinal fibrosis. AhR RNA and protein expression were evaluated in intestinal fibroblasts of CD patients and controls. CD fibroblasts were stimulated with TGF-β1 or TNF-α in the presence or absence of the AhR activator Ficz, an AhR antagonist CH223191, or a specific AhR-silencing RNA. In CD fibroblasts, TGF-β1 and TNF-α increased Col1A1, Col3A1 and α-SMA transcripts and collagen secretion and this effect was reduced by Ficz and upregulated by CH22319. TGF-β1 or TNF-α induced activation of p38 and ERK1/2 MAP kinases was decreased by Ficz and increased by CH223191. The inhibitory effect of Ficz on Map kinase activation and collagen induction was abolished by AhR silencing. To assess the role of AhR in vivo, mice with trinitrobenzene-sulfonic-acid induced colonic fibrosis were given Ficz or CH223191. Mice given either Ficz or CH223191 produced less or more collagen respectively as compared with control mice. Our results indicate that AhR is a negative regulator of profibrotic signals in the gut. PMID:26786786

  10. Cigarette smoke condensate induces aryl hydrocarbon receptor-dependent changes in gene expression in spermatocytes.

    Science.gov (United States)

    Esakky, Prabagaran; Hansen, Deborah A; Drury, Andrea M; Moley, Kelle H

    2012-12-01

    Cigarette smoke contains numerous compounds that cause oxidative stress and alter gene expression in many tissues, and cigarette smoking is correlated with male infertility. To identify mechanisms by which this occurs, we evaluated expression of antioxidant genes in mouse spermatocytes in response to cigarette smoke condensate (CSC). CSC exposure led to oxidative stress and dose-dependent up-regulation of Hsp90aa1, Ahr, Arnt, Sod1, Sod2, and Cyp1a1 expression in a mouse spermatocyte cell line. An antagonist of the aryl hydrocarbon receptor (AHR) abrogated several CSC-mediated changes in mRNA and protein levels. Consistent with these results, spermatocytes isolated by laser-capture microdissection from CSC-treated mice showed increased expression of several antioxidant genes. In vivo exposure to CSC was genotoxic to spermatocytes, resulting in apoptosis and disruptions to the seminiferous tubules. Our in vivo and in vitro data indicate that CSC-mediated damage to murine spermatocytes is AHR-dependent and is mediated by oxidative stress. PMID:23069111

  11. Phosphorylation inhibits DNA-binding of alternatively spliced aryl hydrocarbon receptor nuclear translocator

    International Nuclear Information System (INIS)

    The basic helix-loop-helix/PER-ARNT-SIM homology (bHLH/PAS) transcription factor ARNT (aryl hydrocarbon receptor nuclear translocator) is a key component of various pathways which induce the transcription of cytochrome P450 and hypoxia response genes. ARNT can be alternatively spliced to express Alt ARNT, containing an additional 15 amino acids immediately N-terminal to the DNA-binding basic region. Here, we show that ARNT and Alt ARNT proteins are differentially phosphorylated by protein kinase CKII in vitro. Phosphorylation had an inhibitory effect on DNA-binding to an E-box probe by Alt ARNT, but not ARNT, homodimers. This inhibitory phosphorylation occurs through Ser77. Moreover, a point mutant, Alt ARNT S77A, shows increased activity on an E-box reporter gene, consistent with Ser77 being a regulatory site in vivo. In contrast, DNA binding by an Alt ARNT/dioxin receptor heterodimer to the xenobiotic response element is not inhibited by phosphorylation with CKII, nor does Alt ARNT S77A behave differently from wild type Alt ARNT in the context of a dioxin receptor heterodimer

  12. The aryl hydrocarbon receptor controls cyclin O to promote epithelial multiciliogenesis

    Science.gov (United States)

    Villa, Matteo; Crotta, Stefania; Dingwell, Kevin S.; Hirst, Elizabeth M. A.; Gialitakis, Manolis; Ahlfors, Helena; Smith, James C.; Stockinger, Brigitta; Wack, Andreas

    2016-01-01

    Epithelia function as barriers against environmental insults and express the transcription factor aryl hydrocarbon receptor (AhR). However, AhR function in these tissues is unknown. Here we show that AhR regulates multiciliogenesis in both murine airway epithelia and in Xenopus laevis epidermis. In air-exposed airway epithelia, induction of factors required for multiciliogenesis, including cyclin O (Ccno) and Multicilin (Mcidas), is AhR dependent, and air exposure induces AhR binding to the Ccno promoter. Submersion and hypoxic conditions impede AhR-dependent Ccno induction. This is mediated by the persistence of Notch signalling, as Notch blockade renders multiciliogenesis and Ccno induction by AhR independent from air exposure. In contrast to Ccno induction, air exposure does not induce the canonical AhR target cytochrome P450 1a1 (Cyp1a1). Inversely, exposure to AhR ligands induces Cyp1a1 but not Ccno and impeded ciliogenesis. These data indicate that AhR involvement in detoxification of environmental pollutants may impede its physiological role, resulting in respiratory pathology. PMID:27554288

  13. Ecological factors drive natural selection pressure of avian aryl hydrocarbon receptor 1 genotypes.

    Science.gov (United States)

    Hwang, Ji-Hee; Park, Jin-Young; Park, Hae-Jeong; Bak, Su-Min; Hirano, Masashi; Iwata, Hisato; Park, Young-Suk; Kim, Eun-Young

    2016-01-01

    The aryl hydrocarbon receptor (AHR) mediates dioxin toxicities. Several studies have suggested that two amino acid residues corresponding to the 324(th) and 380(th) positions in the ligand binding domain (LBD) of the chicken AHR1 (Ile_Ser as high sensitivity, Ile_Ala as moderate sensitivity, and Val_Ala as low sensitivity), could be an important factor determining dioxin sensitivity in avian species. Here, we analyzed the association between ecological factors and AHR1 LBD genotypes of 113 avian species. Cluster analyses showed that 2 major clusters and sub-clusters of the cluster 3 were associated with specific AHR1 genotypes depending on the food, habitat, and migration of the animal. The majority of the species with Ile_Ala type were the Passeriformes, which are omnivorous or herbivorous feeders in the terrestrial environment. The species with Val_Ala type was primarily composed of raptors and waterbirds, which have been exposed to naturally occurring dioxins. An in vitro reporter gene assay revealed that the sensitivity to a natural dioxin, 1,3,7-tribromodibenzo-p-dioxin was in the order of Ile_Ser > Ile_Ala > Val_Ala. These results suggest that ecological factors related to the exposure of natural dioxins contribute to natural selection of the avian AHR1 genotype, which consequently leads to different sensitivity to man-made dioxins. PMID:27283192

  14. CARD9 impacts colitis by altering gut microbiota metabolism of tryptophan into aryl hydrocarbon receptor ligands.

    Science.gov (United States)

    Lamas, Bruno; Richard, Mathias L; Leducq, Valentin; Pham, Hang-Phuong; Michel, Marie-Laure; Da Costa, Gregory; Bridonneau, Chantal; Jegou, Sarah; Hoffmann, Thomas W; Natividad, Jane M; Brot, Loic; Taleb, Soraya; Couturier-Maillard, Aurélie; Nion-Larmurier, Isabelle; Merabtene, Fatiha; Seksik, Philippe; Bourrier, Anne; Cosnes, Jacques; Ryffel, Bernhard; Beaugerie, Laurent; Launay, Jean-Marie; Langella, Philippe; Xavier, Ramnik J; Sokol, Harry

    2016-06-01

    Complex interactions between the host and the gut microbiota govern intestinal homeostasis but remain poorly understood. Here we reveal a relationship between gut microbiota and caspase recruitment domain family member 9 (CARD9), a susceptibility gene for inflammatory bowel disease (IBD) that functions in the immune response against microorganisms. CARD9 promotes recovery from colitis by promoting interleukin (IL)-22 production, and Card9(-/-) mice are more susceptible to colitis. The microbiota is altered in Card9(-/-) mice, and transfer of the microbiota from Card9(-/-) to wild-type, germ-free recipients increases their susceptibility to colitis. The microbiota from Card9(-/-) mice fails to metabolize tryptophan into metabolites that act as aryl hydrocarbon receptor (AHR) ligands. Intestinal inflammation is attenuated after inoculation of mice with three Lactobacillus strains capable of metabolizing tryptophan or by treatment with an AHR agonist. Reduced production of AHR ligands is also observed in the microbiota from individuals with IBD, particularly in those with CARD9 risk alleles associated with IBD. Our findings reveal that host genes affect the composition and function of the gut microbiota, altering the production of microbial metabolites and intestinal inflammation. PMID:27158904

  15. Interaction of fish aryl hydrocarbon receptor paralogs (AHR1 and AHR2) with the retinoblastoma protein

    International Nuclear Information System (INIS)

    The aryl hydrocarbon receptor (AHR) mediates the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. In some mammalian cell lines, TCDD induces G1 cell cycle arrest, which depends on an interaction between the AHR and the retinoblastoma tumor suppressor (RB). Mammals possess one AHR, whereas fishes possess two or more AHR paralogs that differ in the domains important for AHR-RB interactions in mammals. To test the hypothesis that fish AHR paralogs differ in their ability to interact with RB, we cloned RB cDNA from Atlantic killifish, Fundulus heteroclitus, and studied the interactions of killifish RB protein with killifish AHR1 and AHR2. In coimmunoprecipitation experiments, in vitro-expressed killifish RB coprecipitated with both AHR1 and AHR2. Consistent with these results, both killifish AHR1 and AHR2 interacted with RB in mammalian two-hybrid assays. These results suggest that both fish AHR1 and AHR2 paralogs may have the potential to influence cell proliferation through interactions with RB.

  16. Toxicological implications of polymorphisms in receptors for xenobiotic chemicals: The case of the aryl hydrocarbon receptor

    International Nuclear Information System (INIS)

    Mechanistic toxicology has predominantly been focused on adverse effects that are caused by reactive metabolites or by reactive oxygen species. However, many important xenobiotics exert their toxicity, not by generating reactive products, but rather by altering expression of specific genes. In particular, some environmental contaminants target nuclear receptors that function as regulators of transcription. For example, binding of xenobiotic chemicals to steroid receptors is a principle mechanism of endocrine disruption. The aryl hydrocarbon receptor (AHR) mediates toxicity of dioxin-like compounds. In mice, a polymorphism in the AHR ligand-binding domain reduces binding affinity by about 10-fold in the DBA/2 strain compared with the C57BL/6 strain; consequently, dose-response curves for numerous biochemical and toxic effects are shifted about one log to the right in DBA/2 mice. In the Han/Wistar (Kuopio) (H/W) rat strain, a polymorphism causes a deletion of 38 or 43 amino acids from the AHR transactivation domain. This deletion is associated with a greater than 1000-fold resistance to lethality from 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Genes in the conventional AH gene battery (e.g. CYP1A1, CYP1A2, CYP1B1, ALDH3A1, NQO1 and UGT1A1) remain responsive to TCDD in H/W rats despite the large deletion. However, the deletion may selectively alter the receptor's ability to dysregulate specific genes that are key to dioxin toxicity. We are identifying these genes using an expression array approach in dioxin-sensitive vs. dioxin-resistant rat strains and lines. Polymorphisms exist in the human AH receptor, but thus far they have not been shown to have any substantial effect on human responses to AHR-ligands

  17. Aryl hydrocarbon receptor deletion in cerebellar granule neuron precursors impairs neurogenesis.

    Science.gov (United States)

    Dever, Daniel P; Adham, Zachariah O; Thompson, Bryan; Genestine, Matthieu; Cherry, Jonathan; Olschowka, John A; DiCicco-Bloom, Emanuel; Opanashuk, Lisa A

    2016-05-01

    The aryl hydrocarbon receptor (AhR) is a ligand-activated member of the basic-helix-loop-helix/PER-ARNT-SIM(PAS) transcription factor superfamily that also mediates the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Increasing evidence suggests that AhR influences the development of many tissues, including the central nervous system. Our previous studies suggest that sustained AhR activation by TCDD and/or AhR deletion disrupts cerebellar granule neuron precursor (GNP) development. In the current study, to determine whether endogenous AhR controls GNP development in a cell-autonomous manner, we created a GNP-specific AhR deletion mouse, AhR(fx/fx) /Math1(CRE/+) (AhR CKO). Selective AhR deletion in GNPs produced abnormalities in proliferation and differentiation. Specifically, fewer GNPs were engaged in S-phase, as demonstrated by ∼25% reductions in thymidine (in vitro) and Bromodeoxyuridine (in vivo) incorporation. Furthermore, total granule neuron numbers in the internal granule layer at PND21 and PND60 were diminished in AhR conditional knockout (CKO) mice compared with controls. Conversely, differentiation was enhanced, including ∼40% increase in neurite outgrowth and 50% increase in GABARα6 receptor expression in deletion mutants. Our results suggest that AhR activity plays a role in regulating granule neuron number and differentiation, possibly by coordinating this GNP developmental transition. These studies provide novel insights for understanding the normal roles of AhR signaling during cerebellar granule cell neurogenesis and may have important implications for the effects of environmental factors in cerebellar dysgenesis. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 533-550, 2016. PMID:26243376

  18. Harman induces CYP1A1 enzyme through an aryl hydrocarbon receptor mechanism

    International Nuclear Information System (INIS)

    Harman is a common compound in several foods, plants and beverages. Numerous studies have demonstrated its mutagenic, co-mutagenic and carcinogenic effects; however, the exact mechanism has not been fully identified. Aryl hydrocarbon receptor (AhR) is a transcription factor regulating the expression of the carcinogen-activating enzyme; cytochrome P450 1A1 (CYP1A1). In the present study, we examined the ability of harman to induce AhR-mediated signal transduction in human and rat hepatoma cells; HepG2 and H4IIE cells. Our results showed that harman significantly induced CYP1A1 mRNA in a time- and concentration-dependent manner. Similarly, harman significantly induced CYP1A1 at protein and activity levels in a concentration-dependent manner. Moreover, the AhR antagonist, resveratrol, inhibited the increase in CYP1A1 activity by harman. The RNA polymerase inhibitor, actinomycin D, completely abolished the CYP1A1 mRNA induction by harman, indicating a transcriptional activation. The role of AhR in CYP1A1 induction by harman was confirmed by using siRNA specific for human AhR. The ability of harman to induce CYP1A1 was strongly correlated with its ability to stimulate AhR-dependent luciferase activity and electrophoretic mobility shift assay. At post-transcriptional and post-translational levels, harman did not affect the stability of CYP1A1 at the mRNA and the protein levels, excluding other mechanisms participating in the obtained effects. We concluded that harman can directly induce CYP1A1 gene expression in an AhR-dependent manner and may represent a novel mechanism by which harman promotes mutagenicity, co-mutagenicity and carcinogenicity.

  19. Analysis of photoaffinity-labeled aryl hydrocarbon receptor heterogeneity by two-dimensional gel electrophoresis

    International Nuclear Information System (INIS)

    The level of charge heterogeneity in the aryl hydrocarbon receptor (AhR) was examined by high-resolution denaturing two-dimensional (2D) gel electrophoresis. Hepa 1c1c7 cell cytosolic fraction was photoaffinity-labeled with 2-azido-3-[125I]-iodo-7,8-dibromodibenzo-p-dioxin and applied to isoelectric focusing (IEF) tube gels. After optimization of focusing conditions a broad peak of radioactivity was detected in the apparent pI range of 5.2-5.7. IEF tube gels were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by visualization of the radiolabeled AhR by autoradiography; three distinct isoforms were detected. The same 2D electrophoretic isoform pattern was obtained when the AhR from Hepa 1c1c7 was photoaffinity-labeled in cell culture. BPrCl cells, a mutant line derived from Hepa 1c1c7 cells, contain an AhR that is unable to bind to DNA. Photoaffinity-labeled BPrCl cytosolic fractions were subjected to 2D gel electrophoretic analysis resulting in essentially the same molecular weight and isoform pattern as seen in Hepa 1c1c7 cytosol. This result would suggest that if a mutation is present in the BPrCl AhR it has not caused a significant change in its IEF pattern, although a small shift in the pI values was observed. Two-dimensional gel electrophoresis of photoaffinity-labeled cytosolic fractions from HeLa cells, the rat liver tumor cell line McA-RH777, and buffalo rat thymus revealed three isoforms, essentially the same isoform pattern as in Hepa 1c1c7 cells. This would indicate that despite the considerable molecular weight polymorphism between species the level of charge heterogeneity is high conserved

  20. Correlating gene expression with deformities caused by aryl hydrocarbon receptor agonists in zebrafish (Danio rerio)

    Energy Technology Data Exchange (ETDEWEB)

    Bugiak, B.; Weber, L. [Saskatchewan Univ., Saskatoon, SK (Canada)

    2009-07-01

    Exposure to aryl hydrocarbon receptor (AhR) agonists in fish causes lethal disturbances in fish development, but the effects of acute AhR agonist exposure on the cardiovascular system and deformities remain unclear. This study addressed this issue by performing a series of experiments on zebrafish (Danio rerio). The authors hypothesized that genes needed for cardiovascular regulation (PTGS) would exhibit a stronger link to deformities than detoxification enzymes (CYPs). Zebrafish eggs were exposed aqueously until 4 days post-fertilization (dpf) to the AhR agonists benzo(a)pyrene (BaP) or 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD) alone and in combination with the putative AhR antagonists resveratrol or alpha-naphthoflavone (ANF). Gene expression was measured using real-time, reverse transcriptase PCR in zebrafish at 5 and 10 dpf. Although the mortalities did not differ considerably among groups at 10 dpf, the deformities increased significantly after BaP-ANF at 5 dpf and after BaP at 10 dpf, but not after TCDD treatment. CYP and PTGS isozymes exhibited small, but statistically significant changes at 5 dpf. By 10 dpf, the expression returned to control values. In general, CYP1A and PTGS-1 expression at 5 dpf were positively correlated with deformities, while all other genes were negatively correlated with deformities. It was concluded that changes in CYP1A, CYP1C2, and PTGS-1 gene expression at 5 dpf are associated with developmental deformities, but additional work is needed to determine which has the most important mechanistic link.

  1. Identification of a probiotic bacteria-derived activator of the aryl hydrocarbon receptor that inhibits colitis.

    Science.gov (United States)

    Fukumoto, Suguru; Toshimitsu, Takayuki; Matsuoka, Shuji; Maruyama, Atsushi; Oh-Oka, Kyoko; Takamura, Takeyuki; Nakamura, Yuki; Ishimaru, Kayoko; Fujii-Kuriyama, Yoshiaki; Ikegami, Shuji; Itou, Hiroyuki; Nakao, Atsuhito

    2014-01-01

    The aryl hydrocarbon receptor (AhR) recognizes environmental xenobiotics and is originally thought to be involved in the metabolism (detoxification) of the substances. Recently, AhR is highlighted as an important regulator of inflammation. Notably, accumulating evidence suggests that activation of the AhR suppresses inflammatory bowel diseases (IBDs). Therefore, non-toxic AhR activators become attractive drug candidates for IBD. This study identified 1,4-dihydroxy-2-naphthoic acid (DHNA), a precursor of menaquinone (vitamin K2) abundantly produced by Propionibacterium freudenreichii ET-3 isolated from Swiss-type cheese, as an AhR activator. DHNA activated the AhR pathway in human intestinal epithelial cell line Caco2 cells and in the mouse intestine. Oral treatment of mice with DHNA induced anti-microbial proteins RegIIIβ and γ in the intestine, altered intestinal microbial flora and inhibited dextran sodium sulfate (DSS)-induced colitis, which recapitulated the phenotypes of AhR activation in the gut. As DHNA is commercially available in Japan as a prebiotic supplement without severe adverse effects, DHNA or its derivatives might become a promising drug candidate for IBD via AhR activation. The results also implicate that intestinal AhR might act not only as a sensor for xenobiotics in diet and water but also for commensal bacterial activity because DHNA is a precursor of vitamin K2 produced by vitamin K2-synthesizing commensal bacteria as well as propionic bacteria. Hence, DHNA might be a key bacterial metabolite in the host-microbe interaction to maintain intestinal microbial ecosystem. PMID:24518984

  2. Aryl hydrocarbon receptor mediates both proinflammatory and anti-inflammatory effects in lipopolysaccharide-activated microglia.

    Science.gov (United States)

    Lee, Yi-Hsuan; Lin, Chun-Hua; Hsu, Pei-Chien; Sun, Yu-Yo; Huang, Yu-Jie; Zhuo, Jiun-Horng; Wang, Chen-Yu; Gan, Yu-Ling; Hung, Chia-Chi; Kuan, Chia-Yi; Shie, Feng-Shiun

    2015-07-01

    The aryl hydrocarbon receptor (AhR) regulates peripheral immunity; but its role in microglia-mediated neuroinflammation in the brain remains unknown. Here, we demonstrate that AhR mediates both anti-inflammatory and proinflammatory effects in lipopolysaccharide (LPS)-activated microglia. Activation of AhR by its ligands, formylindolo[3,2-b]carbazole (FICZ) or 3-methylcholanthrene (3MC), attenuated LPS-induced microglial immune responses. AhR also showed proinflammatory effects, as evidenced by the findings that genetic silence of AhR ameliorated the LPS-induced microglial immune responses and LPS-activated microglia-mediated neurotoxicity. Similarly, LPS-induced expressions of tumor necrosis factor α (TNFα) and inducible nitric oxide synthase (iNOS) were reduced in the cerebral cortex of AhR-deficient mice. Intriguingly, LPS upregulated and activated AhR in the absence of AhR ligands via the MEK1/2 signaling pathway, which effects were associated with a transient inhibition of cytochrome P450 1A1 (CYP1A1). Although AhR ligands synergistically enhance LPS-induced AhR activation, leading to suppression of LPS-induced microglial immune responses, they cannot do so on their own in microglia. Chromatin immunoprecipitation results further revealed that LPS-FICZ co-treatment, but not LPS alone, not only resulted in co-recruitment of both AhR and NFκB onto the κB site of TNFα gene promoter but also reduced LPS-induced AhR binding to the DRE site of iNOS gene promoter. Together, we provide evidence showing that microglial AhR, which can be activated by LPS, exerts bi-directional effects on the regulation of LPS-induced neuroinflammation, depending on the availability of external AhR ligands. These findings confer further insights into the potential link between environmental factors and the inflammatory brain disorders. PMID:25690886

  3. Association between polymorphisms in the aryl hydrocarbon receptor repressor gene and disseminated testicular germ cell cancer

    Science.gov (United States)

    Brokken, Leon J. S.; Lundberg-Giwercman, Yvonne; Meyts, Ewa Rajpert-De; Eberhard, Jakob; Ståhl, Olof; Cohn-Cedermark, Gabriella; Daugaard, Gedske; Arver, Stefan; Giwercman, Aleksander

    2013-01-01

    In the Western world, testicular germ cell cancer (TGCC) is the most common malignancy of young men. The malignant transformation of germ cells is thought to be caused by developmental and hormonal disturbances, probably related to environmental and lifestyle factors because of rapidly increasing incidence of TGCC in some countries. Additionally, there is a strong genetic component that affects susceptibility. However, genetic polymorphisms that have been identified so far only partially explain the risk of TGCC. Many of the persistent environmental pollutants act through the aryl hydrocarbon receptor (AHR). AHR signaling pathway is known to interfere with reproductive hormone signaling, which is supposed to play a role in the pathogenesis and invasive progression of TGCC. The aim of the present study was to identify whether AHR-related polymorphisms were associated with risk as well as histological and clinical features of TGCC in 367 patients and 537 controls. Haplotype-tagging single-nucleotide polymorphisms (SNPs) were genotyped in genes encoding AHR and AHR repressor (AHRR). Binary logistic regression was used to calculate the risk of TGCC, non-seminoma versus seminoma, and metastasis versus localized disease. Four SNPs in AHRR demonstrated a significant allele association with risk to develop metastases (rs2466287: OR = 0.43, 95% CI 0.21–0.90; rs2672725: OR = 0.49, 95% CI: 0.25–0.94; rs6879758: OR = 0.27, 95% CI: 0.08–0.92; rs6896163: OR = 0.34, 95% CI: 0.12–0.98). This finding supports the hypothesis that compounds acting through AHR may play a role in the invasive progression of TGCC, either directly or through modification of reproductive hormone action. PMID:23420531

  4. Insulin like growth factor 2 regulation of aryl hydrocarbon receptor in MCF-7 breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Tomblin, Justin K.; Salisbury, Travis B., E-mail: salisburyt@marshall.edu

    2014-01-17

    Highlights: •IGF-2 stimulates concurrent increases in AHR and CCND1 expression. •IGF-2 promotes the binding of AHR to the endogenous cyclin D1 promoter. •AHR knockdown inhibits IGF-2 stimulated increases in CCND1 mRNA and protein. •AHR knockdown inhibits IGF-2 stimulated increases in MCF-7 proliferation. -- Abstract: Insulin like growth factor (IGF)-1 and IGF-2 stimulate normal growth, development and breast cancer cell proliferation. Cyclin D1 (CCND1) promotes cell cycle by inhibiting retinoblastoma protein (RB1). The aryl hydrocarbon receptor (AHR) is a major xenobiotic receptor that also regulates cell cycle. The purpose of this study was to investigate whether IGF-2 promotes MCF-7 breast cancer proliferation by inducing AHR. Western blot and quantitative real time PCR (Q-PCR) analysis revealed that IGF-2 induced an approximately 2-fold increase (P < .001) in the expression of AHR and CCND1. Chromatin immunoprecipitation (ChIP), followed by Q-PCR indicated that IGF-2 promoted (P < .001) a 7-fold increase in AHR binding on the CCND1 promoter. AHR knockdown significantly (P < .001) inhibited IGF-2 stimulated increases in CCND1 mRNA and protein. AHR knockdown cells were less (P < .001) responsive to the proliferative effects of IGF-2 than control cells. Collectively, our findings have revealed a new regulatory mechanism by which IGF-2 induction of AHR promotes the expression of CCND1 and the proliferation of MCF-7 cells. This previously uncharacterized pathway could be important for the proliferation of IGF responsive cancer cells that also express AHR.

  5. Aryl hydrocarbon receptor downregulates MYCN expression and promotes cell differentiation of neuroblastoma.

    Directory of Open Access Journals (Sweden)

    Pei-Yi Wu

    Full Text Available Neuroblastoma (NB is the most common malignant disease of infancy. MYCN amplification is a prognostic factor for NB and is a sign of highly malignant disease and poor patient prognosis. In this study, we aimed to investigate novel MYCN-related genes and assess how they affect NB cell behavior. The different gene expression found in 10 MYCN amplification NB tumors and 10 tumors with normal MYCN copy number were analyzed using tissue oligonucleotide microarrays. Ingenuity Pathway Analysis was subsequently performed to identify the potential genes involved in MYCN regulation pathways. Aryl hydrocarbon receptor (AHR, a receptor for dioxin-like compounds, was found to be inversely correlated with MYCN expression in NB tissues. This correlation was confirmed in a further 14 human NB samples. Moreover, AHR expression in NB tumors was found to correlate highly with histological grade of differentiation. In vitro studies revealed that AHR overexpression in NB cells induced spontaneous cell differentiation. In addition, it was found that ectopic expression of AHR suppressed MYCN promoter activity resulting in downregulation of MYCN expression. The suppression effect of AHR on the transcription of MYCN was compensated for by E2F1 overexpression, indicating that E2F1 is involved in the AHR-regulating MYCN pathway. Furthermore, AHR shRNA promotes the expression of E2F1 and MYCN in NB cells. These findings suggest that AHR is one of the upstream regulators of MYCN. Through the modulation of E2F1, AHR regulates MYCN gene expression, which may in turn affect NB differentiation.

  6. Aryl Hydrocarbon Receptor Protects Lungs from Cockroach Allergen-Induced Inflammation by Modulating Mesenchymal Stem Cells.

    Science.gov (United States)

    Xu, Ting; Zhou, Yufeng; Qiu, Lipeng; Do, Danh C; Zhao, Yilin; Cui, Zhuang; Wang, Heng; Liu, Xiaopeng; Saradna, Arjun; Cao, Xu; Wan, Mei; Gao, Peisong

    2015-12-15

    Exposure to cockroach allergen leads to allergic sensitization and increased risk of developing asthma. Aryl hydrocarbon receptor (AhR), a receptor for many common environmental contaminants, can sense not only environmental pollutants but also microbial insults. Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity to modulate immune responses. In this study, we investigated whether AhR can sense cockroach allergens and modulate allergen-induced lung inflammation through MSCs. We found that cockroach allergen-treated AhR-deficient (AhR(-/-)) mice showed exacerbation of lung inflammation when compared with wild-type (WT) mice. In contrast, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an AhR agonist, significantly suppressed allergen-induced mouse lung inflammation. MSCs were significantly reduced in cockroach allergen-challenged AhR(-/-) mice as compared with WT mice, but increased in cockroach allergen-challenged WT mice when treated with TCDD. Moreover, MSCs express AhR, and AhR signaling can be activated by cockroach allergen with increased expression of its downstream genes cyp1a1 and cyp1b1. Furthermore, we tracked the migration of i.v.-injected GFP(+) MSCs and found that cockroach allergen-challenged AhR(-/-) mice displayed less migration of MSCs to the lungs compared with WT. The AhR-mediated MSC migration was further verified by an in vitro Transwell migration assay. Epithelial conditioned medium prepared from cockroach extract-challenged epithelial cells significantly induced MSC migration, which was further enhanced by TCDD. The administration of MSCs significantly attenuated cockroach allergen-induced inflammation, which was abolished by TGF-β1-neutralizing Ab. These results suggest that AhR plays an important role in protecting lungs from allergen-induced inflammation by modulating MSC recruitment and their immune-suppressive activity. PMID:26561548

  7. The activated aryl hydrocarbon receptor synergizes mitogen-induced murine liver hyperplasia

    International Nuclear Information System (INIS)

    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) 24 h 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.

  8. Association between polymorphisms in the aryl hydrocarbon receptor repressor gene and disseminated testicular germ cell cancer

    Directory of Open Access Journals (Sweden)

    Leon J. S. Brokken

    2013-02-01

    Full Text Available In the Western world, testicular germ cell cancer (TGCC is the most common malignancy of young men. The malignant transformation of germ cells is thought to be caused by developmental and hormonal disturbances, probably related to environmental and lifestyle factors because of rapidly increasing incidence of TGCC in some countries. Additionally, there is a strong genetic component that affects susceptibility. However, genetic polymorphisms that have been identified so far only partially explain the risk of TGCC. Many of the persistent environmental pollutants act through the aryl hydrocarbon receptor (AHR. AHR signalling pathway is known to interfere with reproductive hormone signalling, which is supposed to play a role in the pathogenesis and invasive progression of TGCC. The aim of the present study was to identify whether AHR-related polymorphisms were associated with risk as well as histological and clinical features of TGCC in 367 patients and 537 controls. Haplotype-tagging single nucleotide polymorphisms (SNPs were genotyped in genes encoding AHR and AHR repressor (AHRR. Binary logistic regression was used to calculate the risk of TGCC, nonseminoma versus seminoma, and metastasis versus localised disease.Four SNPs in AHRR demonstrated a significant allele association with risk to develop metastases (rs2466287: OR = 0.43, 95% CI 0.21-0.90; rs2672725: OR = 0.49, 95% CI: 0.25-0.94; rs6879758: OR = 0.27, 95% CI: 0.08-0.92; rs6896163: OR = 0.34, 95% CI: 0.12-0.98.This finding supports the hypothesis that compounds acting through AHR may play a role in the invasive progression of TGCC, either directly or through modification of reproductive hormone action.

  9. The aryl hydrocarbon receptor: differential contribution to T helper 17 and T cytotoxic 17 cell development.

    Directory of Open Access Journals (Sweden)

    Mark D Hayes

    Full Text Available The aryl hydrocarbon receptor (AhR has been shown to be required for optimal Thelper (Th 17 cell activation. Th17 cells provide immunity against extracellular pathogens and are implicated in autoimmune diseases. Herein, the role of the AhR in cytokine production by Th17, and by the analogous population of T cytotoxic (Tc17 cells, has been examined. Lymph node Tc (CD8(+ and Th (CD4(+ cells were isolated by negative selection from naive AhR(+/- and AhR(-/- mice and polarised to Tc1/Th1 or Tc17/Th17 phenotypes with appropriate cytokines. Cell differentiation was assessed as a function of mRNA and protein (ELISA and flow cytometry expression for interferon (IFN-γ and for key Th17 cytokines. In AhR(+/- mice, Th17 cells displayed an exclusive IL-17 profile, which was markedly inhibited by a selective AhR antagonist to levels observed in AhR knockout mice. Addition of the natural AhR agonist 6-formylindolo[3,2-b]carbazole (FICZ markedly enhanced Th17 cell activity in the heterozygotes. In contrast, Tc17 cells polarised into 3 distinct subsets: producing either IL-17 or IFN-γ alone, or both cytokines. Blocking AhR was also detrimental to Tc17 development, with reduced responses recorded in AhR(-/- mice and antagonist-mediated reduction of IL-17 expression in the heterozygotes. However, Tc17 cells were largely refractory to exogenous FICZ, presumably because Tc17 cells express baseline AhR mRNA, but unlike Th17 cells, there is no marked up-regulation during polarisation. Thus, Th17 cell development is more dependent upon AhR activation than is Tc17 cell development, suggesting that endogenous AhR ligands play a much greater role in driving Th17 cell responses.

  10. The aryl hydrocarbon receptor: differential contribution to T helper 17 and T cytotoxic 17 cell development.

    Science.gov (United States)

    Hayes, Mark D; Ovcinnikovs, Vitalijs; Smith, Andrew G; Kimber, Ian; Dearman, Rebecca J

    2014-01-01

    The aryl hydrocarbon receptor (AhR) has been shown to be required for optimal Thelper (Th) 17 cell activation. Th17 cells provide immunity against extracellular pathogens and are implicated in autoimmune diseases. Herein, the role of the AhR in cytokine production by Th17, and by the analogous population of T cytotoxic (Tc)17 cells, has been examined. Lymph node Tc (CD8(+)) and Th (CD4(+)) cells were isolated by negative selection from naive AhR(+/-) and AhR(-/-) mice and polarised to Tc1/Th1 or Tc17/Th17 phenotypes with appropriate cytokines. Cell differentiation was assessed as a function of mRNA and protein (ELISA and flow cytometry) expression for interferon (IFN)-γ and for key Th17 cytokines. In AhR(+/-) mice, Th17 cells displayed an exclusive IL-17 profile, which was markedly inhibited by a selective AhR antagonist to levels observed in AhR knockout mice. Addition of the natural AhR agonist 6-formylindolo[3,2-b]carbazole (FICZ) markedly enhanced Th17 cell activity in the heterozygotes. In contrast, Tc17 cells polarised into 3 distinct subsets: producing either IL-17 or IFN-γ alone, or both cytokines. Blocking AhR was also detrimental to Tc17 development, with reduced responses recorded in AhR(-/-) mice and antagonist-mediated reduction of IL-17 expression in the heterozygotes. However, Tc17 cells were largely refractory to exogenous FICZ, presumably because Tc17 cells express baseline AhR mRNA, but unlike Th17 cells, there is no marked up-regulation during polarisation. Thus, Th17 cell development is more dependent upon AhR activation than is Tc17 cell development, suggesting that endogenous AhR ligands play a much greater role in driving Th17 cell responses. PMID:25203682

  11. AHR2 mutant reveals functional diversity of aryl hydrocarbon receptors in zebrafish.

    Directory of Open Access Journals (Sweden)

    Britton C Goodale

    Full Text Available The aryl hydrocarbon receptor (AHR is well known for mediating the toxic effects of TCDD and has been a subject of intense research for over 30 years. Current investigations continue to uncover its endogenous and regulatory roles in a wide variety of cellular and molecular signaling processes. A zebrafish line with a mutation in ahr2 (ahr2(hu3335, encoding the AHR paralogue responsible for mediating TCDD toxicity in zebrafish, was developed via Targeting Induced Local Lesions IN Genomes (TILLING and predicted to express a non-functional AHR2 protein. We characterized AHR activity in the mutant line using TCDD and leflunomide as toxicological probes to investigate function, ligand binding and CYP1A induction patterns of paralogues AHR2, AHR1A and AHR1B. By evaluating TCDD-induced developmental toxicity, mRNA expression changes and CYP1A protein in the AHR2 mutant line, we determined that ahr2(hu3335 zebrafish are functionally null. In silico modeling predicted differential binding of TCDD and leflunomide to the AHR paralogues. AHR1A is considered a non-functional pseudogene as it does not bind TCCD or mediate in vivo TCDD toxicity. Homology modeling, however, predicted a ligand binding conformation of AHR1A with leflunomide. AHR1A-dependent CYP1A immunohistochemical expression in the liver provided in vivo confirmation of the in silico docking studies. The ahr2(hu3335 functional knockout line expands the experimental power of zebrafish to unravel the role of the AHR during development, as well as highlights potential activity of the other AHR paralogues in ligand-specific toxicological responses.

  12. The anti-inflammatory drug leflunomide is an agonist of the aryl hydrocarbon receptor.

    Directory of Open Access Journals (Sweden)

    Edmond F O'Donnell

    Full Text Available BACKGROUND: The aryl hydrocarbon receptor (AhR is a ligand-activated transcription factor that mediates the toxicity and biological activity of dioxins and related chemicals. The AhR influences a variety of processes involved in cellular growth and differentiation, and recent studies have suggested that the AhR is a potential target for immune-mediated diseases. METHODOLOGY/PRINCIPAL FINDINGS: During a screen for molecules that activate the AhR, leflunomide, an immunomodulatory drug presently used in the clinic for the treatment of rheumatoid arthritis, was identified as an AhR agonist. We aimed to determine whether any biological activity of leflunomide could be attributed to a previously unappreciated interaction with the AhR. The currently established mechanism of action of leflunomide involves its metabolism to A771726, possibly by cytochrome P450 enzymes, followed by inhibition of de novo pyrimidine biosynthesis by A771726. Our results demonstrate that leflunomide, but not its metabolite A771726, caused nuclear translocation of AhR into the nucleus and increased expression of AhR-responsive reporter genes and endogenous AhR target genes in an AhR-dependent manner. In silico Molecular Docking studies employing AhR ligand binding domain revealed favorable binding energy for leflunomide, but not for A771726. Further, leflunomide, but not A771726, inhibited in vivo epimorphic regeneration in a zebrafish model of tissue regeneration in an AhR-dependent manner. However, suppression of lymphocyte proliferation by leflunomide or A771726 was not dependent on AhR. CONCLUSIONS: These data reveal that leflunomide, an anti-inflammatory drug, is an agonist of the AhR. Our findings link AhR activation by leflunomide to inhibition of fin regeneration in zebrafish. Identification of alternative AhR agonists is a critical step in evaluating the AhR as a therapeutic target for the treatment of immune disorders.

  13. Balancing intestinal and systemic inflammation through cell type-specific expression of the aryl hydrocarbon receptor repressor

    OpenAIRE

    Olga Brandstätter; Oliver Schanz; Julia Vorac; Jessica König; Tetsushi Mori; Toru Maruyama; Markus Korkowski; Thomas Haarmann-Stemmann; Dorthe von Smolinski; Schultze, Joachim L.; Josef Abel; Charlotte Esser; Haruko Takeyama; Heike Weighardt; Irmgard Förster

    2016-01-01

    As a sensor of polyaromatic chemicals the aryl hydrocarbon receptor (AhR) exerts an important role in immune regulation besides its requirement for xenobiotic metabolism. Transcriptional activation of AhR target genes is counterregulated by the AhR repressor (AhRR) but the exact function of the AhRR in vivo is currently unknown. We here show that the AhRR is predominantly expressed in immune cells of the skin and intestine, different from other AhR target genes. Whereas AhRR antagonizes the a...

  14. Effectiveness of a Prudhoe Bay crude oil and its aliphatic, aromatic and heterocyclic fractions in inducing mortality and aryl hydrocarbon hydroxylase in chick embryo in ovo

    Energy Technology Data Exchange (ETDEWEB)

    Walters, P.; Khan, S.; O' Brien, P.J.O.; Rahimtula, A.T.; Payne, J.F.

    1987-08-01

    Prudhoe Bay crude oil (PBCO) and its aliphatic, aromatic and heterocyclic fractions were tested on the developing chick embryo for (i) embryotoxicity (ii) their ability to induce hepatic and renal cytochrome P450 levels as well as hepatic, renal and pulmonary aryl hydrocarbon hydroxylase activities. On the basis of its concentration in PBCO, the aromatic fraction was responsible for most of the embryotoxicity as well as for the enzyme inducing ability. The NOS fraction constituted less than 7% (w/v) of PbCO but, on a weight equivalent basis, was roughly as potent as the aromatic fraction in causing embryotoxicity and in inducing cytochrome P450 levels and aryl hydrocarbon hydroxylase. The aliphatic fraction was found to be essentially inactive. The results are consistent with the concept that elevation of aryl hydrocarbon hydroxylase levels by certain components of PBCO may lead to increased embroyotoxicity.

  15. Aryl hydrocarbon receptor protects lung adenocarcinoma cells against cigarette sidestream smoke particulates-induced oxidative stress

    International Nuclear Information System (INIS)

    Environmental cigarette smoke has been suggested to promote lung adenocarcinoma progression through aryl hydrocarbon receptor (AhR)-signaled metabolism. However, whether AhR facilitates metabolic activation or detoxification in exposed adenocarcinoma cells remains ambiguous. To address this question, we have modified the expression level of AhR in two human lung adenocarcinoma cell lines and examined their response to an extract of cigarette sidestream smoke particulates (CSSP). We found that overexpression of AhR in the CL1-5 cell line reduced CSSP-induced ROS production and oxidative DNA damage, whereas knockdown of AhR expression increased ROS level in CSSP-exposed H1355 cells. Oxidative stress sensor Nrf2 and its target gene NQO1 were insensitive to AhR expression level and CSSP treatment in human lung adenocarcinoma cells. In contrast, induction of AhR expression concurrently increased mRNA expression of xenobiotic-metabolizing genes CYP1B1, UGT1A8, and UGT1A10 in a ligand-independent manner. It appeared that AhR accelerated xenobiotic clearing and diminished associated oxidative stress by coordinate regulation of a set of phase I and II metabolizing genes. However, the AhR-signaled protection could not shield cells from constant oxidative stress. Prolonged exposure to high concentrations of CSSP induced G0/G1 cell cycle arrest via the p53–p21–Rb1 signaling pathway. Despite no effect on DNA repair rate, AhR facilitated the recovery of cells from growth arrest when CSSP exposure ended. AhR-overexpressing lung adenocarcinoma cells exhibited an increased anchorage-dependent and independent proliferation when recovery from exposure. In summary, our data demonstrated that AhR protected lung adenocarcinoma cells against CSSP-induced oxidative stress and promoted post-exposure clonogenicity. -- Highlights: ► AhR expression level influences cigarette sidestream smoke-induced ROS production. ► AhR reduces oxidative stress by coordinate regulation of

  16. An evolutionarily conserved role for the aryl hydrocarbon receptor in the regulation of movement.

    Directory of Open Access Journals (Sweden)

    Evan G Williams

    2014-09-01

    Full Text Available The BXD genetic reference population is a recombinant inbred panel descended from crosses between the C57BL/6 (B6 and DBA/2 (D2 strains of mice, which segregate for about 5 million sequence variants. Recently, some of these variants have been established with effects on general metabolic phenotypes such as glucose response and bone strength. Here we phenotype 43 BXD strains and observe they have large variation (-5-fold in their spontaneous activity during waking hours. QTL analyses indicate that -40% of this variance is attributable to a narrow locus containing the aryl hydrocarbon receptor (Ahr, a basic helix-loop-helix transcription factor with well-established roles in development and xenobiotic metabolism. Strains with the D2 allele of Ahr have reduced gene expression compared to those with the B6 allele, and have significantly higher spontaneous activity. This effect was also observed in B6 mice with a congenic D2 Ahr interval, and in B6 mice with a humanized AHR allele which, like the D2 allele, is expressed much less and has less enzymatic activity than the B6 allele. Ahr is highly conserved in invertebrates, and strikingly inhibition of its orthologs in D. melanogaster and C. elegans (spineless and ahr-1 leads to marked increases in basal activity. In mammals, Ahr has numerous ligands, but most are either non-selective (e.g. resveratrol or highly toxic (e.g., 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD. Thus, we chose to examine a major environmental influence--long term feeding with high fat diet (HFD--to see if the effects of Ahr are dependent on major metabolic differences. Interestingly, while HFD robustly halved movement across all strains, the QTL position and effects of Ahr remained unchanged, indicating that the effects are independent. The highly consistent effects of Ahr on movement indicate that changes in its constitutive activity have a role on spontaneous movement and may influence human behavior.

  17. Embryotoxicity, teratogenicity, and aryl hydrocarbon hydroxylase activity in Forster's terns on Green Bay, Lake Michigan

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, D.J.; Rattner, B.A.; Sileo, L.; Docherty, D.; Kubiak, T.J.

    1987-02-01

    Known reproductive problems, including congenital malformations and poor hatching success, exist for the state endangered Forster's tern (Sterna forsteri) in Green Bay, Wisconsin. Twenty Forster's tern eggs were collected from separate nests at (i) a natural colony with documented reproductive problems, situated at Green Bay, Lake Michigan, and (ii) an inland colony at Lake Poygan (control) where reproduction was documented as normal. Eggs from the two locations were placed in the same laboratory incubator and candled throughout incubation. Hatching success of Green Bay eggs was 52% of that for controls. Several early embryonic deaths occurred, but most mortality occurred close to the time of hatching. Liver microsomal aryl hydrocarbon hydroxylase activity was elevated approximately threefold in Green Bay hatchlings compared to controls. Green Bay terns that hatched weighed less than controls, had an increased liver to body weight ratio, and had a shorter femur length. Two Green Bay embryos that failed to hatch had anomalies, one with a crossed beak and one with poor ossification of the foot. One Green Bay hatchling had an abnormally ossified ilium. These effects were observed in eggs where there were measurable levels of aryl hydrocarbon hydroxylase inducers including polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins.

  18. Differential effects of indirubin and 2,3,7,8-tetrachlorodibenzo-p-dioxin on the aryl hydrocarbon receptor (AhR) signalling in liver progenitor cells

    Czech Academy of Sciences Publication Activity Database

    Procházková, Jiřina; Kozubík, Alois; Machala, M.; Vondráček, Jan

    2011-01-01

    Roč. 279, 1-3 (2011), s. 146-154. ISSN 0300-483X R&D Projects: GA ČR(CZ) GA524/06/0517 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : indirubin * aryl hydrocarbon receptor * plakoglobin Subject RIV: BO - Biophysics Impact factor: 3.681, year: 2011

  19. Aryl hydrocarbon receptor (AhR) inducers and estrogen receptor (ER) activities in surface sediments of Three Gorges Reservoir, China evaluated with in vitro cell bioassays

    NARCIS (Netherlands)

    Wang, J.; Bovee, T.F.H.; Bi, Y.; Bernhöft, S.; Schramm, K.W.

    2014-01-01

    Two types of biological tests were employed for monitoring the toxicological profile of sediment cores in the Three Gorges Reservoir (TGR), China. In the present study, sediments collected in June 2010 from TGR were analyzed for estrogen receptor (ER)- and aryl hydrocarbon receptor (AhR)-mediated ac

  20. EWS-FLI1 impairs aryl hydrocarbon receptor activation by blocking tryptophan breakdown via the kynurenine pathway.

    Science.gov (United States)

    Mutz, Cornelia N; Schwentner, Raphaela; Kauer, Maximilian O; Katschnig, Anna M; Kromp, Florian; Aryee, Dave N T; Erhardt, Sophie; Goiny, Michel; Alonso, Javier; Fuchs, Dietmar; Kovar, Heinrich

    2016-07-01

    Ewing sarcoma (ES) is an aggressive pediatric tumor driven by the fusion protein EWS-FLI1. We report that EWS-FLI1 suppresses TDO2-mediated tryptophan (TRP) breakdown in ES cells. Gene expression and metabolite analyses reveal an EWS-FLI1-dependent regulation of TRP metabolism. TRP consumption increased in the absence of EWS-FLI1, resulting in kynurenine and kynurenic acid accumulation, both aryl hydrocarbon receptor (AHR) ligands. Activated AHR binds to the promoter region of target genes. We demonstrate that EWS-FLI1 knockdown results in AHR nuclear translocation and activation. Our data suggest that EWS-FLI1 suppresses autocrine AHR signaling by inhibiting TDO2-catalyzed TRP breakdown. PMID:27282934

  1. Aromatic hydrocarbons upregulate glyceraldehyde-3-phosphate dehydrogenase and induce changes in actin cytoskeleton. Role of the aryl hydrocarbon receptor (AhR)

    International Nuclear Information System (INIS)

    Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional enzyme involved in several cellular functions including glycolysis, membrane transport, microtubule assembly, DNA replication and repair, nuclear RNA export, apoptosis, and the detection of nitric oxide stress. Therefore, modifications in the regulatory ability and function of GAPDH may alter cellular homeostasis. We report here that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and β-naphthoflavone, which are well-known ligands for the aryl hydrocarbon receptor (AhR), increase GAPDH mRNA levels in vivo and in vitro, respectively. These compounds fail to induce GAPDH transcription in an AhR-null mouse model, suggesting that the increase in GAPDH level is dependent upon AhR activation. To analyse the consequences of AhR ligands on GAPDH function, mice were treated with TCDD and the level of liver activity of GAPDH was determined. The results showed that TCDD treatment increased GAPDH activity. On the other hand, treatment of Hepa-1 cells with β-naphthoflavone leads to an increase in microfilament density when compared to untreated cultures. Collectively, these results suggest that AhR ligands, such as polycyclic hydrocarbons, can modify GAPDH expression and, therefore, have the potential to alter the multiple functions of this enzyme.

  2. TCDD-Induced Activation of Aryl Hydrocarbon Receptor Inhibits Th17 Polarization and Regulates Non-Eosinophilic Airway Inflammation in Asthma

    OpenAIRE

    Xiao-Ming Li; Juan Peng; Wen Gu; Xue-Jun Guo

    2016-01-01

    The aryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family, has recently been demonstrated to regulate T cell differentiation. Whether AhR activation participates in allergic airway inflammation remains unknown. In the current study, using a non-eosinophilic asthma model, we demonstrate that 2, 3, 7, 8-tetrachlorodibenzo-P-dioxin (TCDD), a potent AhR ligand, reduced the airway infiltration of neutrophils, airway hyperresponsiveness and Th17 cytokine expression. Further...

  3. Association of serum aryl hydrocarbon receptor activity and RBC omega-3 polyunsaturated fatty acids with flow-mediated dilation in healthy, young Hispanic cigarette smokers

    OpenAIRE

    Wiest, Elani F.; Warneke, Alex; Walsh, Mary T.; Langsfeld, Mark; Anderson, Joe; Walker, Mary K

    2014-01-01

    Impaired flow-mediated dilation (FMD) occurs prior to clinical disease in young cigarette smokers. We investigated two potential biomarkers of FMD: serum aryl hydrocarbon receptor (AHR) activity and RBC omega-3 polyunsaturated fatty acids in healthy young Hispanic cigarette smokers. We recruited never (n = 16) and current (n = 16) Hispanic smokers (32 ± 7 years old), excluding individuals with clinical cardiovascular disease. We measured FMD with duplex ultrasound, RBC fatty acids and serum A...

  4. Effect of dioxins on regulation of tyrosine hydroxylase gene expression by aryl hydrocarbon receptor: a neurotoxicology study

    Directory of Open Access Journals (Sweden)

    Akahoshi Eiichi

    2009-06-01

    Full Text Available Abstract Background Dioxins and related compounds are suspected of causing neurological disruption. Epidemiological studies indicated that exposure to these compounds caused neurodevelopmental disturbances such as learning disability and attention deficit hyperactivity disorder, which are thought to be closely related to dopaminergic dysfunction. Although the molecular mechanism of their actions has not been fully investigated, a major participant in the process is aryl hydrocarbon receptor (AhR. This study focused on the effect of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD exposure on the regulation of TH, a rate-limiting enzyme of dopamine synthesis, gene expression by AhR. Methods N2a-Rβ cells were established by transfecting murine neuroblastoma Neuro2a with the rat AhR cDNA. TH expression induced by TCDD was assessed by RT-PCR and Western blotting. Participation of AhR in TCDD-induced TH gene expression was confirmed by suppressing AhR expression using the siRNA method. Catecholamines including dopamine were measured by high-performance liquid chromatography. A reporter gene assay was used to identify regulatory motifs in the promoter region of TH gene. Binding of AhR with the regulatory motif was confirmed by an electrophoretic mobility shift assay (EMSA. Results Induction of TH by TCDD through AhR activation was detected at mRNA and protein levels. Induced TH protein was functional and its expression increased dopamine synthesis. The reporter gene assay and EMSA indicated that AhR directly regulated TH gene expression. Regulatory sequence called aryl hydrocarbon receptor responsive element III (AHRE-III was identified upstream of the TH gene from -285 bp to -167 bp. Under TCDD exposure, an AhR complex was bound to AHRE-III as well as the xenobiotic response element (XRE, though AHRE-III was not identical to XRE, the conventional AhR-binding motif. Conclusion Our results suggest TCDD directly regulate the dopamine system by TH gene

  5. Carnosol, a Constituent of Zyflamend, Inhibits Aryl Hydrocarbon Receptor-Mediated Activation of CYP1A1 and CYP1B1 Transcription and Mutagenesis

    OpenAIRE

    Mohebati, Arash; Guttenplan, Joseph B.; Kochhar, Amit; Zhao, Zhong-Lin; Kosinska, Wieslawa; Subbaramaiah, Kotha; Dannenberg, Andrew J.

    2012-01-01

    The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic-helix-loop-helix family of transcription factors, plays a significant role in polycyclic aromatic hydrocarbon (PAH) induced carcinogenesis. In the upper aerodigestive tract of humans, tobacco smoke, a source of PAHs, activates the AhR leading to increased expression of CYP1A1 and CYP1B1, which encode proteins that convert PAHs to genotoxic metabolites. Inhibitors of Hsp90 ATPase cause a rapid decrease in levels of AhR...

  6. Gene-environment interactions in male reproductive health: special reference to the aryl hydrocarbon receptor signaling pathway

    Directory of Open Access Journals (Sweden)

    Leon J S Brokken

    2014-02-01

    Full Text Available Over the last few decades, there have been numerous reports of adverse effects on the reproductive health of wildlife and laboratory animals caused by exposure to endocrine disrupting chemicals (EDCs. The increasing trends in human male reproductive disorders and the mounting evidence for causative environmental factors have therefore sparked growing interest in the health threat posed to humans by EDCs, which are substances in our food, environment and consumer items that interfere with hormone action, biosynthesis or metabolism, resulting in disrupted tissue homeostasis or reproductive function. The mechanisms of EDCs involve a wide array of actions and pathways. Examples include the estrogenic, androgenic, thyroid and retinoid pathways, in which the EDCs may act directly as agonists or antagonists, or indirectly via other nuclear receptors. Dioxins and dioxin-like EDCs exert their biological and toxicological actions through activation of the aryl hydrocarbon-receptor, which besides inducing transcription of detoxifying enzymes also regulates transcriptional activity of other nuclear receptors. There is increasing evidence that genetic predispositions may modify the susceptibility to adverse effects of toxic chemicals. In this review, potential consequences of hereditary predisposition and EDCs are discussed, with a special focus on the currently available publications on interactions between dioxin and androgen signaling.

  7. Aryl hydrocarbon receptor-dependent enrichment of a megakaryocytic precursor with a high potential to produce proplatelets.

    Science.gov (United States)

    Strassel, Catherine; Brouard, Nathalie; Mallo, Lea; Receveur, Nicolas; Mangin, Pierre; Eckly, Anita; Bieche, Ivan; Tarte, Karin; Gachet, Christian; Lanza, François

    2016-05-01

    The mechanisms regulating megakaryopoiesis and platelet production (thrombopoiesis) are still incompletely understood. Identification of a progenitor with enhanced thrombopoietic capacity would be useful to decipher these mechanisms and to improve our capacity to produce platelets in vitro. Differentiation of peripheral blood CD34(+) cells in the presence of bone marrow-human mesenchymal stromal cells (MSCs) enhanced the production of proplatelet-bearing megakaryocytes (MKs) and platelet-like elements. This was accompanied by enrichment in a MK precursor population exhibiting an intermediate level of CD41 positivity while maintaining its expression of CD34. Following sorting and subculture with MSCs, this CD34(+)CD41(low) population was able to efficiently generate proplatelet-bearing MKs and platelet-like particles. Similarly, StemRegenin 1 (SR1), an antagonist of the aryl hydrocarbon receptor (AhR) transcription factor known to maintain CD34 expression of progenitor cells, led to an enriched CD34(+)CD41(low) fraction and to an increased capacity to generate proplatelet-producing MKs and platelet-like elements ultrastructurally and functionally similar to circulating platelets. The effect of MSCs, like that of SR1, appeared to be mediated by an AhR-dependent mechanism because both culture conditions resulted in repression of its downstream effector CYP1B1. This newly described isolation of a precursor exhibiting strong MK potential could be exploited to study normal and abnormal thrombopoiesis and for in vitro platelet production. PMID:26966088

  8. Ikaros Inhibits Group 3 Innate Lymphoid Cell Development and Function by Suppressing the Aryl Hydrocarbon Receptor Pathway.

    Science.gov (United States)

    Li, Shiyang; Heller, Jennifer J; Bostick, John W; Lee, Aileen; Schjerven, Hilde; Kastner, Philippe; Chan, Susan; Chen, Zongming E; Zhou, Liang

    2016-07-19

    Group 3 innate lymphoid cells (ILC3s) expressing the transcription factor (TF) RORγt are important for the defense and homeostasis of host intestinal tissues. The zinc finger TF Ikaros, encoded by Ikzf1, is essential for the development of RORγt(+) fetal lymphoid tissue inducer (LTi) cells and lymphoid organogenesis, but its role in postnatal ILC3s is unknown. Here, we show that small-intestinal ILC3s had lower Ikaros expression than ILC precursors and other ILC subsets. Ikaros inhibited ILC3s in a cell-intrinsic manner through zinc-finger-dependent inhibition of transcriptional activity of the aryl hydrocarbon receptor, a key regulator of ILC3 maintenance and function. Ablation of Ikzf1 in RORγt(+) ILC3s resulted in increased expansion and cytokine production of intestinal ILC3s and protection against infection and colitis. Therefore, in contrast to being required for LTi development, Ikaros inhibits postnatal ILC3 development and function to regulate gut immune responses at steady state and in disease. PMID:27438771

  9. Differential influences of the aryl hydrocarbon receptor on Th17 mediated responses in vitro and in vivo.

    Directory of Open Access Journals (Sweden)

    João H Duarte

    Full Text Available The aryl hydrocarbon receptor (AhR has been attributed with anti-inflammatory effects in the development of pathological immune responses leading to experimental autoimmune encephalomyelitis (EAE via the induction of regulatory T cells. In agreement with previously published findings, we find that TCDD administration confers protection from EAE, however, this immuno-modulatory effect was not the consequence of de novo Treg generation, but the inhibition of Th17 cell differentiation. Systemic application of FICZ at the time of immunization also reduced EAE pathology albeit to a lesser degree than TCDD. In vitro Th17 differentiation in the presence of AhR agonists, including TCDD, promoted IL-17 and IL-22 expression, but did not induce Treg differentiation. AhR affinity influenced the amounts of IL-17 and IL-22 protein that was secreted by Th17 cells, but did not seem to affect susceptibility to EAE in vivo. Making use of conditional AhR-deficient mice, we show that the anti-inflammatory effect of TCDD depends on AhR activation in both T cells and dendritic cells, further emphasising the ability of TCDD to interfere with T effector cell differentiation in vivo. The dichotomy between the in vivo and in vitro effects of AhR reveals the complexity of the AhR pathway, which has the capacity of affecting different AhR-expressing cell types involved in mounting immune responses, thus participating in defining their outcome.

  10. Toward Understanding the Role of Aryl Hydrocarbon Receptor in the Immune System: Current Progress and Future Trends

    Directory of Open Access Journals (Sweden)

    Hamza Hanieh

    2014-01-01

    Full Text Available The immune system is regulated by distinct signaling pathways that control the development and function of the immune cells. Accumulating evidence suggest that ligation of aryl hydrocarbon receptor (Ahr, an environmentally responsive transcription factor, results in multiple cross talks that are capable of modulating these pathways and their downstream responsive genes. Most of the immune cells respond to such modulation, and many inflammatory response-related genes contain multiple xenobiotic-responsive elements (XREs boxes upstream. Active research efforts have investigated the physiological role of Ahr in inflammation and autoimmunity using different animal models. Recently formed paradigm has shown that activation of Ahr by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or 3,3′-diindolylmethane (DIM prompts the differentiation of CD4+Foxp3+ regulatory T cells (Tregs and inhibits T helper (Th-17 suggesting that Ahr is an innovative therapeutic strategy for autoimmune inflammation. These promising findings generate a basis for future clinical practices in humans. This review addresses the current knowledge on the role of Ahr in different immune cell compartments, with a particular focus on inflammation and autoimmunity.

  11. Aryl hydrocarbon receptor–dependent enrichment of a megakaryocytic precursor with a high potential to produce proplatelets

    Science.gov (United States)

    Brouard, Nathalie; Mallo, Lea; Receveur, Nicolas; Mangin, Pierre; Eckly, Anita; Bieche, Ivan; Tarte, Karin; Gachet, Christian; Lanza, François

    2016-01-01

    The mechanisms regulating megakaryopoiesis and platelet production (thrombopoiesis) are still incompletely understood. Identification of a progenitor with enhanced thrombopoietic capacity would be useful to decipher these mechanisms and to improve our capacity to produce platelets in vitro. Differentiation of peripheral blood CD34+ cells in the presence of bone marrow–human mesenchymal stromal cells (MSCs) enhanced the production of proplatelet-bearing megakaryocytes (MKs) and platelet-like elements. This was accompanied by enrichment in a MK precursor population exhibiting an intermediate level of CD41 positivity while maintaining its expression of CD34. Following sorting and subculture with MSCs, this CD34+CD41low population was able to efficiently generate proplatelet-bearing MKs and platelet-like particles. Similarly, StemRegenin 1 (SR1), an antagonist of the aryl hydrocarbon receptor (AhR) transcription factor known to maintain CD34 expression of progenitor cells, led to an enriched CD34+CD41low fraction and to an increased capacity to generate proplatelet-producing MKs and platelet-like elements ultrastructurally and functionally similar to circulating platelets. The effect of MSCs, like that of SR1, appeared to be mediated by an AhR-dependent mechanism because both culture conditions resulted in repression of its downstream effector CYP1B1. This newly described isolation of a precursor exhibiting strong MK potential could be exploited to study normal and abnormal thrombopoiesis and for in vitro platelet production. PMID:26966088

  12. Kynurenine Modulates MMP-1 and Type-I Collagen Expression Via Aryl Hydrocarbon Receptor Activation in Dermal Fibroblasts.

    Science.gov (United States)

    Poormasjedi-Meibod, Malihe-Sadat; Salimi Elizei, Sanam; Leung, Victor; Baradar Jalili, Reza; Ko, Frank; Ghahary, Aziz

    2016-12-01

    Dermal fibrosis is characterized by a high deposition of extracellular matrix (ECM) and tissue cellularity. Unfortunately all means of treating this condition are unsatisfactory. We have previously reported the anti-fibrotic effects of Kynurenine (Kyn), a tryptophan metabolite, in fibrotic rabbit ear model. Here, we report the mechanism by which Kyn modulates the expression of key ECM components in dermal fibroblasts. The results showed that Kyn activates aryl hydrocarbon receptor (AHR) nuclear translocation and up-regulates cytochrome-P450 (CYP1A-1) expression, the AHR target gene. A specific AHR antagonist, 6,2',4'-trimethoxyflavone, inhibited the Kyn-dependent modulation of CYP1A-1, MMP-1, and type-I collagen expression. Establishing the anti-fibrogenic effect of Kyn and its mechanism of action, we then developed nano-fibrous Kyn slow-releasing dressings and examined their anti-fibrotic efficacy in vitro and in a rat model. Our results showed the feasibility of incorporating Kyn into PVA/PLGA nanofibers, prolonging the Kyn release up to 4 days tested. Application of medicated-dressings significantly improved the dermal fibrosis indicated by MMP-1 induction, alpha-smooth muscle actin and type-I collagen suppression, and reduced tissue cellularity, T-cells and myofibroblasts. This study clarifies the mechanism by which Kyn modulates ECM expression and reports the development of a new slow-releasing anti-fibrogenic dressing. J. Cell. Physiol. 231: 2749-2760, 2016. © 2016 Wiley Periodicals, Inc. PMID:26992058

  13. Effects of triclocarban on the transcription of estrogen, androgen and aryl hydrocarbon receptor responsive genes in human breast cancer cells.

    Science.gov (United States)

    Tarnow, Patrick; Tralau, Tewes; Hunecke, Danele; Luch, Andreas

    2013-08-01

    Triclocarban (TCC) is an antimicrobial agent that is used in detergents, soaps and other personal hygiene products. Similarly to triclosan the widespread use of TCC has raised concerns about its endocrine potential. In luciferase-based reporter assays TCC has been shown to enhance estrogenic and androgenic activities following cellular coexposure with estrogen or dihydrotestosterone, respectively. The present study demonstrates that although coexposure with TCC enhances the estrogenic and androgenic readout of luciferase-based reporter cell lines such as HeLa9908 and MDA-kb2, it fails to act as a xenoandrogen on transcriptional level, nor does it induce cell proliferation in the estrogen sensitive E-screen. In addition TCC did not alter the expression of estrogen responsive genes in human mammary carcinoma MCF-7 cells exposed to 17β-estradiol, bisphenol A, butylparaben or genistein. However, TCC was shown to interfere with the regulon of the aryl hydrocarbon receptor (AhR) as TCC showed a costimulatory effect on transcription of CYP1A1 and CYP1B1, effectively lowering the transcriptional threshold for both genes in the presence of estrogens. It thus seems, that while the induction of the respective luciferase reporter assays by TCC is an unspecific false positive signal caused by luciferase stabilisation, TCC has the potential to interfere with the regulatory crosstalk of the estrogen receptor (ER) and the AhR regulon. PMID:23524099

  14. Balancing intestinal and systemic inflammation through cell type-specific expression of the aryl hydrocarbon receptor repressor.

    Science.gov (United States)

    Brandstätter, Olga; Schanz, Oliver; Vorac, Julia; König, Jessica; Mori, Tetsushi; Maruyama, Toru; Korkowski, Markus; Haarmann-Stemmann, Thomas; von Smolinski, Dorthe; Schultze, Joachim L; Abel, Josef; Esser, Charlotte; Takeyama, Haruko; Weighardt, Heike; Förster, Irmgard

    2016-01-01

    As a sensor of polyaromatic chemicals the aryl hydrocarbon receptor (AhR) exerts an important role in immune regulation besides its requirement for xenobiotic metabolism. Transcriptional activation of AhR target genes is counterregulated by the AhR repressor (AhRR) but the exact function of the AhRR in vivo is currently unknown. We here show that the AhRR is predominantly expressed in immune cells of the skin and intestine, different from other AhR target genes. Whereas AhRR antagonizes the anti-inflammatory function of the AhR in the context of systemic endotoxin shock, AhR and AhRR act in concert to dampen intestinal inflammation. Specifically, AhRR contributes to the maintenance of colonic intraepithelial lymphocytes and prevents excessive IL-1β production and Th17/Tc17 differentiation. In contrast, the AhRR enhances IFN-γ-production by effector T cells in the inflamed gut. Our findings highlight the physiologic importance of cell-type specific balancing of AhR/AhRR expression in response to microbial, nutritional and other environmental stimuli. PMID:27184933

  15. Identification of benzothiazole derivatives and polycyclic aromatic hydrocarbons as aryl hydrocarbon receptor agonists present in tire extracts.

    Science.gov (United States)

    He, Guochun; Zhao, Bin; Denison, Michael S

    2011-08-01

    Leachate from rubber tire material contains a complex mixture of chemicals previously shown to produce toxic and biological effects in aquatic organisms. The ability of these leachates to induce Ah receptor (AhR)-dependent cytochrome P4501A1 expression in fish indicated the presence of AhR active chemicals, but the responsible chemicals and their direct interaction with the AhR signaling pathway were not examined. Using a combination of AhR-based bioassays, we have demonstrated the ability of tire extract to stimulate both AhR DNA binding and AhR-dependent gene expression and confirmed that the responsible chemicals were metabolically labile. The application of CALUX (chemical-activated luciferase gene expression) cell bioassay-driven toxicant identification evaluation not only revealed that tire extract contained a variety of known AhR-active polycyclic aromatic hydrocarbons but also identified 2-methylthiobenzothiazole and 2-mercaptobenzothiazole as AhR agonists. Analysis of a structurally diverse series of benzothiazoles identified many that could directly stimulate AhR DNA binding and transiently activate the AhR signaling pathway and identified benzothiazoles as a new class of AhR agonists. In addition to these compounds, the relatively high AhR agonist activity of a large number of fractions strongly suggests that tire extract contains a large number of physiochemically diverse AhR agonists whose identities and toxicological/biological significances are unknown. PMID:21590714

  16. Fibroblast growth factor (Fgf) 21 is a novel target gene of the aryl hydrocarbon receptor (AhR)

    International Nuclear Information System (INIS)

    The toxic effects of dioxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), mainly through activation of the aryl hydrocarbon receptor (AhR) are well documented. Fibroblast growth factor (Fgf) 21 plays critical roles in metabolic adaptation to fasting by increasing lipid oxidation and ketogenesis in the liver. The present study was performed to determine whether activation of the AhR induces Fgf21 expression. In mouse liver, TCDD increased Fgf21 mRNA in both dose- and time-dependent manners. In addition, TCDD markedly increased Fgf21 mRNA expression in cultured mouse and human hepatocytes. Moreover, TCDD increased mRNA (in liver) and protein levels (in both liver and serum) of Fgf21 in wild-type mice, but not in AhR-null mice. Chromatin immunoprecipitation assays showed that TCDD increased AhR protein binding to the Fgf21 promoter (− 105/+ 1 base pair). Fgf21-null mice administered 200 μg/kg of TCDD died within 20 days, whereas wild-type mice receiving the same treatment were still alive at one month after administration. This indicates that TCDD-induced Fgf21 expression protects against TCDD toxicity. Diethylhexylphthalate (DEHP) pretreatment attenuated TCDD-induced Fgf21 expression in mouse liver and white adipose tissue, which may explain a previous report that DEHP pretreatment decreases TCDD-induced wasting. In conclusion, Fgf21 appears to be a target gene of AhR-signaling pathway in mouse and human liver. - Highlights: • TCDD induced Fgf21 expression at both mRNA and protein levels. • Fgf21 induction by TCDD is AhR-dependent. • DEHP attenuated TCDD-induced Fgf21 expression

  17. Cancer immunoediting and dioxin-activating aryl hydrocarbon receptor: a missing link in the shift toward tumor immunoescape?

    Directory of Open Access Journals (Sweden)

    Ruggero Ridolfi

    2010-05-01

    Full Text Available The aryl hydrocarbon receptor (AhR, a member of the PAS protein family, is found in organisms as diverse as Drosophila melano­gaster, nematodes, and mammals. While several reviews have reported that AhR, once activated by agonist ligands, causes long-term effects such as modification of cell growth through cell cycle control, there is also recent evidence of its decisive role in immunosuppression. The most widely studied AhR agonist is 2,3,7,8-tetrachlorodibenzo-p-dioxin, which binds AhR with the highest known affinity, leading to profound suppression of both humoral and cellular immune responses, with praecox thymus involution, consequent thymocyte loss, and induction of T-cell apoptosis. Dioxin-AhR binding causes a decline in the number of dendritic cells and enhances apoptosis following their inappropriate activation. Dioxin-mediated activation of AhR also has a direct influence on the expansion of regula­tory T-cells CD4+CD25+ FoxP3+ (T-regs and an adverse affect on CD8+ T-cell responses. Dioxin released from industrial and waste incinerators over the last few decades has caused widespread contamination of food, leading to its accumulation in fatty tissue in animals and humans. The elimination half-life of dioxin in humans (7-10 years may favor the potentially continuous and long-lasting activation of AhR, leading to perpetual immune suppression and facilitating the onset, growth, and diffusion of tumors, especially in young people. In the cancer immunoediting hypoth­esis, which subdivides the relationship between tumor and immune system into three phases: elimination, equilibrium, and escape, it is thought that dioxin accumulation may cause an inevitable shift toward tumor escape.

  18. Fibroblast growth factor (Fgf) 21 is a novel target gene of the aryl hydrocarbon receptor (AhR)

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Xingguo, E-mail: chengx@stjohns.edu [Department of Pharmaceutical Sciences, St. John' s University, 8000 Utopia Parkway, Queens, NY 11439 (United States); Vispute, Saurabh G. [Department of Pharmaceutical Sciences, St. John' s University, 8000 Utopia Parkway, Queens, NY 11439 (United States); Liu, Jie [Department of Internal Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160 (United States); Cheng, Christine; Kharitonenkov, Alexei [Lilly Research Laboratories, Division of Eli Lilly and Co., Indianapolis, IN 46285 (United States); Klaassen, Curtis D., E-mail: curtisklaassenphd@gmail.com [Department of Internal Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160 (United States)

    2014-07-01

    The toxic effects of dioxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), mainly through activation of the aryl hydrocarbon receptor (AhR) are well documented. Fibroblast growth factor (Fgf) 21 plays critical roles in metabolic adaptation to fasting by increasing lipid oxidation and ketogenesis in the liver. The present study was performed to determine whether activation of the AhR induces Fgf21 expression. In mouse liver, TCDD increased Fgf21 mRNA in both dose- and time-dependent manners. In addition, TCDD markedly increased Fgf21 mRNA expression in cultured mouse and human hepatocytes. Moreover, TCDD increased mRNA (in liver) and protein levels (in both liver and serum) of Fgf21 in wild-type mice, but not in AhR-null mice. Chromatin immunoprecipitation assays showed that TCDD increased AhR protein binding to the Fgf21 promoter (− 105/+ 1 base pair). Fgf21-null mice administered 200 μg/kg of TCDD died within 20 days, whereas wild-type mice receiving the same treatment were still alive at one month after administration. This indicates that TCDD-induced Fgf21 expression protects against TCDD toxicity. Diethylhexylphthalate (DEHP) pretreatment attenuated TCDD-induced Fgf21 expression in mouse liver and white adipose tissue, which may explain a previous report that DEHP pretreatment decreases TCDD-induced wasting. In conclusion, Fgf21 appears to be a target gene of AhR-signaling pathway in mouse and human liver. - Highlights: • TCDD induced Fgf21 expression at both mRNA and protein levels. • Fgf21 induction by TCDD is AhR-dependent. • DEHP attenuated TCDD-induced Fgf21 expression.

  19. Benzo[a]pyrene induces intercellular adhesion molecule-1 through a caveolae and aryl hydrocarbon receptor mediated pathway

    International Nuclear Information System (INIS)

    Toxicologic and epidemiologic studies have linked benzo[a]pyrene (B[a]P) exposure with cardiovascular diseases such as atherosclerosis. The mechanisms of action leading to these diseases have not been fully understood. One key step in the development of atherosclerosis is vascular endothelial dysfunction, which is characterized by increased adhesiveness. To determine if B[a]P could lead to increased endothelial adhesiveness, the effects of B[a]P on human endothelial cell intercellular adhesion molecule-1 (ICAM-1) expression was investigated. B[a]P was able to increase ICAM-1 protein only after pretreatment with the aryl hydrocarbon receptor (AhR) agonist β-naphthoflavone (β-NF). Knockdown of AhR by siRNA or treatment with AhR antagonist α-naphthoflavone (α-NF) eliminated the induction of ICAM-1 from B[a]P, confirming the necessity of AhR in this process. Likewise, B[a]P only increased monocyte adhesion to the vascular endothelium when cells were pretreated with β-NF. Experiments were done to define a signaling mechanism. B[a]P increased phosphorylation of MEK and p38-MAPK, and inhibitors to these proteins blunted the ICAM-1 induction. B[a]P was also able to increase AP-1 DNA binding and phosphorylation of cJun. Phosphorylation of cJun was disrupted by MEK and p38-MAPK inhibitors linking the signaling cascade. Finally, the importance of membrane microdomains, caveolae, was demonstrated by knockdown of the structural protein caveolin-1. Disruption of caveolae eliminated the B[a]P-induced ICAM-1 expression. These data suggest a possible pro-inflammatory mechanism of action of B[a]P involving caveolae, leading to increased vascular endothelial adhesiveness, and this inflammation may be a critical step in the development of B[a]P-induced atherosclerosis

  20. Aryl hydrocarbon receptor (AHR-regulated transcriptomic changes in rats sensitive or resistant to major dioxin toxicities

    Directory of Open Access Journals (Sweden)

    Okey Allan B

    2010-04-01

    Full Text Available Abstract Background The major toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD appear to result from dysregulation of mRNA levels mediated by the aryl hydrocarbon receptor (AHR. Dioxin-like chemicals alter expression of numerous genes in liver, but it remains unknown which lie in pathways leading to major toxicities such as hepatotoxicity, wasting and lethality. To identify genes involved in these responses we exploited a rat genetic model. Rats expressing an AHR splice-variant lacking a portion of the transactivation domain are highly resistant to dioxin-induced toxicities. We examined changes in hepatic mRNA abundances 19 hours after TCDD treatment in two dioxin-resistant rat strains/lines and two dioxin-sensitive rat strains/lines. Results Resistant rat strains/lines exhibited fewer transcriptional changes in response to TCDD than did rats with wildtype AHR. However, well-known AHR-regulated and dioxin-inducible genes such as CYP1A1, CYP1A2, and CYP1B1 remained fully responsive to TCDD in all strains/lines. Pathway analysis indicated that the genes which respond differently to TCDD between sensitive and resistant rats are mainly involved in lipid metabolism, cellular membrane function and energy metabolism. These pathways previously have been shown to respond differently to dioxin treatment in dioxin-sensitive versus dioxin-resistant rats at a biochemical level and in the differential phenotype of toxicologic responses. Conclusion The transactivation-domain deletion in dioxin-resistant rats does not abolish global AHR transactivational activity but selectively interferes with expression of subsets of genes that are candidates to mediate or protect from major dioxin toxicities such as hepatotoxicity, wasting and death.

  1. beta-TrCP inhibition reduces prostate cancer cell growth via upregulation of the aryl hydrocarbon receptor.

    Directory of Open Access Journals (Sweden)

    Udi Gluschnaider

    Full Text Available BACKGROUND: Prostate cancer is a common and heterogeneous disease, where androgen receptor (AR signaling plays a pivotal role in development and progression. The initial treatment for advanced prostate cancer is suppression of androgen signaling. Later on, essentially all patients develop an androgen independent stage which does not respond to anti hormonal treatment. Thus, alternative strategies targeting novel molecular mechanisms are required. beta-TrCP is an E3 ligase that targets various substrates essential for many aspects of tumorigenesis. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that beta-TrCP depletion suppresses prostate cancer and identify a relevant growth control mechanism. shRNA targeted against beta-TrCP reduced prostate cancer cell growth and cooperated with androgen ablation in vitro and in vivo. We found that beta-TrCP inhibition leads to upregulation of the aryl hydrocarbon receptor (AhR mediating the therapeutic effect. This phenomenon could be ligand independent, as the AhR ligand 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD did not alter prostate cancer cell growth. We detected high AhR expression and activation in basal cells and atrophic epithelial cells of human cancer bearing prostates. AhR expression and activation is also significantly higher in tumor cells compared to benign glandular epithelium. CONCLUSIONS/SIGNIFICANCE: Together these observations suggest that AhR activation may be a cancer counteracting mechanism in the prostate. We maintain that combining beta-TrCP inhibition with androgen ablation could benefit advanced prostate cancer patients.

  2. PCB 126 and other dioxin-like PCBs specifically suppress hepatic PEPCK expression via the aryl hydrocarbon receptor.

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    Wenshuo Zhang

    Full Text Available Dioxins and dioxin-like compounds encompass a group of structurally related heterocyclic compounds that bind to and activate the aryl hydrocarbon receptor (AhR. The prototypical dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, a highly toxic industrial byproduct that incites numerous adverse physiological effects. Global commercial production of the structurally similar polychlorinated biphenyls (PCBs, however, commenced early in the 20(th century and continued for decades; dioxin-like PCBs therefore contribute significantly to total dioxin-associated toxicity. In this study, PCB 126, the most potent dioxin-like PCB, was evaluated with respect to its direct effects on hepatic glucose metabolism using primary mouse hepatocytes. Overnight treatment with PCB 126 reduced hepatic glycogen stores in a dose-dependent manner. Additionally, PCB 126 suppressed forskolin-stimulated gluconeogenesis from lactate. These effects were independent of acute toxicity, as PCB 126 did not increase lactate dehydrogenase release nor affect lipid metabolism or total intracellular ATP. Interestingly, provision of cells with glycerol instead of lactate as the carbon source completely restored hepatic glucose production, indicating specific impairment in the distal arm of gluconeogenesis. In concordance with this finding, PCB 126 blunted the forskolin-stimulated increase in phosphoenolpyruvate carboxykinase (PEPCK mRNA levels without affecting glucose-6-phosphatase expression. Myricetin, a putative competitive AhR antagonist, reversed the suppression of PEPCK induction by PCB 126. Furthermore, other dioxin-like PCBs demonstrated similar effects on PEPCK expression in parallel with their ability to activate AhR. It therefore appears that AhR activation mediates the suppression of PEPCK expression by dioxin-like PCBs, suggesting a role for these pollutants as disruptors of energy metabolism.

  3. The expression level of the transcription factor Aryl hydrocarbon receptor nuclear translocator (ARNT) determines cellular survival after radiation treatment

    International Nuclear Information System (INIS)

    Tumour hypoxia promotes radioresistance and is associated with poor prognosis. The transcription factor Aryl hydrocarbon receptor nuclear translocator (ARNT), also designated as Hypoxia-inducible factor (HIF)-1β, is part of the HIF pathway which mediates cellular adaptations to oxygen deprivation and facilitates tumour progression. The subunits HIF-1α and ARNT are key players within this pathway. HIF-1α is regulated in an oxygen-dependent manner whereas ARNT is considered to be constitutively expressed. However, there is mounting evidence that certain tumour cells are capable to elevate ARNT in hypoxia which suggests a survival benefit. Therefore the objective of this study was to elucidate effects of an altered ARNT expression level on the cellular response to radiation. Different human cell lines (Hep3B, MCF-7, 786-Owt, 786-Ovhl, RCC4wt and RCC4vhl) originating from various tumour entities (Hepatocellular carcinoma, breast cancer and renal cell carcinoma respectively) were X-irradiated using a conventional linear accelerator. Knockdown of ARNT expression was achieved by transient siRNA transfection. Complementary experiments were performed by forced ARNT overexpression using appropriate plasmids. Presence/absence of ARNT protein was confirmed by Western blot analysis. Clonogenic survival assays were performed in order to determine cellular survival post irradiation. Statistical comparison of two groups was achieved by the unpaired t-test. The results of this study indicate that ARNT depletion renders tumour cells susceptible to radiation whereas overexpression of this transcription factor confers radioresistance. These findings provide evidence to consider ARNT as a drug target and as a predictive marker in clinical applications concerning the response to radiation. The online version of this article (doi:10.1186/s13014-015-0539-9) contains supplementary material, which is available to authorized users

  4. Aryl Hydrocarbon Receptor (AhR Modulates Cockroach Allergen-Induced Immune Responses through Active TGFβ1 Release

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    Yufeng Zhou

    2014-01-01

    Full Text Available Background. Aryl hydrocarbon receptor (AhR, a multifunctional regulator that senses and responds to environmental stimuli, plays a role in normal cell development and immune regulation. Recent evidence supports a significant link between environmental exposure and AhR in the development of allergic diseases. We sought to investigate whether AhR plays a role in mediating cockroach allergen-induced allergic immune responses. Methods. AhR expression in human lung fibroblasts from asthmatic and healthy individuals and in cockroach extract (CRE treated human lung fibroblasts (WI-38 was examined. The role of AhR in modulating CRE induced TGFβ1 production was investigated by using AhR agonist, TCDD, antagonist CH122319, and knockdown of AhR. The role of latent TGFβ1 binding protein-1 (LTBP1 in mediating TCDD induced active TGFβ1 release was also examined. Results. AhR expression was higher in airway fibroblasts from asthmatic subjects as compared to healthy controls. AhR in fibroblasts was activated by TCDD with an increased expression of cyp1a1 and cyp1b1. Increased AhR expression was observed in CRE-treated fibroblasts. Importantly, CRE induced TGFβ1 production in fibroblasts was significantly enhanced by TCDD but inhibited by CH122319. Reduced TGFβ1 production was further confirmed in fibroblasts with AhR knockdown. Moreover, AhR knockdown inhibited CRE induced fibroblast differentiation. Furthermore, TCDD induced active TGFβ1 release was significantly inhibited by LTBP1 knockdown. Conclusion. These results provide evidence for the role of AhR in modulating cockroach allergen-induced immune responses through controlling the active TGFβ1 release, suggesting a possible synergistic effect between exposure to allergens and environmental chemicals on the development of allergic diseases.

  5. Development of basal and induced aryl hydrocarbon (benzo[a]pyrene) hydroxylase activity in the chicken embryo in ovo.

    Science.gov (United States)

    Hamilton, J W; Denison, M S; Bloom, S E

    1983-06-01

    The development of the hepatic microsomal mixed-function oxidase system was studied to determine the basal level of embryonic enzyme activity and the inducibility of this system throughout growth and differentiation. Chicken embryo livers were assayed for basal and inducible hepatic aryl hydrocarbon hydroxylase (AHHase; designated elsewhere as AHH) activity from the first appearance of the liver as a discrete organ at 5 days of incubation (DI) through day 10 after hatching. In addition, whole-embryo and viscera preparations were assayed at 3 and 4 DI. Basal AHHase activity was equal to or greater than adult levels from 3 DI through hatching in all preparations (approximately 0.3-0.5 nmol/min per mg). A 3-fold increase in basal activity above adult values occurred at hatching. The onset of inducibility in chicken embryo liver between 5 and 6 DI was concomitant with hepatocyte differentiation. A developmental profile of 24-hr 3,4,3', 4'-tetrachlorobiphenyl-induced AHHase activity showed 15- to 30-fold induction over controls from 7 DI through day 10 after hatching, with a maximum of 15 nmol/min per mg at 14 DI and day 1 after hatching, a specific activity greater than 50% greater than maximal induction in the adult. Embryonic AHHase activity was also induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin, 3-methylcholanthrene, beta-naphthoflavone, and sodium phenobarbital. Induction kinetics throughout embryonic development were similar to those reported for the adult chicken and other animals. These findings demonstrate development of a mixed-function oxidase system in very early embryogenesis and then in the liver as it differentiates. Liver AHHase activity is inducible throughout development and perinatally but such activity is under strict developmental regulation. The chicken embryo has adult levels of AHHase activity which would be sufficient to achieve metabolic activation of promutagens/carcinogens before and after hepatocyte differentiation. PMID:6407011

  6. Aryl hydrocarbon receptor activation leads to impairment of estrogen-driven chicken vitellogenin promoter activity in LMH cells.

    Science.gov (United States)

    Bussmann, Ursula A; Pérez Sáez, Juan M; Bussmann, Leonardo E; Barañao, J Lino

    2013-03-01

    The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates most of the toxic effects of environmental contaminants. Among the multiple pleiotropic responses elicited by AHR agonists, the antiestrogenic and endocrine-disrupting action of the receptor activation is one of the most studied. It has been demonstrated that some AHR agonists disrupt estradiol-induced vitellogenin synthesis in the fish liver via a mechanism that involves crosstalk between the AHR and the estrogen receptor (ER). Chicken hepatocytes have become a model for the study of AHR action in birds and the induction of the signal and its effect in these cells are well established. However, the impact of AHR activation on estradiol-regulated responses in the chicken liver remains to be demonstrated. The aim of the present study was, therefore, to determine the effect of AHR action on ER-driven transcription in a convenient model of chicken liver cells. For this purpose, we designed a reporter construct bearing the 5' regulatory region of the chicken vitellogenin II gene and used it to transfect chicken hepatoma LMH cells. We found that β-naphthoflavone represses ER-driven vitellogenin promoter activity and that this action is mediated by the AHR. This inhibitory crosstalk between both pathways appears to be unidirectional, since estradiol did not alter the transcript levels of an AHR target gene. Besides, and highly relevant, we show that LMH cell line transfected with a reporter construct bearing the chicken vitellogenin promoter sequence is a useful and convenient model for the study of AHR-ER interaction in chicken liver-derived cells. PMID:23103859

  7. Isolation and characterization of revertants from four different classes of aryl hydrocarbon hydroxylase-deficient hepa-1 mutants.

    Science.gov (United States)

    Van Gurp, J R; Hankinson, O

    1984-01-01

    Revertants were selected from aryl hydrocarbon hydroxylase (AHH)-deficient recessive mutants belonging to three complementation groups and from a dominant mutant of the Hepa-1 cell line. The recessive mutants had low spontaneous reversion frequencies (less than 4 X 10(-7] that were increased by mutagenesis. The majority of these revertants also had reacquired only partial AHH activity. Revertants of group A mutants were identical to the wild type with respect to both in vivo and in vitro enzyme stability and the Km for the substrate, benzo [alpha]pyrene, and therefore failed to provide evidence that gene A is the AHH structural gene. Group B and group C mutants are defective in the functioning of the Ah receptor required for AHH induction. Revertants of these groups were normal with respect to in vivo temperature sensitivity for AHH induction and for the 50% effective dose for the inducer, 2,3,7,8-tetrachlorodibenzo-p-dioxin, and thus provided no evidence that the B and C genes code for components of the receptor. Two rare group C revertants possessed AHH activity in the absence of induction. The phenotype of one of these was shown to be recessive to the wild type. Spontaneous revertants of the dominant mutant occurred at a frequency 300-fold greater than those of the recessive mutants, and this frequency was not increased by mutagenesis. These revertants all displayed complete restoration of AHH activity to wild type levels. These observations and the results from cell hybridization studies suggest that the dominant revertants arose by a high frequency event leading to functional elimination of the dominant mutation. PMID:6493230

  8. Stability of the aryl hydrocarbon receptor and its regulated genes in the low activity variant of Hepa-1 cell line.

    Science.gov (United States)

    Humphrey-Johnson, Andria; Abukalam, Rawia; Eltom, Sakina E

    2015-03-01

    We examined the expression kinetics of some of the aryl hydrocarbon receptor (AhR)-regulated genes in LA1 variant cells compared to wild type (WT) Hepa-1 mouse hepatoma cell lines, and we investigated the stability of AhR protein as a key step in the function of this receptor. Treatment of both cell types with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) resulted in increased CYP1A1 and CYP1B1 mRNA with a subsequent down regulation of AhR. We show here that co-treatment with transcription inhibitor actinomycin D (ActD) has reversed the TCDD-induced depletion of AhR protein in WT. However, the proteolytic degradation of AhR in absence of TCDD was significantly higher in LA1 cells than in WT, and ActD treatment reduced this loss. Induction of CYP1A1 and CYP1B1 mRNA by TCDD in WT cells each exhibited bursts of activity in the initial hour which were about 3-fold greater than in LAI cells. The induced mRNA levels in LA1 exhibited a slow and sustained increase approximating the WT levels by 20h. The induction of two other AhR-regulated genes also showed comparable turnover differences between the two types of cell. Thus, altered regulation of the AhR responsive genes in LA1 may result from a difference in AhR stability. PMID:25637755

  9. Activation of the aryl hydrocarbon receptor by carcinogenic aromatic amines and modulatory effects of their N-acetylated metabolites.

    Science.gov (United States)

    Juricek, Ludmila; Bui, Linh-Chi; Busi, Florent; Pierre, Stéphane; Guyot, Erwan; Lamouri, Aazdine; Dupret, Jean-Marie; Barouki, Robert; Coumoul, Xavier; Rodrigues-Lima, Fernando

    2015-12-01

    Aromatic amines (AAs) are an important class of chemicals which account for 12 % of known carcinogens. The biological effects of AAs depend mainly on their biotransformation into reactive metabolites or into N-acetylated metabolites which are generally considered as less toxic. Although the activation of the aryl hydrocarbon receptor (AhR) pathway by certain carcinogenic AAs has been reported, the effects of their N-acetylated metabolites on the AhR have not been addressed. Here, we investigated whether carcinogenic AAs and their N-acetylated metabolites may activate/modulate the AhR pathway in the absence and/or the presence of a bona fide AhR ligand (benzo[a]pyrene/B(a)P]. In agreement with previous studies, we found that certain AAs activated the AhR in human liver and lung cells as assessed by an increase in cytochrome P450 1A1 (CYP1A1) expression and activity. Altogether, we report for the first time that these properties can be modulated by the N-acetylation status of the AA. Whereas 2-naphthylamine significantly activated the AhR and induced CYP1A1 expression, its N-acetylated metabolite was less efficient. In contrast, the N-acetylated metabolite of 2-aminofluorene was able to significantly activate AhR, whereas the parent AA, 2-aminofluorene, did not. In the presence of B(a)P, activation of AhR or antagonist effects were observed depending on the AA or its N-acetylated metabolite. Activation and/or modulation of the AhR pathway by AAs and their N-acetylated metabolites may represent a novel mechanism contributing to the toxicological effects of AAs. More broadly, our data suggest biological interactions between AAs and other classes of xenobiotics through the AhR pathway. PMID:25224404

  10. Rats fed soy protein isolate (SPI) have impaired hepatic CYP1A1 induction by polycyclic aromatic hydrocarbons as a result of interference with aryl hydrocarbon receptor signaling

    International Nuclear Information System (INIS)

    Consumption of soy diets has been found to reduce cancer incidence in animals and is associated with reduced cancer risk in humans. Previously, we have demonstrated that female Sprague-Dawley rats fed purified AIN-93G diets with soy protein isolate (SPI) as the sole protein source had reduced CYP1A1 induction and basal aryl hydrocarbon receptor (AhR) levels relative to those fed the same diet containing casein (CAS). In the present study, the molecular mechanisms underlying reduced AhR expression have been studied. The SPI-effect on AhR was not observed after feeding diets containing the purified soy isoflavones genistein or daidzein. Rat hepatoma FGC-4 cells were treated with the serum obtained from rats fed CAS- or SPI-containing diets. Reduced AhR levels (P < 0.05) were observed after 24 h exposure to SPI-serum without any changes in the overall expression of chaperone proteins-HSP90 and XAP2. SPI-serum-stimulated AhR degradation was inhibited by treating the cells with the proteasome inhibitor, MG132, and was observed to be preceded by ubiquitination of the receptor. A reduced association of XAP2 with the immunoprecipitated AhR complex was observed. SPI-serum-mediated AhR degradation was preceded by nuclear translocation of the receptor. However, the translocated receptor was found to be unable to heterodimerize with ARNT or to bind to XRE elements on the CYP1A1 enhancer. These data suggest that feeding SPI-containing diets antagonizes AhR signaling by a novel mechanism which differs from those established for known AhR antagonists

  11. Breast cancer stem-like cells are inhibited by a non-toxic aryl hydrocarbon receptor agonist.

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    Gérald J Prud'homme

    Full Text Available BACKGROUND: Cancer stem cells (CSCs have increased resistance to cancer chemotherapy. They can be enriched as drug-surviving CSCs (D-CSCs by growth with chemotherapeutic drugs, and/or by sorting of cells expressing CSC markers such as aldehyde dehydrogenase-1 (ALDH. CSCs form colonies in agar, mammospheres in low-adherence cultures, and tumors following xenotransplantation in Scid mice. We hypothesized that tranilast, a non-toxic orally active drug with anti-cancer activities, would inhibit breast CSCs. METHODOLOGY/FINDINGS: We examined breast cancer cell lines or D-CSCs generated by growth of these cells with mitoxantrone. Tranilast inhibited colony formation, mammosphere formation and stem cell marker expression. Mitoxantrone-selected cells were enriched for CSCs expressing stem cell markers ALDH, c-kit, Oct-4, and ABCG2, and efficient at forming mammospheres. Tranilast markedly inhibited mammosphere formation by D-CSCs and dissociated formed mammospheres, at pharmacologically relevant concentrations. It was effective against D-CSCs of both HER-2+ and triple-negative cell lines. Tranilast was also effective in vivo, since it prevented lung metastasis in mice injected i.v. with triple-negative (MDA-MB-231 mitoxantrone-selected cells. The molecular targets of tranilast in cancer have been unknown, but here we demonstrate it is an aryl hydrocarbon receptor (AHR agonist and this plays a key role. AHR is a transcription factor activated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, polycyclic aromatic hydrocarbons and other ligands. Tranilast induced translocation of the AHR to the nucleus and stimulated CYP1A1 expression (a marker of AHR activation. It inhibited binding of the AHR to CDK4, which has been linked to cell-cycle arrest. D-CSCs expressed higher levels of the AHR than other cells. Knockdown of the AHR with siRNA, or blockade with an AHR antagonist, entirely abrogated the anti-proliferative and anti-mammosphere activity of tranilast

  12. Influence of aryl hydrocarbon- (Ah) receptor and genotoxins on DNA repair gene expression and cell survival of mouse hepatoma cells

    International Nuclear Information System (INIS)

    The aryl hydrocarbon receptor (AhR) mediates toxicity of a variety of environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs) and dioxins. However, the underlying mechanisms and genetic programmes regulated by AhR to cause adverse effects but also to counteract poisoning are still poorly understood. Here we analysed the effects of two AhR ligands, benzo[a]pyrene (B[a]P), a DNA damaging tumour initiator and promotor and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a pure tumour promoter, on cell survival and on nucleotide excision repair (NER) gene expression. NER deals with so called 'bulky' DNA adducts including those generated by enzymatically activated B[a]P. Therefore, the hypothesis that AhR may enhance NER gene expression to trigger DNA repair in the presence of genotoxic AhR ligands was tested. Furthermore, we investigated a potential cytoprotective effect of AhR activation by the non-genotoxic ligand TCDD against cell death induced by various genotoxins. Finally, the actions of genotoxins themselves on NER gene expression were studied. As a cell culture model we used mouse hepatoma cells (Hepa-c7) proficient for AhR and its partner protein ARNT as well as subclones deficient in AhR (Hepa-c12) or ARNT (Hepa-c4) to study involvement of AhR and ARNT in response to B[a]P and TCDD. Indeed, the mRNA levels of the two NER genes XP-C and DNA polymerase kappa were increased by B[a]P and TCDD, however, this was not accompanied by an increase in the amount of the respective proteins. Pretreatment of cells with TCDD did not reduce cytotoxicity induced by various genotoxins. Thus, in Hepa-c7 cells AhR has no major effects on the expression of these crucial NER proteins and does not prevent genotoxin-provoked cell death. As expected, the genotoxins B[a]P and cis-platin led to p53 accumulation and induction of its target p21. Interestingly, however, NER gene expression was not enhanced but rather decreased. As two NER genes, XP-C and DNA damage binding

  13. Common commercial and consumer products contain activators of the aryl hydrocarbon (dioxin receptor.

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    Bin Zhao

    Full Text Available Activation of the Ah receptor (AhR by halogenated aromatic hydrocarbons (HAHs, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin, can produce a wide variety of toxic and biological effects. While recent studies have shown that the AhR can bind and be activated by structurally diverse chemicals, how widespread of these AhR agonists are in environmental, biological and synthetic materials remains to be determined. Using AhR-based assays, we demonstrate the presence of potent AhR agonists in a variety of common commercial and consumer items. Solvent extracts of paper, rubber and plastic products contain chemicals that can bind to and stimulate AhR DNA binding and/or AhR-dependent gene expression in hepatic cytosol, cultured cell lines, human epidermis and zebrafish embryos. In contrast to TCDD and other persistent dioxin-like HAHs, activation of AhR-dependent gene expression by these extracts was transient, suggesting that the agonists are metabolically labile. Solvent extracts of rubber products produce AhR-dependent developmental toxicity in zebrafish in vivo, and inhibition of expression of the metabolic enzyme CYP1A, significantly increased their toxic potency. Although the identity of the responsible AhR-active chemicals and their toxicological impact remain to be determined, our data demonstrate that AhR active chemicals are widely distributed in everyday products.

  14. The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells

    International Nuclear Information System (INIS)

    Disruption of cell proliferation control by polycyclic aromatic hydrocarbons (PAHs) may contribute to their carcinogenicity. We investigated role of the aryl hydrocarbon receptor (AhR) in disruption of contact inhibition in rat liver epithelial WB-F344 'stem-like' cells, induced by the weakly mutagenic benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and by the strongly mutagenic benzo[a]pyrene (BaP). There were significant differences between the effects of BaA and BbF, and those of the strongly genotoxic BaP. Both BaA and BbF increased percentage of cells entering S-phase and cell numbers, associated with an increased expression of Cyclin A and Cyclin A/cdk2 complex activity. Their effects were significantly reduced in cells expressing a dominant-negative AhR mutant (dnAhR). Roscovitine, a chemical inhibitor of cdk2, abolished the induction of cell proliferation by BbF. However, neither BaA nor BbF modulated expression of the principal cdk inhibitor involved in maintenance of contact inhibition, p27Kip1, or pRb phosphorylation. The strongly mutagenic BaP induced apoptosis, a decrease in total cell numbers and significantly higher percentage of cells entering S-phase than either BaA or BbF. Given that BaP induced high levels of Cyclin A/cdk2 activity, downregulation of p27Kip1 and hyperphosphorylation of pRb, the accumulation of cells in S-phase was probably due to cell proliferation, although S-phase arrest due to blocked replication forks can not be excluded. Both types of effects of BaP were significantly attenuated in dnAhR cells. Transfection of WB-F344 cells with siRNA targeted against AhR decreased induction of Cyclin A induced by BbF or BaP, further supporting the role of AhR in proliferative effects of PAHs. This suggest that activation of AhR plays a significant role both in disruption of contact inhibition by weakly mutagenic PAHs and in genotoxic effects of BaP possibly leading to enhanced cell proliferation. Thus, PAHs may increase proliferative

  15. The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Andrysik, Zdenek [Laboratory of Cytokinetics, Institute of Biophysics, 612 65 Brno (Czech Republic); Department of Chemistry and Toxicology, Veterinary Research Institute, 621 32 Brno (Czech Republic); Vondracek, Jan [Laboratory of Cytokinetics, Institute of Biophysics, 612 65 Brno (Czech Republic) and Department of Chemistry and Toxicology, Veterinary Research Institute, 621 32 Brno (Czech Republic)]. E-mail: vondracek@ibp.cz; Machala, Miroslav [Department of Chemistry and Toxicology, Veterinary Research Institute, 621 32 Brno (Czech Republic); Krcmar, Pavel [Department of Chemistry and Toxicology, Veterinary Research Institute, 621 32 Brno (Czech Republic); Svihalkova-Sindlerova, Lenka [Laboratory of Cytokinetics, Institute of Biophysics, 612 65 Brno (Czech Republic); Kranz, Anne [Institute of Toxicology, Johannes Gutenberg-University, 55131 Mainz (Germany); Weiss, Carsten [Institute of Toxicology, Johannes Gutenberg-University, 55131 Mainz (Germany); Faust, Dagmar [Institute of Toxicology, Johannes Gutenberg-University, 55131 Mainz (Germany); Kozubik, Alois [Laboratory of Cytokinetics, Institute of Biophysics, 612 65 Brno (Czech Republic); Dietrich, Cornelia [Institute of Toxicology, Johannes Gutenberg-University, 55131 Mainz (Germany)

    2007-02-03

    Disruption of cell proliferation control by polycyclic aromatic hydrocarbons (PAHs) may contribute to their carcinogenicity. We investigated role of the aryl hydrocarbon receptor (AhR) in disruption of contact inhibition in rat liver epithelial WB-F344 'stem-like' cells, induced by the weakly mutagenic benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and by the strongly mutagenic benzo[a]pyrene (BaP). There were significant differences between the effects of BaA and BbF, and those of the strongly genotoxic BaP. Both BaA and BbF increased percentage of cells entering S-phase and cell numbers, associated with an increased expression of Cyclin A and Cyclin A/cdk2 complex activity. Their effects were significantly reduced in cells expressing a dominant-negative AhR mutant (dnAhR). Roscovitine, a chemical inhibitor of cdk2, abolished the induction of cell proliferation by BbF. However, neither BaA nor BbF modulated expression of the principal cdk inhibitor involved in maintenance of contact inhibition, p27{sup Kip1}, or pRb phosphorylation. The strongly mutagenic BaP induced apoptosis, a decrease in total cell numbers and significantly higher percentage of cells entering S-phase than either BaA or BbF. Given that BaP induced high levels of Cyclin A/cdk2 activity, downregulation of p27{sup Kip1} and hyperphosphorylation of pRb, the accumulation of cells in S-phase was probably due to cell proliferation, although S-phase arrest due to blocked replication forks can not be excluded. Both types of effects of BaP were significantly attenuated in dnAhR cells. Transfection of WB-F344 cells with siRNA targeted against AhR decreased induction of Cyclin A induced by BbF or BaP, further supporting the role of AhR in proliferative effects of PAHs. This suggest that activation of AhR plays a significant role both in disruption of contact inhibition by weakly mutagenic PAHs and in genotoxic effects of BaP possibly leading to enhanced cell proliferation. Thus, PAHs may

  16. Cardiac toxicity of 5-ring polycyclic aromatic hydrocarbons is differentially dependent on the aryl hydrocarbon receptor 2 isoform during zebrafish development

    Energy Technology Data Exchange (ETDEWEB)

    Incardona, John P., E-mail: john.incardona@noaa.gov; Linbo, Tiffany L.; Scholz, Nathaniel L.

    2011-12-15

    Petroleum-derived compounds, including polycyclic aromatic hydrocarbons (PAHs), commonly occur as complex mixtures in the environment. Recent studies using the zebrafish experimental model have shown that PAHs are toxic to the embryonic cardiovascular system, and that the severity and nature of this developmental cardiotoxicity varies by individual PAH. In the present study we characterize the toxicity of the relatively higher molecular weight 5-ring PAHs benzo[a]pyrene (BaP), benzo[e]pyrene (BeP), and benzo[k]fluoranthene (BkF). While all three compounds target the cardiovascular system, the underlying role of the ligand-activated aryl hydrocarbon receptor (AHR2) and the tissue-specific induction of the cytochrome p450 metabolic pathway (CYP1A) were distinct for each. BaP exposure (40 {mu}M) produced AHR2-dependent bradycardia, pericardial edema, and myocardial CYP1A immunofluorescence. By contrast, BkF exposure (4-40 {mu}M) caused more severe pericardial edema, looping defects, and erythrocyte regurgitation through the atrioventricular valve that were AHR2-independent (i.e., absent myocardial or endocardial CYP1A induction). Lastly, exposure to BeP (40 {mu}M) yielded a low level of CYP1A+ signal in the vascular endothelium of the head and trunk, without evident toxic effects on cardiac function or morphogenesis. Combined with earlier work on 3- and 4-ring PAHs, our findings provide a more complete picture of how individual PAHs may drive the cardiotoxicity of mixtures in which they predominate. This will improve toxic injury assessments and risk assessments for wild fish populations that spawn in habitats altered by overlapping petroleum-related human impacts such as oil spills, urban stormwater runoff, or sediments contaminated by legacy industrial activities. -- Highlights: Black-Right-Pointing-Pointer PAH compounds with 5 rings in different arrangements caused differential tissue-specific patterns of CYP1A induction in zebrafish embryos. Black

  17. A novel role of the aryl hydrocarbon receptor (AhR in centrosome amplification - implications for chemoprevention

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    Chatterjee Payel

    2010-06-01

    Full Text Available Abstract Background Centrosome aberrations can cause genomic instability and correlate with malignant progression in common human malignancies such as breast and prostate cancer. Deregulation of cyclin/cyclin-dependent kinase 2 (CDK2 activity has previously been shown to be critically involved in centrosome overduplication. We therefore test here whether small molecule CDK inhibitors derived from the bis-indole indirubin can be used to suppress centrosome aberrations as a novel approach to chemoprevention of malignant progression. Results As expected, we found that the CDK inhibitor indirubin-3'-oxime (IO suppresses centrosome amplification in breast cancer cells. However, we made the unexpected discovery that indirubin-derived compounds that have been chemically modified to be inactive as kinase inhibitors such as 1-methyl-indirubin-3'-oxime (MeIO still significantly reduced centrosome amplification. All indirubins used in the present study are potent agonists of the aryl hydrocarbon receptor (AhR, which is known for its important role in the cellular metabolism of xenobiotics. To corroborate our results, we first show that the coincidence of nuclear AhR overexpression, reflecting a constitutive activation, and numerical centrosome aberrations correlates significantly with malignancy in mammary tissue specimens. Remarkably, a considerable proportion (72.7% of benign mammary tissue samples scored also positive for nuclear AhR overexpression. We furthermore provide evidence that continued expression of endogenous AhR is critical to promote centriole overduplication induced by cyclin E and that AhR and cyclin E may function in the same pathway. Overexpression of the AhR in the absence of exogenous ligands was found to rapidly disrupt centriole duplication control. Nonetheless, the AhR agonists IO and MeIO were still found to significantly reduce centriole overduplication stimulated by ectopic AhR expression. Conclusions Our results indicate that

  18. Knockout of the aryl hydrocarbon receptor results in distinct hepatic and renal phenotypes in rats and mice

    Energy Technology Data Exchange (ETDEWEB)

    Harrill, Joshua A. [The Hamner Institute for Health Sciences, Institute for Chemical Safety Sciences, RTP, NC 27709 (United States); Hukkanen, Renee R.; Lawson, Marie; Martin, Greg [The Dow Chemical Company, Midland, MI 48640 (United States); Gilger, Brian [North Carolina State University, College of Veterinary Medicine, Raleigh, NC 27606 (United States); Soldatow, Valerie [University of North Carolina, Department of Environmental Sciences and Engineering, Chapel Hill, NC 27599 (United States); LeCluyse, Edward L. [The Hamner Institute for Health Sciences, Institute for Chemical Safety Sciences, RTP, NC 27709 (United States); Budinsky, Robert A.; Rowlands, J. Craig [The Dow Chemical Company, Midland, MI 48640 (United States); Thomas, Russell S., E-mail: RThomas@thehamner.org [The Hamner Institute for Health Sciences, Institute for Chemical Safety Sciences, RTP, NC 27709 (United States)

    2013-10-15

    The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor which plays a role in the development of multiple tissues and is activated by a large number of ligands, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In order to examine the roles of the AHR in both normal biological development and response to environmental chemicals, an AHR knockout (AHR-KO) rat model was created and compared with an existing AHR-KO mouse. AHR-KO rats harboring either 2-bp or 29-bp deletion mutation in exon 2 of the AHR were created on the Sprague–Dawley genetic background using zinc-finger nuclease (ZFN) technology. Rats harboring either mutation type lacked expression of AHR protein in the liver. AHR-KO rats were also insensitive to thymic involution, increased hepatic weight and the induction of AHR-responsive genes (Cyp1a1, Cyp1a2, Cyp1b1, Ahrr) following acute exposure to 25 μg/kg TCDD. AHR-KO rats had lower basal expression of transcripts for these genes and also accumulated ∼ 30–45-fold less TCDD in the liver at 7 days post-exposure. In untreated animals, AHR-KO mice, but not AHR-KO rats, had alterations in serum analytes indicative of compromised hepatic function, patent ductus venosus of the liver and persistent hyaloid arteries in the eye. AHR-KO rats, but not AHR-KO mice, displayed pathological alterations to the urinary tract: bilateral renal dilation (hydronephrosis), secondary medullary tubular and uroepithelial degenerative changes and bilateral ureter dilation (hydroureter). The present data indicate that the AHR may play significantly different roles in tissue development and homeostasis and toxicity across rodent species. - Highlights: • An AHR knockout rat was generated on a Sprague–Dawley outbred background. • AHR-KO rats lack expression of AHR protein. • AHR-KO rats are insensitive to TCDD-mediated effects. • Data suggests difference in the role of AHR in tissue development of rats and mice. • Abnormalities in vascular

  19. Molecular and functional characterization of a novel aryl hydrocarbon receptor isoform, AHR1β, in the chicken (Gallus gallus).

    Science.gov (United States)

    Lee, Jin-Seon; Iwabuchi, Kohei; Nomaru, Koji; Nagahama, Nobumasa; Kim, Eun-Young; Iwata, Hisato

    2013-12-01

    Dioxins including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) cause toxic effects through activation of the aryl hydrocarbon receptor (AHR)-mediated signaling pathway. Our previous studies have investigated the function of 2 AHR isoforms (AHR1 and AHR2) in avian species and identified a third AHR in the chicken (Gallus gallus) genome. Knowledge of multiple avian AHRs is indispensable to understand molecular mechanisms of AHR-mediated toxic effects and establish risk assessment framework for environmental AHR ligands in avian species. In this study, we successfully isolated a third novel AHR1-like cDNA from chicken and designated it as chicken AHR1 beta (ckAHR1β). The mRNA expression of ckAHR1β was primarily detected in the liver, and the hepatic protein expression was confirmed by Western blotting. Although mRNA expression of ckAHR1β was not altered by in ovo TCDD exposure, ckAHR1β exhibited specific binding to [(3)H]TCDD, TCDD-dependent nuclear translocation, and interaction with xenobiotic responsive elements (XREs) and AHR nuclear translocators (ARNTs). In vitro XRE-driven reporter gene assays revealed ckAHR1β-mediated transactivation of TCDD in a dose-dependent manner, showing a 10-fold reduced sensitivity (high EC50) compared with that mediated by ckAHR1. The mutation of Val(371) to Ser(371) in the ligand-binding domain of ckAHR1β shifted the TCDD-EC50 toward the value observed in ckAHR1, indicating the critical roles of the amino acid in sensitivity. Furthermore, ckAHR1β-mediated transactivation of TCDD was enhanced by 17β-estradiol (E2)-activated chicken estrogen receptor α (ckERα), suggesting a positive cross talk between ckERα and ckAHR1β signaling pathway. Both TCDD-induced and its enhanced activities by E2 were suppressed by the ckAHR repressor in a manner similar to ckAHR1. Collectively, our findings discover the role of ckAHR1β in dioxin toxicity and give an insight into the evolutionary history of the AHR signaling pathway. PMID:23997109

  20. Molecular and functional characterization of Aryl hydrocarbon receptor repressor from the chicken (Gallus gallus): interspecies similarities and differences.

    Science.gov (United States)

    Lee, Jin-Seon; Kim, Eun-Young; Nomaru, Koji; Iwata, Hisato

    2011-02-01

    The aryl hydrocarbon receptor (AHR) repressor (AHRR) has been recognized as a negative feedback modulator of AHR-mediated responses in fish and mammals. However, the repressive mechanism by the AHRR has not been investigated in other animals. To understand the molecular mechanism of dioxin toxicity and the evolutionary history of the AHR signaling pathway in avian species, the present study addresses chicken AHRR (ckAHRR). The complementary DNA sequence of ckAHRR encodes an 84-kDa protein sharing 29-52% identities with other AHRRs. High levels of ckAHRR messenger RNA were recorded in the kidney and intestine of nontreated chicks. In hepatoma LMH cells, the 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) 50% effective concentration value for ckAHRR induction (0.0016nM) was the same as that for chicken cytochrome P450 1A5 (ckCYP1A5), implying a shared transcriptional regulation of ckAHRR and ckCYP1A5 by chicken AHR (ckAHR). In ckAHRR transient transfection assays, ckAHRR repressed both ckAHR1- and ckAHR2-mediated transcriptional activities. Deletion and mutation assays revealed that basic helix-loop-helix/Per-ARNT-Sim A domains of ckAHRR, particularly 217-402 amino acid residues, are indispensable for the repression, but the AHR nuclear translocator sequestration by ckAHRR and SUMOylation of ckAHRR are not involved in its repressive mechanism. Additionally, subcellular localization assay of ckAHR1-enhanced green fluorescent protein fusion protein showed that ckAHRR did not affect nuclear translocation of the ckAHR1. Furthermore, ckAHRR inhibited the TCDD- and 17β estradiol-enhanced ckCYP1A5 transcription through AHR-estrogen receptor α (ERα) cross talk. Taken together, the function of AHRR is conserved in chicken in terms of the negative regulation of AHR and ERα activities, but its functional mechanism is likely distinct from those of the mammalian and fish homologues. PMID:21047992

  1. Aryl hydrocarbon receptor-dependent regulation of miR-196a expression controls lung fibroblast apoptosis but not proliferation

    Energy Technology Data Exchange (ETDEWEB)

    Hecht, Emelia [Department of Medicine, McGill University, Montreal, Quebec (Canada); Zago, Michela [Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec (Canada); Sarill, Miles [Department of Medicine, McGill University, Montreal, Quebec (Canada); Rico de Souza, Angela [Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec (Canada); Gomez, Alvin; Matthews, Jason [Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON (Canada); Hamid, Qutayba; Eidelman, David H. [Department of Medicine, McGill University, Montreal, Quebec (Canada); Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec (Canada); Baglole, Carolyn J., E-mail: Carolyn.baglole@McGill.ca [Department of Medicine, McGill University, Montreal, Quebec (Canada); Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec (Canada)

    2014-11-01

    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor implicated in the regulation of apoptosis and proliferation. Although activation of the AhR by xenobiotics such as dioxin inhibits the cell cycle and control apoptosis, paradoxically, AhR expression also promotes cell proliferation and survival independent of exogenous ligands. The microRNA (miRNA) miR-196a has also emerged as a regulator of proliferation and apoptosis but a relationship between the AhR and miR-196a is not known. Therefore, we hypothesized that AhR-dependent regulation of endogenous miR-196a expression would promote cell survival and proliferation. Utilizing lung fibroblasts from AhR deficient (AhR{sup −/−}) and wild-type (AhR{sup +/+}) mice, we show that there is ligand-independent regulation of miRNA, including low miR-196a in AhR{sup −/−} cells. Validation by qRT-PCR revealed a significant decrease in basal expression of miR-196a in AhR{sup −/−} compared to AhR{sup +/+} cells. Exposure to AhR agonists benzo[a]pyrene (B[a]P) and FICZ as well as AhR antagonist CH-223191 decreased miR-196a expression in AhR{sup +/+} fibroblasts concomitant with decreased AhR protein levels. There was increased proliferation only in AhR{sup +/+} lung fibroblasts in response to serum, corresponding to a decrease in p27{sup KIP1} protein, a cyclin-dependent kinase inhibitor. Increasing the cellular levels of miR-196a had no effect on proliferation or expression of p27{sup KIP1} in AhR{sup −/−} fibroblasts but attenuated cigarette smoke-induced apoptosis. This study provides the first evidence that AhR expression is essential for the physiological regulation of cellular miRNA levels- including miR-196a. Future experiments designed to elucidate the functional relationship between the AhR and miR-196a may delineate additional novel ligand-independent roles for the AhR. - Highlights: • The AhR controls proliferation and apoptosis in lung cells. • The AhR regulates the

  2. TCDD-Induced Activation of Aryl Hydrocarbon Receptor Inhibits Th17 Polarization and Regulates Non-Eosinophilic Airway Inflammation in Asthma.

    Directory of Open Access Journals (Sweden)

    Xiao-ming Li

    Full Text Available The aryl hydrocarbon receptor (AhR, a transcription factor of the bHLH/PAS family, has recently been demonstrated to regulate T cell differentiation. Whether AhR activation participates in allergic airway inflammation remains unknown. In the current study, using a non-eosinophilic asthma model, we demonstrate that 2, 3, 7, 8-tetrachlorodibenzo-P-dioxin (TCDD, a potent AhR ligand, reduced the airway infiltration of neutrophils, airway hyperresponsiveness and Th17 cytokine expression. Furthermore, stimulation with TCDD promoted Treg differentiation and inhibited Th17 differentiation. However, the maturation of dendritic cells may not be inhibited by AhR activation. This study thus indicates a critical role of TCDD-induced AhR activation in the regulation of non-eosinophilic airway inflammation.

  3. TCDD-Induced Activation of Aryl Hydrocarbon Receptor Inhibits Th17 Polarization and Regulates Non-Eosinophilic Airway Inflammation in Asthma.

    Science.gov (United States)

    Li, Xiao-ming; Peng, Juan; Gu, Wen; Guo, Xue-jun

    2016-01-01

    The aryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family, has recently been demonstrated to regulate T cell differentiation. Whether AhR activation participates in allergic airway inflammation remains unknown. In the current study, using a non-eosinophilic asthma model, we demonstrate that 2, 3, 7, 8-tetrachlorodibenzo-P-dioxin (TCDD), a potent AhR ligand, reduced the airway infiltration of neutrophils, airway hyperresponsiveness and Th17 cytokine expression. Furthermore, stimulation with TCDD promoted Treg differentiation and inhibited Th17 differentiation. However, the maturation of dendritic cells may not be inhibited by AhR activation. This study thus indicates a critical role of TCDD-induced AhR activation in the regulation of non-eosinophilic airway inflammation. PMID:26938767

  4. Role of the aryl hydrocarbon receptor in controlling maintenance and functional programs of RORγt+ innate lymphoid cells and intraepithelial γδ T cells

    Directory of Open Access Journals (Sweden)

    Elina A. Kiss

    2012-05-01

    Full Text Available Mucosal RORγt-expressing innate lymphoid cells (ILC play an important role in the defense against intestinal pathogens and in promoting epithelial homeostasis and adaptation thereby effectively protecting the vertebrate host against intestinal inflammatory disorders. The functional activity of RORγt+ ILC is under the control of environmental cues. However, the molecular sensors for such environmental signals are largely unknown. Recently, the aryl hydrocarbon receptor (AhR has emerged as a master regulator for the postnatal maintenance of intestinal RORγt+ ILC and intraepithelial γδ T cells. AhR is a highly conserved transcription factor whose activity is regulated by environmental and dietary small molecule ligands. Here, we review the role of AhR signaling for the maintenance of intestinal immune cells and its impact on the immunological protection against intestinal infections and debilitating chronic inflammatory disorders.

  5. Selective Aryl Hydrocarbon Receptor Modulator 3,3'-Diindolylmethane Impairs AhR and ARNT Signaling and Protects Mouse Neuronal Cells Against Hypoxia.

    Science.gov (United States)

    Rzemieniec, J; Litwa, E; Wnuk, A; Lason, W; Krzeptowski, W; Kajta, M

    2016-10-01

    The neuroprotective potential of 3,3'-diindolylmethane (DIM), which is a selective aryl hydrocarbon receptor modulator, has recently been shown in cellular and animal models of Parkinson's disease and lipopolysaccharide-induced inflammation. However, there are no data concerning the protective capacity and mechanisms of DIM action in neuronal cells exposed to hypoxia. The aim of the present study was to investigate the neuroprotective potential of DIM against the hypoxia-induced damage in mouse hippocampal cells in primary cultures, with a particular focus on DIM interactions with the aryl hydrocarbon receptor (AhR), its nuclear translocator ARNT, and estrogen receptor β (ERβ). In the present study, 18 h of hypoxia induced apoptotic processes, in terms of the mitochondrial membrane potential, activation of caspase-3, and fragmentation of cell nuclei. These effects were accompanied by substantial lactate dehydrogenase release and neuronal cell death. The results of the present study demonstrated strong neuroprotective and anti-apoptotic actions of DIM in hippocampal cells exposed to hypoxia. In addition, DIM decreased the Ahr and Arnt mRNA expression and stimulated Erβ mRNA expression level. DIM-induced mRNA alterations were mirrored by changes in protein levels, except for ERβ, as detected by ELISA, Western blotting, and immunofluorescence labeling. We also demonstrated that DIM decreased the expression of AhR-regulated CYP1A1. Using specific siRNAs, we provided evidence that impairment of AhR and ARNT, but not ERβ plays a key role in the neuroprotective action of DIM against hypoxia-induced cell damage. This study may have implication for identifying new agents that could protect neurons against hypoxia by targeting AhR/ARNT signaling. PMID:26476840

  6. A model for aryl hydrocarbon receptor-activated gene expression shows potency and efficacy changes and predicts squelching due to competition for transcription co-activators.

    Directory of Open Access Journals (Sweden)

    Ted W Simon

    Full Text Available A stochastic model of nuclear receptor-mediated transcription was developed based on activation of the aryl hydrocarbon receptor (AHR by 2,3,7,8-tetrachlorodibenzodioxin (TCDD and subsequent binding the activated AHR to xenobiotic response elements (XREs on DNA. The model was based on effects observed in cells lines commonly used as in vitro experimental systems. Following ligand binding, the AHR moves into the cell nucleus and forms a heterodimer with the aryl hydrocarbon nuclear translocator (ARNT. In the model, a requirement for binding to DNA is that a generic coregulatory protein is subsequently bound to the AHR-ARNT dimer. Varying the amount of coregulator available within the nucleus altered both the potency and efficacy of TCDD for inducing for transcription of CYP1A1 mRNA, a commonly used marker for activation of the AHR. Lowering the amount of available cofactor slightly increased the EC50 for the transcriptional response without changing the efficacy or maximal response. Further reduction in the amount of cofactor reduced the efficacy and produced non-monotonic dose-response curves (NMDRCs at higher ligand concentrations. The shapes of these NMDRCs were reminiscent of the phenomenon of squelching. Resource limitations for transcriptional machinery are becoming apparent in eukaryotic cells. Within single cells, nuclear receptor-mediated gene expression appears to be a stochastic process; however, intercellular communication and other aspects of tissue coordination may represent a compensatory process to maintain an organism's ability to respond on a phenotypic level to various stimuli within an inconstant environment.

  7. Transcriptomic assessment of resistance to effects of an aryl hydrocarbon receptor (AHR agonist in embryos of Atlantic killifish (Fundulus heteroclitus from a marine Superfund site

    Directory of Open Access Journals (Sweden)

    Franks Diana G

    2011-05-01

    Full Text Available Abstract Background Populations of Atlantic killifish (Fundulus heteroclitus have evolved resistance to the embryotoxic effects of polychlorinated biphenyls (PCBs and other halogenated and nonhalogenated aromatic hydrocarbons that act through an aryl hydrocarbon receptor (AHR-dependent signaling pathway. The resistance is accompanied by reduced sensitivity to induction of cytochrome P450 1A (CYP1A, a widely used biomarker of aromatic hydrocarbon exposure and effect, but whether the reduced sensitivity is specific to CYP1A or reflects a genome-wide reduction in responsiveness to all AHR-mediated changes in gene expression is unknown. We compared gene expression profiles and the response to 3,3',4,4',5-pentachlorobiphenyl (PCB-126 exposure in embryos (5 and 10 dpf and larvae (15 dpf from F. heteroclitus populations inhabiting the New Bedford Harbor, Massachusetts (NBH Superfund site (PCB-resistant and a reference site, Scorton Creek, Massachusetts (SC; PCB-sensitive. Results Analysis using a 7,000-gene cDNA array revealed striking differences in responsiveness to PCB-126 between the populations; the differences occur at all three stages examined. There was a sizeable set of PCB-responsive genes in the sensitive SC population, a much smaller set of PCB-responsive genes in NBH fish, and few similarities in PCB-responsive genes between the two populations. Most of the array results were confirmed, and additional PCB-regulated genes identified, by RNA-Seq (deep pyrosequencing. Conclusions The results suggest that NBH fish possess a gene regulatory defect that is not specific to one target gene such as CYP1A but rather lies in a regulatory pathway that controls the transcriptional response of multiple genes to PCB exposure. The results are consistent with genome-wide disruption of AHR-dependent signaling in NBH fish.

  8. 芳香烃受体参与自身免疫性皮肤病发病机制的研究进展%Aryl hydrocarbon receptor participates in the development of autoimmune dermatoses: an update on mechanisms

    Institute of Scientific and Technical Information of China (English)

    王筱雯; 李春英; 高天文

    2012-01-01

    芳香烃受体是一种胞质转录因子,参与免疫应答、小分子物质代谢、内分泌稳态及黑素合成等多种生物学过程.近年来研究发现,芳香烃受体能够介导外源性小分子化学物质干扰免疫系统,导致机体产生变态反应和自身免疫反应,其在自身免疫性皮肤病的发生发展中也发挥着作用.概述芳香烃受体的信号通路、免疫功能及其与自身免疫性皮肤病相关性的研究进展,进一步了解自身免疫性皮肤病的发病机制,为疾病的免疫治疗提供新思路.%Aryl hydrocarbon receptor,a cytosolic transcription factor,takes part in many biological processes including immune response,endocrine secretion,melanin synthesis and metabolism of low-molecular-weight molecules.Recent research has confirmed that aryl hydrocarbon receptor can interfere with immune system and result in allergic reaction and autoimmune response via interacting with low-molecular-weight chemicals.Also,aryl hydrocarbon receptor plays an important role in the development of autoimmune dermatoses.The authors review aryl hydrocarbon receptor signaling pathway,immunological functions and its association with autoimmune dermatoses,which may help to understand the pathogenesis of autoimmune dermatoses,and offer new ideas for immunotherapy of diseases.

  9. Identification of the Aryl Hydrocarbon Receptor Target Gene TiPARP as a Mediator of Suppression of Hepatic Gluconeogenesis by 2,3,7,8-Tetrachlorodibenzo-p-dioxin and of Nicotinamide as a Corrective Agent for This Effect*

    OpenAIRE

    Diani-Moore, Silvia; Ram, Payal; Li, Xintian; Mondal, Prosenjit; Youn, Dou Yeon; Sauve, Anthony A.; Rifkind, Arleen B.

    2010-01-01

    The environmental toxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin, dioxin) produces diverse toxic effects including a lethal wasting syndrome whose hallmark is suppressed hepatic gluconeogenesis. All TCDD toxicities require activation of the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor. Whereas the mechanism for AHR induction of target genes is well understood, it is not known how AHR activation produces any TCDD toxicity. This report identifies for the first time ...

  10. 2,3,7,8-Tetrachlorodibenzo-p-dioxin treatment alters eicosanoid levels in several organs of the mouse in an aryl hydrocarbon receptor-dependent fashion

    Energy Technology Data Exchange (ETDEWEB)

    Bui, Peter; Solaimani, Parrisa [Molecular Toxicology Program, University of California, Los Angeles, California 90095 (United States); Dept of Pathology and Laboratory Medicine, University of California, Los Angeles, California 90095 (United States); Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California 90095 (United States); Wu, Xiaomeng [Dept of Pathology and Laboratory Medicine, University of California, Los Angeles, California 90095 (United States); Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California 90095 (United States); Hankinson, Oliver, E-mail: ohank@mednet.ucla.edu [Molecular Toxicology Program, University of California, Los Angeles, California 90095 (United States); Dept of Pathology and Laboratory Medicine, University of California, Los Angeles, California 90095 (United States); Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California 90095 (United States); Molecular Biology Institute, University of California, Los Angeles, California 90095 (United States)

    2012-03-01

    2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) adversely affects many mammalian organs and tissues. These effects are mediated by the aryl hydrocarbon receptor (AHR). CYP1A1, CYP1A2 and CYP1B1 are upregulated by the liganded AHR. These (and other) cytochromes P450 can metabolize arachidonic acid into a variety of bioactive eicosanoids. Towards investigating a potential role of eicosanoids in TCDD toxicity, arachidonic acid, two other unsaturated long-chain fatty acids, and up to twenty-five eicosanoids were measured in five organs/tissues of male and female wild-type and Ahr null mice treated or untreated with TCDD. TCDD generally increased the levels of the four dihydroxyeicosatrienoic acids (DHETs) and (where measured) 5,6-epoxyeicosatrienoic acid and 18-, 19- and 20-hydroxyeicosatrienoic acids (HETEs) in the serum, liver, spleen and lungs, but not the heart, of both sexes, and increased the levels in the serum, liver and spleen of several metabolites that are usually considered products of lipoxygenase activity, but which may also be generated by cytochromes P450. TCDD also increased the levels of the esterified forms of these eicosanoids in the liver in parallel with the corresponding free forms. The levels of prostanoids were generally not affected by TCDD. The above changes did not occur in Ahr null mice, and are therefore mediated by the AHR. TCDD increased the mRNA levels of Cyp1a1, Cyp1a2, Cyp1b1 and the Pla2g12a form of phospholipase A{sub 2} to varying degrees in the different organs, and these increases correlated with some but not all the changes in eicosanoids levels in the organs, suggesting that other enzymes may also be involved. -- Highlights: ► TCDD treatment increases the levels of many eicosanoids in several mouse organs. ► Products of both the cytochrome P450 and classical lipoxygenase pathways are increased. ► These increases are dependent on the aryl hydrocarbon receptor. ► Cyp1a1, Cyp1a2 and Cyp1b1 appear to be responsible for much but

  11. Hypoxia perturbs aryl hydrocarbon receptor signaling and CYP1A1 expression induced by PCB 126 in human skin and liver-derived cell lines

    Energy Technology Data Exchange (ETDEWEB)

    Vorrink, Sabine U. [Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA (United States); Department of Radiation Oncology, The University of Iowa, Iowa City, IA (United States); Severson, Paul L. [Department of Pharmacology and Toxicology, The University of Arizona, Tucson, AZ (United States); Kulak, Mikhail V. [Department of Surgery, The University of Iowa, Iowa City, IA (United States); Futscher, Bernard W. [Department of Pharmacology and Toxicology, The University of Arizona, Tucson, AZ (United States); Domann, Frederick E., E-mail: frederick-domann@uiowa.edu [Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA (United States); Department of Radiation Oncology, The University of Iowa, Iowa City, IA (United States); Department of Surgery, The University of Iowa, Iowa City, IA (United States)

    2014-02-01

    The aryl hydrocarbon receptor (AhR) is an important mediator of toxic responses after exposure to xenobiotics including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like polychlorinated biphenyls (PCBs). Activation of AhR responsive genes requires AhR dimerization with the aryl hydrocarbon receptor nuclear translocator (ARNT), a heterodimeric partner also shared by the hypoxia-inducible factor-1α (HIF-1α) protein. TCDD-stimulated AhR transcriptional activity can be influenced by hypoxia; however, it less well known whether hypoxia interferes with AhR transcriptional transactivation in the context of PCB-mediated AhR activation in human cells. Elucidation of this interaction is important in liver hepatocytes which extensively metabolize ingested PCBs and experience varying degrees of oxygen tension during normal physiologic function. This study was designed to assess the effect of hypoxia on AhR transcriptional responses after exposure to 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126). Exposure to 1% O{sub 2} prior to PCB 126 treatment significantly inhibited CYP1A1 mRNA and protein expression in human HepG2 and HaCaT cells. CYP1A1 transcriptional activation was significantly decreased upon PCB 126 stimulation under conditions of hypoxia. Additionally, hypoxia pre-treatment reduced PCB 126 induced AhR binding to CYP1 target gene promoters. Importantly, ARNT overexpression rescued cells from the inhibitory effect of hypoxia on XRE-luciferase reporter activity. Therefore, the mechanism of interference of the signaling crosstalk between the AhR and hypoxia pathways appears to be at least in part dependent on ARNT availability. Our results show that AhR activation and CYP1A1 expression induced by PCB 126 were significantly inhibited by hypoxia and hypoxia might therefore play an important role in PCB metabolism and toxicity. - Highlights: • Significant crosstalk exists between AhR and HIF-1α signaling. • Hypoxia perturbs PCB 126 induced AhR function and

  12. Identification of aryl hydrocarbon receptor binding targets in mouse hepatic tissue treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Raymond; Celius, Trine [Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario (Canada); Forgacs, Agnes L. [Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI (United States); Center for Integrative Toxicology, Michigan State University, East Lansing, MI (United States); Dere, Edward [Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI (United States); MacPherson, Laura [Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario (Canada); Harper, Patricia [Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario (Canada); Research Institute, The Hospital for Sick Children, Toronto, Ontario (Canada); Zacharewski, Timothy [Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI (United States); Center for Integrative Toxicology, Michigan State University, East Lansing, MI (United States); Matthews, Jason, E-mail: jason.matthews@utoronto.ca [Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario (Canada)

    2011-11-15

    Genome-wide, promoter-focused ChIP-chip analysis of hepatic aryl hydrocarbon receptor (AHR) binding sites was conducted in 8-week old female C57BL/6 treated with 30 {mu}g/kg/body weight 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for 2 h and 24 h. These studies identified 1642 and 508 AHR-bound regions at 2 h and 24 h, respectively. A total of 430 AHR-bound regions were common between the two time points, corresponding to 403 unique genes. Comparison with previous AHR ChIP-chip studies in mouse hepatoma cells revealed that only 62 of the putative target genes overlapped with the 2 h AHR-bound regions in vivo. Transcription factor binding site analysis revealed an over-representation of aryl hydrocarbon response elements (AHREs) in AHR-bound regions with 53% (2 h) and 68% (24 h) of them containing at least one AHRE. In addition to AHREs, E2f-Myc activator motifs previously implicated in AHR function, as well as a number of other motifs, including Sp1, nuclear receptor subfamily 2 factor, and early growth response factor motifs were also identified. Expression microarray studies identified 133 unique genes differentially regulated after 4 h treatment with TCDD. Of which, 39 were identified as AHR-bound genes at 2 h. Ingenuity Pathway Analysis on the 39 AHR-bound TCDD responsive genes identified potential perturbation in biological processes such as lipid metabolism, drug metabolism, and endocrine system development as a result of TCDD-mediated AHR activation. Our findings identify direct AHR target genes in vivo, highlight in vitro and in vivo differences in AHR signaling and show that AHR recruitment does not necessarily result in changes in target gene expression. -- Highlights: Black-Right-Pointing-Pointer ChIP-chip analysis of hepatic AHR binding after 2 h and 24 h of TCDD. Black-Right-Pointing-Pointer We identified 1642 and 508 AHR-bound regions at 2 h and 24 h. Black-Right-Pointing-Pointer 430 regions were common to both time points and highly enriched with

  13. Effects of currently used pesticides and their mixtures on the function of thyroid hormone and aryl hydrocarbon receptor in cell culture

    International Nuclear Information System (INIS)

    Evidence suggest that exposure to pesticides can interfere with the endocrine system by multiple mechanisms. The endocrine disrupting potential of currently used pesticides in Denmark was analyzed as single compounds and in an equimolar mixture of 5 selected pesticides. The pesticides were previously analyzed for effects on the function of estrogen and androgen receptors, the aromatase enzyme and steroidogenesis in vitro. In this study, the effect on thyroid hormone (TH) function and aryl hydrocarbon receptor (AhR) transactivity was assessed using GH3 cell proliferation assay (T-screen) and AhR responsive luciferase reporter gene bioassay, respectively. Thirteen pesticides were analyzed as follows: 2-methyl-4-chlorophenoxyacetic acid, terbuthylazine, iodosulfuron-methyl-sodium, mesosulfuron-methyl, metsulfuron-methyl, chlormequat chloride, bitertanol, propiconazole, prothioconazole, mancozeb and its metabolite ethylene thiourea, cypermethrin, tau-fluvalinate, and malathion (currently banned in DK). In the T-screen, prothioconazole, malathion, tau-fluvalinate, cypermethrin, terbuthylazine and mancozeb significantly stimulated and bitertanol and propiconazole slightly reduced the GH3 cell proliferation. In the presence of triiodothyronine (T3), prothioconazole, tau-fluvalinate, propiconazole, cypermethrin and bitertanol significantly antagonized the T3-induced GH3 cell proliferation. Eleven of the tested pesticides agonized the AhR function, and bitertanol and prothioconazole inhibited the basal AhR activity. Bitertanol, propiconazole, prothioconazole and cypermethrin antagonized the TCDD-induced AhR transactivation at the highest tested concentration. The 5-component mixture had inducing effect but the combined effect could not be predicted due to the presence of bitertanol eliciting inhibitory effect. Upon removal of bitertanol from the mixture, the remaining four pesticides acted additively. In conclusion, our data suggest that pesticides currently used in Denmark

  14. 2,3,7,8-Tetrachlorodibenzo-p-dioxin treatment alters eicosanoid levels in several organs of the mouse in an aryl hydrocarbon receptor-dependent fashion

    International Nuclear Information System (INIS)

    2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) adversely affects many mammalian organs and tissues. These effects are mediated by the aryl hydrocarbon receptor (AHR). CYP1A1, CYP1A2 and CYP1B1 are upregulated by the liganded AHR. These (and other) cytochromes P450 can metabolize arachidonic acid into a variety of bioactive eicosanoids. Towards investigating a potential role of eicosanoids in TCDD toxicity, arachidonic acid, two other unsaturated long-chain fatty acids, and up to twenty-five eicosanoids were measured in five organs/tissues of male and female wild-type and Ahr null mice treated or untreated with TCDD. TCDD generally increased the levels of the four dihydroxyeicosatrienoic acids (DHETs) and (where measured) 5,6-epoxyeicosatrienoic acid and 18-, 19- and 20-hydroxyeicosatrienoic acids (HETEs) in the serum, liver, spleen and lungs, but not the heart, of both sexes, and increased the levels in the serum, liver and spleen of several metabolites that are usually considered products of lipoxygenase activity, but which may also be generated by cytochromes P450. TCDD also increased the levels of the esterified forms of these eicosanoids in the liver in parallel with the corresponding free forms. The levels of prostanoids were generally not affected by TCDD. The above changes did not occur in Ahr null mice, and are therefore mediated by the AHR. TCDD increased the mRNA levels of Cyp1a1, Cyp1a2, Cyp1b1 and the Pla2g12a form of phospholipase A2 to varying degrees in the different organs, and these increases correlated with some but not all the changes in eicosanoids levels in the organs, suggesting that other enzymes may also be involved. -- Highlights: ► TCDD treatment increases the levels of many eicosanoids in several mouse organs. ► Products of both the cytochrome P450 and classical lipoxygenase pathways are increased. ► These increases are dependent on the aryl hydrocarbon receptor. ► Cyp1a1, Cyp1a2 and Cyp1b1 appear to be responsible for much but not

  15. Deletion of ARNT (Aryl hydrocarbon receptor nuclear translocator in β-cells causes islet transplant failure with impaired β-cell function.

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    Amit Lalwani

    Full Text Available BACKGROUND: Replacing β-cells by islet-transplantation can cure type 1 diabetes, but up to 70% of β-cells die within 10 days of transplantation. ARNT (Aryl hydrocarbon Receptor Nuclear Translocator regulates β-cell function, and potentially survival. Lack of ARNT impairs the ability of β-cells to respond to physiological stress and potentiates the onset of diabetes, but the exact role of ARNT in graft outcome is unknown. AIM: To investigate the effect of β-cell deletion of ARNT on graft outcomes. METHODS: Islets were isolated from donor mice which had β-cell specific ARNT-deletion (β-ARNT or littermate floxed controls. The islets were transplanted into diabetic SCID recipients in ratios of (a 3 donors: 1 recipient, (b 1 donor: 1 recipient or (c ½ of the islets from 1 donor: 1 recipient. After 28 days, the kidney containing the graft was removed (nephrectomy to exclude regeneration of the endogenous pancreas. RESULTS: In the supra-physiological-mass model (3:1, both groups achieved reasonable glycaemia, with slightly higher levels in β-ARNT-recipients. In adequate-mass model (1:1, β-ARNT recipients had poor glucose control versus floxed-control recipients and versus the β-ARNT donors. In the low-β-cell-mass model (½:1 β-ARNT transplants completely failed, whereas controls had good outcomes. Unexpectedly, there was no difference in the graft insulin content or β-cell mass between groups indicating that the defect was not due to early altered β-cell survival. CONCLUSION: Outcomes for islet transplants lacking β-cell ARNT were poor, unless markedly supra-physiological masses of islets were transplanted. In the 1:1 transplant model, there was no difference in β-cell volume. This is surprising because transplants of islets lacking one of the ARNT-partners HIF-1α have increased apoptosis and decreased islet volume. ARNT also partners HIF-2α and AhR (aryl hydrocarbon receptor to form active transcriptional complexes, and further work

  16. Effects of currently used pesticides and their mixtures on the function of thyroid hormone and aryl hydrocarbon receptor in cell culture

    Energy Technology Data Exchange (ETDEWEB)

    Ghisari, Mandana; Long, Manhai; Tabbo, Agnese; Bonefeld-Jørgensen, Eva Cecilie, E-mail: ebj@mil.au.dk

    2015-05-01

    Evidence suggest that exposure to pesticides can interfere with the endocrine system by multiple mechanisms. The endocrine disrupting potential of currently used pesticides in Denmark was analyzed as single compounds and in an equimolar mixture of 5 selected pesticides. The pesticides were previously analyzed for effects on the function of estrogen and androgen receptors, the aromatase enzyme and steroidogenesis in vitro. In this study, the effect on thyroid hormone (TH) function and aryl hydrocarbon receptor (AhR) transactivity was assessed using GH3 cell proliferation assay (T-screen) and AhR responsive luciferase reporter gene bioassay, respectively. Thirteen pesticides were analyzed as follows: 2-methyl-4-chlorophenoxyacetic acid, terbuthylazine, iodosulfuron-methyl-sodium, mesosulfuron-methyl, metsulfuron-methyl, chlormequat chloride, bitertanol, propiconazole, prothioconazole, mancozeb and its metabolite ethylene thiourea, cypermethrin, tau-fluvalinate, and malathion (currently banned in DK). In the T-screen, prothioconazole, malathion, tau-fluvalinate, cypermethrin, terbuthylazine and mancozeb significantly stimulated and bitertanol and propiconazole slightly reduced the GH3 cell proliferation. In the presence of triiodothyronine (T3), prothioconazole, tau-fluvalinate, propiconazole, cypermethrin and bitertanol significantly antagonized the T3-induced GH3 cell proliferation. Eleven of the tested pesticides agonized the AhR function, and bitertanol and prothioconazole inhibited the basal AhR activity. Bitertanol, propiconazole, prothioconazole and cypermethrin antagonized the TCDD-induced AhR transactivation at the highest tested concentration. The 5-component mixture had inducing effect but the combined effect could not be predicted due to the presence of bitertanol eliciting inhibitory effect. Upon removal of bitertanol from the mixture, the remaining four pesticides acted additively. In conclusion, our data suggest that pesticides currently used in Denmark

  17. Hypoxia perturbs aryl hydrocarbon receptor signaling and CYP1A1 expression induced by PCB 126 in human skin and liver-derived cell lines

    International Nuclear Information System (INIS)

    The aryl hydrocarbon receptor (AhR) is an important mediator of toxic responses after exposure to xenobiotics including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like polychlorinated biphenyls (PCBs). Activation of AhR responsive genes requires AhR dimerization with the aryl hydrocarbon receptor nuclear translocator (ARNT), a heterodimeric partner also shared by the hypoxia-inducible factor-1α (HIF-1α) protein. TCDD-stimulated AhR transcriptional activity can be influenced by hypoxia; however, it less well known whether hypoxia interferes with AhR transcriptional transactivation in the context of PCB-mediated AhR activation in human cells. Elucidation of this interaction is important in liver hepatocytes which extensively metabolize ingested PCBs and experience varying degrees of oxygen tension during normal physiologic function. This study was designed to assess the effect of hypoxia on AhR transcriptional responses after exposure to 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126). Exposure to 1% O2 prior to PCB 126 treatment significantly inhibited CYP1A1 mRNA and protein expression in human HepG2 and HaCaT cells. CYP1A1 transcriptional activation was significantly decreased upon PCB 126 stimulation under conditions of hypoxia. Additionally, hypoxia pre-treatment reduced PCB 126 induced AhR binding to CYP1 target gene promoters. Importantly, ARNT overexpression rescued cells from the inhibitory effect of hypoxia on XRE-luciferase reporter activity. Therefore, the mechanism of interference of the signaling crosstalk between the AhR and hypoxia pathways appears to be at least in part dependent on ARNT availability. Our results show that AhR activation and CYP1A1 expression induced by PCB 126 were significantly inhibited by hypoxia and hypoxia might therefore play an important role in PCB metabolism and toxicity. - Highlights: • Significant crosstalk exists between AhR and HIF-1α signaling. • Hypoxia perturbs PCB 126 induced AhR function and target

  18. The Group 3 Innate Lymphoid Cell Defect in Aryl Hydrocarbon Receptor Deficient Mice Is Associated with T Cell Hyperactivation during Intestinal Infection.

    Directory of Open Access Journals (Sweden)

    Sagie Wagage

    Full Text Available Intestinal infection with the intracellular parasite Toxoplasma gondii results in the translocation of commensal bacteria to peripheral organs and the development of a T cell response specific to the microbiota. In naïve mice, the recently described RORγt+ group 3 innate lymphoid cell (ILC population plays a critical role in promoting intestinal barrier function and limiting responses to gut-resident commensal bacteria. Given this role for group 3 ILCs, studies were performed to evaluate whether these cells might influence the immune response to mucosal infection with T. gondii. Phenotypic characterization of RORγt+ ILCs in T. gondii infected mice revealed that this population decreased following challenge but the population that remained expressed costimulatory molecules and IL-22. One factor that influences the maintenance of RORγt+ ILCs is the aryl hydrocarbon receptor (AHR, a ligand-activated transcription factor, and Ahr-/- mice have a marked defect in the lamina propria group 3 ILC population. When Ahr-/- mice were challenged with T. gondii, they lost more weight than wild type controls. This disease course in Ahr-/- animals was associated with increased T cell responses to Toxoplasma antigen and crude commensal antigen preparations. Together, these data suggest that group 3 ILCs have a role in limiting T cell activation during intestinal infection.

  19. 芳香烃受体在肠道免疫研究中的进展%Role of aryl hydrocarbon receptor in intestinal immune function

    Institute of Scientific and Technical Information of China (English)

    邱远; 于敏; 杨桦

    2013-01-01

    As a transcription factor whose activity is controlled by environmental ligands,the aryl hydrocarbon receptor(AhR) plays an important role in intestinal immune fuction.AhR has emerged as a master regulator for the intestinal receptor-related orphan receptor (ROR) γ t-expressing innate lymphoid cells (ILCs) and intraepithelial lymphocytes (IELs).The colonization,secretion,proliferation and apoptosis of these cells are tightly regulated by AhR.AhR also provides a new potential therapeutic target for inflammatory bowel disease(ZBD).Here,the role of AhR in intestinal immune system and its impact on IBD is reviewed.%芳香烃受体(AhR)作为配体激活的转录因子,近年来其对肠道免疫功能的调控已经成为研究热点.表达视黄醇类核内受体(ROR)γt的固有淋巴细胞(ILCs)和肠上皮间淋巴细胞(IELs)是肠道免疫系统受AhR调控的重要细胞.这两群细胞在肠道的定植,分泌功能以及增殖凋亡都与AhR密切相关.AhR的特殊作用使其已然成为炎性肠病(IBD)治疗中的新靶点.

  20. G protein-coupled receptor 30 ligand G-1 increases aryl hydrocarbon receptor signalling by inhibition of tubulin assembly and cell cycle arrest in human MCF-7 cells.

    Science.gov (United States)

    Tarnow, Patrick; Tralau, Tewes; Luch, Andreas

    2016-08-01

    Regulatory crosstalk between the aryl hydrocarbon receptor (AHR) and oestrogen receptor α (ERα) is well established. Apart from the nuclear receptors ERα and ERβ, oestrogen signalling further involves an unrelated G protein-coupled receptor termed GPR30. In order to investigate potential regulatory crosstalk, this study investigated the influence of G-1 as one of the few GPR30-specific ligands on the AHR regulon in MCF-7 cells. As a well-characterised model system, these human mammary carcinoma cells co-express all three receptors (AHR, ERα and GPR30) and are thus ideally suited to study corresponding regulatory pathway interactions on transcript level. Indeed, treatment with micromolar concentrations of the GPR30-specific agonist G-1 resulted in up-regulation of AHR as well as the transcripts for cytochromes P450 1A1 and 1B1, two well-known targets of the AHR regulon. While this was partly attributable to G-1-mediated inhibition of tubulin assembly and subsequent cell cycle arrest in the G2/M phase, the effects nevertheless required functional AHR. However, G-1-induced up-regulation of CYP 1A1 was not mediated by GPR30, as G15 antagonist treatment as well as a knockdown of GPR30 and AHR failed to inhibit this effect. PMID:26475489

  1. Expression of the Aryl Hydrocarbon Receptor in Growth Plate Cartilage and the Impact of Its Local Modulation on Longitudinal Bone Growth

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    Therése Cedervall

    2015-04-01

    Full Text Available Although dioxin has been reported to impair bone growth in both humans and animals, the underlying mechanisms have not been clarified. We conducted this study to rule out if dioxin may directly target the growth plate, via local modulation of the aryl hydrocarbon receptor (AhR. Initial studies in rare tissue samples of the human growth plate confirmed that the AhR protein is widely expressed in growth plate cartilage. To explore the local role of the AhR, mechanistic studies were performed in a well-established model of cultured fetal rat metatarsal bones. The longitudinal growth of these bones was monitored while being exposed to AhR modulators. The AhR agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin, did not affect bone growth at any concentrations tested (1 pM–10 nM. In contrast, the AhR antagonist, alpha-naphthoflavone, suppressed bone growth and increased chondrocyte apoptosis, although only at a high, potentially cytotoxic concentration (50 µM. We conclude that although the AhR is widely expressed in the growth plate, bone growth is not modulated when locally activated, and therefore, dioxin-induced growth failure is likely mediated through systemic rather than local actions.

  2. The Group 3 Innate Lymphoid Cell Defect in Aryl Hydrocarbon Receptor Deficient Mice Is Associated with T Cell Hyperactivation during Intestinal Infection.

    Science.gov (United States)

    Wagage, Sagie; Harms Pritchard, Gretchen; Dawson, Lucas; Buza, Elizabeth L; Sonnenberg, Gregory F; Hunter, Christopher A

    2015-01-01

    Intestinal infection with the intracellular parasite Toxoplasma gondii results in the translocation of commensal bacteria to peripheral organs and the development of a T cell response specific to the microbiota. In naïve mice, the recently described RORγt+ group 3 innate lymphoid cell (ILC) population plays a critical role in promoting intestinal barrier function and limiting responses to gut-resident commensal bacteria. Given this role for group 3 ILCs, studies were performed to evaluate whether these cells might influence the immune response to mucosal infection with T. gondii. Phenotypic characterization of RORγt+ ILCs in T. gondii infected mice revealed that this population decreased following challenge but the population that remained expressed costimulatory molecules and IL-22. One factor that influences the maintenance of RORγt+ ILCs is the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, and Ahr-/- mice have a marked defect in the lamina propria group 3 ILC population. When Ahr-/- mice were challenged with T. gondii, they lost more weight than wild type controls. This disease course in Ahr-/- animals was associated with increased T cell responses to Toxoplasma antigen and crude commensal antigen preparations. Together, these data suggest that group 3 ILCs have a role in limiting T cell activation during intestinal infection. PMID:26010337

  3. Characterizing the role of endothelin-1 in the progression of cardiac hypertrophy in aryl hydrocarbon receptor (AhR) null mice

    International Nuclear Information System (INIS)

    The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor characterized to play a role in detection and adaptation to environmental stimuli. Genetic deletion of AhR results in hypertension, and cardiac hypertrophy and fibrosis, associated with elevated plasma angiotensin II (Ang II) and endothelin-1 (ET-1), thus AhR appears to contribute to cardiovascular homeostasis. In these studies, we tested the hypothesis that ET-1 mediates cardiovascular pathology in AhR null mice via ETA receptor activation. First, we determine the time courses of cardiac hypertrophy, and of plasma and tissue ET-1 expression in AhR wildtype and null mice. AhR null mice exhibited increases in heart-to-body weight ratio and age-related expression of cardiac hypertrophy markers, β-myosin heavy chain (β-MHC), and atrial natriuretic factor (ANF), which were significant at 2 months. Similarly, plasma and tissue ET-1 expression was significantly elevated at 2 months and increased further with age. Second, AhR null mice were treated with ETA receptor antagonist, BQ-123 (100 nmol/kg/day), for 7, 28, or 58 days and blood pressure, cardiac fibrosis, and cardiac hypertrophy assessed, respectively. BQ-123 for 7 days significantly reduced mean arterial pressure in conscious, catheterized mice. BQ-123 for 28 days significantly reduced the histological appearance of cardiac fibrosis. Treatment for 58 days significantly reduced cardiac mass, assessed by heart weight, echocardiography, and β-MHC and ANF expression; and reduced cardiac fibrosis as determined by osteopontin and collagen I mRNA expression. These findings establish ET-1 and the ETA receptor as primary determinants of hypertension and cardiac pathology in AhR null mice

  4. The Mitochondria-Targeted Antioxidant SkQ1 Downregulates Aryl Hydrocarbon Receptor-Dependent Genes in the Retina of OXYS Rats with AMD-Like Retinopathy

    Directory of Open Access Journals (Sweden)

    M. L. Perepechaeva

    2014-01-01

    Full Text Available The mitochondria-targeted antioxidant SkQ1 is a novel drug thought to retard development of age-related diseases. It has been shown that SkQ1 reduces clinical signs of retinopathy in senescence-accelerated OXYS rats, which are a known animal model of human age-related macular degeneration (AMD. The aim of this work was to test whether SkQ1 affects transcriptional activity of AhR (aryl hydrocarbon receptor and Nrf2 (nuclear factor erythroid 2-related factor 2, which are considered as AMD-associated genes in the retina of OXYS and Wistar rats. Our results showed that only AhR and AhR-dependent genes were sensitive to SkQ1. Dietary supplementation with SkQ1 decreased the AhR mRNA level in both OXYS and Wistar rats. At baseline, the retinal Cyp1a1 mRNA level was lower in OXYS rats. SkQ1 supplementation decreased the Cyp1a1 mRNA level in Wistar rats, but this level remained unchanged in OXYS rats. Baseline Cyp1a2 and Cyp1b1 mRNA expression was stronger in OXYS than in Wistar rats. In the OXYS strain, Cyp1a2 and Cyp1b1 mRNA levels decreased as a result of SkQ1 supplementation. These data suggest that the Cyp1a2 and Cyp1b1 enzymes are involved in the pathogenesis of AMD-like retinopathy of OXYS rats and are possible therapeutic targets of SkQ1.

  5. Diphenylarsinic acid, a chemical warfare-related neurotoxicant, promotes liver carcinogenesis via activation of aryl hydrocarbon receptor signaling and consequent induction of oxidative DAN damage in rats

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Min; Yamada, Takanori; Yamano, Shotaro; Kato, Minoru; Kakehashi, Anna; Fujioka, Masaki; Tago, Yoshiyuki; Kitano, Mistuaki; Wanibuchi, Hideki, E-mail: wani@med.osaka-cu.ac.jp

    2013-11-15

    Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes in the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies. - Highlights: • DPAA, an environmental neurotoxicant, promotes liver carcinogenesis in rats. • DPAA is an activator of AhR signaling pathway. • DPAA promoted oxidative DNA damage in rat livers. • AhR target gene CYP 1B1 might be involved in the metabolism of DPAA.

  6. Aryl hydrocarbon receptor knockout rats are insensitive to the pathological effects of repeated oral exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

    Science.gov (United States)

    Harrill, Joshua A; Layko, Debra; Nyska, Abraham; Hukkanen, Renee R; Manno, Rosa Anna; Grassetti, Andrea; Lawson, Marie; Martin, Greg; Budinsky, Robert A; Rowlands, J Craig; Thomas, Russell S

    2016-06-01

    Sustained activation of the aryl hydrocarbon receptor (AHR) is believed to be the initial key event in AHR receptor-mediated tumorigenesis in the rat liver. The role of AHR in mediating pathological changes in the liver prior to tumor formation was investigated in a 4-week, repeated-dose study using adult female wild-type (WT) and AHR knockout (AHR-KO) rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Beginning at 8 weeks of age, AHR-KO and WT rats were dosed by oral gavage with varying concentrations of TCDD (0, 3, 22, 100, 300 and 1000 ng kg(-1)  day(-1) ). Lung, liver and thymus histopathology, hematology, serum chemistry and the distribution of TCDD in liver and adipose tissue were examined. Treatment-related increases in the severity of liver and thymus pathology were observed in WT, but not AHR-KO rats. In the liver, these included hepatocellular hypertrophy, bile duct hyperplasia, multinucleated hepatocytes and inflammatory cell foci. A loss of cellularity in the thymic cortex and thymic atrophy was observed. Treatment-related changes in serum chemistry parameters were also observed in WT, but not AHR-KO rats. Finally, dose-dependent accumulation of TCDD was observed primarily in the liver of WT rats and primarily in the adipose tissue of AHR-KO rats. The results suggest that AHR activation is the initial key event underlying the progression of histological effects leading to liver tumorigenesis following TCDD treatment. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26278112

  7. Skatole (3-Methylindole Is a Partial Aryl Hydrocarbon Receptor Agonist and Induces CYP1A1/2 and CYP1B1 Expression in Primary Human Hepatocytes.

    Directory of Open Access Journals (Sweden)

    Martin Krøyer Rasmussen

    Full Text Available Skatole (3-methylindole is a product of bacterial fermentation of tryptophan in the intestine. A significant amount of skatole can also be inhaled during cigarette smoking. Skatole is a pulmonary toxin that induces the expression of aryl hydrocarbon receptor (AhR regulated genes, such as cytochrome P450 1A1 (CYP1A1, in human bronchial cells. The liver has a high metabolic capacity for skatole and is the first organ encountered by the absorbed skatole; however, the effect of skatole in the liver is unknown. Therefore, we investigated the impact of skatole on hepatic AhR activity and AhR-regulated gene expression. Using reporter gene assays, we showed that skatole activates AhR and that this is accompanied by an increase of CYP1A1, CYP1A2 and CYP1B1 expression in HepG2-C3 and primary human hepatocytes. Specific AhR antagonists and siRNA-mediated AhR silencing demonstrated that skatole-induced CYP1A1 expression is dependent on AhR activation. The effect of skatole was reduced by blocking intrinsic cytochrome P450 activity and indole-3-carbinole, a known skatole metabolite, was a more potent inducer than skatole. Finally, skatole could reduce TCDD-induced CYP1A1 expression, suggesting that skatole is a partial AhR agonist. In conclusion, our findings suggest that skatole and its metabolites affect liver homeostasis by modulating the AhR pathway.

  8. Activation of aryl hydrocarbon receptor (AhR leads to reciprocal epigenetic regulation of FoxP3 and IL-17 expression and amelioration of experimental colitis.

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    Narendra P Singh

    Full Text Available BACKGROUND: Aryl hydrocarbon receptor (AhR, a transcription factor of the bHLH/PAS family, is well characterized to regulate the biochemical and toxic effects of environmental chemicals. More recently, AhR activation has been shown to regulate the differentiation of Foxp3(+ Tregs as well as Th17 cells. However, the precise mechanisms are unclear. In the current study, we investigated the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, a potent AhR ligand, on epigenetic regulation leading to altered Treg/Th17 differentiation, and consequent suppression of colitis. METHODOLOGY/PRINCIPAL FINDINGS: Dextran sodium sulphate (DSS administration induced acute colitis in C57BL/6 mice, as shown by significant weight loss, shortening of colon, mucosal ulceration, and increased presence of CXCR3(+ T cells as well as inflammatory cytokines. Interestingly, a single dose of TCDD (25 µg/kg body weight was able to attenuate all of the clinical and inflammatory markers of colitis. Analysis of T cells in the lamina propria (LP and mesenteric lymph nodes (MLN, during colitis, revealed decreased presence of Tregs and increased induction of Th17 cells, which was reversed following TCDD treatment. Activation of T cells from AhR(+/+ but not AhR (-/- mice, in the presence of TCDD, promoted increased differentiation of Tregs while inhibiting Th17 cells. Analysis of MLN or LP cells during colitis revealed increased methylation of CpG islands of Foxp3 and demethylation of IL-17 promoters, which was reversed following TCDD treatment. CONCLUSIONS/SIGNIFICANCE: These studies demonstrate for the first time that AhR activation promotes epigenetic regulation thereby influencing reciprocal differentiation of Tregs and Th17 cells, and amelioration of inflammation.

  9. Skatole (3-Methylindole) Is a Partial Aryl Hydrocarbon Receptor Agonist and Induces CYP1A1/2 and CYP1B1 Expression in Primary Human Hepatocytes.

    Science.gov (United States)

    Rasmussen, Martin Krøyer; Balaguer, Patrick; Ekstrand, Bo; Daujat-Chavanieu, Martine; Gerbal-Chaloin, Sabine

    2016-01-01

    Skatole (3-methylindole) is a product of bacterial fermentation of tryptophan in the intestine. A significant amount of skatole can also be inhaled during cigarette smoking. Skatole is a pulmonary toxin that induces the expression of aryl hydrocarbon receptor (AhR) regulated genes, such as cytochrome P450 1A1 (CYP1A1), in human bronchial cells. The liver has a high metabolic capacity for skatole and is the first organ encountered by the absorbed skatole; however, the effect of skatole in the liver is unknown. Therefore, we investigated the impact of skatole on hepatic AhR activity and AhR-regulated gene expression. Using reporter gene assays, we showed that skatole activates AhR and that this is accompanied by an increase of CYP1A1, CYP1A2 and CYP1B1 expression in HepG2-C3 and primary human hepatocytes. Specific AhR antagonists and siRNA-mediated AhR silencing demonstrated that skatole-induced CYP1A1 expression is dependent on AhR activation. The effect of skatole was reduced by blocking intrinsic cytochrome P450 activity and indole-3-carbinole, a known skatole metabolite, was a more potent inducer than skatole. Finally, skatole could reduce TCDD-induced CYP1A1 expression, suggesting that skatole is a partial AhR agonist. In conclusion, our findings suggest that skatole and its metabolites affect liver homeostasis by modulating the AhR pathway. PMID:27138278

  10. Modulation of aryl hydrocarbon receptor target genes in circulating lymphocytes from dairy cows bred in a dioxin-like PCB contaminated area

    International Nuclear Information System (INIS)

    Animal productions (i.e. fish, eggs, milk and dairy products) represent the major source of exposure to dioxins, furans, and dioxin-like (DL) polychlorobiphenyls for humans. The negative effects of these highly toxic and persistent pollutants are mediated by the activation of the aryl hydrocarbon receptor (AHR) that elicits the transcriptional induction of several genes, including those involved in xenobiotic metabolism. Previously we demonstrated the presence and functioning of the AHR signaling pathway in primary cultures of bovine blood lymphocytes. The aim of the present study was to investigate by real time PCR the expression and the inducibility of selected target genes (i.e. AHR, AHR nuclear translocator (ARNT), AHR repressor, CYP1A1 and CYP1B1) in uncultured cells from dairy cows naturally exposed to DL-compounds. The study was carried out on two groups of animals bred in a highly polluted area and characterized by a different degree of contamination, as assessed by bulk milk TEQ values, and a control group reared in an industry free area. Bovine lymphocytes expressed only AHR, ARNT and CYP1B1 genes to a detectable level; moreover, only CYP1B1 expression appeared to be correlated to TEQ values, being higher in the most contaminated group, and decreasing along with animal decontamination. Finally, lymphocytes from exposed cows displayed a lower inducibility of both CYP1A1 and CYP1B1 after the in vitro treatment with a specific AHR ligand. In conclusion, our results indicate that DL-compound contaminated cows may display significant changes in AHR-target gene expression of circulating lymphocytes. - Highlights: ► The expression of AHR-target genes in blood bovine lymphocytes was evaluated. ► The lymphocyte CYP1B1 expression appears to be related to bulk milk TEQ values. ► Blood lymphocytes from dairy cows might represent a matrix for dioxin biomonitoring

  11. Notch-regulated miR-223 targets the aryl hydrocarbon receptor pathway and increases cytokine production in macrophages from rheumatoid arthritis patients

    Science.gov (United States)

    Ogando, Jesús; Tardáguila, Manuel; Díaz-Alderete, Andrea; Usategui, Alicia; Miranda-Ramos, Vanessa; Martínez-Herrera, Dannys Jorge; de la Fuente, Lorena; García-León, María J.; Moreno, María C.; Escudero, Sara; Cañete, Juan D.; Toribio, María L.; Cases, Ildefonso; Pascual-Montano, Alberto; Pablos, José Luis; Mañes, Santos

    2016-01-01

    Evidence links aryl hydrocarbon receptor (AHR) activation to rheumatoid arthritis (RA) pathogenesis, although results are inconsistent. AHR agonists inhibit pro-inflammatory cytokine expression in macrophages, pivotal cells in RA aetiopathogenesis, which hints at specific circuits that regulate the AHR pathway in RA macrophages. We compared microRNA (miR) expression in CD14+ cells from patients with active RA or with osteoarthritis (OA). Seven miR were downregulated and one (miR-223) upregulated in RA compared to OA cells. miR-223 upregulation correlated with reduced Notch3 and Notch effector expression in RA patients. Overexpression of the Notch-induced repressor HEY-1 and co-culture of healthy donor monocytes with Notch ligand-expressing cells showed direct Notch-mediated downregulation of miR-223. Bioinformatics predicted the AHR regulator ARNT (AHR nuclear translocator) as a miR-223 target. Pre-miR-223 overexpression silenced ARNT 3’UTR-driven reporter expression, reduced ARNT (but not AHR) protein levels and prevented AHR/ARNT-mediated inhibition of pro-inflammatory cytokine expression. miR-223 counteracted AHR/ARNT-induced Notch3 upregulation in monocytes. Levels of ARNT and of CYP1B1, an AHR/ARNT signalling effector, were reduced in RA compared to OA synovial tissue, which correlated with miR-223 levels. Our results associate Notch signalling to miR-223 downregulation in RA macrophages, and identify miR-223 as a negative regulator of the AHR/ARNT pathway through ARNT targeting. PMID:26838552

  12. Modulation of aryl hydrocarbon receptor target genes in circulating lymphocytes from dairy cows bred in a dioxin-like PCB contaminated area

    Energy Technology Data Exchange (ETDEWEB)

    Girolami, Flavia, E-mail: flavia.girolami@unito.it [Department of Animal Pathology, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy); Spalenza, Veronica, E-mail: veronica.spalenza@unito.it [Department of Animal Production, Epidemiology and Ecology, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy); Carletti, Monica, E-mail: monica.carletti@unito.it [Department of Animal Pathology, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy); Sacchi, Paola, E-mail: paola.sacchi@unito.it [Department of Animal Production, Epidemiology and Ecology, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy); Rasero, Roberto, E-mail: roberto.rasero@unito.it [Department of Animal Production, Epidemiology and Ecology, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy); Nebbia, Carlo, E-mail: carlo.nebbia@unito.it [Department of Animal Pathology, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy)

    2013-04-15

    Animal productions (i.e. fish, eggs, milk and dairy products) represent the major source of exposure to dioxins, furans, and dioxin-like (DL) polychlorobiphenyls for humans. The negative effects of these highly toxic and persistent pollutants are mediated by the activation of the aryl hydrocarbon receptor (AHR) that elicits the transcriptional induction of several genes, including those involved in xenobiotic metabolism. Previously we demonstrated the presence and functioning of the AHR signaling pathway in primary cultures of bovine blood lymphocytes. The aim of the present study was to investigate by real time PCR the expression and the inducibility of selected target genes (i.e. AHR, AHR nuclear translocator (ARNT), AHR repressor, CYP1A1 and CYP1B1) in uncultured cells from dairy cows naturally exposed to DL-compounds. The study was carried out on two groups of animals bred in a highly polluted area and characterized by a different degree of contamination, as assessed by bulk milk TEQ values, and a control group reared in an industry free area. Bovine lymphocytes expressed only AHR, ARNT and CYP1B1 genes to a detectable level; moreover, only CYP1B1 expression appeared to be correlated to TEQ values, being higher in the most contaminated group, and decreasing along with animal decontamination. Finally, lymphocytes from exposed cows displayed a lower inducibility of both CYP1A1 and CYP1B1 after the in vitro treatment with a specific AHR ligand. In conclusion, our results indicate that DL-compound contaminated cows may display significant changes in AHR-target gene expression of circulating lymphocytes. - Highlights: ► The expression of AHR-target genes in blood bovine lymphocytes was evaluated. ► The lymphocyte CYP1B1 expression appears to be related to bulk milk TEQ values. ► Blood lymphocytes from dairy cows might represent a matrix for dioxin biomonitoring.

  13. Diphenylarsinic acid, a chemical warfare-related neurotoxicant, promotes liver carcinogenesis via activation of aryl hydrocarbon receptor signaling and consequent induction of oxidative DAN damage in rats

    International Nuclear Information System (INIS)

    Diphenylarsinic acid (DPAA), a chemical warfare-related neurotoxic organic arsenical, is present in the groundwater and soil in some regions of Japan due to illegal dumping after World War II. Inorganic arsenic is carcinogenic in humans and its organic arsenic metabolites are carcinogenic in animal studies, raising serious concerns about the carcinogenicity of DPAA. However, the carcinogenic potential of DPAA has not yet been evaluated. In the present study we found that DPAA significantly enhanced the development of diethylnitrosamine-induced preneoplastic lesions in the liver in a medium-term rat liver carcinogenesis assay. Evaluation of the expression of cytochrome P450 (CYP) enzymes in the liver revealed that DPAA induced the expression of CYP1B1, but not any other CYP1, CYP2, or CYP3 enzymes, suggesting that CYP1B1 might be the enzyme responsible for the metabolic activation of DPAA. We also found increased oxidative DNA damage, possibly due to elevated CYP1B1 expression. Induction of CYP1B1 has generally been linked with the activation of AhR, and we found that DPAA activates the aryl hydrocarbon receptor (AhR). Importantly, the promotion effect of DPAA was observed only at a dose that activated the AhR, suggesting that activation of AhR and consequent induction of AhR target genes and oxidative DNA damage plays a vital role in the promotion effects of DPAA. The present study provides, for the first time, evidence regarding the carcinogenicity of DPAA and indicates the necessity of comprehensive evaluation of its carcinogenic potential using long-term carcinogenicity studies. - Highlights: • DPAA, an environmental neurotoxicant, promotes liver carcinogenesis in rats. • DPAA is an activator of AhR signaling pathway. • DPAA promoted oxidative DNA damage in rat livers. • AhR target gene CYP 1B1 might be involved in the metabolism of DPAA

  14. Skatole (3-Methylindole) Is a Partial Aryl Hydrocarbon Receptor Agonist and Induces CYP1A1/2 and CYP1B1 Expression in Primary Human Hepatocytes

    Science.gov (United States)

    Balaguer, Patrick; Ekstrand, Bo; Daujat-Chavanieu, Martine; Gerbal-Chaloin, Sabine

    2016-01-01

    Skatole (3-methylindole) is a product of bacterial fermentation of tryptophan in the intestine. A significant amount of skatole can also be inhaled during cigarette smoking. Skatole is a pulmonary toxin that induces the expression of aryl hydrocarbon receptor (AhR) regulated genes, such as cytochrome P450 1A1 (CYP1A1), in human bronchial cells. The liver has a high metabolic capacity for skatole and is the first organ encountered by the absorbed skatole; however, the effect of skatole in the liver is unknown. Therefore, we investigated the impact of skatole on hepatic AhR activity and AhR-regulated gene expression. Using reporter gene assays, we showed that skatole activates AhR and that this is accompanied by an increase of CYP1A1, CYP1A2 and CYP1B1 expression in HepG2-C3 and primary human hepatocytes. Specific AhR antagonists and siRNA-mediated AhR silencing demonstrated that skatole-induced CYP1A1 expression is dependent on AhR activation. The effect of skatole was reduced by blocking intrinsic cytochrome P450 activity and indole-3-carbinole, a known skatole metabolite, was a more potent inducer than skatole. Finally, skatole could reduce TCDD-induced CYP1A1 expression, suggesting that skatole is a partial AhR agonist. In conclusion, our findings suggest that skatole and its metabolites affect liver homeostasis by modulating the AhR pathway. PMID:27138278

  15. Epigenetic Determinants of CYP1A1 Induction by the Aryl Hydrocarbon Receptor Agonist 3,3',4,4',5-Pentachlorobiphenyl (PCB 126

    Directory of Open Access Journals (Sweden)

    Sabine U. Vorrink

    2014-08-01

    Full Text Available Many enzymes involved in xenobiotic metabolism, including cytochrome P450 (CYP 1A1, are regulated by the aryl hydrocarbon receptor (AhR. 3,3',4,4',5-Penta chlorobiphenyl (PCB 126 is a potent ligand for AhR and can thus induce the expression of CYP1A1. Interestingly, we observed that human carcinoma cell lines derived from different types of epithelial cells displayed divergent degrees of CYP1A1 induction after exposure to PCB 126. Since epigenetic mechanisms are known to be involved in cell type-specific gene expression, we sought to assess the epigenetic determinants of CYP1A1 induction in these carcinoma cell lines. In contrast to HepG2 hepatocarcinoma cells, HeLa cervical carcinoma cells showed significantly lower levels of CYP1A1 mRNA expression following PCB 126 exposure. Our results show that the two cell lines maintained differences in the chromatin architecture along the CYP1A1 promoter region. Furthermore, treatment with the epigenetic modifiers, trichostatin A (TSA and 5-aza-2'-deoxycytidine (5-Aza-dC, significantly increased the expression of CYP1A1 after PCB 126 treatment in HeLa cells. However, we did not observe apparent differences in methylation levels or specific location of CpG DNA methylation between the two cell lines in the analyzed CYP1A1 promoter region. Taken together, our findings suggest that the differences in CYP1A1 expression between HepG2 and HeLa cells are due to differences in the chromatin architecture of the CYP1A1 promoter and thus establish a role of epigenetic regulation in cell-specific CYP1A1 expression.

  16. Down-regulation of aryl hydrocarbon receptor-regulated genes by tumor necrosis factor-alpha and lipopolysaccharide in murine hepatoma Hepa 1c1c7 cells.

    Science.gov (United States)

    Gharavi, Negar; El-Kadi, Ayman O S

    2005-03-01

    Although much is known concerning the effects of inflammation and oxidative stress on the cytochrome P450 1A1 (CYP1A1), little is known about the modulation of other aryl hydrocarbon receptor (AHR)-regulated genes such as glutathione-S-transferase Ya (GST Ya) and NAD(P)H:quinone oxidoreductase (QOR) by inflammation. In the present study, the effect of tumor necrosis factor (TNF)-alpha and lipopolysaccharides (LPS) on the constitutive and inducible expression of the AHR-regulated genes cyp1a1, GST Ya, and QOR was determined in murine hepatoma Hepa 1c1c7 (WT), AHR-deficient (C12), and AHR nuclear translocator protein (ARNT)-deficient (C4) cells. We found that both TNF-alpha and LPS strongly repressed the constitutive expression and the beta-naphthoflavone-mediated induction of cyp1a1, GST Ya, and QOR in WT but not in C12 and C4 cells. The induction of GST Ya and QOR activities and mRNA levels by phenolic antioxidant, tert-butylhydroquinone, through the antioxidant response element was not significantly affected by TNF-alpha or LPS. In addition, a significant increase in reactive oxygen species was observed in WT, C12, and C4 cells treated with TNF-alpha or LPS which was completely prevented by tert-butylhydroquinone. These results show that the down-regulation of AHR-regulated genes by TNF-alpha and LPS is dependent on the presence of both heterodimeric transcription factors, AHR and ARNT. Furthermore, reactive oxygen species may be involved in the down-regulation of AHR-regulated genes. PMID:15627257

  17. Amino acid sequence of the ligand-binding domain of the aryl hydrocarbon receptor 1 predicts sensitivity of wild birds to effects of dioxin-like compounds.

    Science.gov (United States)

    Farmahin, Reza; Manning, Gillian E; Crump, Doug; Wu, Dongmei; Mundy, Lukas J; Jones, Stephanie P; Hahn, Mark E; Karchner, Sibel I; Giesy, John P; Bursian, Steven J; Zwiernik, Matthew J; Fredricks, Timothy B; Kennedy, Sean W

    2013-01-01

    The sensitivity of avian species to the toxic effects of dioxin-like compounds (DLCs) varies up to 1000-fold among species, and this variability has been associated with interspecies differences in aryl hydrocarbon receptor 1 ligand-binding domain (AHR1 LBD) sequence. We previously showed that LD(50) values, based on in ovo exposures to DLCs, were significantly correlated with in vitro EC(50) values obtained with a luciferase reporter gene (LRG) assay that measures AHR1-mediated induction of cytochrome P4501A in COS-7 cells transfected with avian AHR1 constructs. Those findings suggest that the AHR1 LBD sequence and the LRG assay can be used to predict avian species sensitivity to DLCs. In the present study, the AHR1 LBD sequences of 86 avian species were studied, and differences at amino acid sites 256, 257, 297, 324, 337, and 380 were identified. Site-directed mutagenesis, the LRG assay, and homology modeling highlighted the importance of each amino acid site in AHR1 sensitivity to 2,3,7,8-tetrachlorodibenzo-p-dioxin and other DLCs. The results of the study revealed that (1) only amino acids at sites 324 and 380 affect the sensitivity of AHR1 expression constructs of the 86 avian species to DLCs and (2) in vitro luciferase activity of AHR1 constructs containing only the LBD of the species of interest is significantly correlated (r (2) = 0.93, p toxicity data for those species. These results indicate promise for the use of AHR1 LBD amino acid sequences independently, or combined with the LRG assay, to predict avian species sensitivity to DLCs. PMID:22923492

  18. Gene Expression Profiling Identifies Cell Proliferation and Inflammation as the Predominant Pathways Regulated by Aryl Hydrocarbon Receptor in Primary Human Fetal Lung Cells Exposed to Hyperoxia.

    Science.gov (United States)

    Shivanna, Binoy; Maity, Suman; Zhang, Shaojie; Patel, Ananddeep; Jiang, Weiwu; Wang, Lihua; Welty, Stephen E; Belmont, John; Coarfa, Cristian; Moorthy, Bhagavatula

    2016-07-01

    Exposure to hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. We observed that aryl hydrocarbon receptor (AhR) signaling protects newborn mice and primary fetal human pulmonary microvascular endothelial cells (HPMECs) against hyperoxic injury. Additionally, a recent genome-wide transcriptome study in a newborn mouse model of BPD identified AhR as a key regulator of hyperoxia-induced gene dysregulation. Whether the AhR similarly deregulates genes in HPMEC is unknown. Therefore, the objective of this study was to characterize transcriptome level gene expression profile in AhR-sufficient and -deficient HPMEC exposed to normoxic and hyperoxic conditions. Global gene expression profiling was performed using Illumina microarray platform and selected genes were validated by real-time RT-PCR. AhR gene expression and hyperoxia independently affected the expression of 540 and 593 genes, respectively. Two-way ANOVA further identified 85 genes that were affected by an interaction between AhR expression and exposure to hyperoxia. Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology, and Reactome pathway analysis identified cell proliferation, immune function, cytokine signaling, and organ development as the major pathways affected in AhR-deficient cells. The biological processes that were significantly enriched by hyperoxia included metabolic process, stress response, signal transduction, cell cycle, and immune regulation. Cell cycle was the predominant pathway affected by the combined effect of AhR knockdown and hyperoxia. Functional analysis of cell cycle showed that AhR-deficient cells had decreased proliferation compared with AhR-sufficient cells. These findings suggest that AhR modulates hyperoxic lung injury by regulating the genes that are necessary for cell proliferation and inflammation. PMID:27103661

  19. New insights to the role of aryl hydrocarbon receptor in bone phenotype and in dioxin-induced modulation of bone microarchitecture and material properties

    International Nuclear Information System (INIS)

    Bone is a target for high affinity aryl hydrocarbon receptor (AHR) ligands, such as dioxins. Although bone morphology, mineral density and strength are sensitive endpoints of dioxin toxicity, less is known about effects on bone microarchitecture and material properties. This study characterizes TCDD-induced modulations of bone tissue, and the role of AHR in dioxin-induced bone toxicity and for normal bone phenotype. Six AHR-knockout (Ahr−/−) and wild-type (Ahr+/+) mice of both genders were exposed to TCDD weekly for 10 weeks, at a total dose of 200 μg/kg bw. Bones were examined with micro-computed tomography, nanoindentation and biomechanical testing. Serum levels of bone remodeling markers were analyzed, and the expression of genes related to osteogenic differentiation was profiled using PCR array. In Ahr+/+ mice, TCDD-exposure resulted in harder bone matrix, thinner and more porous cortical bone, and a more compact trabecular bone compartment. Bone remodeling markers and altered expression of a number of osteogenesis related genes indicated imbalanced bone remodeling. Untreated Ahr−/− mice displayed a slightly modified bone phenotype as compared with untreated Ahr+/+ mice, while TCDD exposure caused only a few changes in bones of Ahr−/− mice. Part of the effects of both TCDD-exposure and AHR-deficiency were gender dependent. In conclusion, exposure of adult mice to TCDD resulted in harder bone matrix, thinner cortical bone, mechanically weaker bones and most notably, increased trabecular bone volume fraction in Ahr+/+ mice. AHR is involved in bone development of a normal bone phenotype, and is crucial for manifestation of TCDD-induced bone alterations. - Highlights: • TCDD disrupts bone remodeling resulting in altered cortical and trabecular bone. • In trabecular bone an anabolic effect is observed. • Cortical bone is thinner, more porous, harder, stiffer and mechanically weaker. • AHR ablation results in increased trabecular bone and softer

  20. Molecular characterization and tissue distribution of aryl hydrocarbon receptor nuclear translocator isoforms, ARNT1 and ARNT2, and identification of novel splice variants in common cormorant (Phalacrocorax carbo).

    Science.gov (United States)

    Lee, Jin-Seon; Kim, Eun-Young; Iwata, Hisato; Tanabe, Shinsuke

    2007-04-01

    High levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related planar halogenated aromatic hydrocarbons (PHAHs) are accumulated in fish-eating birds including common cormorant (Phalacrocorax carbo). Most of the biochemical and toxic effects of TCDD are mediated by a basic helix-loop-helix and a conserved region among Per, ARNT, and Sim (bHLH/PAS) proteins, aryl hydrocarbon receptor (AHR) and AHR nuclear translocator (ARNT). To study the molecular mechanism of TCDD toxicity in common cormorant as an avian model species, characterization of the AHR/ARNT signaling pathway in this species is necessary. The present study focuses on molecular characterization of ARNT from common cormorant (ccARNT). The cDNA of the ccARNT isoform, ccARNT1 obtained by the screening of hepatic cDNA library contains a 2424-bp open reading frame that encodes 807 amino acids, exhibiting high identities (92%) with chicken ARNT. This isoform contains a unique 22 amino acid residue in 3' end of PAS A domain as is also recognized in chicken ARNT. The ccARNT2 cDNA isolated from brain tissue has a 2151-bp open reading frame. The deduced amino acid sequence of ccARNT2 protein (716 aa) shows a conservation of bHLH and PAS motif in its N-terminal region with high similarities (96% and 78%, respectively) to that of ccARNT1. Using quantitative RT-PCR methods, the tissue distribution profiles of ccARNT1 and ccARNT2 were unveiled. Both ccARNT1 and ccARNT2 mRNAs were ubiquitously expressed in all examined tissues including liver. The expression profile of ccARNT1 was comparable with that of rodent ARNT1, but ccARNT2 was not with rodent ARNT2, implying different roles of ARNT2 between the two species. There was a significant positive correlation between ARNT1 and ARNT2 mRNA expression levels in the liver of wild cormorant population, indicating that their expressions may be enforced by similar transcriptional regulation mechanism. Novel variants of ccARNT1 and ccARNT2 isoforms that were supposed to

  1. Inhibition of aryl hydrocarbon receptor transactivation and DNA adduct formation by CYP1 isoform-selective metabolic deactivation of benzo[a]pyrene

    International Nuclear Information System (INIS)

    Benzo[a]pyrene (BaP), a polyaromatic hydrocarbon produced by the combustion of cigarettes and coke ovens, is a known procarcinogen. BaP activates the aryl hydrocarbon receptor (AhR) and induces the expression of a battery of genes, including CYP1A1, which metabolize BaP to toxic compounds. The possible role of CYP1 enzymes in mediating BaP detoxification or metabolic activation remains to be elucidated. In this study, we assessed the effects of CYP1 enzymes (CYP1A1, CYP1A2 and CYP1B1) on BaP-induced AhR transactivation and DNA adduct formation in HEK293 cells and HepG2 cells. Transfection of CYP1A1 and CYP1B1, but not CYP1A2, suppressed BaP-induced activation of AhR. Expression of CYP1A1 and CYP1A2, but not CYP1B1, inhibited DNA adduct formation in BaP-treated HepG2 cells. These results indicate that CYP1A1 and CYP1B1 play a role in deactivation of BaP on AhR and that CYP1A1 and CYP1A2 are involved in BaP detoxification by suppressing DNA adduct formation. BaP treatment did not induce DNA adduct formation in HEK293 cells, even after transfection of CYP1 enzymes, suggesting that expression of CYP1 enzymes is not sufficient for DNA adduct formation. Lower expression of epoxide hydrolase and higher expression of glutathione S-transferase P1 (GSTP1) and GSTM1/M2 were observed in HEK293 cells compared with HepG2 cells. Dynamic expression of CYP1A1, CYP1A2 and CYP1B1 along with expression of other enzymes such as epoxide hydrolase and phase II enzymes may determine the detoxification or metabolic activation of BaP

  2. Discovery and Biological Characterization of 1-(1H-indol-3-yl)-9H-pyrido[3,4-b]indole as an Aryl Hydrocarbon Receptor Activator Generated by Photoactivation of Tryptophan by Sunlight

    OpenAIRE

    Diani-Moore, Silvia; Ma, Yuliang; Labitzke, Erin; Tao, Hui; Warren, J. David; Anderson, Jared; Chen, Qiuying; Gross, Steven S.; Rifkind, Arleen B.

    2011-01-01

    Activation of the aryl hydrocarbon receptor (AHR) by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is required for AHR dependent transcriptional activation and TCDD toxicity. We previously reported that aqueous tryptophan exposed to sunlight through window glass (aTRP) contains multiple photoproducts, including the well characterized 6-formylindolo[3,2-b]carbazole (FICZ), capable of activating the AHR and inducing CYP1A and CYP1A-mediated enzyme activities. We report here the isolation from aTRP...

  3. Aryl hydrocarbon receptor (AhR agonists suppress interleukin-6 expression by bone marrow stromal cells: an immunotoxicology study

    Directory of Open Access Journals (Sweden)

    Schlezinger Jennifer J

    2003-12-01

    Full Text Available Abstract Background Bone marrow stromal cells produce cytokines required for the normal growth and development of all eight hematopoietic cell lineages. Aberrant cytokine production by stromal cells contributes to blood cell dyscrasias. Consequently, factors that alter stromal cell cytokine production may significantly compromise the development of normal blood cells. We have shown that environmental chemicals, such as aromatic hydrocarbon receptor (AhR agonists, suppress B lymphopoiesis by modulating bone marrow stromal cell function. Here, we extend these studies to evaluate the potential for two prototypic AhR agonists, 7,12-dimethylbenz [a]anthracene (DMBA and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, to alter stromal cell cytokine responses. Methods Bone marrow stromal cells were treated with AhR agonists and bacterial lipopolysaccharide (LPS to mimic innate inflammatory cytokine responses and to study the effects of AhR ligands on those responses. Steady state cytokine RNA levels were screened by RNAse protection assays (RPA and quantified by real-time PCR. Cytokine (IL-6 protein production was measured by ELISA. NF-κB EMSAs were used to study IL-6 transcriptional regulation. Results RPAs indicated that AhR+ bone marrow stromal cells consistently up-regulated genes encoding IL-6 and LIF in response to LPS, presumably through activation of Toll-like receptor 4. Pre-treatment with low doses of DMBA or TCDD selectively abrogated IL-6 gene induction but had no effect on LIF mRNA. Real-time-PCR indicated a significant inhibition of IL-6 mRNA by AhR ligands within 1 hour of LPS challenge which was reflected in a profound down-regulation of IL-6 protein induction, with DMBA and TCDD suppressing IL-6 levels as much as 65% and 88%, respectively. This potent inhibitory effect persisted for at least 72 hours. EMSAs measuring NF-κB binding to IL-6 promoter sequences, an event known to induce IL-6 transcription, indicated a significant decrease in

  4. A luciferase reporter gene assay and aryl hydrocarbon receptor 1 genotype predict the LD50 of polychlorinated biphenyls in avian species

    International Nuclear Information System (INIS)

    Birds differ in sensitivity to the embryotoxic effects of polychlorinated biphenyls (PCBs), which complicates environmental risk assessments for these chemicals. Recent research has shown that the identities of amino acid residues 324 and 380 in the avian aryl hydrocarbon receptor 1 (AHR1) ligand binding domain (LBD) are primarily responsible for differences in avian species sensitivity to selected dibenzo-p-dioxins and furans. A luciferase reporter gene (LRG) assay was developed in our laboratory to measure AHR1-mediated induction of a cytochrome P450 1A5 reporter gene in COS-7 cells transfected with different avian AHR1 constructs. In the present study, the LRG assay was used to measure the concentration-dependent effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and PCBs 126, 77, 105 and 118 on luciferase activity in COS-7 cells transfected with AHR1 constructs representative of 86 avian species in order to predict their sensitivity to PCB-induced embryolethality and the relative potency of PCBs in these species. The results of the LRG assay indicate that the identity of amino acid residues 324 and 380 in the AHR1 LBD are the major determinants of avian species sensitivity to PCBs. The relative potency of PCBs did not differ greatly among AHR1 constructs. Luciferase activity was significantly correlated with embryolethality data obtained from the literature (R2 ≥ 0.87, p < 0.0001). Thus, the LRG assay in combination with the knowledge of a species' AHR1 LBD sequence can be used to predict PCB-induced embryolethality in potentially any avian species of interest without the use of lethal methods on a large number of individuals. -- Highlights: ► PCB embryolethality in birds can be predicted from a species' AHR1 genotype. ► The reporter gene assay is useful for predicting species sensitivity to PCBs. ► The relative potency of PCBs does not appear to differ between AHR1 genotypes. ► Contamination of PCB 105 and PCB 118 did not affect their relative

  5. New insights to the role of aryl hydrocarbon receptor in bone phenotype and in dioxin-induced modulation of bone microarchitecture and material properties

    Energy Technology Data Exchange (ETDEWEB)

    Herlin, Maria, E-mail: maria.herlin@ki.se [Institute of Environmental Medicine, Karolinska Institutet, Stockholm (Sweden); Finnilä, Mikko A.J., E-mail: mikko.finnila@oulu.fi [Department of Medical Technology, Institute of Biomedicine, University of Oulu, Oulu (Finland); Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, Oulu (Finland); Zioupos, Peter, E-mail: p.zioupos@cranfield.ac.uk [Biomechanics Laboratories, Department of Engineering and Applied Science, Cranfield University, Shrivenham SN6 8LA (United Kingdom); Aula, Antti, E-mail: antti.aula@gmail.com [Department of Medical Physics, Imaging Centre, Tampere University Hospital, Tampere (Finland); Department of Biomedical Engineering, Tampere University of Technology, Tampere (Finland); Risteli, Juha, E-mail: juha.risteli@ppshp.fi [Department of Clinical Chemistry, Oulu University Hospital, Oulu (Finland); Miettinen, Hanna M., E-mail: hanna.miettinen@crl.com [Department of Environmental Health, National Institute for Health and Welfare, Kuopio (Finland); Jämsä, Timo, E-mail: timo.jamsa@oulu.fi [Department of Medical Technology, Institute of Biomedicine, University of Oulu, Oulu (Finland); Department of Diagnostic Radiology, Oulu University Hospital, Oulu (Finland); Tuukkanen, Juha, E-mail: juha.tuukkanen@oulu.fi [Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, Oulu (Finland); Korkalainen, Merja, E-mail: merja.korkalainen@thl.fi [Department of Environmental Health, National Institute for Health and Welfare, Kuopio (Finland); Håkansson, Helen, E-mail: Helen.Hakansson@ki.se [Institute of Environmental Medicine, Karolinska Institutet, Stockholm (Sweden); Viluksela, Matti, E-mail: matti.viluksela@thl.fi [Department of Environmental Health, National Institute for Health and Welfare, Kuopio (Finland); Department of Environmental Science, University of Eastern Finland, Kuopio (Finland)

    2013-11-15

    Bone is a target for high affinity aryl hydrocarbon receptor (AHR) ligands, such as dioxins. Although bone morphology, mineral density and strength are sensitive endpoints of dioxin toxicity, less is known about effects on bone microarchitecture and material properties. This study characterizes TCDD-induced modulations of bone tissue, and the role of AHR in dioxin-induced bone toxicity and for normal bone phenotype. Six AHR-knockout (Ahr{sup −/−}) and wild-type (Ahr{sup +/+}) mice of both genders were exposed to TCDD weekly for 10 weeks, at a total dose of 200 μg/kg bw. Bones were examined with micro-computed tomography, nanoindentation and biomechanical testing. Serum levels of bone remodeling markers were analyzed, and the expression of genes related to osteogenic differentiation was profiled using PCR array. In Ahr{sup +/+} mice, TCDD-exposure resulted in harder bone matrix, thinner and more porous cortical bone, and a more compact trabecular bone compartment. Bone remodeling markers and altered expression of a number of osteogenesis related genes indicated imbalanced bone remodeling. Untreated Ahr{sup −/−} mice displayed a slightly modified bone phenotype as compared with untreated Ahr{sup +/+} mice, while TCDD exposure caused only a few changes in bones of Ahr{sup −/−} mice. Part of the effects of both TCDD-exposure and AHR-deficiency were gender dependent. In conclusion, exposure of adult mice to TCDD resulted in harder bone matrix, thinner cortical bone, mechanically weaker bones and most notably, increased trabecular bone volume fraction in Ahr{sup +/+} mice. AHR is involved in bone development of a normal bone phenotype, and is crucial for manifestation of TCDD-induced bone alterations. - Highlights: • TCDD disrupts bone remodeling resulting in altered cortical and trabecular bone. • In trabecular bone an anabolic effect is observed. • Cortical bone is thinner, more porous, harder, stiffer and mechanically weaker. • AHR ablation

  6. Metformin suppresses CYP1A1 and CYP1B1 expression in breast cancer cells by down-regulating aryl hydrocarbon receptor expression

    Energy Technology Data Exchange (ETDEWEB)

    Do, Minh Truong; Kim, Hyung Gyun; Tran, Thi Thu Phuong; Khanal, Tilak; Choi, Jae Ho [Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon (Korea, Republic of); Chung, Young Chul [Department of Food Science and Culinary, International University of Korea, Jinju (Korea, Republic of); Jeong, Tae Cheon, E-mail: taecheon@ynu.ac.kr [College of Pharmacy, Yeungnam University, Gyeongsan (Korea, Republic of); Jeong, Hye Gwang, E-mail: hgjeong@cnu.ac.kr [Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon (Korea, Republic of)

    2014-10-01

    Induction of cytochrome P450 (CYP) 1A1 and CYP1B1 by environmental xenobiotic chemicals or endogenous ligands through the activation of the aryl hydrocarbon receptor (AhR) has been implicated in a variety of cellular processes related to cancer, such as transformation and tumorigenesis. Here, we investigated the effects of the anti-diabetes drug metformin on expression of CYP1A1 and CYP1B1 in breast cancer cells under constitutive and inducible conditions. Our results indicated that metformin down-regulated the expression of CYP1A1 and CYP1B1 in breast cancer cells under constitutive and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced conditions. Down-regulation of AhR expression was required for metformin-mediated decreases in CYP1A1 and CYP1B1 expression, and the metformin-mediated CYP1A1 and CYP1B1 reduction is irrelevant to estrogen receptor α (ERα) signaling. Furthermore, we found that metformin markedly down-regulated Sp1 protein levels in breast cancer cells. The use of genetic and pharmacological tools revealed that metformin-mediated down-regulation of AhR expression was mediated through the reduction of Sp1 protein. Metformin inhibited endogenous AhR ligand-induced CYP1A1 and CYP1B1 expression by suppressing tryptophan-2,3-dioxygenase (TDO) expression in MCF-7 cells. Finally, metformin inhibits TDO expression through a down-regulation of Sp1 and glucocorticoid receptor (GR) protein levels. Our findings demonstrate that metformin reduces CYP1A1 and CYP1B1 expression in breast cancer cells by down-regulating AhR signaling. Metformin would be able to act as a potential chemopreventive agent against CYP1A1 and CYP1B1-mediated carcinogenesis and development of cancer. - Graphical abstract: Schematic of the CYP1A1 and CYP1B1 gene regulation by metformin. - Highlights: • Metformin inhibits CYP1A1 and CYP1B1 expression. • Metformin down-regulates the AhR signaling. • Metformin reduces Sp1 protein expression. • Metformin suppresses TDO expression.

  7. Aryl hydrocarbon receptor pathway activation enhances gastric cancer cell invasiveness likely through a c-Jun-dependent induction of matrix metalloproteinase-9

    Directory of Open Access Journals (Sweden)

    Song Xin

    2009-04-01

    Full Text Available Abstract Background Abberant aryl hydrocarbon receptor (AhR expression and AhR pathway activation are involved in gastric carcinogenesis. However, the relationship between AhR pathway activation and gastric cancer progression is still unclear. In present study, we used 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD, a classic and most potent ligand of AhR, to activate AhR pathway and investigated the effect of AhR pathway activation on human gastric cancer AGS cell invasion and explored the corresponding mechanism. Results To determine whether AhR pathway can be activated in AGS cells, we examined the expression of CYP1A1, a classic target gene of AhR pathway, following TCDD exposure. RT-PCR and western blot analysis showed that both CYP1A1 mRNA and protein expression were increased in a dose-dependent manner following TCDD treatment and AhR antagonist resveratrol (RSV could reverse this TCDD-induced CYP1A1 expression. To determine whether TCDD treatment of AGS cells results in an induction of MMP-9 expression, we detected MMP-9 mRNA using RT-PCR and detected MMP-9 enzymatic activity using gelatin zymography. The results showed that both MMP-9 mRNA expression and enzymatic activity were gradually increased with the concentration increase of TCDD in media and these changes could be reversed by RSV treatment in a dose-dependent manner. To examine whether AhR activation-induced MMP-9 expression and activity in AGS cells results in increased migration and invasion, we performed wound healing migration assay and transwell migration and invasion assay. After TCDD treatment, the migration distance and the migration and invasion abilities of AGS cells were increased with a dose-dependent manner. To demonstrate AhR activation-induced MMP-9 expression is mediated by c-Jun, siRNA transfection was performed to silence c-Jun mRNA in AGS cells. The results showed that MMP-9 mRNA expression and activity in untreated control AGS cells were very weak; After TCDD

  8. The aryl hydrocarbon receptor and estrogen receptor alpha differentially modulate nuclear factor erythroid-2-related factor 2 transactivation in MCF-7 breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Raymond; Matthews, Jason, E-mail: jason.matthews@utoronto.ca

    2013-07-15

    Nuclear factor erythroid-2-related factor 2 (NRF2; NFE2L2) plays an important role in mediating cellular protection against reactive oxygen species. NRF2 signaling is positively modulated by the aryl hydrocarbon receptor (AHR) but inhibited by estrogen receptor alpha (ERα). In this study we investigated the crosstalk among NRF2, AHR and ERα in MCF-7 breast cancer cells treated with the NRF2 activator sulforaphane (SFN), a dual AHR and ERα activator, 3,3′-diindolylmethane (DIM), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 17β-estradiol (E2). SFN-dependent increases in NADPH-dependent oxidoreductase 1 (NQO1) and heme oxygenase I (HMOX1) mRNA levels were significantly reduced after co-treatment with E2. E2-dependent repression of NQO1 and HMOX1 was associated with increased ERα but reduced p300 recruitment and reduced histone H3 acetylation at both genes. In contrast, DIM + SFN or TCDD + SFN induced NQO1 and HMOX1 mRNA expression to levels higher than SFN alone, which was prevented by RNAi-mediated knockdown of AHR. DIM + SFN but not TCDD + SFN also induced recruitment of ERα to NQO1 and HMOX1. However, the presence of AHR at NQO1 and HMOX1 restored p300 recruitment and histone H3 acetylation, thereby reversing the ERα-dependent repression of NRF2. Taken together, our study provides further evidence of functional interplay among NRF2, AHR and ERα signaling pathways through altered p300 recruitment to NRF2-regulated target genes. - Highlights: • We examined crosstalk among ERα, AHR, and NRF2 in MCF-7 breast cancer cells. • AHR enhanced the mRNA expression levels of two NRF2 target genes – HMOX1 and NQO1. • ERα repressed HMOX1 and NQO1 expression via decreased histone acetylation. • AHR prevented ERα-dependent repression of HMOX1 and NQO1.

  9. Aryl hydrocarbon receptor (AhR-mediated perturbations in gene expression during early stages of CD4+ T-cell differentiation

    Directory of Open Access Journals (Sweden)

    Diana eRohlman

    2012-08-01

    Full Text Available Activation of the aryl hydrocarbon receptor (AhR by its prototypic ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, mediates potent suppression of T-cell dependent immune responses. The suppressive effects of TCDD occur early during CD4+ T-cell differentiation in the absence of effects on proliferation and have recently been associated with the induction of AhR-dependent regulatory T-cells (Treg. Since AhR functions as a ligand-activated transcription factor, changes in gene expression induced by TCDD during the early stages of CD4+ T-cell differentiation are likely to reflect fundamental mechanisms of AhR action. A custom panel of genes associated with T-cell differentiation was used to query changes in gene expression induced by exposure to 1 nM TCDD. CD4+ T-cells from AhR+/+ and AhR-/- mice were cultured with cytokines known to polarize the differentiation of T-cells to various effector lineages. Treatment with TCDD induced expression of Cyp1a1, Cyp1b1 and Ahrr in CD4+ T-cells from AhR+/+ mice under all culture conditions, validating the presence and activation of AhR in these cells. The highest levels of AhR activation occurred under Th17 conditions at 24 hours and Tr1 conditions at 48 hours. Unexpectedly, expression levels of most genes associated with early T-cell differentiation were unaltered by AhR activation, including lineage-specific genes that drive CD4+ T-cell polarization. The major exception was AhR-dependent up-regulation of Il22 that was seen under all culture conditions. Independent of TCDD, AhR down-regulated the expression of Il17a and Rorc based on increased expression of these genes in AhR-deficient cells across culture conditions. These findings are consistent with a role for AhR in down-regulation of inflammatory immune responses and implicate IL-22 as a potential contributor to the immunosuppressive effects of TCDD.

  10. A luciferase reporter gene assay and aryl hydrocarbon receptor 1 genotype predict the LD{sub 50} of polychlorinated biphenyls in avian species

    Energy Technology Data Exchange (ETDEWEB)

    Manning, Gillian E., E-mail: gmann017@uottawa.ca [Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N5 (Canada); Environment Canada, National Wildlife Research Centre, Ottawa, ON, Canada K1A 0H3 (Canada); Farmahin, Reza, E-mail: mfarm070@uottawa.ca [Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N5 (Canada); Environment Canada, National Wildlife Research Centre, Ottawa, ON, Canada K1A 0H3 (Canada); Crump, Doug, E-mail: doug.crump@ec.gc.ca [Environment Canada, National Wildlife Research Centre, Ottawa, ON, Canada K1A 0H3 (Canada); Jones, Stephanie P., E-mail: stephanie.jones@ec.gc.ca [Environment Canada, National Wildlife Research Centre, Ottawa, ON, Canada K1A 0H3 (Canada); Klein, Jeff, E-mail: jeffery@well-labs.com [Wellington Laboratories Inc., Research Division, Guelph, ON, Canada N1G 3M5 (Canada); Konstantinov, Alex, E-mail: alex@well-labs.com [Wellington Laboratories Inc., Research Division, Guelph, ON, Canada N1G 3M5 (Canada); Potter, Dave, E-mail: dpotter@well-labs.com [Wellington Laboratories Inc., Research Division, Guelph, ON, Canada N1G 3M5 (Canada); Kennedy, Sean W., E-mail: sean.kennedy@ec.gc.ca [Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N5 (Canada); Environment Canada, National Wildlife Research Centre, Ottawa, ON, Canada K1A 0H3 (Canada)

    2012-09-15

    Birds differ in sensitivity to the embryotoxic effects of polychlorinated biphenyls (PCBs), which complicates environmental risk assessments for these chemicals. Recent research has shown that the identities of amino acid residues 324 and 380 in the avian aryl hydrocarbon receptor 1 (AHR1) ligand binding domain (LBD) are primarily responsible for differences in avian species sensitivity to selected dibenzo-p-dioxins and furans. A luciferase reporter gene (LRG) assay was developed in our laboratory to measure AHR1-mediated induction of a cytochrome P450 1A5 reporter gene in COS-7 cells transfected with different avian AHR1 constructs. In the present study, the LRG assay was used to measure the concentration-dependent effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and PCBs 126, 77, 105 and 118 on luciferase activity in COS-7 cells transfected with AHR1 constructs representative of 86 avian species in order to predict their sensitivity to PCB-induced embryolethality and the relative potency of PCBs in these species. The results of the LRG assay indicate that the identity of amino acid residues 324 and 380 in the AHR1 LBD are the major determinants of avian species sensitivity to PCBs. The relative potency of PCBs did not differ greatly among AHR1 constructs. Luciferase activity was significantly correlated with embryolethality data obtained from the literature (R{sup 2} ≥ 0.87, p < 0.0001). Thus, the LRG assay in combination with the knowledge of a species' AHR1 LBD sequence can be used to predict PCB-induced embryolethality in potentially any avian species of interest without the use of lethal methods on a large number of individuals. -- Highlights: ► PCB embryolethality in birds can be predicted from a species' AHR1 genotype. ► The reporter gene assay is useful for predicting species sensitivity to PCBs. ► The relative potency of PCBs does not appear to differ between AHR1 genotypes. ► Contamination of PCB 105 and PCB 118 did not affect

  11. Aryl hydrocarbon receptor is necessary to protect fetal human pulmonary microvascular endothelial cells against hyperoxic injury: Mechanistic roles of antioxidant enzymes and RelB

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shaojie; Patel, Ananddeep; Chu, Chun; Jiang, Weiwu; Wang, Lihua; Welty, Stephen E.; Moorthy, Bhagavatula; Shivanna, Binoy, E-mail: shivanna@bcm.edu

    2015-07-15

    Hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. Activation of the aryl hydrocarbon receptor (AhR) protects adult and newborn mice against hyperoxic lung injury by mediating increases in the expression of phase I (cytochrome P450 (CYP) 1A) and phase II (NADP(H) quinone oxidoreductase (NQO1)) antioxidant enzymes (AOE). AhR positively regulates the expression of RelB, a component of the nuclear factor-kappaB (NF-κB) protein that contributes to anti-inflammatory processes in adult animals. Whether AhR regulates the expression of AOE and RelB, and protects fetal primary human lung cells against hyperoxic injury is unknown. Therefore, we tested the hypothesis that AhR-deficient fetal human pulmonary microvascular endothelial cells (HPMEC) will have decreased RelB activation and AOE, which will in turn predispose them to increased oxidative stress, inflammation, and cell death compared to AhR-sufficient HPMEC upon exposure to hyperoxia. AhR-deficient HPMEC showed increased hyperoxia-induced reactive oxygen species (ROS) generation, cleavage of poly(ADP-ribose) polymerase (PARP), and cell death compared to AhR-sufficient HPMEC. Additionally, AhR-deficient cell culture supernatants displayed increased macrophage inflammatory protein 1α and 1β, indicating a heightened inflammatory state. Interestingly, loss of AhR was associated with a significantly attenuated CYP1A1, NQO1, superoxide dismutase 1(SOD1), and nuclear RelB protein expression. These findings support the hypothesis that decreased RelB activation and AOE in AhR-deficient cells is associated with increased hyperoxic injury compared to AhR-sufficient cells. - Highlights: • AhR deficiency potentiates oxygen toxicity in human fetal lung cells. • Deficient AhR signaling increases hyperoxia-induced cell death. • AhR deficiency increases hyperoxia-induced ROS generation and inflammation. • Anti-oxidant enzyme levels are attenuated in AhR-deficient lung cells

  12. Metformin suppresses CYP1A1 and CYP1B1 expression in breast cancer cells by down-regulating aryl hydrocarbon receptor expression

    International Nuclear Information System (INIS)

    Induction of cytochrome P450 (CYP) 1A1 and CYP1B1 by environmental xenobiotic chemicals or endogenous ligands through the activation of the aryl hydrocarbon receptor (AhR) has been implicated in a variety of cellular processes related to cancer, such as transformation and tumorigenesis. Here, we investigated the effects of the anti-diabetes drug metformin on expression of CYP1A1 and CYP1B1 in breast cancer cells under constitutive and inducible conditions. Our results indicated that metformin down-regulated the expression of CYP1A1 and CYP1B1 in breast cancer cells under constitutive and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced conditions. Down-regulation of AhR expression was required for metformin-mediated decreases in CYP1A1 and CYP1B1 expression, and the metformin-mediated CYP1A1 and CYP1B1 reduction is irrelevant to estrogen receptor α (ERα) signaling. Furthermore, we found that metformin markedly down-regulated Sp1 protein levels in breast cancer cells. The use of genetic and pharmacological tools revealed that metformin-mediated down-regulation of AhR expression was mediated through the reduction of Sp1 protein. Metformin inhibited endogenous AhR ligand-induced CYP1A1 and CYP1B1 expression by suppressing tryptophan-2,3-dioxygenase (TDO) expression in MCF-7 cells. Finally, metformin inhibits TDO expression through a down-regulation of Sp1 and glucocorticoid receptor (GR) protein levels. Our findings demonstrate that metformin reduces CYP1A1 and CYP1B1 expression in breast cancer cells by down-regulating AhR signaling. Metformin would be able to act as a potential chemopreventive agent against CYP1A1 and CYP1B1-mediated carcinogenesis and development of cancer. - Graphical abstract: Schematic of the CYP1A1 and CYP1B1 gene regulation by metformin. - Highlights: • Metformin inhibits CYP1A1 and CYP1B1 expression. • Metformin down-regulates the AhR signaling. • Metformin reduces Sp1 protein expression. • Metformin suppresses TDO expression

  13. Differences between rats and mice in the involvement of the aryl hydrocarbon receptor in 4-vinylcyclohexene diepoxide-induced ovarian follicle loss

    International Nuclear Information System (INIS)

    Repeated dosing with the occupational chemical 4-vinylcyclohexene diepoxide (VCD) selectively depletes small pre-antral follicles in the ovaries of rats and mice via apoptosis. The aryl hydrocarbon receptor (AhR) plays a role in mediating the effects of several xenobiotics. Therefore, this study was designed to investigate a potential role of the AhR in VCD-induced ovotoxicity. Female F344 rats, C57BL/6 mice, or AhR-deficient (-/-, AhRKO) mice were dosed daily (15 days) with vehicle, VCD (80 mg/kg, i.p.) and/or the AhR antagonist, alpha-naphthoflavone (ANF; 80 mg/kg, i.p.). Compared with controls, VCD caused a 60% reduction (P < 0.05) in primordial and primary follicles in mice and rats. Concurrent dosing with ANF protected against the VCD-induced follicle loss in rats, but not in mice. As with AhR-intact mice and rats, VCD induced a 70% loss (P < 0.05) of small pre-antral follicles in AhRKO mice. AhR mRNA expression was increased (P < 0.05) by VCD dosing in small pre-antral follicles isolated from ovaries of rats but not mice. AhR protein in rats was increased by VCD dosing in oocyte nuclei in primordial and primary follicles when measured by immunofluorescence and confocal microscopy. In rat small pre-antral follicles, apoptosis-associated caspase-3-like activity was increased (P < 0.05) by VCD treatment, decreased (P < 0.05) by ANF treatment, and unaffected by VCD plus ANF treatment. VCD had no effect on expression of GST Ya1 or GST Ya2 mRNA or CYP 1A1 protein in rats. Taken together, these findings demonstrate a difference between rats and mice in the potential involvement of AhR as related to VCD-induced ovotoxicity. Whereas, AhR appears to be involved in rats, no evidence for a similar role in mice was obtained. Overall, these findings point out that there can be mechanistic species differences in ovarian responses to xenobiotic chemicals

  14. Aryl hydrocarbon receptor is necessary to protect fetal human pulmonary microvascular endothelial cells against hyperoxic injury: Mechanistic roles of antioxidant enzymes and RelB

    International Nuclear Information System (INIS)

    Hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. Activation of the aryl hydrocarbon receptor (AhR) protects adult and newborn mice against hyperoxic lung injury by mediating increases in the expression of phase I (cytochrome P450 (CYP) 1A) and phase II (NADP(H) quinone oxidoreductase (NQO1)) antioxidant enzymes (AOE). AhR positively regulates the expression of RelB, a component of the nuclear factor-kappaB (NF-κB) protein that contributes to anti-inflammatory processes in adult animals. Whether AhR regulates the expression of AOE and RelB, and protects fetal primary human lung cells against hyperoxic injury is unknown. Therefore, we tested the hypothesis that AhR-deficient fetal human pulmonary microvascular endothelial cells (HPMEC) will have decreased RelB activation and AOE, which will in turn predispose them to increased oxidative stress, inflammation, and cell death compared to AhR-sufficient HPMEC upon exposure to hyperoxia. AhR-deficient HPMEC showed increased hyperoxia-induced reactive oxygen species (ROS) generation, cleavage of poly(ADP-ribose) polymerase (PARP), and cell death compared to AhR-sufficient HPMEC. Additionally, AhR-deficient cell culture supernatants displayed increased macrophage inflammatory protein 1α and 1β, indicating a heightened inflammatory state. Interestingly, loss of AhR was associated with a significantly attenuated CYP1A1, NQO1, superoxide dismutase 1(SOD1), and nuclear RelB protein expression. These findings support the hypothesis that decreased RelB activation and AOE in AhR-deficient cells is associated with increased hyperoxic injury compared to AhR-sufficient cells. - Highlights: • AhR deficiency potentiates oxygen toxicity in human fetal lung cells. • Deficient AhR signaling increases hyperoxia-induced cell death. • AhR deficiency increases hyperoxia-induced ROS generation and inflammation. • Anti-oxidant enzyme levels are attenuated in AhR-deficient lung cells

  15. Induction of hepatic carbonyl reductase/20β-hydroxysteroid dehydrogenase mRNA in rainbow trout downstream from sewage treatment works-Possible roles of aryl hydrocarbon receptor agonists and oxidative stress

    International Nuclear Information System (INIS)

    Carbonyl reductase/20β-hydroxysteroid dehydrogenase (CR/20β-HSD) serves both as a key enzyme in the gonadal synthesis of maturing-inducing hormone in salmonids, and as an enzyme protecting against certain reactive oxygen species. We have previously shown that mRNA of the hepatic CR/20β-HSD B isoform is increased in rainbow trout caged downstream from a Swedish sewage treatment plant. Here, we report an increase of both the A as well as B form in fish kept downstream from a second sewage treatment plant. The two mRNAs were also induced in fish hepatoma cells in vitro after exposure to effluent extract. This indicates that the effects observed in vivo could be a direct effect on the liver, i.e. the mRNA induction does not require a signal from any other organ. When fish were exposed in vivo to several effluents treated with more advanced methods (ozone, moving bed biofilm reactor or membrane bioreactor) the expression of hepatic mRNA CR/20β-HSD A and B was significantly reduced. Their abundance did not parallel the reduction of estrogen-responsive transcripts, in agreement with our previous observations that ethinylestradiol is not a potent inducer. Treatment with norethisterone, methyltestosterone or hydrocortisone in vivo did not induce the hepatic CR/20β-HSD A and B mRNA expression. In contrast, both isoforms were markedly induced by the aryl hydrocarbon receptor agonist β-naphthoflavone as well as by the pro-oxidant herbicide paraquat. We hypothesize that the induction of CR/20β-HSD A and B by sewage effluents could be due to anthropogenic contaminants stimulating the aryl hydrocarbon receptor and/or causing oxidative stress.

  16. Aryl hydrocarbon receptor-mediated induction of the cytosolic phospholipase A(2)alpha gene by 2,3,7,8-tetrachlorodibenzo-p-dioxin in mouse hepatoma Hepa-1c1c7 cells.

    Science.gov (United States)

    Kinehara, Masaki; Fukuda, Itsuko; Yoshida, Ken-ichi; Ashida, Hitoshi

    2009-10-01

    Upon binding to ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) is activated to form a heterodimer with an aryl hydrocarbon receptor nuclear translocator (Arnt). This complex binds to DNA. It has been shown that the AhR bonds to a DNA sequence called the dioxin response element (DRE), which controls the expression of battery genes. It is reported that TCDD releases arachidonic acid from membrane phospholipids via activation of phospholipase A(2)s (PLA(2)s) in various cell types. Recently, we demonstrated that the TCDD-activated AhR binds to the second intron of the Pla2g4a gene, which encodes cytosolic phospholipase A(2)alpha (cPLA(2)alpha), in mouse hepatoma Hepa-1c1c7 cells. This result suggests that Pla2g4a appears to be a target gene of the AhR. In the present study, we investigated whether the transcriptional regulation of Pla2g4a is dependent on the AhR in Hepa-1c1c7 cells. Treatment of the cells with TCDD increased mRNA expression of Pla2g4a and enzymatic activity of PLA(2,) while this increased expression was not observed in AhR-defective c12 cells. After transient transfection of an Ahr gene-expressing plasmid into the c12 cells, expression of Pla2g4a was increased by TCDD. These results indicate that Pla2g4a may be a novel target gene of the AhR, and its transcriptional induction is mediated through binding of the AhR to the second intron of Pla2g4a, although this target site does not have a typical DRE sequence. PMID:19716514

  17. High-throughput evaluation of aryl hydrocarbon receptor-binding sites selected via chromatin immunoprecipitation-based screening in Hepa-1c1c7 cells stimulated with 2,3,7,8-tetrachlorodibenzo-p-dioxin.

    Science.gov (United States)

    Kinehara, Masaki; Fukuda, Itsuko; Yoshida, Ken-Ichi; Ashida, Hitoshi

    2008-12-01

    Upon binding to ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) is activated to form a heterodimer with an aryl hydrocarbon receptor nuclear translocator (Arnt) and binds to DNA. It has been shown that the binding of AhR to DNA depends on the dioxin response element (DRE) and controls xenobiotic-response genes. AhR-binding DNA fragments from mouse hepatoma Hepa-1c1c7 cells stimulated with TCDD were once enriched in a chromatin immunoprecipitation (ChIP) DNA library and screened through a high-throughput southwestern chemistry-based enzyme-linked immunosorbent assay (SW-ELISA). After screening 1700 fragments, the ChIP-SW-ELISA screening strategy allowed us to isolate 77 fragments tightly interacting with AhR in the presence of TCDD. Only 39 of the 77 fragments appeared to contain a typical DRE, indicating that in some cases the DRE was dispensable for AhR-binding, while 75 fragments were located within promoter-distal regions. Genomic mapping of the 77 fragments enabled us to estimate 121 potential AhR targets including known targets such as Cyp1A1 and Cyp1B1, but only a limited number exhibited an altered expression dependent on TCDD. This study revealed the fact that TCDD-activated AhR frequently binds to promoter-distal regions even without a DRE and is not always involved in transcriptional regulation, suggesting that within the genome DNA-binding of AhR could take place often in many regions without cis-regulatory elements and might not be a key determinant to establish its regulatory function. PMID:19282623

  18. Role of the Aryl Hydrocarbon Receptor in Controlling Maintenance and Functional Programs of RORγt+ Innate Lymphoid Cells and Intraepithelial Lymphocytes

    OpenAIRE

    Kiss, Elina A.; Diefenbach, Andreas

    2012-01-01

    Mucosal retinoic receptor-related orphan receptor (ROR)γt-expressing innate lymphoid cells (ILC) play an important role in the defense against intestinal pathogens and in promoting epithelial homeostasis and adaptation, thereby effectively protecting the vertebrate host against intestinal inflammatory disorders. The functional activity of RORγt+ ILC is under the control of environmental cues. However, the molecular sensors for such environmental signals are largely unknown. Recently, the aryl...

  19. Hydroxylation of methane through component interactions in soluble methane monooxygenases.

    Science.gov (United States)

    Lee, Seung Jae

    2016-04-01

    Methane hydroxylation through methane monooxygenases (MMOs) is a key aspect due to their control of the carbon cycle in the ecology system and recent applications of methane gas in the field of bioenergy and bioremediation. Methanotropic bacteria perform a specific microbial conversion from methane, one of the most stable carbon compounds, to methanol through elaborate mechanisms. MMOs express particulate methane monooxygenase (pMMO) in most strains and soluble methane monooxygenase (sMMO) under copper-limited conditions. The mechanisms of MMO have been widely studied from sMMO belonging to the bacterial multicomponent monooxygenase (BMM) superfamily. This enzyme has diiron active sites where different types of hydrocarbons are oxidized through orchestrated hydroxylase, regulatory and reductase components for precise control of hydrocarbons, oxygen, protons, and electrons. Recent advances in biophysical studies, including structural and enzymatic achievements for sMMO, have explained component interactions, substrate pathways, and intermediates of sMMO. In this account, oxidation of methane in sMMO is discussed with recent progress that is critical for understanding the microbial applications of C-H activation in one-carbon substrates. PMID:27033202

  20. Dioxin-induced retardation of development through a reduction in the expression of pituitary hormones and possible involvement of an aryl hydrocarbon receptor in this defect: A comparative study using two strains of mice with different sensitivities to dioxin

    International Nuclear Information System (INIS)

    We have previously revealed that treating pregnant rats with 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD) reduces the expression of gonadotropins and growth hormone (GH) in the fetal and neonatal pituitary. A change in gonadotropin expression impairs the testicular expression of steroidogenic proteins in perinatal pups, and imprint defects in sexual behavior after reaching maturity. In this study, we examined whether TCDD also affects the expression of gonadotropin and GH in mice using C57BL/6J and DBA/2J strains which express the aryl hydrocarbon receptor (Ahr) exhibiting a different affinity for TCDD. When pregnant C57BL/6J mice at gestational day (GD) 12 were given oral TCDD (0.2–20 μg/kg), all doses significantly attenuated the pituitary expression of gonadotropin mRNAs in fetuses at GD18. On the other hand, in DBA/2J mice, a much higher dose of TCDD (20 μg/kg) was needed to produce a significant attenuation. Such reduction in the C57BL/6J strain continued until at least postnatal day (PND) 4. In agreement with this, TCDD reduced the testicular expression of steroidogenic proteins in C57BL/6J neonates at PND2 and 4, although the same did not occur in the fetal testis and ovary. Furthermore, TCDD reduced the perinatal expression of GH, litter size and the body weight of newborn pups only in the C57BL/6J strain. These results suggest that 1) also in mice, maternal exposure to TCDD attenuates gonadotropin-regulated steroidogenesis and GH expression leading to the impairment of pup development and sexual immaturity; and 2) Ahr activation during the late fetal and early postnatal stages is required for these defects. - Highlights: • The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on mouse growth was studied. • TCDD reduced the levels of luteinizing hormone and growth hormone in perinatal pups. • Maternal exposure to TCDD also attenuated testicular steroidogenesis in pups. • The above effects of TCDD were more pronounced in C57BL/6J than in DBA/2J

  1. Dioxin-induced retardation of development through a reduction in the expression of pituitary hormones and possible involvement of an aryl hydrocarbon receptor in this defect: A comparative study using two strains of mice with different sensitivities to dioxin

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Tomoki; Taura, Junki; Hattori, Yukiko; Ishii, Yuji; Yamada, Hideyuki, E-mail: hyamada@phar.kyushu-u.ac.jp

    2014-08-01

    We have previously revealed that treating pregnant rats with 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD) reduces the expression of gonadotropins and growth hormone (GH) in the fetal and neonatal pituitary. A change in gonadotropin expression impairs the testicular expression of steroidogenic proteins in perinatal pups, and imprint defects in sexual behavior after reaching maturity. In this study, we examined whether TCDD also affects the expression of gonadotropin and GH in mice using C57BL/6J and DBA/2J strains which express the aryl hydrocarbon receptor (Ahr) exhibiting a different affinity for TCDD. When pregnant C57BL/6J mice at gestational day (GD) 12 were given oral TCDD (0.2–20 μg/kg), all doses significantly attenuated the pituitary expression of gonadotropin mRNAs in fetuses at GD18. On the other hand, in DBA/2J mice, a much higher dose of TCDD (20 μg/kg) was needed to produce a significant attenuation. Such reduction in the C57BL/6J strain continued until at least postnatal day (PND) 4. In agreement with this, TCDD reduced the testicular expression of steroidogenic proteins in C57BL/6J neonates at PND2 and 4, although the same did not occur in the fetal testis and ovary. Furthermore, TCDD reduced the perinatal expression of GH, litter size and the body weight of newborn pups only in the C57BL/6J strain. These results suggest that 1) also in mice, maternal exposure to TCDD attenuates gonadotropin-regulated steroidogenesis and GH expression leading to the impairment of pup development and sexual immaturity; and 2) Ahr activation during the late fetal and early postnatal stages is required for these defects. - Highlights: • The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on mouse growth was studied. • TCDD reduced the levels of luteinizing hormone and growth hormone in perinatal pups. • Maternal exposure to TCDD also attenuated testicular steroidogenesis in pups. • The above effects of TCDD were more pronounced in C57BL/6J than in DBA/2J

  2. 七种染料对鲤鱼肝微粒体芳烃羟化酶的诱导%THE INDUCTION OF ARYL HYDROCARBON HYDROXYLASE(AHH)OF CARP(CYPRINUS CARPIO) LIVER MICROSOME BY SEVEN DYES

    Institute of Scientific and Technical Information of China (English)

    徐楠; 王春霞; 莫争; 呼世斌

    2001-01-01

    The aryl hydrocarbon hydroxylase(AHH)activity of carp(Cyprinus Carpio)liver microsome induced by seven dyes was examined.The all tested dyes induced AHH activity to different extent.The AHH activity increased according to the increase of the dye concentration.The intense of AHH activity induced by seven dyes was as following order:acid red B>acid complex blue RRN>weak acid brilliant red B>reactive brilliant red K-2BP>reactive brilliant red K-2G,acid mordant red S-80>disperse red E-4B.The intense of AHH activity was related to the toxicity of the chemicals.%以鲤鱼肝微粒体为实验体系,研究了七种染料化合物对其芳烃羟化酶(AHH)的诱导,发现七种染料都可以诱导AHH的活性,随染料浓度增大AHH的活性升高.七种染料对AHH活性诱导能力大小为:酸性红B>派拉丁蓝RRN>普拉红B>活性艳红K-2BP>活性艳红K-2G,媒介大红S-80>分散红E-4B,与其毒性大小相关.

  3. Aryl hydrocarbon receptor-mediated disruption of contact inhibition is associated with connexin43 downregulation and inhibition of gap junctional intercellular communication

    Czech Academy of Sciences Publication Activity Database

    Andrysík, Zdeněk (ed.); Procházková, Jiřina; Kabátková, Markéta; Umannová, Lenka; Šimečková, P.; Kohoutek, J.; Machala, M.; Vondráček, Jan

    2013-01-01

    Roč. 87, č. 3 (2013), s. 491-503. ISSN 0340-5761 R&D Projects: GA ČR(CZ) GA524/09/1337 Institutional research plan: CEZ:AV0Z50040702 Institutional support: RVO:68081707 Keywords : POLYCYCLIC AROMATIC-HYDROCARBONS * LIVER EPITHELIAL-CELLS * RAT- LIVER * GENE-EXPRESSION Subject RIV: BO - Biophysics Impact factor: 5.078, year: 2013

  4. Mechanism-based inactivation of benzo[a]pyrene hydroxylase by aryl acetylenes and aryl olefins

    International Nuclear Information System (INIS)

    A series of aryl acetylenes and aryl olefins have been examined as substrates and inhibitors of cytochrome P-450 dependent monooxgenases in liver microsomes from 5,6-benzoflavone or phenobarbital pretreated rats. 1-Ethynylpyrene, 3-ethynylperylene, 2-ethynylfluorene, methyl 1-pyrenyl acetylene, cis- and trans-1-(2-bromovinyl)pyrene, and 1-allylpyrene serve as mechanism-based irreversible inactivators (suicide inhibitors) of benzo[a]pyrene hydroxylase, while 1-vinylpyrene and phenyl 1-pyrenyl acetylene do not cause a detectable suicide inhibition of benzo[a]pyrene hydroxylase. The mechanism-based loss of benzo[a]pyrene hydroxylase caused by the aryl acetylenes is not accompanied by a corresponding loss of the P-450 content of the microsomes (suicide destruction). The suicide inhibition by these aryl acetylenes therefore does not involve covalent binding to the heme moiety of the monooxygenase. Nevertheless, in the presence of NADPH, 3H-labeled 1-ethynylpyrene becomes covalently attached to the cytochrome P-450 protein; the measured stoichiometry of binding is one 1-ethynylpyrene per P-450 heme unit. The authors conclude that the inhibition of benzo[a]pyrene hydroxylase produced by 1-ethynylpyrene may be related to the mechanism of suicide inhibition of P-450 activity by chloramphenicol rather than the mechanism of suicide destruction of P-450 previously described for acetylene and propyne

  5. Modern Arylation Methods

    CERN Document Server

    Ackermann, Lutz

    2009-01-01

    Today, arylation methods are belonging to the most important reaction types in organic synthesis. Lutz Ackermann, a young and ambitious professor has gathered a number of top international authors to present the first comprehensive book on the topic. Starting from a historical review, the book covers hot topics like Palladium-catalyzed arylation of N-H and alpha-C-H-acidic Bonds, Copper-catalyzed arylation of N-H and O-H Bonds, direct arylation reactions, carbanion aromatic synthesis, arylation reactions of alkenes, alkynes and much more. This compact source of high quality information is indi

  6. Lyophilization conditions for the storage of monooxygenases

    NARCIS (Netherlands)

    van Beek, Hugo L.; Beyer, Nina; Janssen, Dick B.; Fraaije, Marco W.

    2015-01-01

    Cyclohexanone monooxygenase (CHMO) was used as a model enzyme to find suitable freeze-drying conditions for long-term storage of an isolated monooxygenase. CHMO is a Baeyer-Villiger monooxygenase (BVMO) known for its ability to catalyze a large number of oxidation reactions. With a focus on establis

  7. Benzimidazoisoquinolines: a new class of rapidly metabolized aryl hydrocarbon receptor (AhR ligands that induce AhR-dependent Tregs and prevent murine graft-versus-host disease.

    Directory of Open Access Journals (Sweden)

    Sumit Punj

    Full Text Available The aryl hydrocarbon receptor (AhR is a ligand-activated transcription factor that plays multiple roles in regulation of immune and inflammatory responses. The ability of certain AhR ligands to induce regulatory T cells (Tregs has generated interest in developing AhR ligands for therapeutic treatment of immune-mediated diseases. To this end, we designed a screen for novel Treg-inducing compounds based on our understanding of the mechanisms of Treg induction by the well-characterized immunosuppressive AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD. We screened a ChemBridge small molecule library and identified 10-chloro-7H-benzimidazo[2,1-a]benzo[de]Iso-quinolin-7-one (10-Cl-BBQ as a potent AhR ligand that was rapidly metabolized and not cytotoxic to proliferating T cells. Like TCDD,10-Cl-BBQ altered donor CD4(+ T cell differentiation during the early stages of a graft versus host (GVH response resulting in expression of high levels of CD25, CTLA-4 and ICOS, as well as several genes associated with Treg function. The Treg phenotype required AhR expression in the donor CD4(+ T cells. Foxp3 was not expressed in the AhR-induced Tregs implicating AhR as an independent transcription factor for Treg induction. Structure-activity studies showed that unsubstituted BBQ as well as 4, 11-dichloro-BBQ were capable of inducing AhR-Tregs. Other substitutions reduced activation of AhR. Daily treatment with 10-Cl-BBQ during the GVH response prevented development of GVH disease in an AhR-dependent manner with no overt toxicity. Together, our data provide strong support for development of select BBQs that activate the AhR to induce Tregs for treatment of immune-mediated diseases.

  8. 2,3,7,8-Tetrachlorodibenzo-p-dioxin activates the aryl hydrocarbon receptor and alters sex steroid hormone secretion without affecting growth of mouse antral follicles in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Karman, Bethany N., E-mail: bklement@illinois.edu; Basavarajappa, Mallikarjuna S., E-mail: mbshivapur@gmail.com; Craig, Zelieann R., E-mail: zelieann@illinois.edu; Flaws, Jodi A., E-mail: jflaws@illinois.edu

    2012-05-15

    The persistent environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an ovarian toxicant. These studies were designed to characterize the actions of TCDD on steroidogenesis and growth of intact mouse antral follicles in vitro. Specifically, these studies tested the hypothesis that TCDD exposure leads to decreased sex hormone production/secretion by antral follicles as well as decreased growth of antral follicles in vitro. Since TCDD acts through binding to the aryl hydrocarbon receptor (AHR), and the AHR has been identified as an important factor in ovarian function, we also conducted experiments to confirm the presence and activation of the AHR in our tissue culture system. To do so, we exposed mouse antral follicles for 96 h to a series of TCDD doses previously shown to have effects on ovarian tissues and cells in culture, which also encompass environmentally relevant and pharmacological exposures (0.1–100 nM), to determine a dose response for TCDD in our culture system for growth, hormone production, and expression of the Ahr and Cyp1b1. The results indicate that TCDD decreases progesterone, androstenedione, testosterone, and estradiol levels in a non-monotonic dose response manner without altering growth of antral follicles. The addition of pregnenolone substrate (10 μM) restores hormone levels to control levels. Additionally, Cyp1b1 levels were increased by 3–4 fold regardless of the dose of TCDD exposure, evidence of AHR activation. Overall, these data indicate that TCDD may act prior to pregnenolone formation and through AHR transcriptional control of Cyp1b1, leading to decreased hormone levels without affecting growth of antral follicles. -- Highlights: ►TCDD disrupts sex steroid hormone levels, but not growth of antral follicles. ►Pregnenolone co-treatment by-passes TCDD-induced steroid hormone disruption. ►TCDD affects steroid hormone levels through an AHR pathway in antral follicles.

  9. The inhibition effect of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin-induced aryl hydrocarbon receptor activation in human hepatoma cells with the treatment of cadmium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Chao, How-Ran [Department of Environmental Science and Engineering, National Pingtung University of Science and Technology, Neipu, Pingtung 912, Taiwan (China); Emerging Compounds Research Center, National Pingtung University of Science and Technology, Neipu, Pingtung 912, Taiwan (China); Tsou, Tsui-Chun [Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli 350, Taiwan (China); Chen, Hung-Ta [Sustainable Environment Research Center, National Cheng Kung University, Tainan 701, Taiwan (China); Chang, Eddy Essen; Tsai, Feng-Yuan [Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli 350, Taiwan (China); Lin, Ding-Yan [Department of Environmental Science and Engineering, National Pingtung University of Science and Technology, Neipu, Pingtung 912, Taiwan (China); Chen, Fu-An [Graduate Institute of Pharmaceutical Science, Department of Pharmacy, Tajen University, Yan-Pu, Pingtung 907, Taiwan (China); Wang, Ya-Fen, E-mail: yfwang@cycu.edu.tw [Department of Bioenvironmental Engineering, Chung Yuan Christian University, Chungli, Taoyuan 320, Taiwan (China); R and D Center of Membrane Technology, Chung Yuan Christian University, Chungli 320, Taiwan (China)

    2009-10-15

    Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), considered as endocrine disruptors, tend to accumulate in fatty tissues. Dioxin-responsive element chemical activated luciferase gene expression assay (DRE-luciferase assay) has been recognized as a semi-quantitative method for screening dioxins for its fast and low-cost as compared with HRGC/HRMS. However, some problems with the bioassay, including specificity, detection variation resulted from different cleanup strategies, and uncertainty of false-negative or false-positive results, remain to be overcome. Cadmium is a prevalent environmental contaminant around the world. This study was aimed to examine the effects of cadmium on the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced activation of aryl hydrocarbon receptor (AhR)-mediated gene expression in human hepatoma cells (Huh7-DRE-Luc cells and Huh7 cells). Ethoxyresorufin-O-deethylase (EROD) and DRE-luciferase assay were employed to determine the enzyme activity of cytochrome P450 1A1 (CYP1A1) and activation of AhR, respectively. The results showed that Cd{sup 2+} levels significantly inhibited the induction of TCDD-induced CYP1A1 and DRE luciferase activation in hepatoma cells. The 50% inhibited concentrations (IC{sub 50}) of CdCl{sub 2} were 0.414 {mu}M (95% confidence interval (C.I.): 0.230-0.602 {mu}M) in Huh7-DRE-Luc cells and 23.2 {mu}M (95% C.I.: 21.7-25.4 {mu}M) in Huh7 cells. Accordingly, prevention of interference with non-dioxin-like compounds in a DRE-luciferase assay is of great importance in an extensive cleanup procedure.

  10. The inhibition effect of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin-induced aryl hydrocarbon receptor activation in human hepatoma cells with the treatment of cadmium chloride

    International Nuclear Information System (INIS)

    Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), considered as endocrine disruptors, tend to accumulate in fatty tissues. Dioxin-responsive element chemical activated luciferase gene expression assay (DRE-luciferase assay) has been recognized as a semi-quantitative method for screening dioxins for its fast and low-cost as compared with HRGC/HRMS. However, some problems with the bioassay, including specificity, detection variation resulted from different cleanup strategies, and uncertainty of false-negative or false-positive results, remain to be overcome. Cadmium is a prevalent environmental contaminant around the world. This study was aimed to examine the effects of cadmium on the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced activation of aryl hydrocarbon receptor (AhR)-mediated gene expression in human hepatoma cells (Huh7-DRE-Luc cells and Huh7 cells). Ethoxyresorufin-O-deethylase (EROD) and DRE-luciferase assay were employed to determine the enzyme activity of cytochrome P450 1A1 (CYP1A1) and activation of AhR, respectively. The results showed that Cd2+ levels significantly inhibited the induction of TCDD-induced CYP1A1 and DRE luciferase activation in hepatoma cells. The 50% inhibited concentrations (IC50) of CdCl2 were 0.414 μM (95% confidence interval (C.I.): 0.230-0.602 μM) in Huh7-DRE-Luc cells and 23.2 μM (95% C.I.: 21.7-25.4 μM) in Huh7 cells. Accordingly, prevention of interference with non-dioxin-like compounds in a DRE-luciferase assay is of great importance in an extensive cleanup procedure.

  11. Regulation of Bach2 by the aryl hydrocarbon receptor as a mechanism for suppression of B-cell differentiation by 2,3,7,8-tetrachlorodibenzo-p-dioxin

    International Nuclear Information System (INIS)

    Exposure to the aryl hydrocarbon receptor (AHR) agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters B-cell differentiation and suppresses antibody production. Previous genomic studies in mouse B cells identified Bach2 as a direct target of the AHR. Bach2 is known to repress expression of Prdm1, a key transcription factor involved in B-cell differentiation, by binding to Maf elements (MAREs) in the regulatory regions of the gene. Chromatin immunoprecipitation followed by quantitative PCR in TCDD-treated lipopolysaccharide (LPS)-activated B cells showed increased binding of the AHR within the first intron in the Bach2 gene. The binding was further confirmed by electrophoretic mobility shift assay (EMSA). TCDD also induced expression of Bach2 in activated as well as resting B cells from 2 to 24 h post-treatment in a time- and concentration-dependent manner. Expression of Prdm1 was decreased by TCDD at 24 h and was consistent with repression by Bach2. Increased DNA binding activity to the intron 5 MARE with increasing TCDD concentrations was observed by EMSA. Supershifts identified the presence of Bach2 in the DNA binding complex associated with the intron 5 MARE of Prdm1. Functional validation of the role of Bach2 in the suppression of B-cell differentiation by TCDD was performed using RNA interference (RNAi). Knockdown of Bach2 showed approximately 40% reversal in the TCDD-induced suppression of IgM secretion when compared to controls. The results suggest that the transcriptional regulation of Bach2 by the AHR is one of the mechanisms involved in the suppression of B-cell differentiation by TCDD.

  12. 2,3,7,8-Tetrachlorodibenzo-p-dioxin activates the aryl hydrocarbon receptor and alters sex steroid hormone secretion without affecting growth of mouse antral follicles in vitro

    International Nuclear Information System (INIS)

    The persistent environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an ovarian toxicant. These studies were designed to characterize the actions of TCDD on steroidogenesis and growth of intact mouse antral follicles in vitro. Specifically, these studies tested the hypothesis that TCDD exposure leads to decreased sex hormone production/secretion by antral follicles as well as decreased growth of antral follicles in vitro. Since TCDD acts through binding to the aryl hydrocarbon receptor (AHR), and the AHR has been identified as an important factor in ovarian function, we also conducted experiments to confirm the presence and activation of the AHR in our tissue culture system. To do so, we exposed mouse antral follicles for 96 h to a series of TCDD doses previously shown to have effects on ovarian tissues and cells in culture, which also encompass environmentally relevant and pharmacological exposures (0.1–100 nM), to determine a dose response for TCDD in our culture system for growth, hormone production, and expression of the Ahr and Cyp1b1. The results indicate that TCDD decreases progesterone, androstenedione, testosterone, and estradiol levels in a non-monotonic dose response manner without altering growth of antral follicles. The addition of pregnenolone substrate (10 μM) restores hormone levels to control levels. Additionally, Cyp1b1 levels were increased by 3–4 fold regardless of the dose of TCDD exposure, evidence of AHR activation. Overall, these data indicate that TCDD may act prior to pregnenolone formation and through AHR transcriptional control of Cyp1b1, leading to decreased hormone levels without affecting growth of antral follicles. -- Highlights: ►TCDD disrupts sex steroid hormone levels, but not growth of antral follicles. ►Pregnenolone co-treatment by-passes TCDD-induced steroid hormone disruption. ►TCDD affects steroid hormone levels through an AHR pathway in antral follicles.

  13. Early steps in bilirubin-mediated apoptosis in murine hepatoma (Hepa 1c1c7) cells are characterized by aryl hydrocarbon receptor-independent oxidative stress and activation of the mitochondrial pathway.

    Science.gov (United States)

    Oakes, Garth H; Bend, John R

    2005-01-01

    Unconjugated bilirubin (UCB), the end product of heme catabolism, causes apoptosis in cells of the central nervous system, endothelial cells, and hepatotoma cells. However, the molecular mechanisms that contribute to UCB cytotoxicity remain unclear. The purpose of this study was to characterize the sequence of early events leading to UCB-mediated cytotoxicity in murine hepatoma Hepa 1c1c7 cells. In the present study, UCB (5-50 microM) was found to markedly increase the intracellular generation of reactive oxygen species (ROS) in a concentration-dependent manner, which is significantly elevated by 30 min post-treatment. This generation of ROS by UCB is not dependent on aryl hydrocarbon receptor (Ahr) signaling, as cells deficient in the Ahr (C12 cells) or the Ahr nuclear translocator protein (Arnt; C4 cells) were as efficient at generating ROS as wild type (WT) Hepa 1c1c7 cells. Mitochondrial membrane depolarization, evaluated with the lipophilic cationic dye, JC-1, occurred at least by 2 h after treatment with 50 muM UCB. Analysis of the caspase cascade demonstrated that activation of caspase-9 preceded activation of caspase-3. No conversion of procaspase-2 to active caspase-2 was detected in this study. These results demonstrate that UCB-mediated apoptosis in Hepa 1c1c7 cells is associated with increased oxidative stress and that caspase-9, and definitely not caspase-2, is the initiator caspase for apoptosis in UCB-treated Hepa 1c1c7 cells. PMID:16173058

  14. Assays of polychlorinated biphenyl congeners and co-contaminated heavy metals in the transgenic Arabidopsis plants carrying the recombinant guinea pig aryl hydrocarbon receptor-mediated β-glucuronidase reporter gene expression system.

    Science.gov (United States)

    Shimazu, Sayuri; Ohta, Masaya; Ohkawa, Hideo; Ashida, Hitoshi

    2012-01-01

    The transgenic Arabidopsis plant XgD2V11-6 carrying the recombinant guinea pig (g) aryl hydrocarbon receptor (AhR)-mediated β-glucuronidase (GUS) reporter gene expression system was examined for assay of polychlorinated biphenyl (PCB) congeners and co-contaminated heavy metals. When the transgenic Arabidopsis plants were treated with PCB126 (toxic equivalency factor; TEF: 0.1) and PCB169 (TEF: 0.03), the GUS activity of the whole plants was increased significantly. After treatment with PCB80 (TEF: 0), the GUS activity was nearly the same level as that treated with 0.1% dimethylsulfoxide (DMSO) as a vehicle control. After exposure to a 1:1 mixture of PCB126 and PCB169, the GUS activity was increased additively. However, after exposure to a mixture of PCB126 and PCB80, the GUS activity was lower than that of the treatment with PCB126 alone. Thus, PCB80 seemed to be an antagonist towards AhR. When the transgenic plants were treated with each of the heavy metals Fe, Cu, Zn, Cd and Pb together with PCB126, Cd and Pb increased the PCB126-induced GUS activity. On the other hand, Fe, Cu and Zn did not affect the PCB126-induced GUS activity. In the presence of the biosurfactant mannosylerythritol lipid-B (MEL-B) and the carrier protein bovine serum albumin (BSA), the PCB126-induced GUS activity was increased, but the Cd-assisted PCB126-induced GUS activity was not affected. Thus, MEL-B and BSA seemed to increase uptake and transport of PCB126, respectively. PMID:22938576

  15. Aryl hydrocarbon receptor-dependent upregulation of Cyp1b1 by TCDD and diesel exhaust particles in rat brain microvessels

    Directory of Open Access Journals (Sweden)

    Jacob Aude

    2011-08-01

    Full Text Available Abstract Background AhR activates the transcription of several target genes including CYP1B1. Recently, we showed CYP1B1 as the major cytochrome P450 (CYP enzyme expressed in human brain microvessels. Here, we studied the effect of AhR activation by environmental pollutants on the expression of Cyp1b1 in rat brain microvessels. Methods Expression of AhR and Cyp1b1 was detected in isolated rat brain microvessels. AhR was immunovisualised in brain microvessel endothelial cells. The effect of AhR ligands on Cyp1b1 expression was studied using isolated brain microvessels after ex vivo and/or in vivo exposure to TCDD, heavy hydrocarbons containing diesel exhaust particles (DEP or Δ9-tetrahydrocannabinol (Δ9-THC. Results After ex vivo exposure to TCDD (a highly potent AhR ligand for 3 h, Cyp1b1 expression was significantly increased by 2.3-fold in brain microvessels. A single i.p. dose of TCDD also increased Cyp1b1 transcripts (22-fold and Cyp1b1 protein (2-fold in rat brain microvessels at 72 h after TCDD. Likewise, DEP treatment (in vivo and ex vivo strongly induced Cyp1b1 protein in brain microvessels. DEP-mediated Cyp1b1 induction was inhibited by actinomycin D, cycloheximide, or by an AhR antagonist. In contrast, a sub-chronic in vivo treatment with Δ9-THC once daily for 7 seven days had no effect on Cyp1b1 expression Conclusions Our results show that TCDD and DEP strongly induced Cyp1b1 in rat brain microvessels, likely through AhR activation.

  16. BFCOD activity in fish cell lines and zebrafish embryos and its modulation by chemical ligands of human aryl hydrocarbon and nuclear receptors.

    Science.gov (United States)

    Creusot, N; Brion, F; Piccini, B; Budzinski, H; Porcher, J M; Aït-Aïssa, S

    2015-11-01

    Assessment of exposure and effect of fish to pharmaceuticals that contaminate aquatic environment is a current major issue in ecotoxicology and there is a need to develop specific biological marker to achieve this goal. Benzyloxy-4-trifluoromethylcoumarin-O-debenzyloxylase (BFCOD) enzymatic activity has been commonly used to monitor CYP3A activity in fish. In this study, we assessed the capacity of a panel of toxicologically relevant chemicals to modulate BFCOD activity in fish, by using in vitro and in vivo bioassays based on fish liver cell lines (PLHC-1, ZFL, RTL-W1) and zebrafish embryos, respectively. Basal BFCOD activity was detectable in all biological models and was differently modulated by chemicals. Ligands of human androgens, glucocorticoids, or pregnanes X receptors (i.e., dexamethasone, RU486, rifampicin, SR12813, T0901317, clotrimazole, ketoconazole, testosterone, and dihydrotestosterone) moderately increased or inhibited BFCOD activity, with some variations between the models. No common feature could be drawn by regards to their capacity to bind to these receptors, which contrasts with their known effect on mammalian CYP3A. In contrast, dioxins and polycyclic aromatic hydrocarbons (PAHs) strongly induced BFCOD activity (up to 30-fold) in a time- and concentration-dependent manner, both in vitro in all cell lines and in vivo in zebrafish embryos. These effects were AhR dependent as indicated by suppression of induced BFCOD by the AhR pathway inhibitors 8-methoxypsoralen and α-naphthoflavone. Altogether our result further question the relevance of using liver BFCOD activity as a biomarker of fish exposure to CYP3A-active compounds such as pharmaceuticals. PMID:25471715

  17. Metformin inhibits 7,12-dimethylbenz[a]anthracene-induced breast carcinogenesis and adduct formation in human breast cells by inhibiting the cytochrome P4501A1/aryl hydrocarbon receptor signaling pathway

    International Nuclear Information System (INIS)

    Recent studies have established that metformin (MET), an oral anti-diabetic drug, possesses antioxidant activity and is effective against different types of cancer in several carcinogen-induced animal models and cell lines. However, whether MET can protect against breast cancer has not been reported before. Therefore, the overall objectives of the present study are to elucidate the potential chemopreventive effect of MET in non-cancerous human breast MCF10A cells and explore the underlying mechanism involved, specifically the role of cytochrome P4501A1 (CYP1A1)/aryl hydrocarbon receptor (AhR) pathway. Transformation of the MCF10A cells into initiated breast cancer cells with DNA adduct formation was conducted using 7,12-dimethylbenz[a]anthracene (DMBA), an AhR ligand. The chemopreventive effect of MET against DMBA-induced breast carcinogenesis was evidenced by the capability of MET to restore the induction of the mRNA levels of basic excision repair genes, 8-oxoguanine DNA glycosylase (OGG1) and apurinic/apyrimidinic endonuclease1 (APE1), and the level of 8-hydroxy-2-deoxyguanosine (8-OHdG). Interestingly, the inhibition of DMBA-induced DNA adduct formation was associated with proportional decrease in CYP1A1 and in NAD(P)H:quinone oxidoreductase 1 (NQO1) gene expression. Mechanistically, the involvements of AhR and nuclear factor erythroid 2-related factor-2 (Nrf2) in the MET-mediated inhibition of DMBA-induced CYP1A1 and NQO1 gene expression were evidenced by the ability of MET to inhibit DMBA-induced xenobiotic responsive element and antioxidant responsive element luciferase reporter gene expression which suggests an AhR- and Nrf2-dependent transcriptional control. However, the inability of MET to bind to AhR suggests that MET is not an AhR ligand. In conclusion, the present work shows a strong evidence that MET inhibits the DMBA-mediated carcinogenicity and adduct formation by inhibiting the expression of CYP1A1 through an AhR ligand-independent mechanism

  18. Metformin inhibits 7,12-dimethylbenz[a]anthracene-induced breast carcinogenesis and adduct formation in human breast cells by inhibiting the cytochrome P4501A1/aryl hydrocarbon receptor signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Maayah, Zaid H. [Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh 11451 (Saudi Arabia); Ghebeh, Hazem [Stem Cell & Tissue Re-Engineering, King Faisal Specialist Hospital and Research Center, Riyadh 11211 (Saudi Arabia); Alhaider, Abdulqader A. [Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh 11451 (Saudi Arabia); Camel Biomedical Research Unit, College of Pharmacy and Medicine, King Saud University, Riyadh 11451 (Saudi Arabia); El-Kadi, Ayman O.S. [Faculty of Pharmacy & Pharmaceutical Sciences, University of Alberta, Edmonton (Canada); Soshilov, Anatoly A.; Denison, Michael S. [Department of Environmental Toxicology, University of California at Davis, Davis, CA 95616 (United States); Ansari, Mushtaq Ahmad [Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh 11451 (Saudi Arabia); Korashy, Hesham M., E-mail: hkorashy@ksu.edu.sa [Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh 11451 (Saudi Arabia)

    2015-04-15

    Recent studies have established that metformin (MET), an oral anti-diabetic drug, possesses antioxidant activity and is effective against different types of cancer in several carcinogen-induced animal models and cell lines. However, whether MET can protect against breast cancer has not been reported before. Therefore, the overall objectives of the present study are to elucidate the potential chemopreventive effect of MET in non-cancerous human breast MCF10A cells and explore the underlying mechanism involved, specifically the role of cytochrome P4501A1 (CYP1A1)/aryl hydrocarbon receptor (AhR) pathway. Transformation of the MCF10A cells into initiated breast cancer cells with DNA adduct formation was conducted using 7,12-dimethylbenz[a]anthracene (DMBA), an AhR ligand. The chemopreventive effect of MET against DMBA-induced breast carcinogenesis was evidenced by the capability of MET to restore the induction of the mRNA levels of basic excision repair genes, 8-oxoguanine DNA glycosylase (OGG1) and apurinic/apyrimidinic endonuclease1 (APE1), and the level of 8-hydroxy-2-deoxyguanosine (8-OHdG). Interestingly, the inhibition of DMBA-induced DNA adduct formation was associated with proportional decrease in CYP1A1 and in NAD(P)H:quinone oxidoreductase 1 (NQO1) gene expression. Mechanistically, the involvements of AhR and nuclear factor erythroid 2-related factor-2 (Nrf2) in the MET-mediated inhibition of DMBA-induced CYP1A1 and NQO1 gene expression were evidenced by the ability of MET to inhibit DMBA-induced xenobiotic responsive element and antioxidant responsive element luciferase reporter gene expression which suggests an AhR- and Nrf2-dependent transcriptional control. However, the inability of MET to bind to AhR suggests that MET is not an AhR ligand. In conclusion, the present work shows a strong evidence that MET inhibits the DMBA-mediated carcinogenicity and adduct formation by inhibiting the expression of CYP1A1 through an AhR ligand-independent mechanism

  19. Inhibition of the aryl hydrocarbon receptor prevents Western diet-induced obesity. Model for AHR activation by kynurenine via oxidized-LDL, TLR2/4, TGFβ, and IDO1.

    Science.gov (United States)

    Moyer, Benjamin J; Rojas, Itzel Y; Kerley-Hamilton, Joanna S; Hazlett, Haley F; Nemani, Krishnamurthy V; Trask, Heidi W; West, Rachel J; Lupien, Leslie E; Collins, Alan J; Ringelberg, Carol S; Gimi, Barjor; Kinlaw, William B; Tomlinson, Craig R

    2016-06-01

    Obesity is an increasingly urgent global problem, yet, little is known about its causes and less is known how obesity can be effectively treated. We showed previously that the aryl hydrocarbon receptor (AHR) plays a role in the regulation of body mass in mice fed Western diet. The AHR is a ligand-activated nuclear receptor that regulates genes involved in a number of biological pathways, including xenobiotic metabolism and T cell polarization. This study was an investigation into whether inhibition of the AHR prevents Western diet-based obesity. Male C57Bl/6J mice were fed control and Western diets with and without the AHR antagonist α-naphthoflavone or CH-223191, and a mouse hepatocyte cell line was used to delineate relevant cellular pathways. Studies are presented showing that the AHR antagonists α-naphthoflavone and CH-223191 significantly reduce obesity and adiposity and ameliorates liver steatosis in male C57Bl/6J mice fed a Western diet. Mice deficient in the tryptophan metabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) were also resistant to obesity. Using an AHR-directed, luciferase-expressing mouse hepatocyte cell line, we show that the transforming growth factor β1 (TGFβ1) signaling pathway via PI3K and NF-κB and the toll-like receptor 2/4 (TLR2/4) signaling pathway stimulated by oxidized low-density lipoproteins via NF-κB, each induce luciferase expression; however, TLR2/4 signaling was significantly reduced by inhibition of IDO1. At physiological levels, kynurenine but not kynurenic acid (both tryptophan metabolites and known AHR agonists) activated AHR-directed luciferase expression. We propose a hepatocyte-based model, in which kynurenine production is increased by enhanced IDO1 activity stimulated by TGFβ1 and TLR2/4 signaling, via PI3K and NF-κB, to perpetuate a cycle of AHR activation to cause obesity; and inhibition of the AHR, in turn, blocks the cycle's output to prevent obesity. The AHR with its broad ligand binding specificity

  20. The aryl hydrocarbon receptor-dependent disruption of contact inhibition in rat liver WB-F344 epithelial cells is linked with induction of survivin, but not with inhibition of apoptosis

    International Nuclear Information System (INIS)

    Inhibition of apoptosis by the ligands of the aryl hydrocarbon receptor (AhR) has been proposed to play a role in their tumor promoting effects on liver parenchymal cells. However, little is presently known about the impact of toxic AhR ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on apoptosis in other liver cell types, such as in liver epithelial/progenitor cells. In the present study, we focused on the effects of TCDD on apoptosis regulation in a model of liver progenitor cells, rat WB-F344 cell line, during the TCDD-elicited release from contact inhibition. The stimulation of cell proliferation in this cell line was associated with deregulated expression of a number of genes known to be under transcriptional control of the Hippo signaling pathway, a principal regulatory pathway involved in contact inhibition of cell proliferation. Interestingly, we found that mRNA and protein levels of survivin, a known Hippo target, which plays a role both in cell division and inhibition of apoptosis, were significantly up-regulated in rat liver epithelial cell model, as well as in undifferentiated human liver HepaRG cells. Using the short interfering RNA-mediated knockdown, we confirmed that survivin plays a central role in cell division of WB-F344 cells. When evaluating the effects of TCDD on apoptosis induction by camptothecin, a genotoxic topoisomerase I inhibitor, we observed that the pre-treatment of WB-F344 cells with TCDD increased number of cells with apoptotic nuclear morphology, and it potentiated cleavage of both caspase-3 and poly(ADP-ribose) polymerase I. This indicated that despite the observed up-regulation of survivin, apoptosis induced by the genotoxin was potentiated in the model of rat liver progenitor cells. The present results indicate that, unlike in hepatocytes, AhR agonists may not prevent induction of apoptosis elicited by DNA-damaging agents in a model of rat liver progenitor cells

  1. Differential effects of mercury, lead and copper on the constitutive and inducible expression of aryl hydrocarbon receptor (AHR)-regulated genes in cultured hepatoma Hepa 1c1c7 cells.

    Science.gov (United States)

    Korashy, Hesham M; El-Kadi, Ayman O S

    2004-09-01

    Both simultaneous and sequential exposure to heavy metals and aryl hydrocarbon receptor (AHR)-ligands potentially occur in human populations, yet there have been relatively few studies of combined effects of heavy metals and AHR-ligands on AHR-regulated genes. To investigate the effects of heavy metals on AHR-regulated genes; cytochrome P450 1a1 (cyp1a1), NAD(P)H:quinone oxidoreductase (QOR) and glutathione S-transferase Ya (GST Ya), murine hepatoma Hepa 1c1c7 cells were incubated with increasing concentrations of Hg2+ (2.5-10 microM), Pb2+ (10-100 microM), and Cu2+ (1-100 microM) alone or with the AHR-ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (0.1 nM), 3-methylcholanthrene (0.25 microM), beta-naphthoflavone (10 microM), or benzo[a]pyrene (1 microM). The results clearly showed that metals alone did not significantly alter the cyp1a1 activity and protein levels but increased its mRNA expression, whereas a significant reduction in AHR ligand-mediated induction of cyp1a1 activity was observed by all metals. The decrease in cyp1a1 activity was associated with an increase, no change, or decrease in cyp1a1 mRNA and protein levels by Hg2+, Pb2+ and Cu2+ respectively, suggesting pre- and post-transcription mechanisms are involved. With respect to QOR, the activity and mRNA levels were increased by all metals in the absence or presence of an AHR-ligand, with the exception of Cu2+ which significantly decreased the induction of QOR. Differently, GST Ya activity was significantly increased by Cu2+ and Pb2+ and inhibited by Hg2+, while its mRNA was increased by Hg2+ and Pb2+ and decreased by Cu2+. All metals significantly increased the expression of heme oxygenase-1, which coincided with the changes in the phase I and phase II enzyme activities. These results demonstrate that heavy metals differentially modulate the constitutive and the inducible expression of AHR-regulated genes. PMID:15297030

  2. The Aryl Hydrocarbon Receptor and Food Allergy

    NARCIS (Netherlands)

    Schulz, V.J.

    2013-01-01

    Currently, food allergy is a major health problem with an estimated prevalence of about 5% in young children and 3-4% in adults and the prevalence is increasing. However, no cure or approved treatment is available, despite the increased knowledge of mechanisms playing a role in food allergy. The ary

  3. Moonlighting Cytochrome P450 Monooxygenases

    OpenAIRE

    Zhao, Bin; Waterman, Michael R.

    2011-01-01

    Recently, cytochrome P450 170A1 (CYP170A1) has been found to be a bifunctional protein, which catalyzes both monooxygenase activity and terpene synthase activity by two distinct active sites in the well established P450 protein structure. Therefore, CYP170A1 is identified clearly as a moonlighting protein. The known activities of a small number of the 13,000 members of the P450 superfamily fall into two general classes; promiscuous enzymes that are not considered as moonlighting and forms tha...

  4. Differential susceptibilities of Holtzman and Sprague-Dawley rats to fetal death and placental dysfunction induced by 2,3,7,8-teterachlorodibenzo-p-dioxin (TCDD) despite the identical primary structure of the aryl hydrocarbon receptor

    International Nuclear Information System (INIS)

    placental function, than SD-IGS rats. Direct sequencing analysis of the aryl hydrocarbon receptor (AhR) gene revealed no difference in the primary structure of the receptor between the HLZ and SD-IGS rats. In addition, no significant differences were observed between the two strains of rats in the levels of induction of placental cytochrome P450 1A1, 1B1, AhR, and AhRR mRNAs following administration of serially increasing doses of TCDD (0.0125, 0.05, 0.2, 0.8, and 1.6 μg TCDD/kg), indicating that the activity of TCDD-AhR complex in the placenta is similar between the HLZ and SD-IGS rats. Taken together, the above-described findings indicate that the higher susceptibility of HLZ rats to TCDD-induced placental dysfunction and fetal death may be modulated by other factor(s) in the genetic background of HLZ rats than the AhR

  5. TCDD Protects the Mouse Kidneys against Ischemia-reperfusion Injury by Activating the Aryl Hydrocarbon Receptor%TCDD激活芳香烃受体减轻小鼠肾脏缺血再灌注损伤

    Institute of Scientific and Technical Information of China (English)

    蔡兰军; 余道武; 高义; 杨超; 周鸿敏; 陈忠华

    2013-01-01

    Objective To investigate the protective effects of 2 ,3 ,7 ,8-tetrachlorodibenzo-p-dioxin (TCDD) on ischemia-reperfusion injury (IRI) of the kidneys in mice and the possible mechanism. Methods Kidney IRI models were established in C57BL/6 (H-2b) mice. Animals were divided into TCDD-treated group (0. 5 μg TCDD intraperitoneally given to a mouse 24 h before operation) ,PBS control group (200 μL PBS intraperitoneally administered to a mouse 24 h before operation) ,sham group and normal group. The life time of the animals was recorded ,and the kidney function [blood urea nitrogen (BUN ) and serum creatinine (Scr)]measured. Morphologic changes of the IRI kidney were evaluated by light microscopy. The effect of TCDD on the differentiation of naive T cells into regulatory T cells (Treg cells) was observed invitro. The phenotype of T cells in the peripheral blood or spleens of IRI models was measured by flow cytometry. Results The life time was significantly prolonged and the kidney function improved in the TCDD-treated group as compared with those in the PBS control group (P<0. 05 ). The pathological changes of the kidney in TCDD-treated group were significantly alleviated when compared with those in PBS con -trol group. TCDD selectively expanded the subgroup of CD4+ CD25+ Foxp3+ regulatory T cells invitro (P<0. 05 ) ,as well as Treg cells in the peripheral blood and spleens of IRI models in vivo (P<0. 05). Conclusion Activation of the arly hydrocarbon receptor (AHR) by TCDD could obviously improve the kidney function of IRI models ,which may be associated with the expansion of the Treg cell subgroup.%目的 论证2,3,7,8-四氯联苯对二恶英(2,3,7,8-tetrachlorodibenzo-p-dioxin,TCDD)激活芳香烃受体(aryl hydrocarbon receptor,AHR)在小鼠肾脏缺血再灌注损伤(ischemia-reperfusion injury,IRI)中的保护作用并探讨其机制.方法 建立C57BL/6小鼠肾脏缺血再灌注损伤模型,设TCDD治疗组(术前24 h腹腔注射TCDD 0.5 μg /

  6. Oxidation Reactions Performed by Soluble Methane Monooxygenase Hydroxylase Intermediates Hperoxo and Q Proceed by Distinct Mechanisms†

    OpenAIRE

    Tinberg, Christine E.; Lippard, Stephen J.

    2010-01-01

    Soluble methane monooxygenase is a bacterial enzyme that converts methane to methanol at a carboxylate-bridged diiron center with exquisite control. Because the oxidizing power required for this transformation is demanding, it is not surprising that the enzyme is also capable of hydroxylating and epoxidizing a broad range of hydrocarbon substrates in addition to methane. In this work we took advantage of this promiscuity of the enzyme to gain insight into the mechanisms of action of Hperoxo a...

  7. Lack of antagonism of 2,3,7,8-tetrachlorodibenzo-p-dioxin's (TCDDs) induction of cytochrome P4501A1 (CYP1A1) by the putative selective aryl hydrocarbon receptor modulator 6-alkyl-1,3,8-trichlorodibenzofuran (6-MCDF) in the mouse hepatoma cell line Hepa-1c1c7.

    Science.gov (United States)

    Fretland, Adrian J; Safe, Stephen; Hankinson, Oliver

    2004-11-20

    Regulation of gene expression by the aryl hydrocarbon (AHR) receptor is a much-studied pathway of molecular toxicology. Activation of AHR by the xenobiotic ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is hypothesized as the mechanism by which TCDD exerts its toxic and carcinogenic effects. Paradoxically, some studies have shown that TCDD acts as an antiestrogen. This has led to the hypothesis that so-called selective aryl hydrocarbon receptor modulators (SAhRMs), AHR ligands that retain the antiestrogenic effects but lack the transcriptional effects of TCDD associated with toxicity, may be utilized as cancer chemotherapeutics in conjunction with other antiestrogenic compounds such as tamoxifen. The present study attempts to further define the molecular mechanism of action of the putative SAhRMs, 6-alkyl-1,3,8-trichlorodibenzofuran (6-MCDF), and diindolylmethane (DIM), focusing particularly on the former. We tested 6-MCDF and DIM for the recruitment of AHR and RNA polymerase II (pol II) to the regulatory region of the AHR responsive gene, cytochrome P4501A1 (CYP1A1), using the chromatin immunoprecipitation (ChIP) assay in the mouse hepatoma cell line Hepa-1c1c7 (Hepa-1). We also tested the level of CYP1A1 induction in Hepa-1 cells using quantitative real-time PCR. We show no difference in the recruitment of AHR or pol II to the regulatory region of CYP1A1 in response to TCDD, 6-MCDF, or co-treatment with both TCDD and 6-MCDF. Our results also show no antagonism of CYP1A1 induction with co-treatment of Hepa-1 cells with TCDD and 6-MCDF. These data suggest that 6-MCDF exhibits agonist activity with respect to induction of CYP1A1 in the Hepa-1 cell line. PMID:15535986

  8. Structural and Catalytic Characterization of a Fungal Baeyer-Villiger Monooxygenase.

    Science.gov (United States)

    Ferroni, Felix Martin; Tolmie, Carmien; Smit, Martha Sophia; Opperman, Diederik Johannes

    2016-01-01

    Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts that convert ketones to esters. Due to their high regio-, stereo- and enantioselectivity and ability to catalyse these reactions under mild conditions, they have gained interest as alternatives to chemical Baeyer-Villiger catalysts. Despite their widespread occurrence within the fungal kingdom, most of the currently characterized BVMOs are from bacterial origin. Here we report the catalytic and structural characterization of BVMOAFL838 from Aspergillus flavus. BVMOAFL838 converts linear and aryl ketones with high regioselectivity. Steady-state kinetics revealed BVMOAFL838 to show significant substrate inhibition with phenylacetone, which was more pronounced at low pH, enzyme and buffer concentrations. Para substitutions on the phenyl group significantly improved substrate affinity and increased turnover frequencies. Steady-state kinetics revealed BVMOAFL838 to preferentially oxidize aliphatic ketones and aryl ketones when the phenyl group are separated by at least two carbons from the carbonyl group. The X-ray crystal structure, the first of a fungal BVMO, was determined at 1.9 Å and revealed the typical overall fold seen in type I bacterial BVMOs. The active site Arg and Asp are conserved, with the Arg found in the "in" position. Similar to phenylacetone monooxygenase (PAMO), a two residue insert relative to cyclohexanone monooxygenase (CHMO) forms a bulge within the active site. Approximately half of the "variable" loop is folded into a short α-helix and covers part of the active site entry channel in the non-NADPH bound structure. This study adds to the current efforts to rationalize the substrate scope of BVMOs through comparative catalytic and structural investigation of different BVMOs. PMID:27472055

  9. Palladium-Catalyzed α-Arylation of Aryl Acetic Acid Derivatives via Dienolate Intermediates with Aryl Chlorides and Bromides

    OpenAIRE

    Sha, Sheng-Chun; Zhang, Jiadi; Walsh, Patrick J.

    2015-01-01

    To date, examples of α-arylation of carboxylic acids remain scarce. Using a deprotonative cross-coupling process (DCCP), a method for palladium-catalyzed γ-arylation of aryl acetic acids with aryl halides has been developed. This protocol is applicable to a wide range of aryl bromides and chlorides. A procedure for the palladium-catalyzed α-arylation of styryl acetic acids is also described.

  10. Starch-degrading polysaccharide monooxygenases.

    Science.gov (United States)

    Vu, Van V; Marletta, Michael A

    2016-07-01

    Polysaccharide degradation by hydrolytic enzymes glycoside hydrolases (GHs) is well known. More recently, polysaccharide monooxygenases (PMOs, also known as lytic PMOs or LPMOs) were found to oxidatively degrade various polysaccharides via a copper-dependent hydroxylation. PMOs were previously thought to be either GHs or carbohydrate binding modules (CBMs), and have been re-classified in carbohydrate active enzymes (CAZY) database as auxiliary activity (AA) families. These enzymes include cellulose-active fungal PMOs (AA9, formerly GH61), chitin- and cellulose-active bacterial PMOs (AA10, formerly CBM33), and chitin-active fungal PMOs (AA11). These PMOs significantly boost the activity of GHs under industrially relevant conditions, and thus have great potential in the biomass-based biofuel industry. PMOs that act on starch are the latest PMOs discovered (AA13), which has expanded our perspectives in PMOs studies and starch degradation. Starch-active PMOs have many common structural features and biochemical properties of the PMO superfamily, yet differ from other PMO families in several important aspects. These differences likely correlate, at least in part, to the differences in primary and higher order structures of starch and cellulose, and chitin. In this review we will discuss the discovery, structural features, biochemical and biophysical properties, and possible biological functions of starch-active PMOs, as well as their potential application in the biofuel, food, and other starch-based industries. Important questions regarding various aspects of starch-active PMOs and possible economical driving force for their future studies will also be highlighted. PMID:27170366

  11. Direct N9-arylation of purines with aryl halides

    DEFF Research Database (Denmark)

    Larsen, Anders Foller; Ulven, Trond

    2014-01-01

    An efficient method for N-arylation of purines is reported. The N-arylation is catalysed by Cu(i) and 4,7-bis(2-hydroxyethylamino)-1,10-phenanthroline (BHPhen) in aqueous DMF or ethanol. The reaction generally proceeds with high selectivity for the N(9)-position....

  12. Iron-catalyzed coupling of aryl sulfamates and aryl/vinyl tosylates with aryl Grignards.

    Science.gov (United States)

    Agrawal, Toolika; Cook, Silas P

    2014-10-01

    The iron-catalyzed coupling of aryl sulfamates and tosylates with aryl Grignard reagents is reported for the first time. The methodology employs air-stable, low-cost FeF3·3H2O and the N-heterocyclic carbene ligand IPr·HCl as the preligand to form a long-lived catalyst upon treatment with aryl Grignards. The reaction provides a range of cross-coupled products in good-to-excellent yields. In contrast to previous reports with aryl chlorides, these reactions proceed with low levels of Grignard homocoupling regardless of the iron source. PMID:25230097

  13. Particulate methane monooxygenase genes in methanotrophs.

    OpenAIRE

    Semrau, J. D.; Chistoserdov, A; Lebron, J.; Costello, A; Davagnino, J.; Kenna, E; Holmes, A. J.; Finch, R; Murrell, J.C.; Lidstrom, M E

    1995-01-01

    A 45-kDa membrane polypeptide that is associated with activity of the particulate methane monooxygenase (pMMO) has been purified from three methanotrophic bacteria, and the N-terminal amino acid sequence was found to be identical in 17 of 20 positions for all three polypeptides and identical in 14 of 20 positions for the N terminus of AmoB, the 43- kDa subunit of ammonia monooxygenase. DNA from a variety of methanotrophs was screened with two probes, an oligonucleotide designed from the N-ter...

  14. Structural basis of kynurenine 3-monooxygenase inhibition

    OpenAIRE

    Amaral, Marta; Levy, Colin; Heyes, Derren J; Lafite, Pierre; Outeiro, Tiago F.; Giorgini, Flaviano; Leys, David; Scrutton, Nigel S.

    2013-01-01

    Inhibition of kynurenine 3-monooxygenase (KMO), an enzyme in the eukaryotic tryptophan catabolic pathway (i.e. kynurenine pathway), leads to amelioration of Huntington’s disease-relevant phenotypes in yeast, fruit fly, and mouse models 1–5 , as well as a mouse model of Alzheimer’s disease 3 . KMO is a FAD-dependent monooxygenase, and is located in the outer mitochondrial membrane where it converts L-kynurenine to 3-hydroxykynurenine. Perturbations in the levels of kynurenine pathway metabolit...

  15. Single-domain flavoenzymes trigger lytic polysaccharide monooxygenases for oxidative degradation of cellulose

    Science.gov (United States)

    Garajova, Sona; Mathieu, Yann; Beccia, Maria Rosa; Bennati-Granier, Chloé; Biaso, Frédéric; Fanuel, Mathieu; Ropartz, David; Guigliarelli, Bruno; Record, Eric; Rogniaux, Hélène; Henrissat, Bernard; Berrin, Jean-Guy

    2016-01-01

    The enzymatic conversion of plant biomass has been recently revolutionized by the discovery of lytic polysaccharide monooxygenases (LPMOs) that carry out oxidative cleavage of polysaccharides. These very powerful enzymes are abundant in fungal saprotrophs. LPMOs require activation by electrons that can be provided by cellobiose dehydrogenases (CDHs), but as some fungi lack CDH-encoding genes, other recycling enzymes must exist. We investigated the ability of AA3_2 flavoenzymes secreted under lignocellulolytic conditions to trigger oxidative cellulose degradation by AA9 LPMOs. Among the flavoenzymes tested, we show that glucose dehydrogenase and aryl-alcohol quinone oxidoreductases are catalytically efficient electron donors for LPMOs. These single-domain flavoenzymes display redox potentials compatible with electron transfer between partners. Our findings extend the array of enzymes which regulate the oxidative degradation of cellulose by lignocellulolytic fungi. PMID:27312718

  16. Gold-Catalyzed Direct Arylation

    OpenAIRE

    Ball, L. T.; Lloyd-jones, G. C.; Russell, C. A.

    2012-01-01

    Biaryls (two directly connected aromatic rings, Ar1-Ar2) are common motifs in pharmaceuticals, agrochemicals, and organic materials. Current methods for establishing the Ar1-Ar2 bond are dominated by the cross-coupling of aryl halides (Ar1-X) with aryl metallics (Ar2-M). We report that, in the presence of 1 to 2 mole percent of a gold catalyst and a mild oxidant, a wide range of arenes (Ar1-H) undergo site-selective arylation by arylsilanes (Ar2-SiMe3) to generate biaryls (Ar1-Ar2), with litt...

  17. Kinetic evidence for an anion binding pocket in the active site of nitronate monooxygenase.

    Science.gov (United States)

    Francis, Kevin; Gadda, Giovanni

    2009-10-01

    A series of monovalent, inorganic anions and aliphatic aldehydes were tested as inhibitors for Hansenula mrakii and Neurospora crassa nitronate monooxygenase, formerly known as 2-nitropropane dioxygenase, to investigate the structural features that contribute to the binding of the anionic nitronate substrates to the enzymes. A linear correlation between the volumes of the inorganic anions and their effectiveness as competitive inhibitors of the enzymes was observed in a plot of pK(is)versus the ionic volume of the anion with slopes of 0.041+/-0.001 mM/A(3) and 0.027+/-0.001 mM/A(3) for the H. mrakii and N. crassa enzymes, respectively. Aliphatic aldehydes were weak competitive inhibitors of the enzymes, with inhibition constants that are independent of their alkyl chain lengths. The reductive half reactions of H. mrakii nitronate monooxygenase with primary nitronates containing two to four carbon atoms all showed apparent K(d) values of approximately 5 mM. These results are consistent with the presence of an anion binding pocket in the active site of nitronate monooxygenase that interacts with the nitro group of the substrate, and suggest a minimal contribution of the hydrocarbon chain of the nitronates to the binding of the ligands to the enzyme. PMID:19683782

  18. [Advances in biomolecular machine: methane monooxygenases].

    Science.gov (United States)

    Lu, Jixue; Wang, Shizhen; Fang, Baishan

    2015-07-01

    Methane monooxygenases (MMO), regarded as "an amazing biomolecular machine", catalyze the oxidation of methane to methanol under aerobic conditions. MMO catalyze the oxidation of methane elaborately, which is a novel way to catalyze methane to methanol. Furthermore, MMO can inspire the biomolecular machine design. In this review, we introduced MMO including structure, gene and catalytic mechanism. The history and the taxonomy of MMO were also introduced. PMID:26647577

  19. An Improved Protocol for the Pd-catalyzed α-Arylation of Aldehydes with Aryl Halides

    OpenAIRE

    Martín, Rubén; Buchwald, Stephen L.

    2008-01-01

    An improved protocol for the Pd-catalyzed α-arylation of aldehydes with aryl halides has been developed. The new catalytic system allows for the coupling of an array of substrates including challenging electron-rich aryl bromides and less reactive aryl chlorides. The utility of this method has been demonstrated in a new total synthesis of (±)-sporochnol.

  20. Hydrocarbon pneumonia

    Science.gov (United States)

    Pneumonia - hydrocarbon ... Coughing Fever Shortness of breath Smell of a hydrocarbon product on the breath Stupor (decreased level of ... Most children who drink or inhale hydrocarbon products and develop ... hydrocarbons may lead to rapid respiratory failure and death.

  1. Biogeochemistry of Halogenated Hydrocarbons

    Science.gov (United States)

    Adriaens, P.; Gruden, C.; McCormick, M. L.

    2003-12-01

    Halogenated hydrocarbons originate from both natural and industrial sources. Whereas direct anthropogenic emissions to the atmosphere and biosphere are often easy to assess, particularly when they are tied to major industrial activities, the attribution of emissions to other human activities (e.g., biomass burning), diffuse sources (e.g., atmospheric discharge, run off), and natural production (e.g., soils, fungi, algae, microorganisms) are difficult to quantify. The widespread occurrence of both alkyl and aryl halides in groundwater, surface water, soils, and various trophic food chains, even those not affected by known point sources, suggests a substantial biogeochemical cycling of these compounds (Wania and Mackay, 1996; Adriaens et al., 1999; Gruden et al., 2003). The transport and reactive fate mechanisms controlling their reactivity are compounded by the differences in sources of alkyl-, aryl-, and complex organic halides, and the largely unknown impact of biogenic processes, such as enzymatically mediated halogenation of organic matter, fungal production of halogenated hydrocarbons, and microbial or abiotic transformation reactions (e.g., Asplund and Grimvall, 1991; Gribble, 1996; Watling and Harper, 1998; Oberg, 2002). The largest source may be the natural halogenation processes in the terrestrial environment, as the quantities detected often exceed the amount that can be explained by human activities in the surrounding areas ( Oberg, 1998). Since biogeochemical processes result in the distribution of a wide range of halogenated hydrocarbon profiles, altered chemical structures, and isomer distributions in natural systems, source apportionment (or environmental forensics) can often only be resolved using multivariate statistical methods (e.g., Goovaerts, 1998; Barabas et al., 2003; Murphy and Morrison, 2002).This chapter will describe the widespread occurrence of halogenated hydrocarbons, interpret their distribution and biogeochemical cycling in light of

  2. Sequencing and characterization of mixed function monooxygenase genes CYP1A1 and CYP1A2 of Mink (Mustela vison) to facilitate study of dioxin-like compounds

    International Nuclear Information System (INIS)

    As part of an ongoing effort to understand aryl hydrocarbon receptor (AhR) mediated toxicity in mink, cDNAs encoding for CYP1A1 and the CYP1A2 mixed function monooxygenases were cloned and characterized. In addition, the effects of selected dibenzofurans on the expression of these genes and the presence of their respective proteins (P4501A) were investigated, and then correlated with the catalytic activities of these proteins as measured by ethoxyresorufin O-deethylase (EROD) and methoxyresorufin O-deethylase (MROD) activities. The predicted protein sequences for CYP1A1 and CYP1A2 comprise 517 and 512 amino acid residues, respectively. The phylogenetic analysis of the mink CYP1As with protein sequences of other mammals revealed high sequence homology with sea otter, seals and the dog, with amino acid identities ranging from 89 to 95% for CYP1A1 and 81 to 93% for CYP1A2. Since exposure to both 2,3,7,8-Tetrachlorodibenzofuran (TCDF) and 2,3,4,7,8-Pentachlorodibenzofuran (PeCDF) resulted in dose-dependent increases of CYP1A1 mRNA, CYP1A2 mRNA and CYP1A protein levels an underlying AhR-mediated mechanism is suggested. The up-regulation of CYP1A mRNA in liver was more consistent to the sum adipose TEQ concentration than to the liver TEQ concentration in minks treated with TCDF or PeCDF. The result suggested that the hepatic-sequestered fraction of PeCDF was biologically inactive to the induction of CYP1A1 and CYP1A2

  3. Structural basis of kynurenine 3-monooxygenase inhibition.

    Science.gov (United States)

    Amaral, Marta; Levy, Colin; Heyes, Derren J; Lafite, Pierre; Outeiro, Tiago F; Giorgini, Flaviano; Leys, David; Scrutton, Nigel S

    2013-04-18

    Inhibition of kynurenine 3-monooxygenase (KMO), an enzyme in the eukaryotic tryptophan catabolic pathway (that is, kynurenine pathway), leads to amelioration of Huntington's-disease-relevant phenotypes in yeast, fruitfly and mouse models, as well as in a mouse model of Alzheimer's disease. KMO is a flavin adenine dinucleotide (FAD)-dependent monooxygenase and is located in the outer mitochondrial membrane where it converts l-kynurenine to 3-hydroxykynurenine. Perturbations in the levels of kynurenine pathway metabolites have been linked to the pathogenesis of a spectrum of brain disorders, as well as cancer and several peripheral inflammatory conditions. Despite the importance of KMO as a target for neurodegenerative disease, the molecular basis of KMO inhibition by available lead compounds has remained unknown. Here we report the first crystal structure of Saccharomyces cerevisiae KMO, in the free form and in complex with the tight-binding inhibitor UPF 648. UPF 648 binds close to the FAD cofactor and perturbs the local active-site structure, preventing productive binding of the substrate l-kynurenine. Functional assays and targeted mutagenesis reveal that the active-site architecture and UPF 648 binding are essentially identical in human KMO, validating the yeast KMO-UPF 648 structure as a template for structure-based drug design. This will inform the search for new KMO inhibitors that are able to cross the blood-brain barrier in targeted therapies against neurodegenerative diseases such as Huntington's, Alzheimer's and Parkinson's diseases. PMID:23575632

  4. Nitrification and Autotrophic Nitrifying Bacteria in a Hydrocarbon-Polluted Soil

    OpenAIRE

    Deni, Jamal; Penninckx, Michel J.

    1999-01-01

    In vitro ammonia-oxidizing bacteria are capable of oxidizing hydrocarbons incompletely. This transformation is accompanied by competitive inhibition of ammonia monooxygenase, the first key enzyme in nitrification. The effect of hydrocarbon pollution on soil nitrification was examined in situ. In a microcosm study, adding diesel fuel hydrocarbon to an uncontaminated soil (agricultural unfertilized soil) treated with ammonium sulfate dramatically reduced the amount of KCl-extractable nitrate bu...

  5. Tetrahydrobiopterin and alkylglycerol monooxygenase substantially alter the murine macrophage lipidome

    OpenAIRE

    Watschinger, K.; Keller, MA; McNeill, E; Alam, MT; Lai, S.; Sailer, S; Rauch, V.; Patel, J.; Hermetter, A; Golderer, G; Geley, S; Werner-Felmayer, G; Plumb, RS; Astarita, G; Ralser, M.

    2015-01-01

    Tetrahydrobiopterin is a cofactor synthesized from GTP with well-known roles in enzymatic nitric oxide synthesis and aromatic amino acid hydroxylation. It is used to treat mild forms of phenylketonuria. Less is known about the role of tetrahydrobiopterin in lipid metabolism, although it is essential for irreversible ether lipid cleavage by alkylglycerol monooxygenase. Here we found intracellular alkylglycerol monooxygenase activity to be an important regulator of alkylglycerol metabolism in i...

  6. Toluene 4-Monooxygenase and its Complex with Effector Protein T4moD

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Lucas J.; Fox, Brian G. (UW)

    2012-10-16

    Toluene 4-monooxygenase (T4MO) is a multiprotein diiron enzyme complex that catalyzes the regiospecific oxidation of toluene to p-cresol. Catalytic function requires the presence of a small protein, called the effector protein. Effector protein exerts substantial control on the diiron hydroxylase catalytic cycle through protein-protein interactions. High-resolution crystal structures of the stoichometric hydroxylase and effector protein complex described here reveal how protein-protein interactions and reduction of the diiron center produce an active site configuration poised for reaction with O{sub 2}. Further information from crystal structures of mutated isoforms of the hydroxylase and a peroxo adduct is combined with catalytic results to give a fuller picture of the geometry of the enzyme-substrate complex used for the high fidelity oxidation of hydrocarbon substrates.

  7. 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

    International Nuclear Information System (INIS)

    Highlights: • Hexachlorobenzene induces cell proliferation in HepG2 cells and preneoplastic foci. • Hexachlorobenzene promotes HepG2 cells accumulation in S and G2/M phase. • Hexachlorobenzene induces ERK1/2phosphorylation in HepG2 cells. • Hexachlorobenzene induces arylhydrocarbon receptor (AhR) protein overexpression. • Hexachlorobenzene-induced cell proliferation is mediated by AhR. - Abstract: Hexachlorobenzene (HCB) is a widespread environmental pollutant, and a liver tumor promoter in rodents. Depending on the particular cell lines studied, exposure to these compounds may lead to cell proliferation, terminal differentiation, or apoptosis. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is involved in drug and xenobiotic metabolism. AhR can also modulate a variety of cellular and physiological processes that can affect cell proliferation and cell fate determination. The mechanisms by which AhR ligands, both exogenous and endogenous, affect these processes involve multiple interactions between AhR and other signaling pathways. In the present study, we examined the effect of HCB on cell proliferation and AhR expression, using an initiation-promotion hepatocarcinogenesis protocol in rat liver and in the human-derived hepatoma cell line, HepG2. Female Wistar rats were initiated with a single dose of 100 mg/kg of diethylnitrosamine (DEN) at the start of the experiment. Two weeks later, daily dosing of 100 mg/kg HCB was maintained for 10 weeks. Partial hepatectomy was performed 3 weeks after initiation. The number and area of glutathione S-transferase-P (GST-P)-positive foci, in the rat liver were used as biomarkers of liver precancerous lesions. Immunohistochemical staining showed an increase in proliferating cell nuclear antigen (PCNA)-positive cells, along with enhanced AhR protein expression in hepatocytes within GST-P-positive foci of (DEN HCB) group, when compared to DEN. In a similar manner, Western blot analysis

  8. Kinetics of Chlorinated Hydrocarbon Degradation by Methylosinus trichosporium OB3b and Toxicity of Trichloroethylene

    NARCIS (Netherlands)

    Oldenhuis, Roelof; Oedzes, Johannes Y.; Waarde, Jacob J. van der; Janssen, Dick B.

    1991-01-01

    The kinetics of the degradation of trichloroethylene (TCE) and seven other chlorinated aliphatic hydrocarbons by Methylosinus trichosporium OB3b were studied. All experiments were performed with cells grown under copper stress and thus expressing soluble methane monooxygenase. Compounds that were re

  9. Synthesis of Dimethyl Aryl Acylsulfonium Bromides from Aryl Methyl Ketones in a DMSO-HBr System

    OpenAIRE

    Zhiling Cao; Dahua Shi; Yingying Qu; Chuanzhou Tao; Weiwei Liu; Guowei Yao

    2013-01-01

    A new, simplified method for the synthesis of dimethyl aryl acylsulfonium salts has been developed. A series of dimethyl aryl acylsulfonium bromides were prepared by the reaction of aryl methyl ketones with hydrobromic acid and dimethylsulfoxide (DMSO). This sulfonium salt confirms that bromine production and the bromination reaction take place in the DMSO-HBr oxidation system. What’s more, it is also a key intermediate for the synthesis of arylglyoxals.

  10. Synthesis of Dimethyl Aryl Acylsulfonium Bromides from Aryl Methyl Ketones in a DMSO-HBr System

    Directory of Open Access Journals (Sweden)

    Zhiling Cao

    2013-12-01

    Full Text Available A new, simplified method for the synthesis of dimethyl aryl acylsulfonium salts has been developed. A series of dimethyl aryl acylsulfonium bromides were prepared by the reaction of aryl methyl ketones with hydrobromic acid and dimethylsulfoxide (DMSO. This sulfonium salt confirms that bromine production and the bromination reaction take place in the DMSO-HBr oxidation system. What’s more, it is also a key intermediate for the synthesis of arylglyoxals.

  11. Nickel-catalyzed reductive arylation of activated alkynes with aryl iodides

    Science.gov (United States)

    Dorn, Stephanie C. M.; Olsen, Andrew K; Kelemen, Rachel E.; Shrestha, Ruja; Weix, Daniel J.

    2015-01-01

    The direct, regioselective, and stereoselective arylation of activated alkynes with aryl iodides using a nickel catalyst and manganese reductant is described. The reaction conditions are mild (40 °C in MeOH, no acid or base) and an intermediate organomanganese reagent is unlikely. Functional groups tolerated include halides and pseudohalides, free and protected anilines, and a benzyl alcohol. Other activated alkynes including an amide and a ketone also reacted to form arylated products in good yields. PMID:26028781

  12. Transition Metal Catalyzed Synthesis of Aryl Sulfides

    Directory of Open Access Journals (Sweden)

    Chad C. Eichman

    2011-01-01

    Full Text Available The presence of aryl sulfides in biologically active compounds has resulted in the development of new methods to form carbon-sulfur bonds. The synthesis of aryl sulfides via metal catalysis has significantly increased in recent years. Historically, thiolates and sulfides have been thought to plague catalyst activity in the presence of transition metals. Indeed, strong coordination of thiolates and thioethers to transition metals can often hinder catalytic activity; however, various catalysts are able to withstand catalyst deactivation and form aryl carbon-sulfur bonds in high-yielding transformations. This review discusses the metal-catalyzed arylation of thiols and the use of disulfides as metal-thiolate precursors for the formation of C-S bonds.

  13. Palladium-catalysed ortho arylation of acetanilides

    Indian Academy of Sciences (India)

    Guo-zhen zhang; Cheng-Qun Chen; Xin-Hua Feng; Guo-Sheng Huang

    2010-03-01

    The palladium-catalysed direct arylation of acetanilides by using C-H activation methodology has been demonstrated. Several acetanilides were coupled with aryl iodides in the presence of 10 mol% of Pd(OAc)2, 1.0 equiv of Cu(OTf)2, and 0.6 equiv of Ag2O to afford the corresponding products in moderate to excellent yields. The results showed that the amount of Ag2O was important for this protocol.

  14. A selective palladium-catalyzed carbonylative arylation of aryl ketones to give vinylbenzoate compounds.

    Science.gov (United States)

    Schranck, Johannes; Tlili, Anis; Neumann, Helfried; Alsabeh, Pamela G; Stradiotto, Mark; Beller, Matthias

    2012-12-01

    Preparation of enols: when treated with [{Pd(cinnamyl)Cl}(2)]/cataCXium A (nBuPAd(2), Ad=adamantyl) under an atmosphere of CO, aryl ketones react with aryl halides in a carbonylative C-O coupling reaction to form (Z)-vinyl benzoates. PMID:23143936

  15. The Remarkable Reactivity of Aryl Halides with Nucleophiles

    Science.gov (United States)

    Bunnett, Joseph F.

    1974-01-01

    Discusses the reactivity of aryl halides with nucleophilic or basic reagents, including nucleophilic attacks on carbon, hydrogen, halogen, and arynes. Suggestions are made concerning revisions of the sections on aryl halide chemistry courses and the corresponding chapters in textbooks. (CC)

  16. Synthesis of O-glycosyl α-aryl nitrones

    Institute of Scientific and Technical Information of China (English)

    Ying Fu; Huai Yuan Zhang; Yan Hua Liu; Xue Feng Li; Dan Feng Huang; Yu Lai Hu

    2010-01-01

    α-Aryl nitrone are one of the most useful kinds of nitrones and have been extensively explored in recent years.However,the sugar moieties have not been introduced into these molecules before.We presented here an efficient synthesis of α-aryl nitrone O-glycosides via condensation of N-substituted hydroxylamine and aryl aldehydes glycosides in benzene.

  17. Kynurenine 3-Monooxygenase: An Influential Mediator of Neuropathology

    OpenAIRE

    Parrott, Jennifer M.; O’Connor, Jason C.

    2015-01-01

    Mounting evidence demonstrates that kynurenine metabolism may play an important pathogenic role in the development of multiple neurological and neuropsychiatric disorders. The kynurenine pathway consists of two functionally distinct branches that generate both neuroactive and oxidatively reactive metabolites. In the brain, the rate-limiting enzyme for one of these branches, kynurenine 3-monooxygenase (KMO), is predominantly expressed in microglia and has emerged as a pivotal point of metaboli...

  18. Structural dynamics and ligand binding in kynurenine-3- monooxygenase

    OpenAIRE

    Wilkinson, Martin

    2013-01-01

    Kynurenine 3-monooxygenase is a FAD-dependent aromatic hydroxylase (FAH) which is a widely suggested therapeutic target for controlling the balance of bioactive metabolite levels produced by the mammalian kynurenine pathway (KP). Prior to starting this work no structural information was known for the enzyme, with studies of the human form complicated by the presence of a C-terminal transmembrane helix. The bacterial Pseudomonas fluorescens enzyme (PfKMO) lacks the transmembrane...

  19. Architecture and active site of particulate methane monooxygenase

    OpenAIRE

    Culpepper, Megen A.; Rosenzweig, Amy C.

    2012-01-01

    Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria, organisms that live on methane gas as their sole carbon source. Understanding pMMO function has important implications for bioremediation applications and for the development of new, environmentally friendly catalysts for the direct conversion of methane to methanol. Crystal structures of pMMOs from three different methanotrophs reveal a trimeric archite...

  20. Electronic structure and tautomerism of aryl ketones

    Energy Technology Data Exchange (ETDEWEB)

    Novak, Igor, E-mail: inovak@csu.edu.au [Charles Sturt University, POB 883, Orange, NSW 2800 (Australia); Klasinc, Leo, E-mail: klasinc@irb.hr [Physical Chemistry Department, Ruđer Bošković Institute, HR-10002 Zagreb (Croatia); Šket, Boris, E-mail: Boris.Sket@fkkt.uni-lj.si [Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 (Slovenia); McGlynn, S.P., E-mail: sean.mcglynn@chemgate.chem.lsu.edu [Louisiana State University, Baton Rouge, LA 70803 (United States)

    2015-07-15

    Graphical abstract: Photoelectron spectroscopy, tautomerism. - Highlights: • UV photoelectron spectroscopy of aryl ketones. • The relative stability of tautomers and their electronic structures. • The factors influencing tautomerism. - Abstract: The electronic structures of several aryl ketones (AK) and their α-halo derivatives have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of the AK derivatives are discussed.

  1. Crystallization and initial crystallographic characterization of the Corynebacterium glutamicum nitrilotriacetate monooxygenase component A

    OpenAIRE

    KIM, KYUNG-JIN; Kim, Sujin; Lee, Sujin; Kang, Beom Sik; Lee, Heung-Soo; Oh, Tae-Kwang; Kim, Myung Hee

    2006-01-01

    The Corynebacterium glutamicum NTA monooxygenase component A protein, which plays the central role in NTA biodegradation, was crystallized. The initial X-ray crystallographic characterization is reported.

  2. Extending the substrate scope of a Baeyer-Villiger monooxygenase by multiple-site mutagenesis

    NARCIS (Netherlands)

    Dudek, Hanna M; Fink, Michael J; Shivange, Amol V; Dennig, Alexander; Mihovilovic, Marko D; Schwaneberg, Ulrich; Fraaije, Marco W

    2014-01-01

    Baeyer-Villiger monooxygenase-catalysed reactions are attractive for industrial processes. Here we report on expanding the substrate scope of phenylacetone monooxygenase (PAMO). In order to introduce activity on alicyclic ketones in PAMO, we generated and screened a library of 1,500 mutants. Based o

  3. Degradation of Chlorinated Aliphatic Hydrocarbons by Methylosinus trichosporium OB3b Expressing Soluble Methane Monooxygenase

    NARCIS (Netherlands)

    Oldenhuis, Roelof; Vink, Ruud L.J.M.; Janssen, Dick B.; Witholt, Bernard

    1989-01-01

    Degradation of trichloroethylene (TCE) by the methanotrophic bacterium Methylosinus trichosporium OB3b was studied by using cells grown in continuous culture. TCE degradation was a strictly cometabolic process, requiring the presence of a cosubstrate, preferably formate, and oxygen. M. trichosporium

  4. The framework of polysaccharide monooxygenase structure and chemistry.

    Science.gov (United States)

    Span, Elise A; Marletta, Michael A

    2015-12-01

    Polysaccharide monooxygenases, or PMOs (also known as lytic PMOs or LPMOs), are a group of enzymes discovered in recent years to catalyze the oxidative degradation of carbohydrate polymers. The PMO catalytic domain has a β-sandwich fold that bears a strong resemblance to both immunoglobulin (Ig) and fibronectin type III (FnIII) domains. PMOs are secreted by fungi and bacteria, and there is recent evidence for their roles in pathogenesis, in addition to biomass processing. This review addresses the biological origins and functions of emerging PMO families, as well as describes the aspects of PMO structure that support the chemistry of copper-catalyzed, oxidative polysaccharide degradation. PMID:26615470

  5. On the catalytic mechanisms of lytic polysaccharide monooxygenases.

    Science.gov (United States)

    Walton, Paul H; Davies, Gideon J

    2016-04-01

    Lytic polysaccharide monooxygenases (LPMOs) are recently discovered copper-containing oxygenases. LPMOs oxidise recalcitrant polysaccharides such as chitin and cellulose, thereby making these substrates more tractable to canonical chitinase or cellulase action. As such, LPMOs are attracting much attention not only for their capacity to greatly increase the efficiency of production of cellulosic-based biofuels, but also for the new questions they pose about the mechanisms of biological oxidation of recalcitrant substrates. This review draws together the current thinking on the catalytic mechanisms of LPMOs and other copper catalysed oxygenations and provides a blueprint for further investigation into the mechanisms of action of these intriguing enzymes. PMID:27094791

  6. Bacterial expression of human kynurenine 3-monooxygenase: solubility, activity, purification.

    Science.gov (United States)

    Wilson, K; Mole, D J; Binnie, M; Homer, N Z M; Zheng, X; Yard, B A; Iredale, J P; Auer, M; Webster, S P

    2014-03-01

    Kynurenine 3-monooxygenase (KMO) is an enzyme central to the kynurenine pathway of tryptophan metabolism. KMO has been implicated as a therapeutic target in several disease states, including Huntington's disease. Recombinant human KMO protein production is challenging due to the presence of transmembrane domains, which localise KMO to the outer mitochondrial membrane and render KMO insoluble in many in vitro expression systems. Efficient bacterial expression of human KMO would accelerate drug development of KMO inhibitors but until now this has not been achieved. Here we report the first successful bacterial (Escherichia coli) expression of active FLAG™-tagged human KMO enzyme expressed in the soluble fraction and progress towards its purification. PMID:24316190

  7. Multimetallic catalysed cross-coupling of aryl bromides with aryl triflates

    Science.gov (United States)

    Ackerman, Laura K. G.; Lovell, Matthew M.; Weix, Daniel J.

    2015-08-01

    The advent of transition-metal catalysed strategies for forming new carbon-carbon bonds has revolutionized the field of organic chemistry, enabling the efficient synthesis of ligands, materials, and biologically active molecules. In cases where a single metal fails to promote a selective or efficient transformation, the synergistic cooperation of two distinct catalysts--multimetallic catalysis--can be used instead. Many important reactions rely on multimetallic catalysis, such as the Wacker oxidation of olefins and the Sonogashira coupling of alkynes with aryl halides, but this approach has largely been limited to the use of metals with distinct reactivities, with only one metal catalyst undergoing oxidative addition. Here, we demonstrate that cooperativity between two group 10 metal catalysts--(bipyridine)nickel and (1,3-bis(diphenylphosphino)propane)palladium--enables a general cross-Ullmann reaction (the cross-coupling of two different aryl electrophiles). Our method couples aryl bromides with aryl triflates directly, eliminating the use of arylmetal reagents and avoiding the challenge of differentiating between multiple carbon-hydrogen bonds that is required for direct arylation methods. Selectivity can be achieved without an excess of either substrate and originates from the orthogonal reactivity of the two catalysts and the relative stability of the two arylmetal intermediates. While (1,3-bis(diphenylphosphino)propane)palladium reacts preferentially with aryl triflates to afford a persistent intermediate, (bipyridine)nickel reacts preferentially with aryl bromides to form a transient, reactive intermediate. Although each catalyst forms less than 5 per cent cross-coupled product in isolation, together they are able to achieve a yield of up to 94 per cent. Our results reveal a new method for the synthesis of biaryls, heteroaryls, and dienes, as well as a general mechanism for the selective transfer of ligands between two metal catalysts. We anticipate that this

  8. Kinetics of chlorinated hydrocarbon degradation by Methylosinus trichosporium OB3b and toxicity of trichloroethylene.

    OpenAIRE

    Oldenhuis, Roelof; Oedzes, Johannes Y.; Waarde, Jacob J. van der; Janssen, Dick B.

    1991-01-01

    The kinetics of the degradation of trichloroethylene (TCE) and seven other chlorinated aliphatic hydrocarbons by Methylosinus trichosporium OB3b were studied. All experiments were performed with cells grown under copper stress and thus expressing soluble methane monooxygenase. Compounds that were readily degraded included chloroform, trans-1,2-dichloroethylene, and TCE, with V(max) values of 550, 330, and 290 nmol min-1 mg of cells-1, respectively. 1,1-Dichloroethylene was a very poor substra...

  9. Apparatus for hydrocarbon extraction

    Science.gov (United States)

    Bohnert, George W.; Verhulst, Galen G.

    2013-03-19

    Systems and methods for hydrocarbon extraction from hydrocarbon-containing material. Such systems and methods relate to extracting hydrocarbon from hydrocarbon-containing material employing a non-aqueous extractant. Additionally, such systems and methods relate to recovering and reusing non-aqueous extractant employed for extracting hydrocarbon from hydrocarbon-containing material.

  10. C(aryl)-O Bond Formation from Aryl Methanesulfonates via Consecutive Deprotection and SNAr Reactions with Aryl Halides in an Ionic Liquid

    OpenAIRE

    Yang Chen; Hui Xu

    2007-01-01

    An efficient K3PO4-mediated synthesis of unsymmetrical diaryl ethers using the ionic liquid [Bmim]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) as solvent has been developed. The procedure involves consecutive deprotection of aryl methane-sulfonates and a nucleophilic aromatic substitution (SNAr) with activated aryl halides.

  11. C(aryl-O Bond Formation from Aryl Methanesulfonates via Consecutive Deprotection and SNAr Reactions with Aryl Halides in an Ionic Liquid

    Directory of Open Access Journals (Sweden)

    Yang Chen

    2007-04-01

    Full Text Available An efficient K3PO4-mediated synthesis of unsymmetrical diaryl ethers using the ionic liquid [Bmim]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate as solvent has been developed. The procedure involves consecutive deprotection of aryl methane-sulfonates and a nucleophilic aromatic substitution (SNAr with activated aryl halides.

  12. Copper-catalysed N-arylation of arylsulfonamides with aryl bromides and aryl iodides using KF/Al2O3

    Indian Academy of Sciences (India)

    Rahman Hosseinzadeh; Mahmood Tajbakhsh; Maryam Mohadjerani; Mohammad Alikarami

    2010-03-01

    An efficient synthesis of -arylsulfonamides with a variety of aryl bromides, aryl iodides and heteroaryl bromides using KF/Al2O3 as a suitable base, CuI as an inexpensive catalyst and ,'-dimethylethylenediamine (,'-DMEDA) as an effective ligand is described.

  13. Role of flavin-containing monooxygenase in drug development.

    Science.gov (United States)

    Cashman, John R

    2008-12-01

    This review summarizes some recent observations and information related to the role of the flavin-containing monooxygenase (FMO) in preclinical drug development. Flavin-containing monooxygenase is a complimentary enzyme system to the cytochrome P450 (CYP) family of enzymes and oxygenates several soft, highly polarizable nucleophilic heteroatom-containing chemicals and drugs. The products of FMO-mediated metabolism are generally benign and highly polar, readily excreted materials. There may be some advantages in designing drugs that are metabolized in part by FMO and not exclusively by CYP. In this review, I describe the practical aspects for the participation of FMO in drug and chemical metabolism including: i) the study of FMO using in vitro preparations; ii) some observations about metabolism of drugs and chemicals by FMO in vivo; and iii) the consequences of studying FMO-related metabolism in various small animal models. Some of the preclinical research and development areas related to FMO are not fully mature areas and there are certain gaps in our knowledge. However, I include discussion of these areas to stimulate further work and invite further discussion. PMID:19040327

  14. Fluoroalkylation of aryl ether perfluorocyclobutyl polymers

    OpenAIRE

    Ligon, Clark; Ameduri, Bruno; Boutevin, Bernard; Smith, Dennis

    2008-01-01

    Post functionalization of aryl ether perfluorocyclobutyl (PFCB) polymers with fluoroalkyl side chains was accomplished with Umemoto's FITS reagents. The fluoroalkylated PFCB polymers (20 % functionalized) showed increases in both hydrophobicity and oleophobicity. Static contact angle for hexadecane was increased after fluoroalkylation from 0° to greater than 30° for the two PFCB polymers tested. Increased oil repellency makes these materials potential candidates for various coatings applicati...

  15. Palladium-Catalyzed Arylation of Fluoroalkylamines

    Science.gov (United States)

    Brusoe, Andrew T.; Hartwig, John F.

    2015-01-01

    We report the synthesis of fluorinated anilines by palladium-catalyzed coupling of fluoroalkylamines with aryl bromides and aryl chlorides. The products of these reactions are valuable because anilines typically require the presence of an electron-withdrawing substituent on nitrogen to suppress aerobic or metabolic oxidation, and the fluoroalkyl groups have steric properties and polarity distinct from those of more common electron-withdrawing amide and sulfonamide units. The fluoroalkylaniline products are unstable under typical conditions for C–N coupling reactions (heat and strong base). However, the reactions conducted with the weaker base KOPh, which has rarely been used in cross-coupling to form C–N bonds, occurred in high yield in the presence of a catalyst derived from commercially available AdBippyPhos and [Pd(allyl)Cl]2. Under these conditions, the reactions occur with low catalyst loadings (<0.50 mol % for most substrates) and tolerate the presence of various functional groups that react with the strong bases that are typically used in Pd-catalyzed C–N cross-coupling reactions of aryl halides. The resting state of the catalyst is the phenoxide complex, (BippyPhosPd(Ar)OPh); due to the electron-withdrawing property of the fluoroalkyl substituent, the turnover-limiting step of the reaction is reductive elimination to form the C–N bond. PMID:26065341

  16. Palladium-Catalyzed alpha-Arylation of Tetramic Acids

    DEFF Research Database (Denmark)

    Storgaard, Morten; Dorwald, F. Z.; Peschke, B.;

    2009-01-01

    A mild, racemization-free, palladium-Catalyzed alpha-arylation of tetramic acids (2,4-pyrrolidinediones) has been developed. Various amino acid-derived tetramic acids were cleanly arylated by treatment with 2 mol % of Pd(OAc)(2), 4 mol % of a sterically demanding biaryl phosphine, 2.3 equiv of K2...... effect on their reactivity: both electron-rich and electron-poor aryl chlorides and bromides or triflates led to good yields. Ortho-substituted aryl halides and heteroaryl halides, however, did not undergo the title reaction....

  17. N-Heterocyclic carbene–palladium catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

    Directory of Open Access Journals (Sweden)

    Ismail Özdemir

    2013-02-01

    Full Text Available New Pd–NHC complexes have been synthesized and employed for palladium-catalyzed direct arylation of pyrrole derivatives by using electron-deficient aryl chlorides as coupling partners. The desired coupling products were obtained in moderate to good yields by using 1 mol % of these air-stable palladium complexes. This is an advantage compared to the procedures employing air-sensitive phosphines, which have been previously shown to promote the coupling of aryl chlorides with heteroarenes.

  18. Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

    Science.gov (United States)

    Wang, Shaoyan; Zhang, Zhiqiang; Hu, Zhizhi; Wang, Yue; Lei, Peng; Chi, Haijun

    2009-01-01

    An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated. PMID:25084408

  19. Expression, purification and characterization of human Dopamine ß-monooxygenase

    DEFF Research Database (Denmark)

    Vendelboe, Trine Vammen

    catalytic domains called ascorbate dependent type IImonooxygenase domains and a C-terminal dimerization domain. DBM is related to peptidylglycine a-hydroxylating monooxygenase (PHM). They are 28 % identical over approximately 300 amino scids (AA) which corresponds to the catalytic domains. This is, among...... others, one of the reasons why these proteins are considered to follow the same mechanism. DBM converts dopamine (DA) into Norepinphrine (NE). Both substrate and product functions as neurotransmitters and the levels of these are involved in many different disorders such as depression and hypertension and...... DBM dimer, going from residue 47-596 in each chain, was hereafter manually built. The structure reveals the first structural insights into the DOMON domain and the C-terminal dimerization domain and it shows two different conformations of the catalytic domains. An open conformation, that resembles the...

  20. [Association of kynurenine-3-monooxygenase gene with schizophrenia].

    Science.gov (United States)

    Golimbet, V E; Lezheiko, T V; Alfimova, M V; Abramova, L I; Kondrat'ev, N V

    2014-06-01

    Neurotoxic products produced during tryptophan metabolism via the kynurenine pathway could be involved in schizophrenia pathogenesis. It has been shown that kynurenine-3-monooxygenase (KMO) is indirectly involved in these products' formation. KMO polymorphic loci rs2275163 (C/T) and rs1053230 (A/G) were examined in 187 schizophrenia patients and 229 healthy subjects. A genetic combination of allele T and genotype GG was observed more often in a patient group compared with healthy controls (p = 0.003, OR 2.0 (95% CI 1.2-2.9). In the latter group, this combination was associated with schizophrenia endophenotype (p = 0.04), which manifested in a higher expression of schizotypal personality traits assessed using the MMPI test. PMID:25715464

  1. Kynurenine-3-monooxygenase: a review of structure, mechanism, and inhibitors.

    Science.gov (United States)

    Smith, Jason R; Jamie, Joanne F; Guillemin, Gilles J

    2016-02-01

    Kynurenine monooxygenase (KMO) is an enzyme of the kynurenine (Kyn) pathway (KP), which is the major catabolic route of tryptophan. Kyn represents a branch point of the KP, being converted into the neurotoxin 3-hydroxykynurenine via KMO, neuroprotectant kynurenic acid, and anthranilic acid. As a result of this branch point, KMO is an attractive drug target for several neurodegenerative and/or neuroinflammatory diseases, especially Huntington's (HD), Alzheimer's (AD), and Parkinson's (PD) diseases. Although a neurological target, administration of KMO inhibitors in the periphery has demonstrated promising pharmacological results. In light of a recent crystal structure release and reports of preclinical candidates, here we provide a concise yet comprehensive update on the current state of research into the enzymology of KMO and related drug discovery efforts, highlighting areas where further work is required. PMID:26589832

  2. Effects of bromocriptine on hepatic cytochrome P-450 monooxygenase system.

    Science.gov (United States)

    Moochhala, S M; Lee, E J; Hu, G T; Koh, O S; Becket, G

    1989-02-01

    We have evaluated the in vitro effects of bromocriptine (Br), on the hepatic cytochrome P-450 monooxygenase system of rats pretreated with saline phenobarbitone (PB) and beta-naphthoflavone (BNF). Br inhibited ethoxyresorufin O-dealkylase (EROD) activity in liver microsomes of rats pretreated with saline and PB but not in BNF pretreated animals. Maximum inhibition of EROD activity by Br in the microsomes of saline and PB pretreated rats were 50%-60% of the control. In contrast, a dual effect was observed on aminopyrine N-demethylase activity (APD) by Br in microsomes of saline, PB and BNF pretreated rats. At a low concentration (25 microM), Br inhibited the activity of APD to a similar extent in all pretreatment groups; however, with higher concentrations of Br (50 microM to 300 microM), enhancement of APD activity was observed. Br (300 microM) increased the APD activity to 2-3 times the control level in microsomes of rats pretreated with saline, PB or BNF. Spectral studies revealed a Type II binding of Br to cytochrome P-450 from microsomes of saline and PB pretreated rats. A reverse type I binding was observed for BNF induced microsomes. In addition, Br also enhanced NADPH cytochrome c (P-450) reductase activity to a similar extent in all pretreatment groups. These results suggest that the inhibition of EROD activity may be due to direct binding by Br to certain isozymes of cytochrome P-450 and that the enhancing effect of Br on APD activity may be in part due to the activation of the NADPH cytochrome c reductase component of the cytochrome P-450 monooxygenase system. PMID:2499727

  3. Selective copper catalysed aromatic N-arylation in water

    DEFF Research Database (Denmark)

    Engel-Andreasen, Jens; Shimpukade, Bharat; Ulven, Trond.

    2013-01-01

    4,7-Dipyrrolidinyl-1,10-phenanthroline (DPPhen) was identified as an efficient ligand for copper catalyzed selective arom. N-arylation in water. N-Arylation of indoles, imidazoles and purines proceeds with moderate to excellent yields and complete selectivity over aliph. amines. Aq. medium and th...

  4. A New Route to Azafluoranthene Natural Products via Direct Arylation

    OpenAIRE

    Ponnala, Shashikanth; Harding, Wayne W.

    2013-01-01

    Microwave-assisted direct arylation was successfully employed in the synthesis of azafluoranthene alkaloids for the first time. Direct arylation reactions on a diverse set of phenyltetrahydroisoquinolines produces the indeno[1,2,3-ij]isoquinoline nucleus en route to a high yielding azafluoranthene synthesis.

  5. Mammalian flavin-containing monooxygenases: structure/function, genetic polymorphisms and role in drug metabolism

    OpenAIRE

    Sharon K. Krueger; Williams, David E.

    2005-01-01

    Flavin-containing monooxygenase (FMO) oxygenates drugs and xenobiotics containing a “soft-nucleophile”, usually nitrogen or sulfur. FMO, like cytochrome P450 (CYP), is a monooxygenase, utilizing the reducing equivalents of NADPH to reduce 1 atom of molecular oxygen to water, while the other atom is used to oxidize the substrate. FMO and CYP also exhibit similar tissue and cellular location, molecular weight, substrate specificity, and exist as multiple enzymes under developmental control. The...

  6. Flavin-dependent monooxygenases as a detoxification mechanism in insects: new insights from the Arctiids (Lepidoptera)

    OpenAIRE

    Sehlmeyer, S.; Wang, L.(Universität Bochum, Institut für Experimentalphysik, Bochum, 44780, Germany); Langel, D.; Heckel, D.; Mohagheghi, H.; Petschenka, G.; Ober, D.

    2010-01-01

    Insects experience a wide array of chemical pressures from plant allelochemicals and pesticides and have developed several effective counterstrategies to cope with such toxins. Among these, cytochrome P450 monooxygenases are crucial in plant-insect interactions. Flavin-dependent monooxygenases (FMOs) seem not to play a central role in xenobiotic detoxification in insects, in contrast to mammals. However, the previously identified senecionine N-oxygenase of the arctiid moth Tyria jacobaeae (Le...

  7. C- versus O-Arylation of an Enol-Lactone Using Potassium tert-butoxide

    Directory of Open Access Journals (Sweden)

    El Moktar Essassi

    2003-05-01

    Full Text Available Abstract: The use of potassium tert-butoxide as the base in arylation reactions of an enollactone with a series of benzyl halides was explored. Our work demonstrates that the ratio of C-arylation to O-arylation varies with the substitution pattern of the aryl halide.

  8. Palladium-Catalyzed Ortho-Arylation of Carbamate-Protected Estrogens.

    Science.gov (United States)

    Bedford, Robin B; Brenner, Peter B; Durrant, Steven J; Gallagher, Timothy; Méndez-Gálvez, Carolina; Montgomery, Michelle

    2016-05-01

    The palladium-catalyzed ortho-arylation of diethyl carbamate-protected estrone and estriol with aryl iodides gives the 2-arylated analogues. Subsequent removal of the carbamate directing group furnishes 2-arylated estrone, estradiol, or estriol depending on the method used. PMID:27057762

  9. The hydrocarbon sphere

    Energy Technology Data Exchange (ETDEWEB)

    Mandev, P.

    1984-01-01

    The hydrocarbon sphere is understood to be the area in which hydrocarbon compounds are available. It is believed that the lower boundary on the hydrocarbon sphere is most probably located at a depth where the predominant temperatures aid in the destruction of hydrocarbons (300 to 400 degrees centigrade). The upper limit on the hydrocarbon sphere obviously occurs at the earth's surface, where hydrocarbons oxidize to H20 and CO2. Within these ranges, the occurrence of the hydrocarbon sphere may vary from the first few hundred meters to 15 kilometers or more. The hydrocarbon sphere is divided into the external (mantle) sphere in which the primary gas, oil and solid hydrocarbon fields are located, and the internal (metamorphic) sphere containing primarily noncommercial accumulations of hydrocarbon gases and solid carbon containing compounds (anthraxilite, shungite, graphite, etc.) based on the nature and scale of hydrocarbon compound concentrations (natural gas, oil, maltha, asphalt, asphaltite, etc.).

  10. Practical Direct α-Arylation of Cyclopentanones by Palladium/Enamine Cooperative Catalysis.

    Science.gov (United States)

    Xu, Yan; Su, Tianshun; Huang, Zhongxing; Dong, Guangbin

    2016-02-12

    Direct arylation of cyclopentanones has been a long-standing challenge because of competitive self-aldol condensation and multiple arylations. Reported herein is a direct mono-α-C-H arylation of cyclopentanones with aryl bromides which is enabled by palladium/amine cooperative catalysis. This method is scalable and chemoselective with broad functional-group tolerance. Application to controlled sequential arylation of cyclopentanones has been also demonstrated. PMID:26840218

  11. Synthesis of 3-fluoro-3-aryl oxindoles: Direct enantioselective α arylation of amides

    KAUST Repository

    Wu, Linglin

    2012-02-06

    Modus operandi: Catalytic access to the title compounds through a new asymmetric α-arylation protocol is reported (see scheme). These products are formed in good yields and excellent enantioselectivities by using a new and easily synthesized chiral N-heterocyclic carbene (NHC) ligand. Advanced DFT calculations reveal the properties of the NHC ligand and the mode of operation of the catalyst. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Metabolic responses of Rhodococcus erythropolis PR4 grown on diesel oil and various hydrocarbons.

    Science.gov (United States)

    Laczi, Krisztián; Kis, Ágnes; Horváth, Balázs; Maróti, Gergely; Hegedüs, Botond; Perei, Katalin; Rákhely, Gábor

    2015-11-01

    Rhodococcus erythropolis PR4 is able to degrade diesel oil, normal-, iso- and cycloparaffins and aromatic compounds. The complete DNA content of the strain was previously sequenced and numerous oxygenase genes were identified. In order to identify the key elements participating in biodegradation of various hydrocarbons, we performed a comparative whole transcriptome analysis of cells grown on hexadecane, diesel oil and acetate. The transcriptomic data for the most prominent genes were validated by RT-qPCR. The expression of two genes coding for alkane-1-monooxygenase enzymes was highly upregulated in the presence of hydrocarbon substrates. The transcription of eight phylogenetically diverse cytochrome P450 (cyp) genes was upregulated in the presence of diesel oil. The transcript levels of various oxygenase genes were determined in cells grown in an artificial mixture, containing hexadecane, cycloparaffin and aromatic compounds and six cyp genes were induced by this hydrocarbon mixture. Five of them were not upregulated by linear and branched hydrocarbons. The expression of fatty acid synthase I genes was downregulated by hydrocarbon substrates, indicating the utilization of external alkanes for fatty acid synthesis. Moreover, the transcription of genes involved in siderophore synthesis, iron transport and exopolysaccharide biosynthesis was also upregulated, indicating their important role in hydrocarbon metabolism. Based on the results, complex metabolic response profiles were established for cells grown on various hydrocarbons. Our results represent a functional annotation of a rhodococcal genome, provide deeper insight into molecular events in diesel/hydrocarbon utilization and suggest novel target genes for environmental monitoring projects. PMID:26346267

  13. Structural and Catalytic Differences between Two FADH2-Dependent Monooxygenases: 2,4,5-TCP 4-Monooxygenase (TftD) from Burkholderia cepacia AC1100 and 2,4,6-TCP 4-Monooxygenase (TcpA) from Cupriavidus necator JMP134

    OpenAIRE

    ChulHee Kang; Luying Xun; Andrew Popchock; Arun Kumar Subramanian; Webb, Brian N.; Robert P. Hayes; Mark Nissen

    2012-01-01

    2,4,5-TCP 4-monooxygenase (TftD) and 2,4,6-TCP 4-monooxygenase (TcpA) have been discovered in the biodegradation of 2,4,5-trichlorophenol (2,4,5-TCP) and 2,4,6-trichlorophenol (2,4,6-TCP). TcpA and TftD belong to the reduced flavin adenine dinucleotide (FADH2)-dependent monooxygenases and both use 2,4,6-TCP as a substrate; however, the two enzymes produce different end products. TftD catalyzes a typical monooxygenase reaction, while TcpA catalyzes a typical monooxygenas...

  14. The liver monooxygenase system of Brazilian freshwater fish.

    Science.gov (United States)

    Leitão, M A; Affonso, E G; da Silva, M F; Meirelles, N C; Rantin, F T; Vercesi, A E; Junqueira, V B; Degterev, I A

    2000-05-01

    Content of cytochromes b5 and P-450, and activities of NADPH-cytochrome c (P-450) reductase (NCR) and 7-ethoxyresorufin O-deethylase (EROD) were measured in liver microsomes prepared from two South American endemic fish, Brycon cephalus and Colossoma macropomum, from tilapia, Oreochromis niloticus, and from Swiss mice, Mus musculus, which served as a control. Strong hemoglobin binding to fish liver microsomal membranes (FLM) altered visible spectra of microsomal cytochromes. Consequently, special precautions during FLM preparation, including liver perfusion followed by repeated washing of microsomes, were required in the study of microsomal cytochromes from these fish. FLM from all fish studied here had a significantly lower content of microsomal cytochromes but a similar level of NCR and EROD activities compared to mouse liver microsomes (MLM). Strong response of the monooxygenase system in O. niloticus to water pollution was detected with both specific cytochrome P-450 content and EROD activity increasing sharply. The optical spectra of hemoglobin from B. cephalus and C. macropomum were analyzed and some differences in shape and relative extinction were observed compared to known hemoglobins. PMID:11048662

  15. Kynurenine 3-Monooxygenase: An Influential Mediator of Neuropathology.

    Science.gov (United States)

    Parrott, Jennifer M; O'Connor, Jason C

    2015-01-01

    Mounting evidence demonstrates that kynurenine metabolism may play an important pathogenic role in the development of multiple neurological and neuropsychiatric disorders. The kynurenine pathway consists of two functionally distinct branches that generate both neuroactive and oxidatively reactive metabolites. In the brain, the rate-limiting enzyme for one of these branches, kynurenine 3-monooxygenase (KMO), is predominantly expressed in microglia and has emerged as a pivotal point of metabolic regulation. KMO substrate and expression levels are upregulated by pro-inflammatory cytokines and altered by functional genetic mutations. Increased KMO metabolism results in the formation of metabolites that activate glutamate receptors and elevate oxidative stress, while recent evidence has revealed neurodevelopmental consequences of reduced KMO activity. Together, the evidence suggests that KMO is positioned at a critical metabolic junction to influence the development or trajectory of a myriad of neurological diseases. Understanding the mechanism(s) by which alterations in KMO activity are able to impair neuronal function, and viability will enhance our knowledge of related disease pathology and provide insight into novel therapeutic opportunities. This review will discuss the influence of KMO on brain kynurenine metabolism and the current understanding of molecular mechanisms by which altered KMO activity may contribute to neurodevelopment, neurodegenerative, and neuropsychiatric diseases. PMID:26347662

  16. The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

    Directory of Open Access Journals (Sweden)

    Volodymyr V. Tkachenko

    2014-12-01

    Full Text Available The switchable three-component reactions of 5-amino-3-methylisoxazole, salicylaldehyde and N-aryl-3-oxobutanamides under different conditions were studied and discussed. The unexpected influence of the aryl substituent in N-aryl-3-oxobutanamides on the behavior of the reaction was discovered. The key influence of ultrasonication and Lewis acid catalysts led to an established protocol to selectively obtain two or three types of heterocyclic scaffolds depending on the substituent in the N-aryl moiety.

  17. 2-aminopyrimidine-4,6-diol as an efficient ligand for solvent-free copper-catalyzed N-arylations of imidazoles with aryl and heteroaryl halides.

    Science.gov (United States)

    Xie, Ye-Xiang; Pi, Shao-Feng; Wang, Jian; Yin, Du-Lin; Li, Jin-Heng

    2006-10-13

    Efficient and solvent-free copper-catalyzed N-arylations of imidazoles with aryl and heteroaryl halides have been demonstrated. In the presence of CuBr, 2-aminopyrimidine-4,6-diol, and TBAF (n-Bu4NF), a variety of imidazoles underwent the N-arylation reaction with aryl and heteroaryl halides smoothly in moderate to excellent yields. Noteworthy is that the reaction is conducted under solvent-free conditions. PMID:17025338

  18. Raman characteristics of hydrocarbon and hydrocarbon inclusions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Nai; TIAN ZuoJi; LENG YingYing; WANG HuiTong; SONG FuQing; MENG JianHua

    2007-01-01

    The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2)branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4)phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hydrocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclusions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydrocarbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram.And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion,saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

  19. Raman characteristics of hydrocarbon and hydrocarbon inclusions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Raman spectrograms of hydrocarbon standard samples show that: (1) the Raman spectrogram of normal paraffin has very strong peaks of methyl and methylene (from 2700 cm-1 to 2970 cm-1); (2) branch methyl has the particular peak of 748 cm-1±; (3) six cyclic has the particular peak of 804 cm-1±; (4) phenyl has two particular peaks of 988 cm-1± and 3058 cm-1± and the 988 cm-1± peak is stronger than the 3058 cm-1± peak; and (5) hexene has three alkenyl spectrum peaks of 1294 cm-1±, 1635 cm-1± and 2996 cm-1±, with the 1635 cm-1± peak being the strongest, showing that the number of carbon in hy-drocarbon does not affect its Raman spectrogram, and the hydrocarbon molecular structure and base groups affect its Raman spectrogram, the same hydrocarbons (such as normal paraffin) have the same Raman spectrogram; the types (such as CH4, C2H6, C3H8) and the content of hydrocarbon in oil inclu-sions are not estimated by their characteristic Raman peaks. According to the Raman spectrograms of hydrocarbon compositions, the Raman spectrogram of hydrocarbon inclusion can be divided into five types: saturated hydrocarbon Raman spectrogram, fluoresce Raman spectrogram, saturated hydro-carbon bitumen Raman spectrogram, bitumen Raman spectrogram, and ethane Raman spectrogram. And according to the characteristics of Raman spectrogram, hydrocarbon inclusions can be divided into five types: saturated hydrocarbon inclusion, less saturated hydrocarbon (oil or gas) inclusion, saturated hydrocarbon bitumen inclusion, bitumen inclusion, and methane water inclusion.

  20. Substrates specialization in lipid compounds and hydrocarbons of Marinobacter genus.

    Science.gov (United States)

    Bonin, Patricia; Vieira, Christophe; Grimaud, Régis; Militon, Cécile; Cuny, Philippe; Lima, Oscar; Guasco, Sophie; Brussaard, Corina P D; Michotey, Valérie

    2015-10-01

    The impact of petroleum contamination and of burrowing macrofauna on abundances of Marinobacter and denitrifiers was tested in marine sediment mesocoms after 3 months incubation. Quantification of this genus by qPCR with a new primer set showed that the main factor favoring Marinobacter abundance was hydrocarbon amendment followed by macrofauna presence. In parallel, proportion of nosZ-harboring bacteria increased in the presence of marcrofauna. Quantitative finding were explained by physiological data from a set of 34 strains and by genomic analysis of 16 genomes spanning 15 different Marinobacter-validated species (Marinobacter hydrocarbonoclasticus, Marinobacter daeopensis, Marinobacter santoriniensis, Marinobacter pelagius, Marinobacter flavimaris, Marinobacter adhaerens, Marinobacter xestospongiae, Marinobacter algicola, Marinobacter vinifirmus, Marinobacter maritimus, Marinobacter psychrophilus, Marinobacter lipoliticus, Marinobacter manganoxydans, Marinobacter excellens, Marinobacter nanhaiticus) and 4 potential novel ones. Among the 105 organic electron donors tested in physiological analysis, Marinobacter pattern appeared narrow for almost all kinds of organic compounds except lipid ones. Strains of this set could oxidize a very large spectrum of lipids belonging to glycerolipids, branched, fatty acyls, and aromatic hydrocarbon classes. Physiological data were comforted by genomic analysis, and genes of alkane 1-monooxygenase, haloalkane dehalogenase, and flavin-binding monooxygenase were detected in most genomes. Denitrification was assessed for several strains belonging to M. hydrocarbonoclasticus, M. vinifirmus, Marinobacter maritinus, and M. pelagius species indicating the possibility to use nitrate as alternative electron acceptor. Higher occurrence of Marinobacter in the presence of petroleum appeared to be the result of a broader physiological trait allowing this genus to use lipids including hydrocarbon as principal electron donors. PMID:25561256

  1. Heck Arylation of Acrylonitrile with Aryl Iodides Catalyzed by a Silica-bound Arsine Palladium(0) Complex

    Institute of Scientific and Technical Information of China (English)

    Ming Zhong CAI; Hong ZHAO; Rong Li ZHANG

    2005-01-01

    Acrylonitrile reacts with aryl iodides in the presence of tri-n-butylamine and a catalytic amount of a silica-bound arsine palladium(0) complex to afford stereoselectively (E)-cinnamonitriles in high yields.

  2. THE BIOCHEMICAL CHARACTERIZATION OF FERRET CAROTENE-9', 10'-MONOOXYGENASE CATALYZING CLEAVAGE OF CAROTENOIDS IN VITRO AND IN VIVO

    Science.gov (United States)

    Previous studies have shown that beta -carotene 15,15'-monooxygenase (CMO1) catalyzes the cleavage of beta -carotene at the central carbon 15, 15’-double bond, but cleaves lycopene with much lower activity. However, expressing the mouse carotene-9’,10’-monooxygenase (CMO2) in beta-carotene/lycopene...

  3. Discovery and industrial applications of lytic polysaccharide mono-oxygenases.

    Science.gov (United States)

    Johansen, Katja S

    2016-02-15

    The recent discovery of copper-dependent lytic polysaccharide mono-oxygenases (LPMOs) has opened up a vast area of research covering several fields of application. The biotech company Novozymes A/S holds patents on the use of these enzymes for the conversion of steam-pre-treated plant residues such as straw to free sugars. These patents predate the correct classification of LPMOs and the striking synergistic effect of fungal LPMOs when combined with canonical cellulases was discovered when fractions of fungal secretomes were evaluated in industrially relevant enzyme performance assays. Today, LPMOs are a central component in the Cellic CTec enzyme products which are used in several large-scale plants for the industrial production of lignocellulosic ethanol. LPMOs are characterized by an N-terminal histidine residue which, together with an internal histidine and a tyrosine residue, co-ordinates a single copper atom in a so-called histidine brace. The mechanism by which oxygen binds to the reduced copper atom has been reported and the general mechanism of copper-oxygen-mediated activation of carbon is being investigated in the light of these discoveries. LPMOs are widespread in both the fungal and the bacterial kingdoms, although the range of action of these enzymes remains to be elucidated. However, based on the high abundance of LPMOs expressed by microbes involved in the decomposition of organic matter, the importance of LPMOs in the natural carbon-cycle is predicted to be significant. In addition, it has been suggested that LPMOs play a role in the pathology of infectious diseases such as cholera and to thus be relevant in the field of medicine. PMID:26862199

  4. Nongenotoxic modes of action of polycyclic aromatic hydrocarbons and their relative potencies in rat liver cellular models. Ecotoxicological significance of individual compounds in abiotic samples

    Czech Academy of Sciences Publication Activity Database

    Machala, M.; Vondráček, Jan; Bláha, L.; Minksová, Kateřina; Neča, J.; Ciganek, M.

    Brno: Masarykova univerzita, 2002. s. 99-100. [SECOTOX 2002. Regional Meeting of the Central and Eastern European Section /7./. 14.10.2002-16.10.2002, Brno] Institutional research plan: CEZ:AV0Z5004920 Keywords : GJIC inhibition * aryl hydrocarbon receptor * proliferation Subject RIV: BO - Biophysics

  5. Monooxygenase activitity in Aedes aegypti population in Tembalang subdistrict, Semarang city

    Directory of Open Access Journals (Sweden)

    Dyah Widiastuti

    2015-06-01

    Full Text Available Dengue Haemorrhagic Fever (DHF is a major health problem in Tembalang sub district, Semarang City. Fogging with insecticide applications was done frequently as an effort to control Dengue vectors. The use of insecticides from the same class in a long time can lead to resistance in mosquitos’ population. The research aimed to observe the activity of monooxygenases in Aedes aegypti populations in Tembalang Subdistrict, Semarang. The study was conducted during February-November 2014 with a cross-sectional design in 10 villages in Tembalang Subdistirict, Semarang City. Field strains of Ae. aegypti eggs were collected using ovitraps. The collected eggs were grown under standard condition to adult mosquitoes. Mosquitos’ homogenate were stored at -85C and used for biochemical assays. The results showed there was increased monooxygenases activity in Ae. aegypti populations. Resistance to synthetic pyrethroid insecticide in Ae. aegypti mosquitoes population in Tembalang Subdistrict might be caused by the mechanism of detoxification enzymes in particular monooxygenases

  6. Environmental Behavior, Sources, and Effects of Chlorinated Polycyclic Aromatic Hydrocarbons

    Directory of Open Access Journals (Sweden)

    Takeshi Ohura

    2007-01-01

    Full Text Available The environmental sources and behaviors of chlorinated 2- to 5-ring polycyclic aromatic hydrocarbons (ClPAHs. ClPAHs are ubiquitous contaminants found in urban air, vehicle exhaust gas, snow, tap water, and sediments. The concentrations of ClPAHs in each of these environments are generally higher than those of dioxins but markedly lower than the concentrations of the parent compounds, PAHs. Environmental data and emission sources analysis for ClPAHs reveal that the dominant process of generation is by reaction of PAHs with chlorine in pyrosynthesis. This secondary reaction process also occurs in aquatic environments. Certain ClPAHs show greater toxicity, such as mutagenicity and aryl hydrocarbon receptor activity, than their corresponding parent PAHs. Investigation of the sources and environmental behavior of ClPAHs is of great importance in the assessment of human health risks.

  7. Mutational and crystallographic analysis of l-amino acid oxidase/monooxygenase from Pseudomonas sp. AIU 813: Interconversion between oxidase and monooxygenase activities

    Directory of Open Access Journals (Sweden)

    Daisuke Matsui

    2014-01-01

    Full Text Available In this study, it was shown for the first time that l-amino acid oxidase of Pseudomonas sp. AIU813, renamed as l-amino acid oxidase/monooxygenase (l-AAO/MOG, exhibits l-lysine 2-monooxygenase as well as oxidase activity. l-Lysine oxidase activity of l-AAO/MOG was increased in a p-chloromercuribenzoate (p-CMB concentration-dependent manner to a final level that was five fold higher than that of the non-treated enzyme. In order to explain the effects of modification by the sulfhydryl reagent, saturation mutagenesis studies were carried out on five cysteine residues, and we succeeded in identifying l-AAO/MOG C254I mutant enzyme, which showed five-times higher specific activity of oxidase activity than that of wild type. The monooxygenase activity shown by the C254I variant was decreased significantly. Moreover, we also determined a high-resolution three-dimensional structure of l-AAO/MOG to provide a structural basis for its biochemical characteristics. The key residue for the activity conversion of l-AAO/MOG, Cys-254, is located near the aromatic cage (Trp-418, Phe-473, and Trp-516. Although the location of Cys-254 indicates that it is not directly involved in the substrate binding, the chemical modification by p-CMB or C254I mutation would have a significant impact on the substrate binding via the side chain of Trp-516. It is suggested that a slight difference of the binding position of a substrate can dictate the activity of this type of enzyme as oxidase or monooxygenase.

  8. Microwave-Promoted Rapid Synthesis of 1-Aryl-1, 2, 3-Triazoles

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Aryl azides and a-keto phosphorus ylides were reacted within 4~10 minutes with silica gel support, under microwave irridiation to afford corresponding l-aryl-l, 2, 3-triazoles in moderate to good yields.

  9. MPN- and Real-Time-Based PCR Methods for the Quantification of Alkane Monooxygenase Homologous Genes (alkB) in Environmental Samples

    Science.gov (United States)

    Pérez-de-Mora, Alfredo; Schulz, Stephan; Schloter, Michael

    Hydrocarbons are major contaminants of soil ecosystems as a result of uncontrolled oil spills and wastes disposal into the environment. Ecological risk assessment and remediation of affected sites is often constrained due to lack of suitable prognostic and diagnostic tools that provide information of abiotic-biotic interactions occurring between contaminants and biological targets. Therefore, the identification and quantification of genes involved in the degradation of hydrocarbons may play a crucial role for evaluating the natural attenuation potential of contaminated sites and the development of successful bioremediation strategies. Besides other gene clusters, the alk operon has been identified as a major player for alkane degradation in different soils. An oxygenase gene (alkB) codes for the initial step of the degradation of aliphatic alkanes under aerobic conditions. In this work, we present an MPN- and a real-time PCR method for the quantification of the bacterial gene alkB (coding for rubredoxin-dependent alkane monooxygenase) in environmental samples. Both approaches enable a rapid culture-independent screening of the alkB gene in the environment, which can be used to assess the intrinsic natural attenuation potential of a site or to follow up the on-going progress of bioremediation assays.

  10. Control of Reactivity and Regioselectivity for On-Surface Dehydrogenative Aryl-Aryl Bond Formation.

    Science.gov (United States)

    Kocić, Nemanja; Liu, Xunshan; Chen, Songjie; Decurtins, Silvio; Krejčí, Ondřej; Jelínek, Pavel; Repp, Jascha; Liu, Shi-Xia

    2016-05-01

    Regioselectivity is of fundamental importance in chemical synthesis. Although many concepts for site-selective reactions are well established for solution chemistry, it is not a priori clear whether they can easily be transferred to reactions taking place on a metal surface. A metal will fix the chemical potential of the electrons and perturb the electronic states of the reactants because of hybridization. Additionally, techniques to characterize chemical reactions in solution are generally not applicable to on-surface reactions. Only recent developments in resolving chemical structures by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) paved the way for identifying individual reaction products on surfaces. Here we exploit a combined STM/AFM technique to demonstrate the on-surface formation of complex molecular architectures built up from a heteroaromatic precursor, the tetracyclic pyrazino[2,3-f][4,7]phenanthroline (pap) molecule. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on Au(111) upon thermal annealing under ultrahigh vacuum (UHV) conditions. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. Our work not only elucidates that ortho-hydrogen atoms of the pyrazine rings are preferentially activated over their pyridine equivalents, but also sheds new light onto the participation of substrate atoms in metal-organic coordination bonding during covalent C-C bond formation. PMID:27059121

  11. Exploiting the enantioselectivity of Baeyer-Villiger monooxygenases via boron oxidation

    NARCIS (Netherlands)

    Brondani, Patricia B.; Dudek, Hanna; Reis, Joel S.; Fraaije, Marco W.; Andrade, Leandro H.

    2012-01-01

    The enantioselective carbon-boron bond oxidation of several chiral boron-containing compounds by Baeyer-Villiger monooxygenases was evaluated. PAMO and M446G PAMO conveniently oxidized 1-phenylethyl boronate into the corresponding 1-(phenyl)ethanol (ee = 82-91%). Cyclopropyl boronic esters were also

  12. Expression of Individual Copies of Methylococcus capsulatus Bath Particulate Methane Monooxygenase Genes

    OpenAIRE

    Stolyar, Sergei; Franke, Marion; Lidstrom, Mary E.

    2001-01-01

    The expression of the two gene clusters encoding the particulate methane monooxygenase (pMMO) in Methylococcus capsulatus Bath was assessed by analysis of transcripts and by use of chromosomal gene fusions. The results suggest that the two clusters are functionally redundant but that relative expression alters depending on the copper levels available for growth.

  13. Flavoprotein monooxygenases for oxidative biocatalysis: recombinant expression in microbial hosts and applications

    Directory of Open Access Journals (Sweden)

    DanielaV.Rial

    2014-02-01

    Full Text Available External flavoprotein monooxygenases comprise a group of flavin-dependent oxidoreductases that catalyze the insertion of one atom of molecular oxygen into an organic substrate and the second atom is reduced to water. These enzymes are involved in a great number of metabolic pathways both in prokaryotes and eukaryotes. Flavoprotein monooxygenases have attracted the attention of researchers for several decades and the advent of recombinant DNA technology caused a great progress in the field. These enzymes are subjected to detailed biochemical and structural characterization and some of them are also regarded as appealing oxidative biocatalysts for the production of fine chemicals and valuable intermediates toward active pharmaceutical ingredients due to their high chemo-, stereo- and regioselectivity. Here, we review the most representative reactions catalyzed both in vivo and in vitro by prototype flavoprotein monooxygenases, highlighting the strategies employed to produce them recombinantly, to enhance the yield of soluble proteins, and to improve cofactor regeneration in order to obtain versatile biocatalysts. Although we describe the most outstanding features of flavoprotein monooxygenases, we mainly focus on enzymes that were cloned, expressed and used for biocatalysis during the last years.

  14. A fluorescence polarization binding assay to identify inhibitors of flavin-dependent monooxygenases.

    Science.gov (United States)

    Qi, Jun; Kizjakina, Karina; Robinson, Reeder; Tolani, Karishma; Sobrado, Pablo

    2012-06-01

    N-Hydroxylating monooxygenases (NMOs) are essential for pathogenesis in fungi and bacteria. NMOs catalyze the hydroxylation of sine and ornithine in the biosynthesis of hydroxamate-containing siderophores. Inhibition of kynurenine monooxygenase (KMO), which catalyzes the conversion of kynurenine to 3-hydroxykynurenine, alleviates neurodegenerative disorders such as Huntington's and Alzheimer's diseases and brain infections caused by the parasite Trypanosoma brucei. These enzymes are examples of flavin-dependent monooxygenases, which are validated drug targets. Here, we describe the development and optimization of a fluorescence polarization assay to identify potential inhibitors of flavin-dependent monooxygenases. Fluorescently labeled ADP molecules were synthesized and tested. An ADP-TAMRA chromophore bound to KMO with a K(d) value of 0.60 ± 0.05 μM and to the NMOs from Aspergillus fumigatus and Mycobacterium smegmatis with K(d) values of 2.1 ± 0.2 and 4.0 ± 0.2 μM, respectively. The assay was tested in competitive binding experiments with substrates and products of KMO and an NMO. Furthermore, we show that this assay can be used to identify inhibitors of NMOs. A Z' factor of 0.77 was calculated, and we show that the assay exhibits good tolerance to temperature, incubation time, and dimethyl sulfoxide concentration. PMID:22410281

  15. Process for producing hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Doi, K.; Komatsu, A.; Moroe, M.; Moroe, T.

    1980-07-22

    A process is described for producing a hydrocarbon product consisting essentially of hydrocarbons having about 10 to 50 carbon atoms with 60% or more of said product consisting of hydrocarbons containing 25 to 32 carbon atoms which comprises subjecting a synthetic polyisoprene rubber having 92 to 97% cis-type double bods to a thermally destructive distillation at about 300 to 400/sup 0/ C for about 30 minutes under a reduced pressure of about 0.1 to 5 mm. Hg to obtain said hydrocarbon product consisting essentially of hydrocarbons having about 10 to 50 carbon atoms with 60% or more of said product consisting of hydrocarbons containing 25 to 35 carbon atoms, said hydrocarbon product not having a bad odor and containing scarcely any resinous material.

  16. Structural and Catalytic Differences between Two FADH2-Dependent Monooxygenases: 2,4,5-TCP 4-Monooxygenase (TftD from Burkholderia cepacia AC1100 and 2,4,6-TCP 4-Monooxygenase (TcpA from Cupriavidus necator JMP134

    Directory of Open Access Journals (Sweden)

    ChulHee Kang

    2012-08-01

    Full Text Available 2,4,5-TCP 4-monooxygenase (TftD and 2,4,6-TCP 4-monooxygenase (TcpA have been discovered in the biodegradation of 2,4,5-trichlorophenol (2,4,5-TCP and 2,4,6-trichlorophenol (2,4,6-TCP. TcpA and TftD belong to the reduced flavin adenine dinucleotide (FADH2-dependent monooxygenases and both use 2,4,6-TCP as a substrate; however, the two enzymes produce different end products. TftD catalyzes a typical monooxygenase reaction, while TcpA catalyzes a typical monooxygenase reaction followed by a hydrolytic dechlorination. We have previously reported the 3D structure of TftD and confirmed the catalytic residue, His289. Here we have determined the crystal structure of TcpA and investigated the apparent differences in specificity and catalysis between these two closely related monooxygenases through structural comparison. Our computational docking results suggest that Ala293 in TcpA (Ile292 in TftD is possibly responsible for the differences in substrate specificity between the two monooxygenases. We have also identified that Arg101 in TcpA could provide inductive effects/charge stabilization during hydrolytic dechlorination. The collective information provides a fundamental understanding of the catalytic reaction mechanism and the parameters for substrate specificity. The information may provide guidance for designing bioremediation strategies for polychlorophenols, a major group of environmental pollutants.

  17. Aryl diazonium salts new coupling agents and surface science

    CERN Document Server

    Chehimi, Mohamed Mehdi

    2012-01-01

    Diazonium compounds are employed as a new class of coupling agents to link polymers, biomacromolecules, and other species (e. g. metallic nanoparticles) to the surface of materials. The resulting high performance materials show improved chemical and physical properties and find widespread applications. The advantage of aryl diazonium salts compared to other surface modifiers lies in their ease of preparation, rapid (electro)reduction, large choice of reactive functional groups, and strong aryl-surface covalent bonding.This unique book summarizes the current knowledge of the surface and

  18. Inhibition of Bfl-1 with N-Aryl Maleimides

    OpenAIRE

    Cashman, John R.; MacDonald, Mary; Ghirmai, Senait; Okolotowicz, Karl J.; Sergienko, Eduard; Brown, Brock; Garcia, Xochella; Zhai, Dayong; John C Reed

    2010-01-01

    High throughput screening of 66,000 compounds using competitive binding of peptides comprising the BH3 domain to anti-apoptotic Bfl-1 led to the identification of fourteen validated “hits” as inhibitors of Bfl-1. N-Aryl maleimide 1 was among the validated “hits”. A chemical library encompassing over 280 analogs of 1 was prepared following a two-step synthesis. Structure-activity studies for inhibition of Bfl-1 by analogs of N-aryl maleimide 1 revealed a preference for electron-withdrawing sub...

  19. In vitro toxicity of polycyclic aromatic hydrocarbons and halogenated aromatic hydrocarbons to cetacean cells and tissues

    Energy Technology Data Exchange (ETDEWEB)

    Carvan, M.J. III.

    1993-01-01

    Cetaceans bioaccumulate high aromatic hydrocarbon tissue residues, and elevated levels of PCB residues in tissues are proposed to have occurred concurrently with recent epizootic deaths of dolphins. The objectives of this study were: (1) to develop and characterize an epithelial cell line derived from dolphin tissues, (2) to investigate the effects of hydrocarbon pollutants on those cells, and (3) to analyze the toxicity of hydrocarbon pollutants on cetacean tissues in vitro. An epithelial cell line, Carvan dolphin kidney (CDK), isolated from a spontaneously aborted female bottlenose dolphin, Tursiops truncatus, grew rapidly. These cells were neither transformed nor immortal. Velocity sedimentation analysis showed CDK cells contained nuclear aryl hydrocarbon receptor, suggestive of cytochrome P450 inducibility. BaP inhibited mitosis in CDK cells in a dose-dependent manner. Data indicate that CDK cells metabolize BaP, that BaP metabolites bind to cellular DNA initiating unscheduled DNA synthesis, and that the inhibition of cytochrome P450 metabolism decrease the BaP-associated inhibition of mitosis in dolphin cells. The data also suggest that TCDD acts synergistically to increase the levels of DNA damage by the procarcinogen BaP. Cetacean liver microsomes was isolated and evaluated for the presence of cytochrome P450 proteins by SDS-PAGE, apparent minimum molecular weight determination, and immunoblot analysis. P450 activity was induced in cetacean tissue samples and CDK cells by exposure in vitro to one of several cytochrome P450-inducing chemicals. The data suggest that cetacean tissues and cells can be utilized to study the in vitro induction of cytochrome P450, resultant metabolism of xenobiotic contaminants, and the subsequent cellular and molecular responses. However, the identity of specific P450 isozymes involved in this process will remain undetermined until monoclonal antibodies that recognize cetacean P450s can be generated.

  20. Chan-Evans-Lam Amination of Boronic Acid Pinacol (BPin) Esters: Overcoming the Aryl Amine Problem.

    Science.gov (United States)

    Vantourout, Julien C; Law, Robert P; Isidro-Llobet, Albert; Atkinson, Stephen J; Watson, Allan J B

    2016-05-01

    The Chan-Evans-Lam reaction is a valuable C-N bond forming process. However, aryl boronic acid pinacol (BPin) ester reagents can be difficult coupling partners that often deliver low yields, in particular in reactions with aryl amines. Herein, we report effective reaction conditions for the Chan-Evans-Lam amination of aryl BPin with alkyl and aryl amines. A mixed MeCN/EtOH solvent system was found to enable effective C-N bond formation using aryl amines while EtOH is not required for the coupling of alkyl amines. PMID:27045570

  1. Derivatives of aryl-4-guanidinomethylbenzoate and N-aryl-4-guanidinomethylbenzamide as new antibacterial agents: synthesis and bioactivity

    Institute of Scientific and Technical Information of China (English)

    Wen-yuan YU; Li-xia YANG; Jian-shu XIE; Ling ZHOU; Xue-yuan JIANG; De-xu ZHU; Mutsumi MURAMATSU; Ming-wei WANG

    2008-01-01

    Aim: The aim of the present study was to design, synthesize, and evaluate novel antibacterial agents, derivatives of aryl-4-guanidinomethylbenzoate and N-aryl-4-guanidinomethylbenzamide. Methods: A total of 44 derivatives of aryl-4-guanidin-omethylbenzoate (series A) and N-aryl-4-guanidinomethylbenzamide (series B) were synthesized and their antibacterial activities were assessed in vitro against a variety of Gram-positive and Gram-negative bacteria by an agar dilution method. Results: Twelve compounds showed potent bactericidal effects against a panel of Gram-positive germs, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), vancomycin-intermediate Sta-phylococcus aureus (VISA), and methicillin-resistant coagulase-negative staphy-lococci (MRCNS), with minimum inhibitory concentrations (MIC) ranging be-tween 0.5 and 8 μg/mL, which were comparable to the MIC values of several marketed antibiotics. They exhibited weak or no activity on the Gram-negative bacteria tested. In addition, these compounds displayed high inhibitory activities towards oligopeptidase B of bacterial origin. Conclusion: In comparison with the previ-ously reported MIC values of several known antibiotics, the derivatives of aryl-4-guanidinomethylbenzoate and N-aryl-4-guanidinomethylbenzamide showed com-parable in vitro bactericidal activities against VRE and VISA as linezolid. Their growth inhibitory effects on MRSA were similar to vancomycin, but were less potent than linezolid and vancomycin against MRCNS. This class of compounds may have the potential to be developed into narrow spectrum antibacterial agents against certain drug-resistant strains of bacteria.

  2. Controlling viral immuno-inflammatory lesions by modulating aryl hydrocarbon receptor signaling.

    Directory of Open Access Journals (Sweden)

    Tamara Veiga-Parga

    2011-12-01

    Full Text Available Ocular herpes simplex virus infection can cause a blinding CD4⁺ T cell orchestrated immuno-inflammatory lesion in the cornea called Stromal Keratitis (SK. A key to controlling the severity of SK lesions is to suppress the activity of T cells that orchestrate lesions and enhance the representation of regulatory cells that inhibit effector cell function. In this report we show that a single administration of TCDD (2, 3, 7, 8- Tetrachlorodibenzo-p-dioxin, a non-physiological ligand for the AhR receptor, was an effective means of reducing the severity of SK lesions. It acted by causing apoptosis of Foxp3⁻ CD4⁺ T cells but had no effect on Foxp3⁺ CD4⁺ Tregs. TCDD also decreased the proliferation of Foxp3⁻ CD4⁺ T cells. The consequence was an increase in the ratio of Tregs to T effectors which likely accounted for the reduced inflammatory responses. In addition, in vitro studies revealed that TCDD addition to anti-CD3/CD28 stimulated naïve CD4⁺ T cells caused a significant induction of Tregs, but inhibited the differentiation of Th1 and Th17 cells. Since a single TCDD administration given after the disease process had been initiated generated long lasting anti-inflammatory effects, the approach holds promise as a therapeutic means of controlling virus induced inflammatory lesions.

  3. 3-methylcholanthrene induces differential recruitment of aryl hydrocarbon receptor to human promoters

    DEFF Research Database (Denmark)

    Pansoy, Andrea; Ahmed, Shaimaa; Valen, Eivind;

    2010-01-01

    responsive element. Conventional ChIP confirmed recruitment of AHR to 26 regions with target gene responses to 3MC varying from activation to inhibition to having no effect. A comparison of identified AHR-3MC bound regions with AHR-TCDD bound regions in from our previous study (Ahmed, S., Valen, E., Sandelin...... periodicity between 1.5 to 2 h. Re-treatment of cells with 3MC failed to alter the oscillatory binding profiles of AHR or ARNT. Cells became responsive to 3MC but not TCDD after 24 h of exposure to 3MC, highlighting important differences in AHR responsiveness between the two ligands. Our results reveal a...

  4. Association between polymorphisms in the aryl hydrocarbon receptor repressor gene and disseminated testicular germ cell cancer

    DEFF Research Database (Denmark)

    Brokken, Leon J S; Lundberg-Giwercman, Yvonne; Rajpert-De Meyts, Ewa;

    2013-01-01

    In the Western world, testicular germ cell cancer (TGCC) is the most common malignancy of young men. The malignant transformation of germ cells is thought to be caused by developmental and hormonal disturbances, probably related to environmental and lifestyle factors because of rapidly increasing...... histological and clinical features of TGCC in 367 patients and 537 controls. Haplotype-tagging single-nucleotide polymorphisms (SNPs) were genotyped in genes encoding AHR and AHR repressor (AHRR). Binary logistic regression was used to calculate the risk of TGCC, non-seminoma versus seminoma, and metastasis...

  5. Interactions of the aryl hydrocarbon receptor with inflammatory mediators: Beyond CYP1A regulation

    Czech Academy of Sciences Publication Activity Database

    Vondráček, Jan; Umannová, Lenka; Machala, M.

    2011-01-01

    Roč. 12, č. 2 (2011), s. 89-103. ISSN 1389-2002 R&D Projects: GA ČR(CZ) GAP503/11/1227 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : AhR * proinflammatory cytokines * antiinflammatory drugs Subject RIV: BO - Biophysics Impact factor: 5.113, year: 2011

  6. Alu retrotransposons promote differentiation of human carcinoma cells through the aryl hydrocarbon receptor.

    Science.gov (United States)

    Morales-Hernández, Antonio; González-Rico, Francisco J; Román, Angel C; Rico-Leo, Eva; Alvarez-Barrientos, Alberto; Sánchez, Laura; Macia, Ángela; Heras, Sara R; García-Pérez, José L; Merino, Jaime M; Fernández-Salguero, Pedro M

    2016-06-01

    Cell differentiation is a central process in development and in cancer growth and dissemination. OCT4 (POU5F1) and NANOG are essential for cell stemness and pluripotency; yet, the mechanisms that regulate their expression remain largely unknown. Repetitive elements account for almost half of the Human Genome; still, their role in gene regulation is poorly understood. Here, we show that the dioxin receptor (AHR) leads to differentiation of human carcinoma cells through the transcriptional upregulation of Alu retrotransposons, whose RNA transcripts can repress pluripotency genes. Despite the genome-wide presence of Alu elements, we provide evidences that those located at the NANOG and OCT4 promoters bind AHR, are transcribed by RNA polymerase-III and repress NANOG and OCT4 in differentiated cells. OCT4 and NANOG repression likely involves processing of Alu-derived transcripts through the miRNA machinery involving the Microprocessor and RISC. Consistently, stable AHR knockdown led to basal undifferentiation, impaired Alus transcription and blockade of OCT4 and NANOG repression. We suggest that transcripts produced from AHR-regulated Alu retrotransposons may control the expression of stemness genes OCT4 and NANOG during differentiation of carcinoma cells. The control of discrete Alu elements by specific transcription factors may have a dynamic role in genome regulation under physiological and diseased conditions. PMID:26883630

  7. No evidence of somatic aryl hydrocarbon receptor interacting protein mutations in sporadic endocrine neoplasia

    DEFF Research Database (Denmark)

    Raitila, A; Georgitsi, M; Karhu, A; Tuppurainen, K; Mäkinen, M J; Birkenkamp-Demtröder, K; Salmenkivi, K; Orntoft, T F; Arola, J; Launonen, V; Vahteristo, P; Aaltonen, L A

    2007-01-01

    as non-secreting pituitary adenomas have been reported, most mutation-positive patients have had growth hormone-producing adenomas diagnosed at relatively young age. Pituitary adenomas are also component tumors of some familial endocrine neoplasia syndromes such as multiple endocrine neoplasia type 1...... (MEN1) and Carney complex (CNC). Genes underlying MEN1 and CNC are rarely mutated in sporadic pituitary adenomas, but more often in other lesions contributing to these two syndromes. Thus far, the occurrence of somatic AIP mutations has not been studied in endocrine tumors other than pituitary adenomas....... Here, we have analyzed 32 pituitary adenomas and 79 other tumors of the endocrine system for somatic AIP mutations by direct sequencing. No somatic mutations were identified. However, two out of nine patients with prolactin-producing adenoma were shown to harbor a Finnish founder mutation (Q14X) with a...

  8. Aryl Hydrocarbon Receptor Negatively Regulates Expression of the Plakoglobin Gene (Jup)

    Czech Academy of Sciences Publication Activity Database

    Procházková, Jiřina; Kabátková, Markéta; Šmerdová, Lenka; Pachernik, J.; Sýkorová, D.; Kohoutek, J.; Šimečková, P.; Hrubá, E.; Kozubík, Alois; Machala, M.; Vondráček, Jan

    2013-01-01

    Roč. 134, č. 2 (2013), s. 258-270. ISSN 1096-6080 R&D Projects: GA ČR(CZ) GA524/09/1337; GA ČR(CZ) GD204/09/H058; GA MŠk(CZ) EE2.3.30.0030 Grant ostatní: GA ČR(CZ) GA301/09/1832 Institutional research plan: CEZ:AV0Z50040702 Institutional support: RVO:68081707 Keywords : EMBRYONIC STEM-CELLS * LIVER EPITHELIAL-CELLS * AH RECEPTOR Subject RIV: BO - Biophysics Impact factor: 4.478, year: 2013

  9. Aryl hydrocarbon receptor ligand effects in RBL2H3 cells

    DEFF Research Database (Denmark)

    Maaetoft-Udsen, Kristina; Shimoda, Lori M. N.; Frøkiær, Hanne;

    2012-01-01

    responses and release a spectrum of pro-inflammatory mediators including histamine, mast cell proteases, and pro-inflammatory cytokines such as IL-6 upon stimulation. The aim was to investigate the AHR in model mast cells and examine how both putative and known AHR ligands, e.g., kynurenine, kynurenic acid...... (KA), Resveratrol, indolmycin, and violacein, affect mast cell activation and signaling. These ligands were tested on calcium signaling, degranulation, and gene expression. The data show that AHR is present in three model mast cell lines, and that various known and putative AHR ligands regulate gene...

  10. CuO-promoted construction of N-2-aryl-substituted-1,2,3-triazoles via azide-chalcone oxidative cycloaddition and post-triazole arylation.

    Science.gov (United States)

    Zhang, Yuanqing; Li, Xiaolong; Li, Jihui; Chen, Jinying; Meng, Xu; Zhao, Mingming; Chen, Baohua

    2012-01-01

    An efficient one-pot three-component stepwise approach for the synthesis of N-2-aryl-substituted-1,2,3-triazoles has been developed. By using this azide-chalcone oxidative cycloaddition and post-triazole arylation, a series of N-2-aryl-substituted-1,2,3-triazoles are readily prepared under mild conditions in excellent yields and high regioselectivity. Both the catalyst and substrates are readily available. PMID:22133007

  11. Iron-Mediated Direct Arylation of Unactivated Arenes in Air

    NARCIS (Netherlands)

    Huang, Yuxing; Moret, Marc-Etienne; Klein Gebbink, Bert

    2014-01-01

    Biaryls are a common motif in both natural and synthetic chemicals. Several methods have recently been reported for the preparation of these compounds using direct arylation catalyzed by iron, other base metals, or transition-metal-free systems. To date, these methods have all required inert and/or

  12. Alkyl Aryl Ether Bond Formation with PhenoFluor**

    OpenAIRE

    Shen, Xiao; Neumann, Constanze N.; Kleinlein, Claudia; Claudia, Nathaniel W.; Ritter, Tobias

    2015-01-01

    An alkyl aryl ether bond formation reaction between phenols and primary and secondary alcohols with PhenoFluor has been developed. The reaction features a broad substrate scope and tolerates many functional groups, and substrates that are challenging for more conventional ether bond forming processes may be coupled. A preliminary mechanistic study indicates reactivity distinct from conventional ether bond formation.

  13. Palladium-catalyzed arylation of simple arenes with iodonium salts.

    Science.gov (United States)

    Storr, Thomas E; Greaney, Michael F

    2013-03-15

    The development of an arylation protocol for simple arenes with diaryliodonium salts using the Herrmann-Beller palladacycle catalyst is reported. The reaction takes simple aromatic feedstocks and creates valuable biaryls for use in all sectors of the chemical industry. PMID:23461706

  14. Kinetic Resolution of Aryl Alkenylcarbinols Catalyzed by Fc-PIP

    Institute of Scientific and Technical Information of China (English)

    胡斌; 孟萌; 姜山山; 邓卫平

    2012-01-01

    An effective kinetic resolution of a variety of aryl alkenylcarbinols catalyzed by nonenzymatic acyl transfer catalyst Fe-PIP was developed, affording corresponding unreacted alcohols in good to excellent ee value up to 99% and with selectivity factors up to 24.

  15. Palladium-catalyzed thiocarbonylation of aryl, vinyl, and benzyl bromides.

    Science.gov (United States)

    Burhardt, Mia N; Ahlburg, Andreas; Skrydstrup, Troels

    2014-12-19

    A catalytic protocol for synthesis of thioesters from aryl, vinyl, and benzyl bromides as well as benzyl chlorides was developed using only stoichiometric amounts of carbon monoxide, produced from a solid CO precursor inside a two-chamber system. As a catalytic system, the combination of bis(benzonitrile) palladium(II) chloride and Xantphos furnished the highest yields of the desired compounds, along with the weak base, NaOAc, in anisole at 120 °C. The choice of catalytic system as well as solvent turned out to be important in order to ensure a high chemoselectivity in the reaction. Both electron-rich and electron-deficient aryl bromides worked well in this reaction. Addition of 1 equiv of sodium iodide to the reaction improved the chemoselectivity with the electron-deficient aryl bromides. The thiol scope included both aryl and alkyl thiols, including 2-mercaptobenzophenones, whereby a thiocarbonylation followed by a subsequent McMurry coupling yielded differently substituted benzothiophenes. It was demonstrated that the methodology could be applied for (13)C introduction into the thiophene ring. PMID:24919457

  16. Mechanism and regulation of the Two-component FMN-dependent monooxygenase ActVA-ActVB from Streptomyces coelicolor.

    OpenAIRE

    Valton, Julien; Mathevon, Carole; Fontecave, Marc; Nivière, Vincent; Ballou, David P.

    2008-01-01

    International audience The ActVA-ActVB system from Streptomyces coelicolor is a two-component flavin-dependent monooxygenase involved in the antibiotic actinorhodin biosynthesis. ActVB is a NADH:flavin oxidoreductase that provides a reduced FMN to ActVA, the monooxygenase that catalyzes the hydroxylation of dihydrokalafungin, the precursor of actinorhodin. In this work, using stopped-flow spectrophotometry, we investigated the mechanism of hydroxylation of dihydrokalafungin catalyzed by Ac...

  17. 4-Hydroxyacetophenone monooxygenase from Pseudomonas fluorescens ACB as an oxidative biocatalyst in the synthesis of optically active sulfoxides

    OpenAIRE

    Gonzalo, Gonzalo de; Torres Pazmiño, Daniel E.; Ottolina, Gianluca; Fraaije, Marco W.; Carrea, Giacomo

    2006-01-01

    Recombinant 4-hydroxyacetophenone monooxygenase (HAPMO) from Pseudomonas fluorescens ACB has been tested as a catalyst in sulfoxidation reactions on a set of aromatic sulfides. With a few exceptions, excellent enantioselectivities in the synthesis of chiral phenyl and benzyl sulfoxides were achieved. The bacterial Baeyer–Villiger monooxygenase was also shown to accept racemic sulfoxides, a prochiral diketone and an organoboron compound as substrates. This study demonstrates the great biocatal...

  18. Effects of methotrexate on rat P-450 cytochrome mono-oxygenases; Action du methotrexate sur les monooxygenases a cytochromes P-450 chez le rat

    Energy Technology Data Exchange (ETDEWEB)

    Guitton, J.; Guilluy, R.; Brazier, J.L. [Faculte de Pharmacie, 69 - Lyon (France); Souillet, G. [Hopital Debrousse, 69 - Lyon (France); Riviere, J.L. [INRA, 69 - Marcy l`Etoile (France); Gerard, F. [Institut Pasteur, 69 - Lyon (France)

    1994-12-31

    Methotrexate, an anti-cancerous agent, acts as an anti-metabolite of the nucleic acids which synthesis is then inhibited. Using aminopyrine breath test after methotrexate processing, the effects of the molecule on activities of the hepatocyte P-450 cytochrome mono-oxygenases, are studied. Breath micro-tests with carbon 13-labelled aminopyrine have been carried out to observe the metabolism evolution. Micro-test results have been compared to microsomal enzymatic activities for various substrates, and also to P-450 cytochrome ratio. Results show that methotrexate induces a reduction in the P-450 cytochrome ratio, and thus reduce the hepatic biotransformation process. 1 fig., 30 refs.

  19. Hydrocarbon Spectral Database

    Science.gov (United States)

    SRD 115 Hydrocarbon Spectral Database (Web, free access)   All of the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules have been tabulated. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported.

  20. Oxygenated Derivatives of Hydrocarbons

    Science.gov (United States)

    For the book entitled “Insect Hydrocarbons: Biology, Biochemistry and Chemical Ecology”, this chapter presents a comprehensive review of the occurrence, structure and function of oxygenated derivatives of hydrocarbons. The book chapter focuses on the occurrence, structural identification and functi...

  1. Baeyer-Villiger Monooxygenases from a Dietzia sp. - Enzyme Discovery, Characterization and Engineering

    OpenAIRE

    Bisagni, Serena

    2014-01-01

    With the emergence of Green Chemistry, biocatalysis is becoming an important approach in many laboratory and industrial processes. Enzymes catalyse chemical reactions with high regio- and stereoselectivity at mild conditions and, most importantly, are able to form products that are not possible to obtain by conventional synthetic chemistry. Monooxygenases are a fascinating group of enzymes which oxidise substrates using atmospheric oxygen and release water as a by-product. These enzymes ha...

  2. Enhancing Indigo Production by Over-Expression of the Styrene Monooxygenase in Pseudomonas putida.

    Science.gov (United States)

    Cheng, Lei; Yin, Sheng; Chen, Min; Sun, Baoguo; Hao, Shuai; Wang, Chengtao

    2016-08-01

    As an important traditional blue dye, indigo has been used in food and textile industry for centuries, which can be produced via the styrene oxygenation pathway in Pseudomonas putida. Hence, the styrene monooxygenase gene styAB and oxide isomerase gene styC are over-expressed in P. putida to investigate their roles in indigo biosynthesis. RT-qPCR analysis indicated that transcriptions of styA and styB were increased by 2500- and 750-folds in the styAB over-expressed strain B4-01, compared with the wild-type strain B4, consequently significantly enhancing the indole monooxygenase activity. Transcription of styC was also increased by 100-folds in the styC over-expressed strain B4-02. Besides, styAB over-expression slightly up-regulated the transcription of styC in B4-01, while styC over-expression hardly exerted an effect on the transcriptional levels of styA and styB and indole monooxygenase activity in B4-02. Furthermore, shaking flask experiments showed that indigo production in B4-01 reached 52.13 mg L(-1) after 24 h, which was sevenfold higher than that in B4. But no obvious increase in indigo yield was observed in B4-02. Over-expression of styAB significantly enhanced the indigo production, revealing that the monooxygenase STYAB rather than oxide isomerase STYC probably acted as the key rate-limiting enzyme in the indigo biosynthesis pathway in P. putida. This work provided a new strategy for enhancing indigo production in Pseudomonas. PMID:27154464

  3. Purification and characterization of chlorophenol 4-monooxygenase from Burkholderia cepacia AC1100.

    OpenAIRE

    Xun, L

    1996-01-01

    Burkholderia (formerly Pseudomonas) cepacia AC1100 mineralizes the herbicide 2,4,5-trichlorophenoxyacetate (2,4,5-T), and the first intermediate of 2,4,5-T degradation is 2,4,5-trichlorophenol. Chlorophenol 4-monooxygenase activity responsible for 2,4,5-trichlorophenol degradation was detected in the cell extract. The enzyme consisted of two components separated during purification, and both were purified to more than 95% homogeneity. The reconstituted enzyme catalyzed the hydroxylation of se...

  4. Soluble methane monooxygenase component B gene probe for identification of methanotrophs that rapidly degrade trichloroethylene.

    OpenAIRE

    Tsien, H C; Hanson, R S

    1992-01-01

    Restriction fragment length polymorphisms, Western blot (immunoblot) analysis, and fluorescence-labelled signature probes were used for the characterization of methanotrophic bacteria as well as for the identification of methanotrophs which contained the soluble methane monooxygenase (MMO) gene and were able to degrade trichloroethylene (TCE). The gene encoding a soluble MMO component B protein from Methylosinus trichosporium OB3b was cloned. It contained a 2.2-kb EcoRI fragment. With this cl...

  5. Structure and boosting activity of a starch-degrading lytic polysaccharide monooxygenase

    DEFF Research Database (Denmark)

    Lo Leggio, Leila; Simmons, Thomas J.; Poulsen, Jens-Christian Navarro;

    2015-01-01

    Lytic polysaccharide monooxygenases (LPMOs) are recently discovered enzymes that oxidatively deconstruct polysaccharides. LPMOs are fundamental in the effective utilization of these substrates by bacteria and fungi; moreover, the enzymes have significant industrial importance. We report here the...... activity, spectroscopy and three-dimensional structure of a starch-active LPMO, a representative of the new CAZy AA13 family. We demonstrate that these enzymes generate aldonic acid-terminated malto-oligosaccharides from retrograded starch and boost significantly the conversion of this recalcitrant...

  6. Cellulose Surface Degradation by a Lytic Polysaccharide Monooxygenase and Its Effect on Cellulase Hydrolytic Efficiency*

    OpenAIRE

    Eibinger, Manuel; Ganner, Thomas; Bubner, Patricia; Rošker, Stephanie; Kracher, Daniel; Haltrich, Dietmar; Ludwig, Roland; Plank, Harald; Nidetzky, Bernd

    2014-01-01

    Lytic polysaccharide monooxygenase (LPMO) represents a unique principle of oxidative degradation of recalcitrant insoluble polysaccharides. Used in combination with hydrolytic enzymes, LPMO appears to constitute a significant factor of the efficiency of enzymatic biomass depolymerization. LPMO activity on different cellulose substrates has been shown from the slow release of oxidized oligosaccharides into solution, but an immediate and direct demonstration of the enzyme action on the cellulos...

  7. Catalase improves saccharification of lignocellulose by reducing lytic polysaccharide monooxygenase-associated enzyme inactivation

    OpenAIRE

    Scott, Brian R.; Huang, Hong Zhi; Frickman, Jesper; Halvorsen, Rune; Johansen, Katja S.

    2015-01-01

    Objectives Efficient enzymatic saccharification of plant cell wall material is key to industrial processing of agricultural and forestry waste such as straw and wood chips into fuels and chemicals. Results Saccharification assays were performed on steam-pretreated wheat straw under ambient and O2-deprived environments and in the absence and presence of a lytic polysaccharide monooxygenase (LPMO) and catalase. A kinetic model was used to calculate catalytic rate and first-order inactivation ra...

  8. FAD C(4a)-hydroxide stabilized in a naturally fused styrene monooxygenase

    OpenAIRE

    Tischler, Dirk; Schlömann, Michael; van Berkel, Willem J H; Gassner, George T.

    2013-01-01

    StyA2B represents a new class of styrene monooxygenases that integrates flavin-reductase and styrene-epoxidase activities into a single polypeptide. This naturally-occurring fusion protein offers new avenues for studying and engineering biotechnologically relevant enantioselective biochemical epoxidation reactions. Stopped-flow kinetic studies of StyA2B reported here identify reaction intermediates similar to those reported for the separate reductase and epoxidase components of related two-co...

  9. Molecular Analysis of the pmo (Particulate Methane Monooxygenase) Operons from Two Type II Methanotrophs

    OpenAIRE

    Gilbert, Bettina; McDonald, Ian R.; Finch, Ruth; Stafford, Graham P.; Nielsen, Allan K.; Murrell, J. Colin

    2000-01-01

    The particulate methane monooxygenase gene clusters, pmoCAB, from two representative type II methanotrophs of the α-Proteobacteria, Methylosinus trichosporium OB3b and Methylocystis sp. strain M, have been cloned and sequenced. Primer extension experiments revealed that the pmo cluster is probably transcribed from a single transcriptional start site located 300 bp upstream of the start of the first gene, pmoC, for Methylocystis sp. strain M. Immediately upstream of the putative start site, co...

  10. Prediction and analysis of the modular structure of cytochrome P450 monooxygenases

    OpenAIRE

    Wagner Florian; Widmann Michael; Sirim Demet; Pleiss Jürgen

    2010-01-01

    Abstract Background Cytochrome P450 monooxygenases (CYPs) form a vast and diverse family of highly variable sequences. They catalyze a wide variety of oxidative reactions and are therefore of great relevance in drug development and biotechnological applications. Despite their differences in sequence and substrate specificity, the structures of CYPs are highly similar. Although being in research focus for years, factors mediating selectivity and activity remain vague. Description This systemat...

  11. Molecular Characterization of Soil Ammonia-Oxidizing Bacteria Based on the Genes Encoding Ammonia Monooxygenase

    OpenAIRE

    Alzerreca, Jose Javier

    1999-01-01

    Ammonia-oxidizing bacteria (AOB) are chemolithotrophs that oxidize ammonia/ammonium to nitrite in a two-step process to obtain energy for survival. AOB are difficult to isolate from the environment and iso lated strains may not represent the diversity in soil. A genetic database and molecular tools were developed based on the ammonia monooxygenase (AMO) encoding genes that can be used to assess the diversity of AOB that exist in soil and aquatic environments without the isolation of pure cult...

  12. Distribution and Diversity of Archaeal Ammonia Monooxygenase Genes Associated with Corals▿ †

    OpenAIRE

    Beman, J. Michael; Roberts, Kathryn J.; Wegley, Linda; Rohwer, Forest; Francis, Christopher A.

    2007-01-01

    Corals are known to harbor diverse microbial communities of Bacteria and Archaea, yet the ecological role of these microorganisms remains largely unknown. Here we report putative ammonia monooxygenase subunit A (amoA) genes of archaeal origin associated with corals. Multiple DNA samples drawn from nine coral species and four different reef locations were PCR screened for archaeal and bacterial amoA genes, and archaeal amoA gene sequences were obtained from five different species of coral coll...

  13. Production of four Neurospora crassa lytic polysaccharide monooxygenases in Pichia pastoris monitored by a fluorimetric assay

    OpenAIRE

    Kittl Roman; Kracher Daniel; Burgstaller Daniel; Haltrich Dietmar; Ludwig Roland

    2012-01-01

    Abstract Background Recent studies demonstrate that enzymes from the glycosyl hydrolase family 61 (GH61) show lytic polysaccharide monooxygenase (PMO) activity. Together with cellobiose dehydrogenase (CDH) an enzymatic system capable of oxidative cellulose cleavage is formed, which increases the efficiency of cellulases and put PMOs at focus of biofuel research. Large amounts of purified PMOs, which are difficult to obtain from the native fungal producers, are needed to study their reaction k...

  14. Bacterial expression of human kynurenine 3-monooxygenase: Solubility, activity, purification ☆

    OpenAIRE

    Wilson, K; Mole, D J; Binnie, M; Homer, N Z M; Zheng, X.; B.A. Yard; Iredale, J P; Auer, M.; Webster, S.P.

    2014-01-01

    Kynurenine 3-monooxygenase (KMO) is an enzyme central to the kynurenine pathway of tryptophan metabolism. KMO has been implicated as a therapeutic target in several disease states, including Huntington’s disease. Recombinant human KMO protein production is challenging due to the presence of transmembrane domains, which localise KMO to the outer mitochondrial membrane and render KMO insoluble in many in vitro expression systems. Efficient bacterial expression of human KMO would accelerate drug...

  15. Bacterial expression of human kynurenine 3-monooxygenase:Solubility, activity, purification

    OpenAIRE

    Wilson, K; Mole, D J; Binnie, M; Homer, N Z M; Zheng, X.; B.A. Yard; Iredale, J P; Auer, M.; Webster, S.P.

    2014-01-01

    Kynurenine 3-monooxygenase (KMO) is an enzyme central to the kynurenine pathway of tryptophan metabolism. KMO has been implicated as a therapeutic target in several disease states, including Huntington's disease. Recombinant human KMO protein production is challenging due to the presence of transmembrane domains, which localise KMO to the outer mitochondrial membrane and render KMO insoluble in many in vitro expression systems. Efficient bacterial expression of human KMO would accelerate drug...

  16. Bioactivation of Anti-Tuberculosis Thioamide and Thiourea Prodrugs by Bacterial and Mammalian Flavin Monooxygenases

    OpenAIRE

    Nishida, Clinton R.; Ortiz de Montellano, Paul R.

    2010-01-01

    The thioamide and thiourea class of antituberculosis agents encompasses prodrugs that are oxidatively converted to their active forms by the flavin monooxygenase EtaA of Mycobacterium tuberculosis. Reactive intermediates produced in the EtaA-catalyzed transformations of ethionamide and prothionamide result in NAD+/NADH adducts that inhibit the enoyl CoA reductase InhA, the ultimate target of these drugs. In the case of thiacetazone and isoxyl, EtaA produces electrophilic metabolites that medi...

  17. Control of Substrate Access to the Active Site in Methane Monooxygenase

    OpenAIRE

    Lee, Seung Jae; McCormick, Michael S.; Lippard, Stephen J.; Cho, Uhn-Soo

    2013-01-01

    Methanotrophs consume methane as their major carbon source and have an essential role in the global carbon cycle by limiting escape of this greenhouse gas to the atmosphere. These bacteria oxidize methane to methanol by soluble and particulate methane monooxygenases (MMOs). Soluble MMO contains three protein components, a 251-kilodalton hydroxylase (MMOH), a 38.6-kilodalton reductase (MMOR), and a 15.9-kilodalton regulatory protein (MMOB), required to couple electron consumption with substrat...

  18. Crystallization and initial crystallographic characterization of the Corynebacterium glutamicum nitrilotriacetate monooxygenase component A

    International Nuclear Information System (INIS)

    The Corynebacterium glutamicum NTA monooxygenase component A protein, which plays the central role in NTA biodegradation, was crystallized. The initial X-ray crystallographic characterization is reported. Safety and environmental concerns have recently dictated the proper disposal of nitrilotriacetate (NTA). Biodegradation of NTA is initiated by NTA monooxygenase, which is composed of two proteins: component A and component B. The NTA monooxygenase component A protein from Corynebacterium glutamicum was crystallized using the sitting-drop vapour-diffusion method in the presence of ammonium sulfate as the precipitant. X-ray diffraction data were collected to a maximum resolution of 2.5 Å on a synchrotron beamline. The crystal belongs to the monoclinic space group C2, with unit-cell parameters a = 111.04, b = 98.51, c = 171.61 Å, β = 101.94°. The asymmetric unit consists of four molecules, corresponding to a packing density of 2.3 Å3 Da−1. The structure was solved by molecular replacement. Structure refinement is in progress

  19. Crystallization and initial crystallographic characterization of the Corynebacterium glutamicum nitrilotriacetate monooxygenase component A

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung-Jin, E-mail: kkj@postech.ac.kr [Beamline Division, Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Kim, Sujin [21C Frontier Microbial Genomics and Applications Center, KRIBB, Daejeon 305-806 (Korea, Republic of); Lee, Sujin [Beamline Division, Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Kang, Beom Sik [School of Life Science and Biotechnology, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Lee, Heung-Soo [Beamline Division, Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of); Oh, Tae-Kwang; Kim, Myung Hee, E-mail: kkj@postech.ac.kr [21C Frontier Microbial Genomics and Applications Center, KRIBB, Daejeon 305-806 (Korea, Republic of); Beamline Division, Pohang Accelerator Laboratory, Pohang, Kyungbuk 790-784 (Korea, Republic of)

    2006-11-01

    The Corynebacterium glutamicum NTA monooxygenase component A protein, which plays the central role in NTA biodegradation, was crystallized. The initial X-ray crystallographic characterization is reported. Safety and environmental concerns have recently dictated the proper disposal of nitrilotriacetate (NTA). Biodegradation of NTA is initiated by NTA monooxygenase, which is composed of two proteins: component A and component B. The NTA monooxygenase component A protein from Corynebacterium glutamicum was crystallized using the sitting-drop vapour-diffusion method in the presence of ammonium sulfate as the precipitant. X-ray diffraction data were collected to a maximum resolution of 2.5 Å on a synchrotron beamline. The crystal belongs to the monoclinic space group C2, with unit-cell parameters a = 111.04, b = 98.51, c = 171.61 Å, β = 101.94°. The asymmetric unit consists of four molecules, corresponding to a packing density of 2.3 Å{sup 3} Da{sup −1}. The structure was solved by molecular replacement. Structure refinement is in progress.

  20. The oxygenating constituent of 3,6-diketocamphane monooxygenase from the CAM plasmid of Pseudomonas putida: the first crystal structure of a type II Baeyer–Villiger monooxygenase

    Energy Technology Data Exchange (ETDEWEB)

    Isupov, Michail N.; Schröder, Ewald; Gibson, Robert P.; Beecher, Jean; Donadio, Giuliana; Saneei, Vahid; Dcunha, Stephlina A.; McGhie, Emma J.; Sayer, Christopher; Davenport, Colin F. [University of Exeter, Stocker Road, Exeter EX4 4QD (United Kingdom); Lau, Peter C. [National Research Council Canada, 6100 Royalmount Avenue, Montreal, QC H4P 2R2 (Canada); Hasegawa, Yoshie; Iwaki, Hiroaki [Kansai University (Japan); Kadow, Maria; Balke, Kathleen; Bornscheuer, Uwe T. [Greifswald University, Felix-Hausdorff-Strasse 4, 17487 Greifswald (Germany); Bourenkov, Gleb [European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, 22607 Hamburg (Germany); Littlechild, Jennifer A., E-mail: j.a.littlechild@exeter.ac.uk [University of Exeter, Stocker Road, Exeter EX4 4QD (United Kingdom)

    2015-10-31

    The first crystal structure of a type II Baeyer–Villiger monooxygenase reveals a different ring orientation of its FMN cofactor compared with other related bacterial luciferase-family enzymes. The three-dimensional structures of the native enzyme and the FMN complex of the overexpressed form of the oxygenating component of the type II Baeyer–Villiger 3,6-diketocamphane monooxygenase have been determined to 1.9 Å resolution. The structure of this dimeric FMN-dependent enzyme, which is encoded on the large CAM plasmid of Pseudomonas putida, has been solved by a combination of multiple anomalous dispersion from a bromine crystal soak and molecular replacement using a bacterial luciferase model. The orientation of the isoalloxazine ring of the FMN cofactor in the active site of this TIM-barrel fold enzyme differs significantly from that previously observed in enzymes of the bacterial luciferase-like superfamily. The Ala77 residue is in a cis conformation and forms a β-bulge at the C-terminus of β-strand 3, which is a feature observed in many proteins of this superfamily.

  1. Rhodium-Catalyzed Highly Regioselective C-H Arylation of Imidazo[1,2-a]pyridines with Aryl Halides and Triflates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; He, Lin [Guandong Pharmaceutical Univ., Zhongshan (China); Yin, Guoqiang; Wu, Guojie; Cui, Yingde [Zhongkai Univ. of Agriculture and Engineering, Guangzhou (China)

    2013-08-15

    A convenient Rh-catalyzed C-H arylation of imidazo[1,2-a]pyridines with a variety of aryl halides or triflates has been reported. This process afforded a range of biaryl compounds in excellent yields and showed high activity and broad scope.

  2. Reaction mechanism for the methane-methanol conversion by soluble methane monooxygenase; Metanmonookishigenaze (MMO) ni yoru metan - metanoru henkan no hanno kiko

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizawa, K.; Ota, Y.; Yamabe, T. [Kyoto Univ. (Japan)

    1998-07-10

    Methane monooxygenase (MMO) is a metalloenzyme with binuclear iron atoms as an active center and has ability to oxidize methane which is the most unreactive hydrocarbon. Among recent studies on the reaction mechanism of MMO, the oxygen rebound mechanism, a sort of radical reaction mechanism is critically examined. The two-step concerted mechanism for the hydroxylation of methane and other reaction mechanisms for MMO are discussed. The intermediate of the catalytic cycle of MMO is proposed to consist of two high valiant iron-oxo species based on the experimental result with EXAFS. Fe0{sup +} is known to oxidize methane into methanol in the gaseous state. This reaction has been analyzed by density functional method and methane is found to be activated efficiently through deformation into C{sub 3v} or D{sub 2d} form and combined with iron atom. Reaction mechanism of the methane-methanol conversion is analyzed by the density functional method and shows that the two-step concerted mechanism reproduces the reactivity of soluble MMO. 34 refs., 16 figs.

  3. New 1-Aryl-3-Substituted Propanol Derivatives as Antimalarial Agents

    Directory of Open Access Journals (Sweden)

    Antonio Monge

    2009-10-01

    Full Text Available This paper describes the synthesis and in vitro antimalarial activity against a P. falciparum 3D7 strain of some new 1-aryl-3-substituted propanol derivatives. Twelve of the tested compounds showed an IC50 lower than 1 μM. These compounds were also tested for cytotoxicity in murine J774 macrophages. The most active compounds were evaluated for in vivo activity against P. berghei in a 4-day suppressive test. Compound 12 inhibited more than 50% of parasite growth at a dose of 50 mg/kg/day. In addition, an FBIT test was performed to measure the ability to inhibit ferriprotoporphyrin biocrystallization. This data indicates that 1-aryl-3-substituted propanol derivatives hold promise as a new therapeutic option for the treatment of malaria.

  4. Impregnated palladium on magnetite as catalyst for direct arylation of heterocycles

    OpenAIRE

    Cano Monserrat, Rafael; Pérez Galera, Juana María; Ramón Dangla, Diego José; McGlacken, Gerard P.

    2016-01-01

    Palladium impregnated on magnetite is an efficient, cheap and easy to prepare catalyst for the direct arylation of heterocycles. Good yields are afforded under relatively mild conditions and a broad substrate scope is evident. The catalyst is regioselective in many cases, affording arylated products, at the C2- or C3-position (depending of the heterocycle used). The methodology can be extended to prepare chromenes through an intramolecular direct arylation reaction. Some evidence is provided ...

  5. Kumada coupling of aryl, heteroaryl, and vinyl chlorides catalyzed by amido pincer nickel complexes.

    Science.gov (United States)

    Liu, Ning; Wang, Zhong-Xia

    2011-12-16

    A series of amido pincer complexes of nickel were examined for their catalysis in the Kumada cross-coupling reaction. The P,N,O-pincer nickel complexes tested are active catalysts for the cross-coupling of aryl, heteroaryl, and vinyl chlorides with aryl Grignard reagents. The reactions can proceed at room temperature and tolerate functional groups in aryl chlorides with the aid of LiCl and ZnCl(2) additives. PMID:22077596

  6. The electrochemistry of arylated anthraquinones in room temperature ionic liquids

    OpenAIRE

    Gomis Berenguer, Alicia; Gómez Mingot, María; García Cruz, Leticia; Thiemann, Thies; Banks, Craig E.; Montiel Leguey, Vicente; Iniesta Valcárcel, Jesús

    2013-01-01

    Arylated anthraquinone derivatives of different sizes and different π-basicities have been prepared, and the electrochemical behaviour of these substances has been studied on screen printed graphite electrodes in the three room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]). Half redox potentials for the first and...

  7. Thraustochytrid protists degrade hydrocarbons

    Digital Repository Service at National Institute of Oceanography (India)

    Raikar, M.T.; Raghukumar, S.; Vani, V.; David, J.J.; Chandramohan, D.

    isolation tubes with crude oil. Three isolates tested showed positive hydrophobicity of cell walls as judged by the Microbial Adhesion to Hydrocarbons (MATH) assay. Addition of Bombay High crude oil to nutrient broth slightly enhanced growth of the protists...

  8. Immunoassay for petroleum hydrocarbons

    International Nuclear Information System (INIS)

    Petroleum hydrocarbon contamination of soil and ground water has become a serious environmental problem. Since the 1940s, it has been a common practice to bury fuel tanks underground to guard against fire and explosions. The leakage of petroleum fuel from these aging tanks creates a long term threat to human health. In order to location and identify these sources of contamination, an on-site screening test is very desirable. A simple, inexpensive petroleum hydrocarbon immunoassay has been developed for this purpose. The EnviroGard Petroleum Hydrocarbon test kit is designed for qualitative or semiquantitative analysis of petroleum hydrocarbon fuel in soil and ground water. The assay can be easily used on-site and takes 15 minutes to perform. Following a 2 minute methanol extraction, the test is performed in polystyrene tubes and can detect gasoline, diesel fuel, kerosene, home heating oil and other major fuels at ppm levels in soil and sub-ppm levels in water samples

  9. Unprecedentedly mild direct Pd-catalyzed arylation of oxazolo[4,5-b]pyridine

    DEFF Research Database (Denmark)

    Zhuravlev, Fedor

    2006-01-01

    Pd-catalyzed C-2 arylation of oxazolo[4,5-b]pyridine proceeds efficiently at 30 degrees C and tolerates a variety of aryl halides, including derivatized amino acids for which no racemization was observed during the reaction. Experimental evidence for facile deprotonation of oxazolo[4,5-b]pyridine......Pd-catalyzed C-2 arylation of oxazolo[4,5-b]pyridine proceeds efficiently at 30 degrees C and tolerates a variety of aryl halides, including derivatized amino acids for which no racemization was observed during the reaction. Experimental evidence for facile deprotonation of oxazolo[4,5-b...

  10. Microwave Assisted Solvent Free Synthesis of Azomethines from Aryl Aldehydes on Melamin Formaldehyde as Solid Support

    OpenAIRE

    Ramin Rezaei; Mohammadi, Mohammad K; Tahereh Ranjbar

    2011-01-01

    Various aryl aldehydes underwent prompt one pot conversion into the corresponding azomethines in high yields by reacting with hydroxylamine hydrochloride supported on melamine formaldehyde under microwave irradiation.

  11. Synthesis and characterization of 5-heteroarylsulfanyl-4-aryl-1,2,3-selena/thiadiazoles

    Indian Academy of Sciences (India)

    Ramaiyan Manikannan; Masilamani Shanmugaraja; Seetharaman Manojveer; Shanmugam Muthusubramanian

    2012-03-01

    Synthesis and spectral characterization of 2-methyl-5-[(4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl]-1,3,4-thiadiazoles, 5-[4-aryl-1,2,3-selenadiazol-5-yl]sulfanyl-1-phenyl-1-1,2,3,4-tetraazoles, 4-aryl-5-[(5-methyl-1,3,4-thiadiazol-2-yl)sulfanyl]-1,2,3-thiadiazole and 5-[4-aryl-1,2,3-thiadiazol-5-yl]sulfanyl-1-phenyl-1-1,2,3,4-tetraazole have been reported.

  12. Synthesis of Novel Aryl(heteroarylsulfonyl Ureas of Possible Biological Interest

    Directory of Open Access Journals (Sweden)

    Maria Gdaniec

    2010-02-01

    Full Text Available The course of reaction of aryl and heteroaryl sulfonamides with diphenylcarbonate (DPC and 4-dimethylaminopyridine (DMAP was found to depend on the pKa of the sulfonamide used. Aryl sulfonamides with pKa ~ 10 gave 4-dimethylamino-pyridinium arylsulfonyl-carbamoylides, while the more acidic heteroaryl sulfonamides (pKa ~ 8 furnished 4-dimethylaminopyridinium heteroarylsulfonyl carbamates. Both the carbamoylides and carbamate salts reacted with aliphatic and aromatic amines with the formation of appropriate aryl(heteroarylsulfonyl ureas, and therefore, can be regarded as safe and stable substitutes of the hazardous and difficult to handle aryl(heteroarylsulfonyl isocyanates.

  13. Direct catalytic conversion of methane and light hydrocarbon gases. Final report, October 1, 1986--July 31, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, R.B. Jr.; Posin, B.M.; Chan, Yee-Wai

    1995-06-01

    This project explored conversion of methane to useful products by two techniques that do not involve oxidative coupling. The first approach was direct catalytic dehydrocoupling of methane to give hydrocarbons and hydrogen. The second approach was oxidation of methane to methanol by using heterogenized versions of catalysts that were developed as homogeneous models of cytochrome-P450, an enzyme that actively hydroxylates hydrocarbons by using molecular oxygen. Two possibilities exist for dehydrocoupling of methane to higher hydrocarbons: The first, oxidative coupling to ethane/ethylene and water, is the subject of intense current interest. Nonoxidative coupling to higher hydrocarbons and hydrogen is endothermic, but in the absence of coke formation the theoretical thermodynamic equilibrium yield of hydrocarbons varies from 25% at 827{degrees}C to 65% at 1100{degrees}C (at atmospheric pressure). In this project we synthesized novel, highly dispersed metal catalysts by attaching metal clusters to inorganic supports. The second approach mimics microbial metabolism of methane to produce methanol. The methane mono-oxygenase enzyme responsible for the oxidation of methane to methanol in biological systems has exceptional selectivity and very good rates. Enzyme mimics are systems that function as the enzymes do but overcome the problems of slow rates and poor stability. Most of that effort has focused on mimics of cytochrome P-450, which is a very active selective oxidation enzyme and has a metalloporphyrin at the active site. The interest in nonporphyrin mimics coincides with the interest in methane mono-oxygenase, whose active site has been identified as a {mu}-oxo dinuclear iron complex.We employed mimics of cytochrome P-450, heterogenized to provide additional stability. The oxidation of methane with molecular oxygen was investigated in a fixed-bed, down-flow reactor with various anchored metal phthalocyanines (PC) and porphyrins (TPP) as the catalysts.

  14. Ligand-Free, Cu- and Fe-Catalyzed Selective Ring-Opening Arylations of Benzoxazoles with Aryl Iodides.

    Science.gov (United States)

    He, Yue; Mao, Jincheng; Rong, Guangwei; Yan, Hong; Zhang, Guoqi

    2016-06-01

    Cu- or Fe-based catalyst systems have been reported to selectively catalyze the N,N-diarylation or N-monoarylation of benzoxazoles ring-opening with aryl iodides in the absence of additional added ligand in polyethylene glycol under an inert atmosphere. Two types of coupling products (triphenylamines and diphenylamines) have been examined and the reaction routes can be simply controlled by changing the metal salts (Cu or Fe) as catalyst. A range of substrates have been investigated for the diverse reactions, and the corresponding arylation products were achieved in good to high yields. This selective, low-cost, and environmentally friendly protocol displays great potential for replacing existing methodologies as well as extending the synthetic applications of benzoxazoles. PMID:27037845

  15. Aryl sulfate formation in sea urchins (Strongylocentrotus droebachiensis) ingesting marine algae (Fucus distichus) containing 2,6-dimethylnapthalene

    International Nuclear Information System (INIS)

    The metabolism of tritiated 2,6-dimethylnapthalene (2,6-DMN) was studied in sea urchins (Strongylocentrotus droebachiensis) feeding on marine algae (Fucus distichus). The Fucus accumulated this hydrocarbon from sea water without converting it to metabolites. Most of the tritium accumulated by the sea urchins (e.g., 70.8% after 3 days) from feeding on 2,6-DMN-exposed Fucus was present in the exoskeleton (shell and spines). Moreover, after 3 days feeding, about 90% of the tritium in the total metabolite fraction of the gonads and digestive tract of the sea urchin was present as sulfate derivatives. These metabolites were identified through hydrolysis with aryl sulfatase, followed by thin-layer chromatography of the products. After 14 days of feeding, the tritium associated with the sulfate derivatives decreased in the gonads and digestive tract to 61 and 65%, respectively, of the total metabolite fraction. Hydroxy compounds from sulfatase hydrolysis were chromatographed using multiple elutions with toluene. The hydroxy isomers were separated and the R/sub f/ values were compared to those of pure reference compounds. The data indicated that 80% of the 2,6-dimethylnaphtyl sulfate contained the sulfate on the 1 and/or 3 position of the aromatic ring. Moreover, 6-methyl-2-naphthalenemethanol was not detected, which implies that sea urchins, unlike fish, metabolize alkyl-substituted aromatic hydrocarbons primarily through aromatic ring oxidations

  16. A three-step process to facilitate the annulation of polycyclic aromatic hydrocarbons.

    Science.gov (United States)

    Martin, Sara E; Streeter, Matthew D; Jones, Laurel L; Klepfer, Matthew S; Atmatzidis, Kyriakos; Wille, Kristen D; Harrison, Sean A; Hoegg, Edward D; Sheridan, Heather M; Kramer, Stephanie; Parrish, Damon A; Amick, Aaron W

    2014-09-01

    A new efficient three-step process to annulate polycyclic aromatic hydrocarbons (PAHs) has been developed, providing access to PAHs with saturated rings that under current chemical methods would be difficult to produce in an efficient manner. This method relies on a palladium-catalyzed cross-coupling reaction of various brominated PAHs with cyclohexanone to yield α-arylated ketones, which are converted to regiospecific vinyl triflates and cyclized by a palladium-catalyzed intramolecular arene-vinyl triflate coupling to produce PAHs with incorporated saturated rings or "tetrahydroindeno-annulated" PAHs. PMID:25137354

  17. TBAHS CATALYZED COUPLING REACTIONS OF ARYL IODIDES AND ARYL BROMIDES WITH THIOLS UNDER SOLVENT FREE CONDITIONS TBAHS katalysierten Kupplungen von Aryliodiden und-Arylbromiden mit Thiolen unter lösungsmittelfreien freien Bedingungen

    Directory of Open Access Journals (Sweden)

    Gajendera Singha, Ajay kumarb , Sakshi Malikc, Preeti Chaudharyd

    2013-04-01

    Full Text Available A recyclable and efficient Tetrabutylammonium hydrogensulfate (TBAHS catalysed coupling reaction of aryl halides (iodide and bromide with aryl and alkyl thiols under solvent-free conditions were developed.

  18. Synthesis of nanodispersible 6-aryl-2,4-diamino-1,3,5-triazine and its derivatives

    International Nuclear Information System (INIS)

    A series of novel branched derivatives of 6-aryl-2,4-diamino-1,3,5-triazine from corresponding aryl nitriles and dicyanodiamide was synthesized. These compounds show a nanodispersibility and good thermal stability.

  19. Mammalian Flavin-Containing Monooxygenase (FMO) as a Source of Hydrogen Peroxide

    OpenAIRE

    Siddens, Lisbeth K.; Krueger, Sharon K.; Henderson, Marilyn C.; Williams, David E.

    2014-01-01

    Flavin-containing monooxygenase (FMO) oxygenates drugs/xenobiotics containing a soft nucleophile through a C4a hydroperoxy-FAD intermediate. Human FMOs 1, 2 and 3, expressed in Sf9 insect microsomes, released 30–50% of O2 consumed as H2O2 upon addition of NADPH. Addition of substrate had little effect on H2O2 production. Two common FMO2 (the major isoform in the lung) genetic polymorphisms, S195L and N413K, were examined for generation of H2O2. FMO2 S195L exhibited higher “l...

  20. The influence of divalent metal ions on a lytic polysaccharide monooxygenase

    OpenAIRE

    Naghshehechi, Kaveh

    2014-01-01

    Med den globale miljøutfordringen som vi er stilt ovenfor i dag, har interessen og forskningen for bærekraftig og ren energi de siste tiårene vært fremtredende. Innenfor bioraffineri feltet har enzymatisk nedbrytning av biomasse vært i fokus, men er fortsatt en kostnadsfull og langsom prosess. Nylig har det blitt vist at bakterielle enzymer kvalifisert som lytisk polysakkaride monooxygenase (LPMO) medlem av familien 10 av auxiliry activities (AA), øker nedbrytninghastigheten av uløselige p...

  1. Alcaligenes eutrophus JMP134 "2,4-dichlorophenoxyacetate monooxygenase" is an alpha-ketoglutarate-dependent dioxygenase.

    OpenAIRE

    Fukumori, F; Hausinger, R P

    1993-01-01

    The Alcaligenes eutrophus JMP134 tfdA gene, encoding the enzyme responsible for the first step in 2,4-dichlorophenoxyacetic acid (2,4-D) biodegradation, was overexpressed in Escherichia coli, and several enzymatic properties of the partially purified gene product were examined. Although the tfdA-encoded enzyme is typically referred to as 2,4-D monooxygenase, we were unable to observe any reductant-dependent activity. Rather, we demonstrate that this enzyme is a ferrous ion-dependent dioxygena...

  2. Studies on whole cell fluorescence-based screening for epoxide hydrolases and Baeyer-Villiger monooxygenases

    Energy Technology Data Exchange (ETDEWEB)

    Bicalho, Beatriz; Chen, Lu S.; Marsaioli, Anita J. [Universidade Estadual de Campinas, SP (Brazil). Inst. de Quimica]. E-mail: anita@iqm.unicamp.br; Grognux, Johann; Reymond, Jean-Louis [University of Berne (Switzerland). Dept. of Chemistry and Biochemistry

    2004-12-01

    Biocatalysis reactions were performed on microtiter plates (200 {mu}L) aiming at the utilization of fluorogenic substrates (100 {mu}mol L{sup -1}) for rapid whole cell screening for epoxide hydrolases (EHs) and Baeyer-Villiger monooxygenases (BVMOs). A final protocol was achieved for EHs, with 3 new enzymatic sources being detected (Agrobacterium tumefaciens, Pichia stipitis, Trichosporom cutaneum). The fluorogenic assay for BVMO did not work as expected. However, an approach to possible variables involved (aeration; pH) provided the first detection of a BVMO activity in T. cutaneum. (author)

  3. Effects of methotrexate on rat P-450 cytochrome mono-oxygenases

    International Nuclear Information System (INIS)

    Methotrexate, an anti-cancerous agent, acts as an anti-metabolite of the nucleic acids which synthesis is then inhibited. Using aminopyrine breath test after methotrexate processing, the effects of the molecule on activities of the hepatocyte P-450 cytochrome mono-oxygenases, are studied. Breath micro-tests with carbon 13-labelled aminopyrine have been carried out to observe the metabolism evolution. Micro-test results have been compared to microsomal enzymatic activities for various substrates, and also to P-450 cytochrome ratio. Results show that methotrexate induces a reduction in the P-450 cytochrome ratio, and thus reduce the hepatic biotransformation process. 1 fig., 30 refs

  4. Studies on whole cell fluorescence-based screening for epoxide hydrolases and Baeyer-Villiger monooxygenases

    International Nuclear Information System (INIS)

    Biocatalysis reactions were performed on microtiter plates (200 μL) aiming at the utilization of fluorogenic substrates (100 μmol L-1) for rapid whole cell screening for epoxide hydrolases (EHs) and Baeyer-Villiger monooxygenases (BVMOs). A final protocol was achieved for EHs, with 3 new enzymatic sources being detected (Agrobacterium tumefaciens, Pichia stipitis, Trichosporom cutaneum). The fluorogenic assay for BVMO did not work as expected. However, an approach to possible variables involved (aeration; pH) provided the first detection of a BVMO activity in T. cutaneum. (author)

  5. Directed Evolution of Toluene ortho-Monooxygenase for Enhanced 1-Naphthol Synthesis and Chlorinated Ethene Degradation

    OpenAIRE

    Canada, Keith A.; Iwashita, Sachiyo; Shim, Hojae; Thomas K. Wood

    2002-01-01

    Trichloroethylene (TCE) is the most frequently detected groundwater contaminant, and 1-naphthol is an important chemical manufacturing intermediate. Directed evolution was used to increase the activity of toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 for both chlorinated ethenes and naphthalene oxidation. When expressed in Escherichia coli, the variant TOM-Green degraded TCE (2.5 ± 0.3 versus 1.39 ± 0.05 nmol/min/mg of protein), 1,1-dichloroethylene, and trans-dichloroethylene ...

  6. Transformation yields of chlorinated ethenes by a methanotrophic mixed culture expressing particulate methane monooxygenase.

    OpenAIRE

    Anderson, J E; McCarty, P L

    1997-01-01

    Transformation yields for the aerobic cometabolic degradation of five chlorinated ethenes were determined by using a methanotrophic mixed culture expressing particulate methane monooxygenase (pMMO). Transformation yields (expressed as moles of chlorinated ethene degraded per mole of methane consumed) were 0.57, 0.25, 0.058, 0.0019, and 0.00022 for trans-1,2-dichloroethylene (t-DCE), vinyl chloride (VC), cis-1,2-dichloroethylene (c-DCE), trichloroethylene (TCE), and 1,1-dichloroethylene (1,1-D...

  7. Genomic organization and splicing variants of a peptidylglycine alpha-hydroxylating monooxygenase from sea anemones

    DEFF Research Database (Denmark)

    Williamson, M; Hauser, F; Grimmelikhuijzen, C J

    2000-01-01

    Cnidarians are primitive animals that use neuropeptides as their transmitters. All the numerous cnidarian neuropeptides isolated, so far, have a carboxy-terminal amide group that is essential for their actions. This strongly suggests that alpha-amidating enzymes are essential for the functioning......, peptidylglycine alpha-amidating monooxygenase (PAM), which is coded for by a single gene. In a previous paper (F. Hauser et al., Biochem. Biophys. Res. Commun. 241, 509-512, 1997) we have cloned the first known cnidarian PHM from the sea anemone Calliactis parasitica. In the present paper we have determined...

  8. Rhizoremediation of Trichloroethylene by a Recombinant, Root-Colonizing Pseudomonas fluorescens Strain Expressing Toluene ortho-Monooxygenase Constitutively

    OpenAIRE

    Yee, Dennis C.; Maynard, Jennifer A.; Thomas K Wood

    1998-01-01

    Trichloroethylene (TCE) was removed from soils by using a wheat rhizosphere established by coating seeds with a recombinant, TCE-degrading Pseudomonas fluorescens strain that expresses the tomA+ (toluene o-monooxygenase) genes from Burkholderia cepacia PR123(TOM23C). A transposon integration vector was used to insert tomA+ into the chromosome of P. fluorescens 2-79, producing a stable strain that expressed constitutively the monooxygenase at a level of 1.1 nmol/min · mg of protein (initial TC...

  9. Radical C-H arylations of (hetero)arenes catalysed by gallic acid.

    Science.gov (United States)

    Perretti, Marcelle D; Monzón, Diego M; Crisóstomo, Fernando P; Martín, Víctor S; Carrillo, Romen

    2016-07-12

    Gallic acid efficiently catalyses radical arylations in water-acetone at room temperature. This methodology proved to be versatile and scalable. Therefore, it constitutes a greener alternative to arylation. Moreover, considering that gallic acid is an abundant vegetable tannin, this work also unleashes an alternative method for the reutilisation of bio-wastes. PMID:26804947

  10. Copper-Catalyzed Diastereoselective Arylation of Tryptophan Derivatives: Total Synthesis of (+)-Naseseazines A and B

    OpenAIRE

    Kieffer, Madeleine E.; Chuang, Kangway V.; Reisman, Sarah E.

    2013-01-01

    A copper-catalyzed arylation of tryptophan derivatives is reported. The reaction proceeds with high site- and diastereoselectivity to provide aryl pyrroloindoline products in one step from simple starting materials. The utility of this transformation is highlighted in the five-step syntheses of the natural products (+)-naseseazine A and B.

  11. p-Toluenesulphonic acid-promoted, I2-catalysed sulphenylation of pyrazolones with aryl sulphonyl hydrazides.

    Science.gov (United States)

    Zhao, Xia; Zhang, Lipeng; Li, Tianjiao; Liu, Guiyan; Wang, Haomeng; Lu, Kui

    2014-11-01

    Aryl pyrazolone thioethers were synthesized via the I2-catalysed cross-coupling of pyrazolones with aryl sulphonyl hydrazides in the presence of p-toluenesulphonic acid, which has been proposed to promote the reaction by facilitating the decomposition of sulphonyl hydrazides. PMID:25225659

  12. C-Arylation reactions catalyzed by CuO-nanoparticles under ligand free conditions

    OpenAIRE

    Mazaahir Kidwai; Saurav Bhardwaj; Roona Poddar

    2010-01-01

    CuO-nanoparticles were found to be an excellent heterogeneous catalyst for C-arylation of active methylene compounds using various aryl halides. The products were obtained in good to excellent yield. The catalyst can be recovered and reused for four cycles with almost no loss in activity.

  13. C-Arylation reactions catalyzed by CuO-nanoparticles under ligand free conditions

    Directory of Open Access Journals (Sweden)

    Mazaahir Kidwai

    2010-04-01

    Full Text Available CuO-nanoparticles were found to be an excellent heterogeneous catalyst for C-arylation of active methylene compounds using various aryl halides. The products were obtained in good to excellent yield. The catalyst can be recovered and reused for four cycles with almost no loss in activity.

  14. Oxidative addition of aryl chlorides to monoligated palladium(0): A DFT-SCRF study

    DEFF Research Database (Denmark)

    Ahlquist, Mårten Sten Gösta; Norrby, Per-Ola

    2007-01-01

    Oxidative addition of aryl chlorides to palladium has been investigated by hybrid density functional theory methods (B3LYP), including a continuum model describing the solvent implicitly. A series of para-substituted aryl chlorides were studied to see the influence of electronic effects on the...

  15. Copper-catalyzed arylation of biguanide derivatives via C-N cross-coupling reactions.

    Science.gov (United States)

    Zhang, Chen; Huang, Bo; Bao, Ai-Qing; Li, Xiao; Guo, Shunna; Zhang, Jin-Quan; Xu, Jun-Zhi; Zhang, Rihao; Cui, Dong-Mei

    2015-12-21

    An efficient copper-catalyzed cross-coupling reaction of biguanide hydrochloride derivatives with both aryl iodides and bromides under mild conditions has been developed. The reaction occurred in good yields and tolerated aryl halides containing functionalities such as nitriles, sulfonamides, ethers, and halogens. Alkyl and cyclic substituted biguanidines were also well tolerated. PMID:26444146

  16. 40 CFR 721.9597 - Salt of a substituted sulfonated aryl azo compound (generic).

    Science.gov (United States)

    2010-07-01

    ... azo compound (generic). 721.9597 Section 721.9597 Protection of Environment ENVIRONMENTAL PROTECTION... New Uses for Specific Chemical Substances § 721.9597 Salt of a substituted sulfonated aryl azo... substance identified generically as salt of a substituted sulfonated aryl azo compound (PMN P-00-0094)...

  17. Palladium-catalyzed carbonylative Heck reaction of aryl bromides with vinyl ethers to 3-alkoxy alkenones and pyrazoles.

    Science.gov (United States)

    Schranck, Johannes; Wu, Xiao-Feng; Neumann, Helfried; Beller, Matthias

    2012-04-16

    Three COming together: The first carbonylative Heck coupling reaction of aryl bromides and vinyl ethers leading to 1-aryl-3-alkoxy-2-propen-1-ones has been established (see scheme). Based on this coupling methodology, a novel one-pot synthesis of aryl-substituted pyrazoles was also realized. PMID:22422673

  18. Superconductivity in aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (Kxpicene, five benzene rings). Its superconducting transition temperatures (Tc’s) were 7 and 18 K. Recently, we found a new superconducting Kxpicene phase with a Tc as high as 14 K, so we now know that Kxpicene possesses multiple superconducting phases. Besides Kxpicene, we discovered new superconductors such as Rbxpicene and Caxpicene. A most serious problem is that the shielding fraction is ⩽15% for Kxpicene and Rbxpicene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of Tc that is clearly observed in some phases of aromatic hydrocarbon superconductors

  19. Regioselectivity of Arylation of 2,3’-Biquinolyl Dianion

    Directory of Open Access Journals (Sweden)

    Yu. I. Smushkevich

    1999-04-01

    Full Text Available The dianion of 2,3’-biquinolyl with aryl- and hetaryl halides forms the products of arylation to 4’-position, which on treatment with alkyl halides or water yield 1’-alkyl-1’,4’dihydro-2,3’-biquinolyls or 4’-aryl-1’,4’-dihydro-2,3’-biquinolyls respectively. The oxidation of the latter leads to 4’-aryl-2,3’-biquinolyls. The cation dependence of the arylation is shown.

  20. Topical viscosity control for light hydrocarbon displacing fluids in petroleum recovery and in fracturing fluids for well stimulation

    Science.gov (United States)

    Heller, John P.; Dandge, Dileep K.

    1986-01-01

    Solvent-type flooding fluids comprising light hydrocarbons in the range of ethane to hexane (and mixtures thereof) are used to displace crude oil in formations having temperatures of about 20 degrees to about 150 degrees Centigrade and pressures above about 650 psi, the light hydrocarbons having dissolved therein from about 0.05% to about 3% of an organotin compound of the formula R.sub.3 SnF where each R is independently an alkyl, aryl or alkyaryl group from 3 to 12 carbon atoms. Under the pressures and temperatures described, the organotin compounds become pentacoordinated and linked through the electronegative bridges, forming polymers within the light hydrocarbon flooding media to render them highly viscous. Under ambient conditions, the viscosity control agents will not readily be produced from the formation with either crude oil or water, since they are insoluble in the former and only sparingly soluble in the latter.

  1. Inactivation of peptidylglycine α-hydroxylating monooxygenase by cinnamic acid analogs.

    Science.gov (United States)

    McIntyre, Neil R; Lowe, Edward W; Battistini, Matthew R; Leahy, James W; Merkler, David J

    2016-08-01

    Peptidylglycine α-amidating monooxygenase (PAM) is a bifunctional enzyme that catalyzes the final reaction in the maturation of α-amidated peptide hormones. Peptidylglycine α-hydroxylating monooxygenase (PHM) is the PAM domain responsible for the copper-, ascorbate- and O2-dependent hydroxylation of a glycine-extended peptide. Peptidylamidoglycolate lyase is the PAM domain responsible for the Zn(II)-dependent dealkylation of the α-hydroxyglycine-containing precursor to the final α-amidated peptide. We report herein that cinnamic acid and cinnamic acid analogs are inhibitors or inactivators of PHM. The inactivation chemistry exhibited by the cinnamates exhibits all the attributes of a suicide-substrate. However, we find no evidence for the formation of an irreversible linkage between cinnamate and PHM in the inactivated enzyme. Our data support the reversible formation of a Michael adduct between an active site nucleophile and cinnamate that leads to inactive enzyme. Our data are of significance given that cinnamates are found in foods, perfumes, cosmetics and pharmaceuticals. PMID:26024288

  2. Stabilization of cyclohexanone monooxygenase by a computationally designed disulfide bond spanning only one residue

    Directory of Open Access Journals (Sweden)

    Hugo L. van Beek

    2014-01-01

    Full Text Available Enzyme stability is an important parameter in biocatalytic applications, and there is a strong need for efficient methods to generate robust enzymes. We investigated whether stabilizing disulfide bonds can be computationally designed based on a model structure. In our approach, unlike in previous disulfide engineering studies, short bonds spanning only a few residues were included. We used cyclohexanone monooxygenase (CHMO, a Baeyer–Villiger monooxygenase (BVMO from Acinetobacter sp. NCIMB9871 as the target enzyme. This enzyme has been the prototype BVMO for many biocatalytic studies even though it is notoriously labile. After creating a small library of mutant enzymes with introduced cysteine pairs and subsequent screening for improved thermostability, three stabilizing disulfide bonds were identified. The introduced disulfide bonds are all within 12 Å of each other, suggesting this particular region is critical for unfolding. This study shows that stabilizing disulfide bonds do not have to span many residues, as the most stabilizing disulfide bond, L323C–A325C, spans only one residue while it stabilizes the enzyme, as shown by a 6 °C increase in its apparent melting temperature.

  3. Increased monooxygenase activity associated with resistance to permethrin in Pediculus humanus capitis (Anoplura: Pediculidae) from Argentina.

    Science.gov (United States)

    González Audino, P; Barrios, S; Vassena, C; Mougabure Cueto, G; Zerba, E; Picollo, M I

    2005-05-01

    We studied the profile of permethrin resistance in populations of head lice infesting children 6-12 yr old in schools and their homes in and around Buenos Aires, Argentina. Five permethrin-resistant populations with different levels of resistance were collected: Hogar Loyola (HL), Republica de Turquia (RT), Hogar Mitre (HM), Guardia de Honor (GH), and Ricardo Guiraldes (RG). One susceptible population, Bandera Argentina (BA), also was collected. Their level of resistance was evaluated, and results showed resistance ratios of 13 for HL, 16 for RT, 22 for HM, 61 for GH, and 69 for RG. To elucidate the possible involvement of the cytochrome P450 monooxygenase system in conferring permethrin resistance, ethoxycoumarin-O-deethylase (ECOD) activity was measured in abdomens of individual third instars and adults by using a fluorometric assay. The ECOD activity was lower in the susceptible BA population (4.7 ng per louse) than in the resistant ones (13.7 ng per louse for RG, 12.3 ng per louse for GH, 8.6 ng per louse for RT, and 8.2 ng per louse for HL). ECOD activity was significantly correlated with the level of resistance in the field populations (r = 0.97, P = 0.0009), suggesting a role for cytochrome monooxygenase P450 system in permethrin resistance by head louse, Pediculus humanus capitis De Geer. PMID:15962785

  4. The reduced flavin-dependent monooxygenase SfnG converts dimethylsulfone to methanesulfinate.

    Science.gov (United States)

    Wicht, Denyce K

    2016-08-15

    The biochemical pathway through which sulfur may be assimilated from dimethylsulfide (DMS) is proposed to proceed via oxidation of DMS to dimethylsulfoxide (DMSO) and subsequent conversion of DMSO to dimethylsulfone (DMSO2). Analogous chemical oxidation processes involving biogenic DMS in the atmosphere result in the deposition of DMSO2 into the terrestrial environment. Elucidating the enzymatic pathways that involve DMSO2 contribute to our understanding of the global sulfur cycle. Dimethylsulfone monooxygenase SfnG and flavin mononucleotide (FMN) reductase MsuE from the genome of the aerobic soil bacterium Pseudomonas fluorescens Pf0-1 were produced in Escherichia coli, purified, and biochemically characterized. The enzyme MsuE functions as a reduced nicotinamide adenine dinucleotide (NADH)-dependent FMN reductase with apparent steady state kinetic parameters of Km = 69 μM and kcat/Km = 9 min(-1) μM (-1) using NADH as the variable substrate, and Km = 8 μM and kcat/Km = 105 min(-1) μM (-1) using FMN as the variable substrate. The enzyme SfnG functions as a flavoprotein monooxygenase and converts DMSO2 to methanesulfinate in the presence of FMN, NADH, and MsuE, as evidenced by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The results suggest that methanesulfinate is a biochemical intermediate in sulfur assimilation. PMID:27392454

  5. Process development for oxidations of hydrophobic compounds applying cytochrome P450 monooxygenases in-vitro.

    Science.gov (United States)

    Brummund, Jan; Müller, Monika; Schmitges, Thomas; Kaluzna, Iwona; Mink, Daniel; Hilterhaus, Lutz; Liese, Andreas

    2016-09-10

    Cytochrome P450 monooxygenases are a unique family of enzymes that are able to catalyze regio- and stereospecific oxidations for a broad substrate range. However, due to limited enzyme activities and stabilities, hydrophobicity of substrates, as well as the necessity of a continuous electron and oxygen supply the implementation of P450s for industrial processes remains challenging. Aim of this study was to point out key aspects for the development of an efficient synthesis concept for cytochrome P450 catalyzed oxidations. In order to regenerate the natural cofactor NADPH, a glucose dehydrogenase was applied. The low water soluble terpene α-ionone was used as substrate for the model reaction system. The studies reveal that an addition of surfactants in combination with low volumetric amounts of co-solvent can significantly increase substrate availability and reaction rates. Furthermore, these additives facilitated a reliable sampling procedure during the process. Another key factor for the process design was the oxygen supply. Based on various investigations, a bubble-aerated stirred tank reactor in batch mode represents a promising reactor concept for P450 oxidations. Main restriction of the investigated reaction system was the low process stability of the P450 monooxygenase, characterized by maximum total turnover numbers of ∼4100molα-ionone/molP450. PMID:27396939

  6. Synthesis of (18) F-Difluoromethylarenes from Aryl (Pseudo) Halides.

    Science.gov (United States)

    Shi, Hang; Braun, Augustin; Wang, Lu; Liang, Steven H; Vasdev, Neil; Ritter, Tobias

    2016-08-26

    A general method for the synthesis of [(18) F]difluoromethylarenes from [(18) F]fluoride for radiopharmaceutical discovery is reported. The method is practical, operationally simple, tolerates a wide scope of functional groups, and enables the labeling of a variety of arenes and heteroarenes with radiochemical yields (RCYs, not decay-corrected) from 10 to 60 %. The (18) F-fluorination precursors are readily prepared from aryl chlorides, bromides, iodides, and triflates. Seven (18) F-difluoromethylarene drug analogues and radiopharmaceuticals including Claritin, fluoxetine (Prozac), and [(18) F]DAA1106 were synthesized to show the potential of the method for applications in PET radiopharmaceutical design. PMID:27491349

  7. Highly Efficient N-Monomethylation of Primary Aryl Amines

    Institute of Scientific and Technical Information of China (English)

    PENG, Yiyuan; LIU, Hanliang; TANG, Min; CAI, Lisheng; PIKE, Victor

    2009-01-01

    A highly efficient method for specific synthesis of N-monomethylarylamines is presented. Anilines were treated with acetic anhydride and triethylamine in dry CH2Cl2 to give the corresponding acetamides. The subsequent N-monomethylation of acetyl aryl amines with methyl iodide and Nail in THF introduced methyl group. Acid hy- drolysis of the N-methyl acetanilides in ethylene glycol generated the corresponding N-methyl-N-aryi amines in high yields. This method was also used to synthesize (E)-2-bromo-5-(4-methylaminostyryl)pyridine that may be useful as an amyloid imaging agent for Alzheimer's disease.

  8. Catalytic arylation methods from the academic lab to industrial processes

    CERN Document Server

    Burke, Anthony J

    2014-01-01

    A current view of the challenging field of catalytic arylation reactions. Clearly structured, the chapters in this one-stop resource are arranged according to the reaction type, and focus on novel, efficient and sustainable processes, rather than the well-known and established cross-coupling methods.The entire contents are written by two authors with academic and industrial expertise to ensure consistent coverage of the latest developments in the field, as well as industrial applications, such as C-H activation, iron and gold-catalyzed coupling reactions, cycloadditions or novel methodologies

  9. Functionalization of Rhenium Aryl Bonds by O-Atom Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Bischof, Steven M. [Scripps Research Inst., Jupiter, FL (United States); Cheng, Mu-Jeng [California Inst. of Technology (CalTech), Pasadena, CA (United States); Nielsen, Robert J. [California Inst. of Technology (CalTech), Pasadena, CA (United States); Gunnoe, T. Brent [Univ. of Virginia, Charlottesville, VA (United States); Goddard, William A. [California Inst. of Technology (CalTech), Pasadena, CA (United States); Periana, Roy A. [Scripps Research Inst., Jupiter, FL (United States)

    2011-03-29

    Aryltrioxorhenium (ArReO3) has been demonstrated to show rapid oxy-functionalization upon reaction with O-atom donors, YO, to selectively generate the corresponding phenols in near quantitative yields. 18O-Labeling experiments show that the oxygen in the products is exclusively from YO. DFT studies reveal a 10.7 kcal/mol barrier (Ar = Ph) for oxy-functionalization with H2O2 via a Baeyer-Villiger type mechanism involving nucleophilic attack of the aryl group on an electrophilic oxygen of YO coordinated to rhenium.

  10. Synthetic studies towards putative yuremamine using an iterative C(sp(3))-H arylation strategy.

    Science.gov (United States)

    Calvert, Matthew B; Sperry, Jonathan

    2016-06-28

    An overview of an iterative, 8-aminoquinoline (AQ)-directed C(sp(3))-H arylation strategy towards the pyrroloindole structure initially assigned to the alkaloid yuremamine is described. During initial efforts using a model indane system, it was discovered that the iodoresorcinol unit was not a viable C(sp(3))-H arylation partner when masked as its dimethyl ether but upon switching to a MOM group, the ether oxygen served to stabilise the high valent Pd intermediate during the reaction, thus promoting reductive elimination and leading to acceptable yields of the C(sp(3))-H arylation product. The second C(sp(3))-H arylation with an iodopyrogallol gave a 1,3-diarylated model yuremamine system possessing the desired 1,3-cis relationship. When the successful model studies were applied to a pyrroloindole system in pursuit of yuremamine, it became apparent that C9 underwent competing C(sp(2))-H arylation if left vacant, but installing a tryptamine side chain at this site prevented the desired C(sp(3))-H arylation from occurring altogether. However, a C9-methyl pyrroloindole underwent iterative C(sp(3))-H arylation at C1 with an iodoresorcinol followed by C3 with an iodopyrogallol to give a diarylated product with the aryl groups in the undesired 1,3-trans-relationship, arising from epimerisation at C1 during the second C(sp(3))-H arylation event. Although the synthesis of putative yuremamine was not accomplished, several findings are disclosed that will serve as useful additions to the burgeoning field of directed C(sp(3))-H arylations and related C-H functionalization reactions. PMID:26891188

  11. HYDROCARBONS DIAGNOSTIC OF POLLUTED SOILS

    Directory of Open Access Journals (Sweden)

    Mohamed Arad

    2010-12-01

    Full Text Available Petroleum hydrocarbons are known as carcinogenic and may contaminate the environment (water, air and soil. In this study, a diagnostic of polluted soils by petroleum hydrocarbons is carried out in order to know the effect of their accumulation as well as their behavior in time. The aging factor, a source of significant changing in hydrocarbon behavior, is integrated on two sites of an industrial refinery as experimental samples. The first site is recently polluted by hydrocarbons while the second is a previously polluted site.The results indicate that the concentration of hydrocarbons on the surface of the first site is greater and remains stable in time, as for the second site, hydrocarbons concentration on the surface is also important and undergoes a weak reduction. At a depth of one meter hydrocarbons exist at a greater concentration. This shows that obstinate hydrocarbons are an environmental danger for fauna and flora.

  12. Practical synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides via conventional and decarboxylative copper-free Sonogashira coupling reactions

    Directory of Open Access Journals (Sweden)

    Andrea Caporale

    2014-02-01

    Full Text Available Two efficient protocols for the palladium-catalyzed synthesis of aryl-2-methyl-3-butyn-2-ols from aryl bromides in the absence of copper were developed. A simple catalytic system consisting of Pd(OAc2 and P(p-tol3 using DBU as the base and THF as the solvent was found to be highly effective for the coupling reaction of 2-methyl-3-butyn-2-ol (4 with a wide range of aryl bromides in good to excellent yields. Analogously, the synthesis of aryl-2-methyl-3-butyn-2-ols was performed also through the decarboxylative coupling reaction of 4-hydroxy-4-methyl-2-pentynoic acid with aryl bromides, using a catalyst containing Pd(OAc2 in combination with SPhos or XPhos in the presence of tetra-n-butylammonium fluoride (TBAF as the base and THF as the solvent. Therefore, new efficient approaches to the synthesis of terminal acetylenes from widely available aryl bromides rather than expensive iodides and using 4 or propiolic acid rather than TMS-acetylene as inexpensive alkyne sources are described.

  13. Degradation of recalcitrant aliphatic and aromatic hydrocarbons by a dioxin-degrader Rhodococcus sp. strain p52.

    Science.gov (United States)

    Yang, Hai-Yan; Jia, Rui-Bao; Chen, Bin; Li, Li

    2014-09-01

    This study investigates the ability of Rhodococcus sp. strain p52, a dioxin degrader, to biodegrade petroleum hydrocarbons. Strain p52 can use linear alkanes (tetradecane, tetracosane, and dotriacontane), branched alkane (pristane), and aromatic hydrocarbons (naphthalene and phenanthrene) as sole carbon and energy sources. Specifically, the strain removes 85.7 % of tetradecane within 48 h at a degradation rate of 3.8 mg h(-1) g(-1) dry cells, and 79.4 % of tetracosane, 66.4 % of dotriacontane, and 63.9 % of pristane within 9-11 days at degradation rates of 20.5, 14.7, and 20.3 mg day(-1) g(-1) dry cells, respectively. Moreover, strain p52 consumes 100 % naphthalene and 55.3 % phenanthrene within 9-11 days at respective degradation rates of 16 and 12.9 mg day(-1) g(-1) dry cells. Metabolites of the petroleum hydrocarbons by strain p52 were analyzed. Genes encoding alkane-hydroxylating enzymes, including cytochrome P450 (CYP450) enzyme (CYP185) and two alkane-1-monooxygenases, were amplified by polymerase chain reaction. The transcriptional activities of these genes in the presence of petroleum hydrocarbons were detected by reverse transcription-polymerase chain reaction. The results revealed potential of strain p52 to degrade petroleum hydrocarbons. PMID:24859700

  14. Selecting hydrocarbon rocket propulsion technology

    Science.gov (United States)

    Martin, J. A.

    1986-01-01

    Past studies have shown that the dry weight of future earth-to-orbit vehicles can be reduced by the combined use of hydrogen and hydrocarbon propulsion compared to all-hydrogen propulsion. This paper shows that the use of certain hydrocarbon engines with hydrogen engines produces the lowest vehicle dry mass. These hydrocarbon engines use propane or RP-1 fuel, hydrogen cooling, and hydrogen-rich gas generators. Integration of the hydrogen and hydrocarbon nozzles is also beneficial.

  15. HYDROCARBONS DIAGNOSTIC OF POLLUTED SOILS

    OpenAIRE

    Mohamed Arad; Abdelkader Anouzla; Mohamed Safi; Salah Souabi; Hicham Rhbal

    2010-01-01

    Petroleum hydrocarbons are known as carcinogenic and may contaminate the environment (water, air and soil). In this study, a diagnostic of polluted soils by petroleum hydrocarbons is carried out in order to know the effect of their accumulation as well as their behavior in time. The aging factor, a source of significant changing in hydrocarbon behavior, is integrated on two sites of an industrial refinery as experimental samples. The first site is recently polluted by hydrocarbons while the s...

  16. Optrode for sensing hydrocarbons

    Science.gov (United States)

    Miller, Holly; Milanovich, Fred P.; Hirschfeld, Tomas B.; Miller, Fred S.

    1987-01-01

    A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons.

  17. A chicory cytochrome P450 mono-oxygenase CYP71AV8 for the oxidation of (+)-valencene

    NARCIS (Netherlands)

    Cankar, K.; Houwelingen, van A.M.M.L.; Bosch, H.J.; Sonke, Th.; Bouwmeester, H.J.; Beekwilder, M.J.

    2011-01-01

    Chicory (Cichorium intybus L.), which is known to have a variety of terpene-hydroxylating activities, was screened for a P450 mono-oxygenase to convert (+)-valencene to (+)-nootkatone. A novel P450 cDNA was identified in a chicory root EST library. Co-expression of the enzyme with a valencene syntha

  18. 3-Ketosteroid 9 alpha-hydroxylase enzymes : Rieske non-heme monooxygenases essential for bacterial steroid degradation

    NARCIS (Netherlands)

    Petrusma, Mirjan; van der Geize, Robert; Dijkhuizen, Lubbert

    2014-01-01

    Various micro-organisms are able to use sterols/steroids as carbon- and energy sources for growth. 3-Ketosteroid 9 alpha-hydroxylase (KSH), a two component Rieske non-heme monooxygenase comprised of the oxygenase KshA and the reductase KshB, is a key-enzyme in bacterial steroid degradation. It initi

  19. Comparative-Analysis of Gene-Sequences Encoding Ammonia Monooxygenase of Nitrosospira Sp Ahb1 and Nitrosolobus- Multiformis C-71

    NARCIS (Netherlands)

    Rotthauwe, J.H.; De Boer, W.; Liesack, W.

    1995-01-01

    DNA encoding ammonia monooxygenase from two phylogenetically related autotrophic nitrifying bacteria, Nitrosospira sp. AHB1 and Nitrosolobus multiformis C-71, was amplified by PCR, The resulting products were cloned into the vector pCR-Script, A continuous region of DNA of about 1.5 kb for strain AH

  20. Whole genome co-expression analysis of soybean cytochrome P450 genes identifies nodulation-specific P450 monooxygenases

    Science.gov (United States)

    Cytochrome P450 monooxygenases (P450s) catalyze oxidation of various substrates using oxygen and NAD(P)H. Plant P450s are involved in the biosynthesis of primary and secondary metabolites performing diverse biological functions. The recent availability of soybean genome sequence allows us to ident...

  1. Method and apparatus for pyrolytically cracking hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Skraba, F.W.

    1992-06-09

    This patent describes a method for pyrolytically cracking a hydrocarbon vapor feedstock in a hydrocarbon pyrolysis unit to produce an olefinic hydrocarbon product. It comprises contacting a hydrocarbon vapor feedstock, then, cracking the hydrocarbon vapor feedstock in the presence of the vaporized water in a pyrolysis furnace to produce a furnace effluent stream comprised of an olefinic hydrocarbon product gas and the vaporized water.

  2. Apparatus and methods for hydrocarbon extraction

    Energy Technology Data Exchange (ETDEWEB)

    Bohnert, George W.; Verhulst, Galen G.

    2016-04-26

    Systems and methods for hydrocarbon extraction from hydrocarbon-containing material. Such systems and methods relate to extracting hydrocarbon from hydrocarbon-containing material employing a non-aqueous extractant. Additionally, such systems and methods relate to recovering and reusing non-aqueous extractant employed for extracting hydrocarbon from hydrocarbon-containing material.

  3. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    Science.gov (United States)

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  4. Using tyrosinase as a monophenol monooxygenase: A combined strategy for effective inhibition of melanin formation.

    Science.gov (United States)

    Lee, Sang-Hyuk; Baek, Kiheon; Lee, Ju-Eun; Kim, Byung-Gee

    2016-04-01

    Tyrosinase is a binuclear copper-containing metalloprotein that leads the fast and regio-selective o-hydroxylation of monophenols to o-diphenols. However, the subsequent second oxidation to produce o-quinones, i.e., melanin precursors, from the o-diphenols has restricted its use to the production of functional o-diphenol derivatives. Herein, we present a combined strategy for the effective inhibition of melanin formation in tyrosinase reaction, which allows the use of tyrosinase as a monophenol monooxygenase. The o-diphenolic products were protected from being oxidized in the tyrosinase reaction by borate ions and L-ascorbic acid (LAA). Borate-o-diphenol complexes were favorable formed at high pH and consequentially protected the o-diphenolic products from the catecholase activity of tyrosinase. LAA not only directly reduced the byproduct, o-quinones, into o-diphenols but also assisted the completion of the tyrosinase reaction cycle by removing a hydroxyl group attached to the copper metal cluster at the active site of the met-form tyrosinase. The regio-selective o-hydroxylation of 7,4'-dihydroxyisoflavone (daidzein) to produce 7,3',4'-trihydroxyisoflavone (3'-ODI) was successfully carried out by whole E. coli cell biotransformation with heterologously expressed tyrosinase from Bacillus megaterium. The yield of this o-hydroxylation of 5 mM daidzein in one-pot 400 mL reaction was ca. 100% in 90 min and the productivity was 16.3 mg 3'-ODI · L(-1)  ·  h(-1)  ·  DCW mg(-1) , which is considerably higher than that of other monooxygenases. The method effectively abolished melanin synthesis, so that the o-diphenolic product remained stable without enzyme inactivation. Other monophenolic phytochemicals such as resveratrol and genistein could be subjected to the same strategy. After 1 h, 1 mM of genistein and resveratrol were both converted to orobol and piceatannol, respectively, with ca. 95% conversion yield. These results support the strong

  5. Superconductivity in aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Kubozono, Yoshihiro, E-mail: kubozono@cc.okayama-u.ac.jp [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Japan Science and Technology Agency, ACT-C, Kawaguchi 332-0012 (Japan); Goto, Hidenori; Jabuchi, Taihei [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Yokoya, Takayoshi [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Research Center of New Functional Materials for Energy Production, Storage and Transport, Okayama University, Okayama 700-8530 (Japan); Kambe, Takashi [Department of Physics, Okayama University, Okayama 700-8530 (Japan); Sakai, Yusuke; Izumi, Masanari; Zheng, Lu; Hamao, Shino; Nguyen, Huyen L.T. [Research Laboratory for Surface Science, Okayama University, Okayama 700-8530 (Japan); Sakata, Masafumi; Kagayama, Tomoko; Shimizu, Katsuya [Center of Science and Technology under Extreme Conditions, Osaka University, Osaka 560-8531 (Japan)

    2015-07-15

    Highlights: • Aromatic superconductor is one of core research subjects in superconductivity. Superconductivity is observed in certain metal-doped aromatic hydrocarbons. Some serious problems to be solved exist for future advancement of the research. This article shows the present status of aromatic superconductors. - Abstract: ‘Aromatic hydrocarbon’ implies an organic molecule that satisfies the (4n + 2) π-electron rule and consists of benzene rings. Doping solid aromatic hydrocarbons with metals provides the superconductivity. The first discovery of such superconductivity was made for K-doped picene (K{sub x}picene, five benzene rings). Its superconducting transition temperatures (T{sub c}’s) were 7 and 18 K. Recently, we found a new superconducting K{sub x}picene phase with a T{sub c} as high as 14 K, so we now know that K{sub x}picene possesses multiple superconducting phases. Besides K{sub x}picene, we discovered new superconductors such as Rb{sub x}picene and Ca{sub x}picene. A most serious problem is that the shielding fraction is ⩽15% for K{sub x}picene and Rb{sub x}picene, and it is often ∼1% for other superconductors. Such low shielding fractions have made it difficult to determine the crystal structures of superconducting phases. Nevertheless, many research groups have expended a great deal of effort to make high quality hydrocarbon superconductors in the five years since the discovery of hydrocarbon superconductivity. At the present stage, superconductivity is observed in certain metal-doped aromatic hydrocarbons (picene, phenanthrene and dibenzopentacene), but the shielding fraction remains stubbornly low. The highest priority research area is to prepare aromatic superconductors with a high superconducting volume-fraction. Despite these difficulties, aromatic superconductivity is still a core research target and presents interesting and potentially breakthrough challenges, such as the positive pressure dependence of T{sub c} that is clearly

  6. Membrane separation of hydrocarbons

    Science.gov (United States)

    Chang, Y. Alice; Kulkarni, Sudhir S.; Funk, Edward W.

    1986-01-01

    Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture through a polymeric membrane. The membrane which is utilized to effect the separation comprises a polymer which is capable of maintaining its integrity in the presence of hydrocarbon compounds and which has been modified by being subjected to the action of a sulfonating agent. Sulfonating agents which may be employed will include fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, etc., the surface or bulk modified polymer will contain a degree of sulfonation ranging from about 15 to about 50%. The separation process is effected at temperatures ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psig.

  7. Mild Palladium-Catalyzed Cyanation of (Hetero)aryl Halides and Triflates in Aqueous Media

    OpenAIRE

    Cohen, Daniel T.; Buchwald, Stephen L.

    2015-01-01

    A mild, efficient, and low-temperature palladium-catalyzed cyanation of (hetero)aryl halides and triflates is reported. Previous palladium-catalyzed cyanations of (hetero)aryl halides have required higher temperatures to achieve good catalytic activity. This current reaction allows the cyanation of a general scope of (hetero)aryl halides and triflates at 2–5 mol % catalyst loadings with temperatures ranging from rt to 40 °C. This mild method was applied to the synthesis of lersivirine, a reve...

  8. Aryl-aldehyde formation in fungal polyketides: Discovery and characterization of a distinct biosynthetic mechanism

    OpenAIRE

    Wang, Meng; Beissner, Mirko; Zhao, Huimin

    2014-01-01

    Aryl-aldehydes are a common feature in fungal polyketides, which are considered to be exclusively generated by the R domain of non-reducing polyketide synthases (NR-PKSs). However, by cloning and heterologous expression of two cryptic NR-PKS and non-ribosomal peptide synthase (NRPS)-like genes from Aspergillus terreus in Saccharomyces cerevisiae, we discovered a distinct mechanism for aryl-aldehyde formation in which a NRPS-like protein activates and reduces an aryl-acid produced by the accom...

  9. Unusual selectivity-determining factors in the phosphine-free Heck arylation of allyl ethers

    DEFF Research Database (Denmark)

    Ambrogio, I.; Fabrizi, G.; Cacchi, S.;

    2008-01-01

    tolerates a variety of functional groups, including ether, amide, alcohol, aldehyde, ketone, ester, cyano, carboxylic acid, and nitro groups. Ortho-substituted arylating agents afforded moderate yields in some cases, though good to high yields were obtained with o-iodotoluene, iodovanillin, and 1......The Heck reaction of aryl iodides and bromides with allyl ethers has been investigated. Using phosphinefree Pd(OAc)(2) in DNIF at 90 degrees C in the presence of Bu4NOAc, the reaction gave cinnamyl derivatives, usually in good to high yields, with a wide range of aryl halides. The reaction...

  10. Well-Defined Copper(I) Fluoroalkoxide Complexes for Trifluoroethoxylation of Aryl and Heteroaryl Bromides

    KAUST Repository

    Huang, Ronglu

    2015-03-17

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Copper(I) fluoroalkoxide complexes bearing dinitrogen ligands were synthesized and the structure and reactivity of the complexes toward trifluoroethoxylation, pentafluoropropoxylation, and tetrafluoropropoxylation of aryl and heteroaryl bromides were investigated. Efficiency drive: A series of copper(I) fluoroalkoxide complexes bearing N,N ligands have been prepared and structurally characterized. These well-defined complexes serve as efficient reagents for the fluoroalkoxylation of aryl and heteroaryl bromides to produce a wide range of trifluoroethyl, pentafluoropropyl, and tetrafluoropropyl (hetero)aryl ethers in good to excellent yields.

  11. Mechanistic Considerations in the Synthesis of 2-Aryl-Indole Analogues under Bischler-Mohlau Conditions

    Science.gov (United States)

    MacDonough, Matthew T.; Shi, Zhe; Pinney, Kevin G.

    2015-01-01

    Mechanistic insight into the pathway of the Bischler-Mohlau indole formation reaction is provided by isotopic labeling utilizing judicious incorporation of a 13C atom within the α-bromoacetophenone analogue reactant. The resulting rearranged 2-aryl indole, isolated as the major product, located the 13C isotope label at the methine carbon of the fused five-membered heterocyclic ring, which suggested that the mechanistic pathway of cyclization, in this specific example, required two equivalents of the aniline analogue reactant partner and proceeded through an imine intermediate rather than by direct formation of the corresponding 3-aryl indole accompanied by a concomitant 1,2-aryl shift rearrangement. PMID:26973358

  12. Enantioselective cross-coupling of meso-epoxides with aryl halides.

    Science.gov (United States)

    Zhao, Yang; Weix, Daniel J

    2015-03-11

    The first enantioselective cross-electrophile coupling of aryl bromides with meso-epoxides to form trans-β-arylcycloalkanols is presented. The reaction is catalyzed by a combination of (bpy)NiCl2 and a chiral titanocene under reducing conditions. Yields range from 57 to 99% with 78-95% enantiomeric excess. The 30 examples include a variety of functional groups (ether, ester, ketone, nitrile, ketal, trifluoromethyl, sulfonamide, sulfonate ester), both aryl and vinyl halides, and five- to seven-membered rings. The intermediacy of a carbon radical is strongly suggested by the conversion of cyclooctene monoxide to an aryl [3.3.0]bicyclooctanol. PMID:25716775

  13. Direct hydrocarbon fuel cells

    Science.gov (United States)

    Barnett, Scott A.; Lai, Tammy; Liu, Jiang

    2010-05-04

    The direct electrochemical oxidation of hydrocarbons in solid oxide fuel cells, to generate greater power densities at lower temperatures without carbon deposition. The performance obtained is comparable to that of fuel cells used for hydrogen, and is achieved by using novel anode composites at low operating temperatures. Such solid oxide fuel cells, regardless of fuel source or operation, can be configured advantageously using the structural geometries of this invention.

  14. Rv1894c Is a Novel Hypoxia-Induced Nitronate Monooxygenase Required for Mycobacterium tuberculosis Virulence

    Science.gov (United States)

    Klinkenberg, Lee G.; Karakousis, Petros C.

    2013-01-01

    Tuberculosis is difficult to cure, requiring a minimum of 6 months of treatment with multiple antibiotics. Small numbers of organisms are able to tolerate the antibiotics and persist in the lungs of infected humans, but they still require some metabolic activity to survive. We studied the role of the hypoxia-induced Rv1894c gene in Mycobacterium tuberculosis virulence in guinea pigs, which develop hypoxic, necrotic granulomas histologically resembling those in humans and found this gene to be necessary for full bacillary growth and survival. We characterized the function of the encoded enzyme as a nitronate monooxygenase, which is needed to prevent the buildup of toxic products during hypoxic metabolism and is negatively regulated by the transcriptional repressor KstR. Future studies will focus on developing small-molecule inhibitors that target Rv1894c and its homologs, with the goal of killing persistent bacteria, thereby shortening the time needed to treat tuberculosis. PMID:23408846

  15. Nitronate monooxygenase, a model for anionic flavin semiquinone intermediates in oxidative catalysis.

    Science.gov (United States)

    Gadda, Giovanni; Francis, Kevin

    2010-01-01

    Nitronate monooxygenase (NMO), formerly referred to as 2-nitropropane dioxygenase, is an FMN-dependent enzyme that uses molecular oxygen to oxidize (anionic) alkyl nitronates and, in the case of the enzyme from Neurospora crassa, (neutral) nitroalkanes to the corresponding carbonyl compounds and nitrite. Over the past 5 years, a resurgence of interest on the enzymology of NMO has driven several studies aimed at the elucidation of the mechanistic and structural properties of the enzyme. This review article summarizes the knowledge gained from these studies on NMO, which has been emerging as a model system for the investigation of anionic flavosemiquinone intermediates in the oxidative catalysis of organic molecules, and for the effect that branching of reaction intermediates has on both the kinetic parameters and isotope effects associated with enzymatic reactions. A comparison of the catalytic mechanism of NMO with other flavin-dependent enzymes that oxidize nitroalkane and nitronates is also presented. PMID:19577534

  16. Interactions of a fungal lytic polysaccharide monooxygenase with β-glucan substrates and cellobiose dehydrogenase

    DEFF Research Database (Denmark)

    Courtade, Gaston; Wimmer, Reinhard; Røhr, Åsmund K;

    2016-01-01

    Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that catalyze oxidative cleavage of glycosidic bonds using molecular oxygen and an external electron donor. We have used NMR and isothermal titration calorimetry (ITC) to study the interactions of a broad-specificity fungal...... LPMO, NcLPMO9C, with various substrates and with cellobiose dehydrogenase (CDH), a known natural supplier of electrons. The NMR studies revealed interactions with cellohexaose that center around the copper site. NMR studies with xyloglucans, i.e., branched β-glucans, showed an extended binding surface...... cyanide, a mimic of O2 (-) Studies with CDH and its isolated heme b cytochrome domain unambiguously showed that the cytochrome domain of CDH interacts with the copper site of the LPMO and that substrate binding precludes interaction with CDH. Apart from providing insights into enzyme...

  17. Structure, dynamics, and function of the monooxygenase P450 BM-3: insights from computer simulations studies

    International Nuclear Information System (INIS)

    The monooxygenase P450 BM-3 is a NADPH-dependent fatty acid hydroxylase enzyme isolated from soil bacterium Bacillus megaterium. As a pivotal member of cytochrome P450 superfamily, it has been intensely studied for the comprehension of structure–dynamics–function relationships in this class of enzymes. In addition, due to its peculiar properties, it is also a promising enzyme for biochemical and biomedical applications. However, despite the efforts, the full understanding of the enzyme structure and dynamics is not yet achieved. Computational studies, particularly molecular dynamics (MD) simulations, have importantly contributed to this endeavor by providing new insights at an atomic level regarding the correlations between structure, dynamics, and function of the protein. This topical review summarizes computational studies based on MD simulations of the cytochrome P450 BM-3 and gives an outlook on future directions. (topical review)

  18. Kynurenine 3-monooxygenase polymorphisms: relevance for kynurenic acid synthesis in patients with schizophrenia and healthy controls

    DEFF Research Database (Denmark)

    Holtze, Maria; Saetre, Peter; Engberg, Göran; Schwieler, Lilly; Werge, Thomas; Andreassen, Ole A; Hall, Håkan; Terenius, Lars; Agartz, Ingrid; Jönsson, Erik G; Schalling, Martin; Erhardt, Sophie

    2012-01-01

    activity of kynurenine 3-monooxygenase (KMO), the enzyme converting kynurenine to 3-hydroxykynurenine. Methods: We analyzed the association between KMO gene polymorphisms and CSF concentrations of KYNA in patients with schizophrenia and healthy controls. Fifteen single nucleotide polymorphisms (SNPs) were...... selected covering KMO and were analyzed in UNPHASED. Results: We included 17 patients with schizophrenia and 33 controls in our study. We found an association between a KMO SNP (rs1053230), encoding an amino acid change of potential importance for substrate interaction, and CSF concentrations of KYNA....... Limitations: Given the limited sample size, the results are tentative until replication. Conclusion: Our results suggest that the nonsynonymous KMO SNP rs1053230 influences CSF concentrations of KYNA....

  19. Structure, dynamics, and function of the monooxygenase P450 BM-3: insights from computer simulations studies

    Science.gov (United States)

    Roccatano, Danilo

    2015-07-01

    The monooxygenase P450 BM-3 is a NADPH-dependent fatty acid hydroxylase enzyme isolated from soil bacterium Bacillus megaterium. As a pivotal member of cytochrome P450 superfamily, it has been intensely studied for the comprehension of structure-dynamics-function relationships in this class of enzymes. In addition, due to its peculiar properties, it is also a promising enzyme for biochemical and biomedical applications. However, despite the efforts, the full understanding of the enzyme structure and dynamics is not yet achieved. Computational studies, particularly molecular dynamics (MD) simulations, have importantly contributed to this endeavor by providing new insights at an atomic level regarding the correlations between structure, dynamics, and function of the protein. This topical review summarizes computational studies based on MD simulations of the cytochrome P450 BM-3 and gives an outlook on future directions.

  20. Comparative Genomics of the Ubiquitous, Hydrocarbon-degrading Genus Marinobacter

    Science.gov (United States)

    Singer, E.; Webb, E.; Edwards, K. J.

    2012-12-01

    The genus Marinobacter is amongst the most ubiquitous in the global oceans and strains have been isolated from a wide variety of marine environments, including offshore oil-well heads, coastal thermal springs, Antarctic sea water, saline soils and associations with diatoms and dinoflagellates. Many strains have been recognized to be important hydrocarbon degraders in various marine habitats presenting sometimes extreme pH or salinity conditions. Analysis of the genome of M. aquaeolei revealed enormous adaptation versatility with an assortment of strategies for carbon and energy acquisition, sensation, and defense. In an effort to elucidate the ecological and biogeochemical significance of the Marinobacters, seven Marinobacter strains from diverse environments were included in a comparative genomics study. Genomes were screened for metabolic and adaptation potential to elucidate the strategies responsible for the omnipresence of the Marinobacter genus and their remedial action potential in hydrocarbon-polluted waters. The core genome predominantly encodes for key genes involved in hydrocarbon degradation, biofilm-relevant processes, including utilization of external DNA, halotolerance, as well as defense mechanisms against heavy metals, antibiotics, and toxins. All Marinobacter strains were observed to degrade a wide spectrum of hydrocarbon species, including aliphatic, polycyclic aromatic as well as acyclic isoprenoid compounds. Various genes predicted to facilitate hydrocarbon degradation, e.g. alkane 1-monooxygenase, appear to have originated from lateral gene transfer as they are located on gene clusters of 10-20% lower GC-content compared to genome averages and are flanked by transposases. Top ortholog hits are found in other hydrocarbon degrading organisms, e.g. Alcanivorax borkumensis. Strategies for hydrocarbon uptake encoded by various Marinobacter strains include cell surface hydrophobicity adaptation via capsular polysaccharide biosynthesis and attachment

  1. Identification of a flavin-containing S-oxygenating monooxygenase involved in alliin biosynthesis in garlic.

    Science.gov (United States)

    Yoshimoto, Naoko; Onuma, Misato; Mizuno, Shinya; Sugino, Yuka; Nakabayashi, Ryo; Imai, Shinsuke; Tsuneyoshi, Tadamitsu; Sumi, Shin-ichiro; Saito, Kazuki

    2015-09-01

    S-Alk(en)yl-l-cysteine sulfoxides are cysteine-derived secondary metabolites highly accumulated in the genus Allium. Despite pharmaceutical importance, the enzymes that contribute to the biosynthesis of S-alk-(en)yl-l-cysteine sulfoxides in Allium plants remain largely unknown. Here, we report the identification of a flavin-containing monooxygenase, AsFMO1, in garlic (Allium sativum), which is responsible for the S-oxygenation reaction in the biosynthesis of S-allyl-l-cysteine sulfoxide (alliin). Recombinant AsFMO1 protein catalyzed the stereoselective S-oxygenation of S-allyl-l-cysteine to nearly exclusively yield (RC SS )-S-allylcysteine sulfoxide, which has identical stereochemistry to the major natural form of alliin in garlic. The S-oxygenation reaction catalyzed by AsFMO1 was dependent on the presence of nicotinamide adenine dinucleotide phosphate (NADPH) and flavin adenine dinucleotide (FAD), consistent with other known flavin-containing monooxygenases. AsFMO1 preferred S-allyl-l-cysteine to γ-glutamyl-S-allyl-l-cysteine as the S-oxygenation substrate, suggesting that in garlic, the S-oxygenation of alliin biosynthetic intermediates primarily occurs after deglutamylation. The transient expression of green fluorescent protein (GFP) fusion proteins indicated that AsFMO1 is localized in the cytosol. AsFMO1 mRNA was accumulated in storage leaves of pre-emergent nearly sprouting bulbs, and in various tissues of sprouted bulbs with green foliage leaves. Taken together, our results suggest that AsFMO1 functions as an S-allyl-l-cysteine S-oxygenase, and contributes to the production of alliin both through the conversion of stored γ-glutamyl-S-allyl-l-cysteine to alliin in storage leaves during sprouting and through the de novo biosynthesis of alliin in green foliage leaves. PMID:26345717

  2. Flavin-dependent monooxygenases as a detoxification mechanism in insects: new insights from the arctiids (lepidoptera).

    Science.gov (United States)

    Sehlmeyer, Sven; Wang, Linzhu; Langel, Dorothee; Heckel, David G; Mohagheghi, Hoda; Petschenka, Georg; Ober, Dietrich

    2010-01-01

    Insects experience a wide array of chemical pressures from plant allelochemicals and pesticides and have developed several effective counterstrategies to cope with such toxins. Among these, cytochrome P450 monooxygenases are crucial in plant-insect interactions. Flavin-dependent monooxygenases (FMOs) seem not to play a central role in xenobiotic detoxification in insects, in contrast to mammals. However, the previously identified senecionine N-oxygenase of the arctiid moth Tyria jacobaeae (Lepidoptera) indicates that FMOs have been recruited during the adaptation of this insect to plants that accumulate toxic pyrrolizidine alkaloids. Identification of related FMO-like sequences of various arctiids and other Lepidoptera and their combination with expressed sequence tag (EST) data and sequences emerging from the Bombyx mori genome project show that FMOs in Lepidoptera form a gene family with three members (FMO1 to FMO3). Phylogenetic analyses suggest that FMO3 is only distantly related to lepidopteran FMO1 and FMO2 that originated from a more recent gene duplication event. Within the FMO1 gene cluster, an additional gene duplication early in the arctiid lineage provided the basis for the evolution of the highly specific biochemical, physiological, and behavioral adaptations of these butterflies to pyrrolizidine-alkaloid-producing plants. The genes encoding pyrrolizidine-alkaloid-N-oxygenizing enzymes (PNOs) are transcribed in the fat body and the head of the larvae. An N-terminal signal peptide mediates the transport of the soluble proteins into the hemolymph where PNOs efficiently convert pro-toxic pyrrolizidine alkaloids into their non-toxic N-oxide derivatives. Heterologous expression of a PNO of the generalist arctiid Grammia geneura produced an N-oxygenizing enzyme that shows noticeably expanded substrate specificity compared with the related enzyme of the specialist Tyria jacobaeae. The data about the evolution of FMOs within lepidopteran insects and the

  3. Form Follows Function: Structural and Catalytic Variation in the Class A Flavoprotein Monooxygenases

    Directory of Open Access Journals (Sweden)

    Graham R. Moran

    2012-11-01

    Full Text Available Flavoprotein monooxygenases (FPMOs exhibit an array of mechanistic solutions to a common chemical objective; the monooxygenation of a target substrate. Each FPMO efficiently couples reduction of a flavin cofactor by NAD(PH to oxygenation of the target substrate via a (hydroperoxyflavin intermediate. This purpose of this review is to describe in detail the Class A flavoprotein hydroxylases (FPMO in the context of the other FPMO classes (B–F. Both one and two component FPMOs are found in nature. Two-component enzymes require, in addition to the monooxygenase, the involvement of a reductase that first catalyzes the reduction of the flavin by NAD(PH. The Class A and B FPMOs are single-component and manage to orchestrate the same net reaction within a single peptide. The Class A enzymes have, by some considerable margin, the most complete research record. These enzymes use choreographed movements of the flavin ring that facilitate access of the organic substrates to the active site, provide a means for interaction of NADPH with the flavin, offer a mechanism to sequester the dioxygen reduction chemistry from solvent and a means to release the product. The majority of the discrete catalytic events of the catalytic cycle can be observed directly in exquisite detail using spectrophotometric kinetic methods and many of the key mechanistic conclusions are further supported by structural data. This review attempts to compile each of the key observations made for both paradigm and newly discovered examples of Class A FPMOs into a complete catalytic description of one enzymatic turnover.

  4. Monooxygenase, a novel beta-cypermethrin degrading enzyme from Streptomyces sp.

    Directory of Open Access Journals (Sweden)

    Shaohua Chen

    Full Text Available The widely used insecticide beta-cypermethrin has become a public concern because of its environmental contamination and toxic effects on mammals. In this study, a novel beta-cypermethrin degrading enzyme designated as CMO was purified to apparent homogeneity from a Streptomyces sp. isolate capable of utilizing beta-cypermethrin as a growth substrate. The native enzyme showed a monomeric structure with a molecular mass of 41 kDa and pI of 5.4. The enzyme exhibited the maximal activity at pH 7.5 and 30°C. It was fairly stable in the pH range from 6.5-8.5 and at temperatures below 10°C. The enzyme activity was significantly stimulated by Fe(2+, but strongly inhibited by Ag(+, Al(3+, and Cu(2+. The enzyme catalyzed the degradation of beta-cypermethrin to form five products via hydroxylation and diaryl cleavage. A novel beta-cypermethrin detoxification pathway was proposed based on analysis of these products. The purified enzyme was identified as a monooxygenase by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry analysis (MALDI-TOF-MS and N-terminal protein sequencing. Given that all the characterized pyrethroid-degrading enzymes are the members of hydrolase family, CMO represents the first pyrethroid-degrading monooxygenase identified from environmental microorganisms. Taken together, our findings depict a novel pyrethroid degradation mechanism and indicate that the purified enzyme may be a promising candidate for detoxification of beta-cypermethrin and environmental protection.

  5. A rapid quantitative activity assay shows that the Vibrio cholerae colonization factor GbpA is an active lytic polysaccharide monooxygenase

    NARCIS (Netherlands)

    Loose, Jennifer S. M.; Forsberg, Zarah; Fraaije, Marco W.; Eijsink, Vincent G. H.; Vaaje-Kolstad, Gustav

    2014-01-01

    The discovery of the copper-dependent lytic polysaccharide monooxygenases (LPMOs) has revealed new territory for chemical and biochemical analysis. These unique mononuclear copper enzymes are abundant, suggesting functional diversity beyond their established roles in the depolymerization of biomass

  6. Fragmentation Mechanism of Trans-α-Aryl-β-enamino Esters

    Institute of Scientific and Technical Information of China (English)

    JIANG,Nan(蒋楠); WANG,Jian-Bo(王剑波); HE,Mei-Yu(何美玉)

    2002-01-01

    Electron impact-induced fragmentation mechanisms of trans-α-aryl-β-enamino esters were investigated using mass-analyzed ion kindetic energy (MIKE) spectrometry and high resolution accurate mass data. It was found that the main characteristic fragmentations of compounds studied were: an odd electron ion M+. - EtOH was formed by losing a neutral molecule of ethanol; and the skeletal rearrangements took place; and the ring opening reaction happened after losing a carbon monoxide;and the typical McLafferty rearrangement underwent in ester group. The cyclization reaction caused by losing neutral molecule of TsNH2 due to the ortho-effects of substituted group of aromatic ring was also observed.

  7. Chain-extended poly(aryl ether ketones)

    Energy Technology Data Exchange (ETDEWEB)

    Robeson, L.M.; Winslow, P.A.; Matzner, M.; Harris, J.E.; Maresca, L.M.

    1992-06-09

    This patent describes a process for preparing a poly(aryl ether ketone) polymer. It comprises reacting (n) moles of HAr H with (n + 1) moles of YCOAr{sub 1}COY under Friedel-Crafts polymerization conditions; reacting the product obtained with 2XAR{sub 2}H under Friedel-Crafts polymerization conditions; reacting the product obtained with HOAr{sub 3}OH in the presence of a base and an aprotic solvent; wherein Ar and Ar{sub 1} are divalent aromatic groups, Ar{sub 2} is a divalent aromatic group wherein the substituents X and CO are in para or ortho position relative to each other, Ar{sub 3} is a residue of a dihydric phenol, X and Y are halogen, n is an integer of 1 to 50 and X is one or greater.

  8. Novel aryl carbamate derivatives of metronidazole as potential antiamoebic agents.

    Science.gov (United States)

    Hayat, Faisal; Wahedi, Hussain Mustatab; Park, Seonghyeok; Tariq, Saba; Azam, Amir; Shin, Dongyun

    2016-01-01

    A series of novel aryl carbamate derivatives of metronidazole (MNZ) were designed, synthesized, and screened for antiamoebic activity. As compared to MNZ, most of the derivatives exhibited moderate to excellent activity against the HM1:IMSS strain of Entamoeba histolytica. Compounds 7, 14, 16, 19, and 21 exhibited the most promising antiamoebic activity with IC50 values of 0.24, 0.08, 0.26, 0.26, and 0.15 μM, respectively, compared to that of MNZ (1.78 μM). Moreover, from the toxicological studies of these compounds on human melanocytes, the melan-a cell line revealed that the potent compounds are nontoxic at concentrations ranging from 2.5 to 50 μM. PMID:26597858

  9. Aryl Polyphosphonates: Useful Halogen-Free Flame Retardants for Polymers

    Directory of Open Access Journals (Sweden)

    Li Chen

    2010-10-01

    Full Text Available Aryl polyphosphonates (ArPPN have been demonstrated to function in wide applications as flame retardants for different polymer materials, including thermosets, polycarbonate, polyesters and polyamides, particularly due to their satisfactory thermal stability compared to aliphatic flame retardants, and to their desirable flow behavior observed during the processing of polymeric materials. This paper provides a brief overview of the main developments in ArPPN and their derivatives for flame-retarding polymeric materials, primarily based on the authors’ research work and the literature published over the last two decades. The synthetic chemistry of these compounds is discussed along with their thermal stabilities and flame-retardant properties. The possible mechanisms of ArPPN and their derivatives containing hetero elements, which exhibit a synergistic effect with phosphorus, are also discussed.

  10. The nuclear aryl hydocarbon receptor is involved in regulation of DNA repair and cell survival following treatment with ionizing radiation.

    Science.gov (United States)

    Dittmann, K H; Rothmund, M C; Paasch, A; Mayer, C; Fehrenbacher, B; Schaller, M; Frauenstein, K; Fritsche, E; Haarmann-Stemmann, T; Braeuning, A; Rodemann, H P

    2016-01-01

    In the present study, we explored the role of the aryl hydrocarbon receptor (AhR) for γ-H2AX associated DNA repair in response to treatment with ionizing radiation. Ionizing radiation was able to stabilize AhR protein and to induce a nuclear translocation in a similar way as described for exposure to aromatic hydrocarbons. A comparable AhR protein stabilization was obtained by treatment with hydroxyl-nonenal-generated by radiation-induced lipid peroxidation. AhR knockdown resulted in significant radio-sensitization of both A549- and HaCaT cells. Under these conditions an increased amount of residual γ-H2AX foci and a delayed decline of γ-H2AX foci was observed. Knockdown of the co-activator ARNT, which is essential for transcriptional activation of AhR target genes, reduced AhR-dependent CYP1A expression in response to irradiation, but was without effect on the amount of residual γ-H2AX foci. Nuclear AhR was found in complex with γ-H2AX, DNA-PK, ATM and Lamin A. AhR and γ-H2AX form together nuclear foci, which disappear during DNA repair. Presence of nuclear AhR protein is associated with ATM activation and chromatin relaxation indicated by acetylation of histone H3. Taken together, we could show, that beyond the function as a transcription factor the nuclear AhR is involved in the regulation of DNA repair. Reduction of nuclear AhR inhibits DNA-double stand repair and radiosensitizes cells. First hints for its molecular mechanism suggest a role during ATM activation and chromatin relaxation, both essential for DNA repair. PMID:26520184

  11. Recent Developments of C-Aryl Glucoside SGLT2 Inhibitors.

    Science.gov (United States)

    Zhang, Yang; Liu, Zhao-Peng

    2016-03-16

    Sodium-glucose cotransporter 2 (SGLT2) is almost exclusively expressed in the proximal renal tubules. It is responsible for about 90% of the glucose reabsorption from tubular fluid. Selective inhibition of SGLT2 is expected to favor in the normalization of plasma glucose levels in T2DM patients through the prevention of renal glucose reabsorption and the promotion of glucose excretion from urine. Selective SGLT2 inhibitors have the merits to minimize the gastrointestinal side effects associated with SGLT1 inhibition, and selective SGLT2 inhibition may have a low risk of hypoglycemia. Since the C-aryl glucosides are metabolically more stable than the O-glucosides, numerous efforts have been made in the development of potent and selective C-aryl glucoside SGLT2 inhibitors, and a number of them are now used as anti-diabetes drugs in clinic or at various stages of clinical developments. Based on their structural features, in this review, these SGLT2 inhibitors are classified as three types: the phenyl/arylmethylphenyl C-glucosides, with an emphasis on the modifications on the proximal and/or the distal phenyl ring, and the spacer; the heteroarylmethylphenyl Cglucosides, with a replacement of the distal phenyl ring by a heterocycle like pyridazine, pyrimidine, thiophene and benzothiophene, thiazole, 1,3,4-thiadiazole, and triazolopyridinone; and the glucose-modified Caryl glucosides, including the glucose C-1 derived O-spiroketals, C-4 gem-difluoro analogues, C-5 and C-6 modified derivatives, dioxa-bicyclo[3.2.1]octane bridged ketals, the thioglucosides, and carbasugars. The structure-activity relationships (SARs) of each type along with their inhibitory potency against human SGLT2 and selectivity over human SGLT1 are discussed. PMID:26861002

  12. Room Temperature N-Arylation of 1,2,4-Triazoles under Ligand-Free Condition

    Directory of Open Access Journals (Sweden)

    Nikhil V. Suramwar

    2012-01-01

    Full Text Available A simple and efficient method for N-arylation of 1,2,4-triazole at room temperature was described by the use of predominant (111 facet CuO nanoparticles as a catalyst in ligand-free condition. The catalyst was recyclable, and a variety of substrates give N-arylation product in high yield with short period of reaction time. The wide scope of this catalyst led us to investigate transformations involving less-reactive nitrogen nucleophiles, such as imidazole and pyrazoles. We were pleased to find that various derivatives of azoles were effectively coupled with aryl iodide to afford the desired N-arylated product in excellent yield.

  13. Microwave activated synthesis of 2-aryl-quinazolin-4(3H)ones

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A highly efficient synthesis of 2-aryl-quinazolin-4(3H)ones was performed by one-pot oxidative heterocyclization of 2-aminobenzamide with aldehydes in the presence of potassium permanganate in dimethylacetamide under microwave irradiation.

  14. Synthesis of 1-Benzoyl-3-aryl-4-hydroxy-4-phenylimidazolidin-2-thiones

    Institute of Scientific and Technical Information of China (English)

    曾润生; 邹建平; 穆学军; 沈琪

    2003-01-01

    l-Benzoyl-3-aryl-4-hydroxy-4-phenylimidazolidin-2-thiones can be synthesized readily from the cyclization of 1-benzoyl-3-arylthioureas with bromine-acetophenone in the presence of excess triethylamiqe.

  15. An aromatic hydroxylation reaction catalyzed by a two-component FMN-dependent Monooxygenase. The ActVA-ActVB system from Streptomyces coelicolor.

    OpenAIRE

    Valton, Julien; Fontecave, Marc; Douki, Thierry; Kendrew, Steven G; Nivière, Vincent

    2006-01-01

    International audience The ActVA-ActVB system from Streptomyces coelicolor isatwo-component flavin-dependent monooxygenase that belongs to an emerging class of enzymes involved in various oxidation reactions in microorganisms. The ActVB component is a NADH:flavin oxidoreductase that provides a reduced FMN to the second component, ActVA the proper monooxygenase. In this work, we demonstrate that the ActVA-ActVB system catalyzes the aromatic monohydroxylation of dihydrokalafungin by molecula...

  16. The ammonia monooxygenase structural gene amoA as a functional marker: molecular fine-scale analysis of natural ammonia-oxidizing populations.

    OpenAIRE

    Rotthauwe, J H; K. P. WITZEL; Liesack, W.

    1997-01-01

    The naturally occurring genetic heterogeneity of autotrophic ammonia-oxidizing populations belonging to the beta subclass of the Proteobacteria was studied by using a newly developed PCR-based assay targeting a partial stretch of the gene which encodes the active-site polypeptide of ammonia monooxygenase (amoA). The PCR yielded a specific 491-bp fragment with all of the nitrifiers tested, but not with the homologous stretch of the particulate methane monooxygenase, a key enzyme of methane-oxi...

  17. An air-stable copper reagent for nucleophilic trifluoromethylthiolation of aryl halides

    KAUST Repository

    Weng, Zhiqiang

    2012-12-12

    A series of copper(I) trifluoromethyl thiolate complexes have been synthesized from the reaction of CuF2 with Me3SiCF 3 and S8 (see scheme; Cu red, F green, N blue, S yellow). These air-stable complexes serve as reagents for the efficient conversion of a wide range of aryl halides into the corresponding aryl trifluoromethyl thioethers in excellent yields. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Systematic Synthesis and Characterization of a Series of Tetra(5-aryl-2-thienyl)thiophenes

    OpenAIRE

    Muraoka, Hiroki; Tanifuji, Takanori; Ogawa, Satoshi

    2011-01-01

    We have succeeded in the synthesis of a series of tetra(5-aryl-2-thienyl)thiophenes as aryl-functionalized tetrathienylthiophenes. Characterization of these chemicals was performed by physical and spectroscopic means. The electrochemical properties were examined by cyclic voltammetry. The CV of all compounds showed that the redox behavior and potentials were controlled by the electronic effect of the p-substituted phenyl groups introduced at the outer α-positions on the four thiophene units l...

  19. Enantioselective CuH-Catalyzed Reductive Coupling of Aryl Alkenes and Activated Carboxylic Acids.

    Science.gov (United States)

    Bandar, Jeffrey S; Ascic, Erhad; Buchwald, Stephen L

    2016-05-11

    A new method for the enantioselective reductive coupling of aryl alkenes with activated carboxylic acid derivatives via copper hydride catalysis is described. Dual catalytic cycles are proposed, with a relatively fast enantioselective hydroacylation cycle followed by a slower diastereoselective ketone reduction cycle. Symmetrical aryl carboxyclic anhydrides provide access to enantioenriched α-substituted ketones or alcohols with excellent stereoselectivity and functional group tolerance. PMID:27121395

  20. Modular Isoquinoline Synthesis Using Catalytic Enolate Arylation and in Situ Functionalization

    OpenAIRE

    Pilgrim, Ben S.; Gatland, Alice E; McTernan, Charlie T.; Procopiou, Panayiotis A; Donohoe, Timothy J

    2013-01-01

    A methyl ketone, an aryl bromide, an electrophile, and ammonium chloride were combined in a four-component, three-step, and one-pot coupling procedure to furnish substituted isoquinolines in overall yields of up to 80%. This protocol utilizes the palladium catalyzed α-arylation reaction of an enolate, followed by in situ trapping with an electrophile, and aromatization with ammonium chloride. tert-Butyl cyanoacetate participated in a similar protocol; after functionalization and decarboxylati...

  1. 2-Alkyl-4-aryl-pyrimidine fused heterocycles as selective 5-HT2A antagonists.

    Science.gov (United States)

    Shireman, Brock T; Dvorak, Curt A; Rudolph, Dale A; Bonaventure, Pascal; Nepomuceno, Diane; Dvorak, Lisa; Miller, Kirsten L; Lovenberg, Timothy W; Carruthers, Nicholas I

    2008-03-15

    The synthesis and SAR for a novel series of 2-alkyl-4-aryl-tetrahydro-pyrido-pyrimidines and 2-alkyl-4-aryl-tetrahydro-pyrimido-azepines is described. Representative compounds were shown to be subtype selective 5-HT(2A) antagonists. Optimal placement of a basic nitrogen relative to the pyrimidine and the presence of a 4-fluorophenyl group in the pyrimidine 4-position was found to have a profound effect on affinity and selectivity. PMID:18282705

  2. Enantioselective Cross-Coupling of meso-Epoxides with Aryl Halides

    OpenAIRE

    Zhao, Yang; Weix, Daniel J.

    2015-01-01

    The first enantioselective cross-electrophile coupling of aryl bromides with meso-epoxides to form trans-β-arylcycloalkanols is presented. The reaction is catalyzed by a combination of (bpy)NiCl2 and a chiral titanocene under reducing conditions. Yields range from 57 to 99% with 78–95% enantiomeric excess. The 30 examples include a variety of functional groups (ether, ester, ketone, nitrile, ketal, trifluoromethyl, sulfonamide, sulfonate ester), both aryl and vinyl halides, and five- to seven...

  3. ULTRASOUND ASSISTED EFFICIENT AND GREENER ONE POT SYNTHESIS OF ARYL-14-H-DIBENZO [a,j]XANTHENE DERIVATIVES Ultraschall unterstützt effizientere und umweltfreundlichere ONE Eintopfsynthese ARYL-14-H-dibenzo [a, j] Xanthenderivate

    Directory of Open Access Journals (Sweden)

    Saurabh Puri, Balbir Kaur, Anupama Parmar and Harish Kumar

    2011-07-01

    Full Text Available Aryl-14-H-dibenzo[a,j]xanthenes have been synthesized in high yields from the condensation of aryl aldehydes and 2-napthol in presence of copper perchlorate hexahydrate as catalyst at room temperature gives aryl-14-H-dibenzo[a,j]xanthenes with excellent yields under ultrasound irradiation (35 kHz. This method has the advantages of high yield, simple methodology, greener and one pot procedure.

  4. Nickel-catalyzed cross-coupling reactions of o-carboranyl with aryl iodides: facile synthesis of 1-aryl-o-carboranes and 1,2-diaryl-o-carboranes.

    Science.gov (United States)

    Tang, Cen; Xie, Zuowei

    2015-06-22

    A nickel-catalyzed arylation at the carbon center of o-carborane cages has been developed, thus leading to the preparation of a series of 1-aryl-o-carboranes and 1,2-diaryl-o-carboranes in high yields upon isolation. This method represents the first example of transition metal catalyzed C,C'-diarylation by cross-coupling reactions of o-carboranyl with aryl iodides. PMID:25959849

  5. Synthesis and NMR Studies of (E)-1-Aryl-3-(2-pyrrolyl)-2-propenones and (E)-3-Aryl-1-(2-pyrrolyl)-2-propenones

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Insook; Jeoung, Eun Ji; Lee, Chang Kiu [Kangwon National Univ., Chuncheon (Korea, Republic of)

    2013-03-15

    Series of (E)-1-aryl-3-(2-pyrrolyl)-2-propenones, that were aldol condensation products between pyrrole-2-carbaldehyde and m- and p-substituted acetophenones, were prepared and their {sup 1}H and {sup 13}C NMR spectra were examined to obtain the information on the conformation of the enone system. Similar studies were carried out with (E)-3-aryl-1-(2-pyrrolyl)-2-propenones that were prepared from 2-acetylpyrrole and m- and p-substituted benzaldehydes. The substituent chemical shifts were studied by applying the Hammett relationship.

  6. A putative flavin-containing mono-oxygenase as a marker for certain defense and cell death pathways

    DEFF Research Database (Denmark)

    Olszak, Brian; Malinovsky, Frederikke Gro; Brodersen, Peter;

    2006-01-01

    mRNA of the putative Arabidopsis flavin mono-oxygenase encoded by At1g19250 (here designated AtFMO GenBank accession no. NM_101783 ) accumulated to high levels in the acd11 and lsd1 mutants that exhibit run-away cell death, but not in mutants with constitutive defense responses. AtFMO mRNA accumu......mRNA of the putative Arabidopsis flavin mono-oxygenase encoded by At1g19250 (here designated AtFMO GenBank accession no. NM_101783 ) accumulated to high levels in the acd11 and lsd1 mutants that exhibit run-away cell death, but not in mutants with constitutive defense responses. AtFMO m...

  7. Structural and biochemical impact of C8-aryl-guanine adducts within the NarI recognition DNA sequence: influence of aryl ring size on targeted and semi-targeted mutagenicity

    OpenAIRE

    Sproviero, Michael; Verwey, Anne M.R.; Rankin, Katherine M.; Witham, Aaron A.; Soldatov, Dmitriy V.; Richard A. Manderville; Fekry, Mostafa I.; Sturla, Shana J.; Sharma, Purshotam; Wetmore, Stacey D.

    2014-01-01

    Chemical mutagens with an aromatic ring system may be enzymatically transformed to afford aryl radical species that preferentially react at the C8-site of 2′-deoxyguanosine (dG). The resulting carbon-linked C8-aryl-dG adduct possesses altered biophysical and genetic coding properties compared to the precursor nucleoside. Described herein are structural and in vitro mutagenicity studies of a series of fluorescent C8-aryl-dG analogues that differ in aryl ring size and are representative of auth...

  8. Two isozymes of particulate methane monooxygenase with different methane oxidation kinetics are found in Methylocystis sp. strain SC2

    OpenAIRE

    Baani, Mohamed; Liesack, Werner

    2008-01-01

    Methane-oxidizing bacteria (methanotrophs) attenuate methane emission from major sources, such as wetlands, rice paddies, and landfills, and constitute the only biological sink for atmospheric methane in upland soils. Their key enzyme is particulate methane monooxygenase (pMMO), which converts methane to methanol. It has long been believed that methane at the trace atmospheric mixing ratio of 1.75 parts per million by volume (ppmv) is not oxidized by the methanotrophs cultured to date, but ra...

  9. Genome-Wide Annotation and Comparative Analysis of Cytochrome P450 Monooxygenases in Basidiomycete Biotrophic Plant Pathogens

    OpenAIRE

    Qhanya, Lehlohonolo Benedict; Matowane, Godfrey; Chen, Wanping; Sun, Yuxin; Letsimo, Elizabeth Mpholoseng; Parvez, Mohammad; Yu, Jae-Hyuk; Mashele, Samson Sitheni; Syed, Khajamohiddin

    2015-01-01

    Fungi are an exceptional source of diverse and novel cytochrome P450 monooxygenases (P450s), heme-thiolate proteins, with catalytic versatility. Agaricomycotina saprophytes have yielded most of the available information on basidiomycete P450s. This resulted in observing similar P450 family types in basidiomycetes with few differences in P450 families among Agaricomycotina saprophytes. The present study demonstrated the presence of unique P450 family patterns in basidiomycete biotrophic plant ...

  10. Fungal cellulose degradation by oxidative enzymes: from dysfunctional GH61 family to powerful lytic polysaccharide monooxygenase family

    OpenAIRE

    Morgenstern, Ingo; Powlowski, Justin; Tsang, Adrian

    2014-01-01

    Our understanding of fungal cellulose degradation has shifted dramatically in the past few years with the characterization of a new class of secreted enzymes, the lytic polysaccharide monooxygenases (LPMO). After a period of intense research covering structural, biochemical, theoretical and evolutionary aspects, we have a picture of them as wedge-like copper-dependent metalloenzymes that on reduction generate a radical copper-oxyl species, which cleaves mainly crystalline cellulose. The main ...

  11. Transcriptional regulation of the grape cytochrome P450 monooxygenase gene CYP736B expression in response to Xylella fastidiosa infection

    Directory of Open Access Journals (Sweden)

    Walker M Andrew

    2010-07-01

    Full Text Available Abstract Background Plant cytochrome P450 monooxygenases (CYP mediate synthesis and metabolism of many physiologically important primary and secondary compounds that are related to plant defense against a range of pathogenic microbes and insects. To determine if cytochrome P450 monooxygenases are involved in defense response to Xylella fastidiosa (Xf infection, we investigated expression and regulatory mechanisms of the cytochrome P450 monooxygenase CYP736B gene in both disease resistant and susceptible grapevines. Results Cloning of genomic DNA and cDNA revealed that the CYP736B gene was composed of two exons and one intron with GT as a donor site and AG as an acceptor site. CYP736B transcript was up-regulated in PD-resistant plants and down-regulated in PD-susceptible plants 6 weeks after Xf inoculation. However, CYP736B expression was very low in stem tissues at all evaluated time points. 5'RACE and 3'RACE sequence analyses revealed that there were three candidate transcription start sites (TSS in the upstream region and three candidate polyadenylation (PolyA sites in the downstream region of CYP736B. Usage frequencies of each transcription initiation site and each polyadenylation site varied depending on plant genotype, developmental stage, tissue, and treatment. These results demonstrate that expression of CYP736B is regulated developmentally and in response to Xf infection at both transcriptional and post-transcriptional levels. Multiple transcription start and polyadenylation sites contribute to regulation of CYP736B expression. Conclusions This report provides evidence that the cytochrome P450 monooxygenase CYP736B gene is involved in defense response at a specific stage of Xf infection in grapevines; multiple transcription initiation and polyadenylation sites exist for CYP736B in grapevine; and coordinative and selective use of transcription initiation and polyadenylation sites play an important role in regulation of CYP736B expression

  12. Prognostic significance of kynurenine 3-monooxygenase and effects on proliferation, migration, and invasion of human hepatocellular carcinoma

    OpenAIRE

    Haojie Jin; Yurong Zhang; Haiyan You; Xuemei Tao; Cun Wang; Guangzhi Jin; Ning Wang; Haoyu Ruan; Dishui Gu; Xisong Huo; Wenming Cong; Wenxin Qin

    2015-01-01

    Kynurenine 3-monooxygenase (KMO) is a pivotal enzyme in the kynurenine pathway of tryptophan degradation and plays a critical role in Huntington’s and Alzheimer’s diseases. This study aimed to examine the expression of KMO in human hepatocellular carcinoma (HCC) and investigate the relationship between its expression and prognosis of HCC patients. We first analyzed KMO expression in 120 paired HCC samples (HCC tissues vs matched adjacent non-cancerous liver tissues), and 205 clinical HCC spec...

  13. Overexpression of human kynurenine-3-monooxygenase protects against 3-hydroxykynurenine-mediated apoptosis through bidirectional nonlinear feedback

    OpenAIRE

    Wilson, K; Auer, M.; Binnie, M; Zheng, X.; Pham, N.T.; Iredale, J P; Webster, S.P.; Mole, D J

    2016-01-01

    Kynurenine 3-monooxygenase (KMO) is a critical regulator of inflammation. The preferred KMO substrate, kynurenine, is converted to 3-hydroxykynurenine (3HK), and this product exhibits cytotoxicity through mechanisms that culminate in apoptosis. Here, we report that overexpression of human KMO with orthotopic localisation to mitochondria creates a metabolic environment during which the cell exhibits increased tolerance for exogenous 3HK-mediated cellular injury. Using the selective KMO inhibit...

  14. Fluorogenic derivatization of aryl halides based on the formation of biphenyl by Suzuki coupling reaction with phenylboronic acid.

    OpenAIRE

    Kishikawa, Naoya; Kubo, Kimiko; Hammad, Sherin Farouk; Mabrouk, Mokhtar Mohamed; Habib, Ahmed; Elfatatry, Hamed; Ohyama, Kaname; Nakashima, Kenichiro; Kuroda, Naotaka

    2009-01-01

    The fluorogenic derivatization method for aryl halide was developed for the first time. This method was based on the formation of fluorescent biphenyl structure by Suzuki coupling reaction between aryl halides and non-fluorescent phenylboronic acid (PBA). We measured the fluorescence spectra of the products obtained by the reaction of p-substituted aryl bromides (i.e., 4-bromobenzonitrile, 4-bromoanisole, 4-bromobenzoic acid ethyl ester and 4-bromotoluene) with PBA in the presence of palladiu...

  15. Boryl (Hetero)aryne Precursors as Versatile Arylation Reagents: Synthesis through C–H Activation and Orthogonal Reactivity

    Science.gov (United States)

    Demory, Emilien; Devaraj, Karthik; Orthaber, Andreas; Gates, Paul J; Pilarski, Lukasz T

    2015-01-01

    (Pinacolato)boryl ortho-silyl(hetero)aryl triflates are presented as a new class of building blocks for arylation. They demonstrate unique versatility by delivering boronate or (hetero)aryne reactivity chemoselectively in a broad range of transformations. This approach enables the unprecedented postfunctionalization of fluoride-activated (hetero)aryne precursors, for example, as substrates in transition-metal catalysis, and offers valuable new possibilities for aryl boronate postfunctionalization without the use of specialized protecting groups. PMID:26270451

  16. Nickel-catalyzed vinylation of aryl chlorides and bromides with vinyl ZnBr.MgBrCl.

    Science.gov (United States)

    Yamamoto, Tetsuya; Yamakawa, Tetsu

    2009-05-01

    The Ni-catalyzed cross-coupling of aryl halides and vinylzinc bromide for the synthesis of styrene derivatives was investigated. Of the catalysts surveyed, the combination of Ni(acac)(2) and Xantphos was found to be the most effective for this cross-coupling. This catalyst could be used in reactions with various aryl bromides and chlorides, including electron-rich aryl chlorides such as chloroanisoles. PMID:19354270

  17. Functional Gene Markers for Fumarate-Adding and Dearomatizing Key Enzymes in Anaerobic Aromatic Hydrocarbon Degradation in Terrestrial Environments.

    Science.gov (United States)

    von Netzer, Frederick; Kuntze, Kevin; Vogt, Carsten; Richnow, Hans H; Boll, Matthias; Lueders, Tillmann

    2016-01-01

    Anaerobic degradation is a key process in many environments either naturally or anthropogenically exposed to petroleum hydrocarbons. Considerable advances into the biochemistry and physiology of selected anaerobic degraders have been achieved over the last decades, especially for the degradation of aromatic hydrocarbons. However, researchers have only recently begun to explore the ecology of complex anaerobic hydrocarbon degrader communities directly in their natural habitats, as well as in complex laboratory systems using tools of molecular biology. These approaches have mainly been facilitated by the establishment of a suite of targeted marker gene assays, allowing for rapid and directed insights into the diversity as well as the identity of intrinsic degrader populations and degradation potentials established at hydrocarbon-impacted sites. These are based on genes encoding either peripheral or central key enzymes in aromatic compound breakdown, such as fumarate-adding benzylsuccinate synthases or dearomatizing aryl-coenzyme A reductases, or on aromatic ring-cleaving hydrolases. Here, we review recent advances in this field, explain the different detection methodologies applied, and discuss how the detection of site-specific catabolic gene markers has improved the understanding of processes at contaminated sites. Functional marker gene-based strategies may be vital for the development of a more elaborate population-based assessment and prediction of aromatic degradation potentials in hydrocarbon-impacted environments. PMID:26959523

  18. Thermophysical Properties of Hydrocarbon Mixtures

    Science.gov (United States)

    SRD 4 NIST Thermophysical Properties of Hydrocarbon Mixtures (PC database for purchase)   Interactive computer program for predicting thermodynamic and transport properties of pure fluids and fluid mixtures containing up to 20 components. The components are selected from a database of 196 components, mostly hydrocarbons.

  19. Volatile Hydrocarbon Pheromones from Beetles

    Science.gov (United States)

    This chapter reviews literature about hydrocarbons from beetles that serve as long-range pheromones. The most thoroughly studied beetles that use volatile hydrocarbon pheromones belong to the family Nitidulidae in the genera Carpophilus and Colopterus. Published pheromone research deals with behav...

  20. Iron-Catalyzed, Highly Regioselective Synthesis of alpha-Aryl Carboxylic Acids from Styrene Derivatives and CO2

    OpenAIRE

    Greenhalgh, Mark D.; Thomas, Stephen P.

    2012-01-01

    The iron-catalyzed hydrocarboxylation of aryl alkenes has been developed using a highly active bench-stable iron(II) precatalyst to give alpha-aryl carboxylic acids in excellent yields and with near-perfect regioselectivity. Using just 1 mol % FeCl2, bis(imino)pyridine 6 (1 mol %), CO2 (atmospheric pressure), and a hydride source (EtMgBr, 1.2 equiv), a range of sterically and electronically differentiated aryl alkenes were transformed to the corresponding alpha-aryl carboxylic acids (up to 96...

  1. Efficient Negishi coupling reactions of aryl chlorides catalyzed by binuclear and mononuclear nickel-N-heterocyclic carbene complexes.

    Science.gov (United States)

    Xi, Zhenxing; Zhou, Yongbo; Chen, Wanzhi

    2008-11-01

    We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of a variety of unactivated aryl chlorides, heterocyclic chlorides, aryl dichlorides, and vinyl chloride. The mononuclear and binuclear nickel-NHC complexes supported by heteroarene-functionalized NHC ligands are found to be highly efficient for the coupling of unactivated aryl chlorides and organozinc reagents, leading to biaryls and terphenyls in good to excellent yields under mild conditions. For all aryl chlorides, the binuclear nickel catalysts show activities higher than those of mononuclear nickel complexes because of possible bimetallic cooperative effect. PMID:18841915

  2. Diterpenoid tetracyclic hydrocarbons of petroleum

    Energy Technology Data Exchange (ETDEWEB)

    Vorob' eva, N.S.; Zemskova, Z.K.; Pekh, T.I.; Petrov, A.A.

    1987-08-01

    Diterpenoid hydrocarbons are fairly widespread in various caustobioliths. However, if petroleums contain mainly acyclic diterpenoids (phytane, pristane and norpristane), cyclic diterpaenes such as fichtelite, pimarane, iosene (kaurane) and hibbane are often found in hydrocarbons isolated from coal and shale. Recent advances in the chemistry of diterpenoids isolated from caustobioliths, are described in a separate paper. Much less is known about petroleum polycyclic diterpenoid hydrocarbons, particularly those with four saturated rings. A series of tetracyclic hydrocarbons C/sub 19/H/sub 32/ (molar mass 260), found in a number of light petroleums and gas condensates from the Jura deposits of Central Kara-Kum (Turkmen S.S.R.), are examined here. These hydrocarbons are present in petroleums and condensates from the Davaly, Erden, Ortakak, Southern Beuideshik deposits, they are always identical and occur in the same ratios. The composition of the tretracyclanes isolated from the Ortakak gas condensates (well 17) will be examined in detail.

  3. Hydrocarbon sensors and materials therefor

    Science.gov (United States)

    Pham, Ai Quoc; Glass, Robert S.

    2000-01-01

    An electrochemical hydrocarbon sensor and materials for use in sensors. A suitable proton conducting electrolyte and catalytic materials have been found for specific application in the detection and measurement of non-methane hydrocarbons. The sensor comprises a proton conducting electrolyte sandwiched between two electrodes. At least one of the electrodes is covered with a hydrocarbon decomposition catalyst. Two different modes of operation for the hydrocarbon sensors can be used: equilibrium versus non-equilibrium measurements and differential catalytic. The sensor has particular application for on-board monitoring of automobile exhaust gases to evaluate the performance of catalytic converters. In addition, the sensor can be utilized in monitoring any process where hydrocarbons are exhausted, for instance, industrial power plants. The sensor is low cost, rugged, sensitive, simple to fabricate, miniature, and does not suffer cross sensitivities.

  4. Characterization of the transcriptome of Achromobacter sp. HZ01 with the outstanding hydrocarbon-degrading ability.

    Science.gov (United States)

    Hong, Yue-Hui; Deng, Mao-Cheng; Xu, Xiao-Ming; Wu, Chou-Fei; Xiao, Xi; Zhu, Qing; Sun, Xian-Xian; Zhou, Qian-Zhi; Peng, Juan; Yuan, Jian-Ping; Wang, Jiang-Hai

    2016-06-15

    Microbial remediation has become one of the most important strategies for eliminating petroleum pollutants. Revealing the transcript maps of microorganisms with the hydrocarbon-degrading ability contributes to enhance the degradation of hydrocarbons and further improve the effectiveness of bioremediation. In this study, we characterized the transcriptome of hydrocarbon-degrading Achromobacter sp. HZ01 after petroleum treatment for 16h. A total of 38,706,280 and 38,954,413 clean reads were obtained by RNA-seq for the petroleum-treated group and control, respectively. By an effective de novo assembly, 3597 unigenes were obtained, including 3485 annotated transcripts. Petroleum treatment had significantly influenced the transcriptional profile of strain HZ01, involving 742 differentially expressed genes. A part of genes were activated to exert specific physiological functions, whereas more genes were down-regulated including specific genes related to cell motility, genes associated with glycometabolism, and genes coding for ribosomal proteins. Identification of genes related to petroleum degradation revealed that the fatty acid metabolic pathway and a part of monooxygenases and dehydrogenases were activated, whereas the TCA cycle was inactive. Additionally, terminal oxidation might be a major aerobic pathway for the degradation of n-alkanes in strain HZ01. The newly obtained data contribute to better understand the gene expression profiles of hydrocarbon-degrading microorganisms after petroleum treatment, to further investigate the genetic characteristics of strain HZ01 and other related species and to develop cost-effective and eco-friendly strategies for remediation of crude oil-polluted environments. PMID:26915487

  5. A direct method to visualise the aryl acylamidase activity on cholinesterases in polyacrylamide gels

    Directory of Open Access Journals (Sweden)

    Boopathy Rathanam

    2000-12-01

    Full Text Available Abstract Background In vertebrates, two types of cholinesterases exist, acetylcholinesterase and butyrylcholinesterase. The function of acetylcholinesterase is to hydrolyse acetylcholine, thereby terminating the neurotransmission at cholinergic synapse, while the precise physiological function of butyrylcholinesterase has not been identified. The presence of cholinesterases in tissues that are not cholinergically innervated indicate that cholinesterases may have functions unrelated to neurotransmission. Furthermore, cholinesterases display a genuine aryl acylamidase activity apart from their predominant acylcholine hydrolase activity. The physiological significance of this aryl acylamidase activity is also not known. The study on the aryl acylamidase has been, in part hampered by the lack of a specific method to visualise this activity. We have developed a method to visualise the aryl acylamidase activity on cholinesterase in polyacrylamide gels. Results The o-nitroaniline liberated from o-nitroacetanilide by the action of aryl acylamidase activity on cholinesterases, in the presence of nitrous acid formed a diazonium compound. This compound gave an azo dye complex with N-(1-napthyl-ethylenediamine, which appeared as purple bands in polyacrylamide gels. Treating the stained gels with trichloroacetic acid followed by Tris-HCl buffer helped in fixation of the stain in the gels. By using specific inhibitors for acetylcholinesterase and butyrylcholinesterase, respectively, differential staining for the aryl acylamidase activities on butyrylcholinesterase and acetylcholinesterase in a sample containing both these enzymes has been demonstrated. A linear relationship between the intensity of colour developed and activity of the enzyme was obtained. Conclusions A novel method to visualise the aryl acylamidase activity on cholinesterases in polyacrylamide gels has been developed.

  6. Retinoic Acid Drives Aryl Hydrocarbon Receptor Expression and Is Instrumental to Dioxin-Induced Toxicity during Palate Development

    OpenAIRE

    Jacobs, Hugues; Dennefeld, Christine; Féret, Betty; Viluksela, Matti; Håkansson, Helen; Mark, Manuel; Ghyselinck, Norbert B.

    2011-01-01

    Background: Palate development depends on complex events and is very sensitive to disruption. Accordingly, clefts are the most common congenital malformations worldwide, and a connection is proposed with fetal exposure to toxic factors or environmental contaminants, such as dioxins. There is increasing evidence that dioxin interferes with all-trans-retinoic acid (atRA), a hormone-like signal derived from vitamin A, which plays an essential role during embryonic development. Although similarit...

  7. The aryl hydrocarbon receptor suppresses osteoblast proliferation and differentiation through the activation of the ERK signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haitao; Du, Yuxuan; Zhang, Xulong; Sun, Ying; Li, Shentao; Dou, Yunpeng [Department of Immunology, School of Basic Medical Sciences, Capital Medical University, No. 10 Xitoutiao, You An Men, Beijing 100069 (China); Li, Zhanguo [Department of Rheumatology and Immunology, Clinical Immunology Center, Peking University People' s Hospital, No. 11 Xizhimen South Street, Beijing 100044 (China); Yuan, Huihui, E-mail: huihui_yuan@163.com [Department of Immunology, School of Basic Medical Sciences, Capital Medical University, No. 10 Xitoutiao, You An Men, Beijing 100069 (China); Zhao, Wenming, E-mail: zhao-wenming@163.com [Department of Immunology, School of Basic Medical Sciences, Capital Medical University, No. 10 Xitoutiao, You An Men, Beijing 100069 (China)

    2014-11-01

    Ahr activation is known to be associated with synovitis and exacerbated rheumatoid arthritis (RA), but its contributions to bone loss have not been completely elucidated. Osteoblast proliferation and differentiation are abnormal at the erosion site in RA. Here, we reported that the expression of Ahr was increased in the hind paws' bone upon collagen-induced arthritis (CIA) in mice, and the levels of Ahr were negatively correlated with bone mineral density (BMD). In addition, immunofluorescent staining showed that the high expression of Ahr was mainly localized in osteoblasts from the CIA mice compared to normal controls. Moreover, the luciferase intensity of Ahr in the nucleus increased by 12.5% in CIA osteoblasts compared to that in normal controls. In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) activation of the Ahr inhibited pre-osteoblast MC3T3-E1 cellular proliferation and differentiation in a dose-dependent manner. Interestingly, the levels of alkaline phosphatase (ALP) mRNA expression in the osteoblasts of CIA mice were reduced compared to normal controls. In contrast, decreased ALP expression by activated Ahr was completely reversed after pretreatment with an Ahr inhibitor (CH-223191) in MC3T3-E1 cell lines and primary osteoblasts on day 5. Our data further showed that activation of Ahr promoted the phosphorylation of ERK after 5 days. Moreover, Ahr-dependent activation of the ERK signaling pathway decreased the levels of proliferation cells and inhibited ALP activity in MC3T3-E1 cells. These results demonstrated that the high expression of Ahr may suppress osteoblast proliferation and differentiation through activation of the ERK signaling pathway, further enabling bone erosion in CIA mice. - Highlights: • The upregulation of Ahr was localized in osteoblasts of CIA mice. • The overexpression of Ahr suppressed osteoblast development. • The Ahr activated ERK signaling pathway to exacerbate bone erosion.

  8. Gene expression changes in human prostate carcinoma cells exposed to genotoxic and nongenotoxic aryl hydrocarbon receptor ligands

    Czech Academy of Sciences Publication Activity Database

    Hrubá, E.; Vondráček, Jan; Líbalová, Helena; Topinka, Jan; Bryja, Vítězslav; Souček, Karel; Machala, M.

    2011-01-01

    Roč. 206, č. 2 (2011), s. 178-188. ISSN 0378-4274 R&D Projects: GA ČR(CZ) GA310/07/0961; GA ČR(CZ) GA524/09/1337 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702; CEZ:AV0Z50390512; CEZ:AV0Z50390703 Keywords : LNCaP cells * AhR ligands * WNT5A Subject RIV: BO - Biophysics Impact factor: 3.230, year: 2011

  9. Role of aryl hydrocarbon receptor in modulation of the expression of the hypoxia marker carbonic anhydrase IX

    Czech Academy of Sciences Publication Activity Database

    Takáčová, M.; Holotňáková, T.; Vondráček, Jan; Machala, M.; Pěnčíková, K.; Gradin, K.; Poellinger, L.; Pastorek, J.; Pastoreková, S.; Kopáček, J.

    2009-01-01

    Roč. 419, - (2009), s. 419-425. ISSN 0264-6021 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : AhR * carbonic anhydrase IX * dioxin Subject RIV: BO - Biophysics Impact factor: 5.155, year: 2009

  10. Role of aryl hydrocarbon receptor in modulation of the expression of the hypoxia marker carbonic anhydrase IX

    Czech Academy of Sciences Publication Activity Database

    Takáčová, M.; Holotňáková, T.; Vondráček, Jan; Machala, M.; Pěnčíková, K.; Gradin, K.; Poellinger, L.; Pastorek, J.; Pastoreková, S.; Kopáček, J.

    Mikulov, 2009. s. 391. [XXV. Xenobiochemické symposium. 22.09.2009-25.09.2009, Mikulov] Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : AhR * hypoxia -inducible factor * CA IX Subject RIV: AQ - Safety, Health Protection, Human - Machine

  11. Genetic basis for evolved tolerance to dioxin-like pollutants in wild Atlantic killifish: more than the aryl hydrocarbon receptor

    Science.gov (United States)

    Atlantic killifish (Fundulus heteroclitus) resident to some US urban and industrialized estuaries demonstrate recently evolved and extreme tolerance to toxic dioxin-like compounds (DLCs). Here we provide an unusually comprehensive accounting (69%) through Quantitative Trait Locu...

  12. The aryl hydrocarbon receptor suppresses osteoblast proliferation and differentiation through the activation of the ERK signaling pathway

    International Nuclear Information System (INIS)

    Ahr activation is known to be associated with synovitis and exacerbated rheumatoid arthritis (RA), but its contributions to bone loss have not been completely elucidated. Osteoblast proliferation and differentiation are abnormal at the erosion site in RA. Here, we reported that the expression of Ahr was increased in the hind paws' bone upon collagen-induced arthritis (CIA) in mice, and the levels of Ahr were negatively correlated with bone mineral density (BMD). In addition, immunofluorescent staining showed that the high expression of Ahr was mainly localized in osteoblasts from the CIA mice compared to normal controls. Moreover, the luciferase intensity of Ahr in the nucleus increased by 12.5% in CIA osteoblasts compared to that in normal controls. In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) activation of the Ahr inhibited pre-osteoblast MC3T3-E1 cellular proliferation and differentiation in a dose-dependent manner. Interestingly, the levels of alkaline phosphatase (ALP) mRNA expression in the osteoblasts of CIA mice were reduced compared to normal controls. In contrast, decreased ALP expression by activated Ahr was completely reversed after pretreatment with an Ahr inhibitor (CH-223191) in MC3T3-E1 cell lines and primary osteoblasts on day 5. Our data further showed that activation of Ahr promoted the phosphorylation of ERK after 5 days. Moreover, Ahr-dependent activation of the ERK signaling pathway decreased the levels of proliferation cells and inhibited ALP activity in MC3T3-E1 cells. These results demonstrated that the high expression of Ahr may suppress osteoblast proliferation and differentiation through activation of the ERK signaling pathway, further enabling bone erosion in CIA mice. - Highlights: • The upregulation of Ahr was localized in osteoblasts of CIA mice. • The overexpression of Ahr suppressed osteoblast development. • The Ahr activated ERK signaling pathway to exacerbate bone erosion

  13. Genetic basis for evolved tolerance to dioxin-like pollutants in wild Atlantic killifish: more than the aryl hydrocarbon receptor

    Science.gov (United States)

    Atlantic killifish (Fundulus heteroclitus) resident to some US urban and industrialized estuaries demonstrate recently evolved and extreme tolerance to toxic dioxin-like compounds (DLCs). Here we provide an unusually comprehensive accounting (69%) through Quantitative Trait Locus (QTL) analysis of ...

  14. Crystal structure and characterization of particulate methane monooxygenase from Methylocystis species strain M.

    Science.gov (United States)

    Smith, Stephen M; Rawat, Swati; Telser, Joshua; Hoffman, Brian M; Stemmler, Timothy L; Rosenzweig, Amy C

    2011-11-29

    Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria. Previous biochemical and structural studies of pMMO have focused on preparations from Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b. A pMMO from a third organism, Methylocystis species strain M, has been isolated and characterized. Both membrane-bound and solubilized Methylocystis sp. strain M pMMO contain ~2 copper ions per 100 kDa protomer and exhibit copper-dependent propylene epoxidation activity. Spectroscopic data indicate that Methylocystis sp. strain M pMMO contains a mixture of Cu(I) and Cu(II), of which the latter exhibits two distinct type 2 Cu(II) electron paramagnetic resonance (EPR) signals. Extended X-ray absorption fine structure (EXAFS) data are best fit with a mixture of Cu-O/N and Cu-Cu ligand environments with a Cu-Cu interaction at 2.52-2.64 Å. The crystal structure of Methylocystis sp. strain M pMMO was determined to 2.68 Å resolution and is the best quality pMMO structure obtained to date. It provides a revised model for the pmoA and pmoC subunits and has led to an improved model of M. capsulatus (Bath) pMMO. In these new structures, the intramembrane zinc/copper binding site has a different coordination environment from that in previous models. PMID:22013879

  15. C. elegans flavin-containing monooxygenase-4 is essential for osmoregulation in hypotonic stress.

    Science.gov (United States)

    Hirani, Nisha; Westenberg, Marcel; Seed, Paul T; Petalcorin, Mark I R; Dolphin, Colin T

    2016-01-01

    Studies in Caenorhabditis elegans have revealed osmoregulatory systems engaged when worms experience hypertonic conditions, but less is known about measures employed when faced with hypotonic stress. Inactivation of fmo-4, which encodes flavin-containing monooxygenase-4, results in dramatic hypoosmotic hypersensitivity; worms are unable to prevent overwhelming water influx and swell rapidly, finally rupturing due to high internal hydrostatic pressure. fmo-4 is expressed prominently in hypodermis, duct and pore cells but is excluded from the excretory cell. Thus, FMO-4 plays a crucial osmoregulatory role by promoting clearance of excess water that enters during hypotonicity, perhaps by synthesizing an osmolyte that acts to establish an osmotic gradient from excretory cell to duct and pore cells. C. elegans FMO-4 contains a C-terminal extension conserved in all nematode FMO-4s. The coincidently numbered human FMO4 also contains an extended C-terminus with features similar to those of FMO-4. Although these shared sequence characteristics suggest potential orthology, human FMO4 was unable to rescue the fmo-4 osmoregulatory defect. Intriguingly, however, mammalian FMO4 is expressed predominantly in the kidney - an appropriate site if it too is, or once was, involved in osmoregulation. PMID:27010030

  16. C. elegans flavin-containing monooxygenase-4 is essential for osmoregulation in hypotonic stress

    Directory of Open Access Journals (Sweden)

    Nisha Hirani

    2016-05-01

    Full Text Available Studies in Caenorhabditis elegans have revealed osmoregulatory systems engaged when worms experience hypertonic conditions, but less is known about measures employed when faced with hypotonic stress. Inactivation of fmo-4, which encodes flavin-containing monooxygenase-4, results in dramatic hypoosmotic hypersensitivity; worms are unable to prevent overwhelming water influx and swell rapidly, finally rupturing due to high internal hydrostatic pressure. fmo-4 is expressed prominently in hypodermis, duct and pore cells but is excluded from the excretory cell. Thus, FMO-4 plays a crucial osmoregulatory role by promoting clearance of excess water that enters during hypotonicity, perhaps by synthesizing an osmolyte that acts to establish an osmotic gradient from excretory cell to duct and pore cells. C. elegans FMO-4 contains a C-terminal extension conserved in all nematode FMO-4s. The coincidently numbered human FMO4 also contains an extended C-terminus with features similar to those of FMO-4. Although these shared sequence characteristics suggest potential orthology, human FMO4 was unable to rescue the fmo-4 osmoregulatory defect. Intriguingly, however, mammalian FMO4 is expressed predominantly in the kidney – an appropriate site if it too is, or once was, involved in osmoregulation.

  17. Effects of the compounds 2-methoxynaphthoquinone, 2-propoxynaphthoquinone, and 2-isopropoxynaphthoquinone on ecdysone 20-monooxygenase activity.

    Science.gov (United States)

    Mitchell, Martin J; Brescia, Aaron I; Smith, Stan L; Morgan, E David

    2007-09-01

    The effects of the natural compound 2-methoxy-1,4-naphthoquinone, isolated from the leaves of Impatiens glandulifera and the synthetic compounds 2-propoxy-1,4-naphthoquinone and 2-isopropoxy-1,4-naphthoquinone on ecdysone 20-monooxygenase (E-20-M) activity were examined in three insect species. Homogenates of wandering stage third instar larvae of Drosophila melanogaster, or abdomens from adult female Aedes aegypti, or fat body or midgut from fifth instar larvae of Manduca sexta were incubated with radiolabelled ecdysone and increasing concentrations (from 1 x 10(-8) to 1 x 10(-3) M) of the three compounds. All three compounds were found to inhibit in a dose-dependent fashion the E-20-M activity in the three insect species. The concentration of these compounds required to elicit a 50% inhibition of this steroid hydroxylase activity in the three insect species examined ranged from approximately 3 x 10(-5) to 7 x 10(-4) M. PMID:17694563

  18. Crystal Structure and Characterization of Particulate Methane Monooxygenase from Methylocystis species Strain M

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Stephen M.; Rawat, Swati; Telser, Joshua; Hoffman, Brian M.; Stemmler, Timothy L.; Rosenzweig, Amy C. (WSU-MED); (NWU)

    2012-02-08

    Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that oxidizes methane to methanol in methanotrophic bacteria. Previous biochemical and structural studies of pMMO have focused on preparations from Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b. A pMMO from a third organism, Methylocystis species strain M, has been isolated and characterized. Both membrane-bound and solubilized Methylocystis sp. strain M pMMO contain {approx}2 copper ions per 100 kDa protomer and exhibit copper-dependent propylene epoxidation activity. Spectroscopic data indicate that Methylocystis sp. strain M pMMO contains a mixture of Cu{sup I} and Cu{sup II}, of which the latter exhibits two distinct type 2 Cu{sup II} electron paramagnetic resonance (EPR) signals. Extended X-ray absorption fine structure (EXAFS) data are best fit with a mixture of Cu-O/N and Cu-Cu ligand environments with a Cu-Cu interaction at 2.52-2.64 {angstrom}. The crystal structure of Methylocystis sp. strain M pMMO was determined to 2.68 {angstrom} resolution and is the best quality pMMO structure obtained to date. It provides a revised model for the pmoA and pmoC subunits and has led to an improved model of M. capsulatus (Bath) pMMO. In these new structures, the intramembrane zinc/copper binding site has a different coordination environment from that in previous models.

  19. Carbon Isotope Fractionations Associated with Methanotrophic Growth with the Soluble and Particulate Methane Monooxygenases

    Science.gov (United States)

    Jahnke, Linda L.; Summons, Roger E.; Chang, Sherwood (Technical Monitor)

    1996-01-01

    Growth experiments with the RuMP-type methanotroph, Methylococcus capsulatus (Bath), have demonstrated that biomass and lipid biomarkers are significantly depleted in C-13 compared to the substrate methane and that the extent of fractionation is dependent on whether cells express the soluble (s) or particulate (p) methane monooxygenase (MMO). The presence or absence of the characteristic sMMO subunits was monitored using SDS-polyacrylamide gels. In M. capsulatus grown with no Cu supplementation, the characteristic sMMO subunits were observed in the soluble fraction throughout the entire growth period and biomass was depleted in C-13 by approximately 14,700 relative to substrate methane. In cells grown with 5uM Cu, no sMMO bands were observed and a greater fractionation of approximately 27,700 in resultant biomass was obtained. Methanol growth experiments with M. capsulatus and with a RuMP methylotroph, Methylophilus methylotrophus, in which biomass measurements yielded depletions in C-13 of 9 and 5%(sub o), respectively, suggest that oxidation of methane is the major fractionation step. Growth of M. capsulatus at a low level of oxygen, approximately 0.5%, had no significant effect on carbon isotope fractionation by either sMMO or pMMO. These observations are significant for identification of molecular biomarkers; and methanotrophic contributions to carbon isotope composition in natural environments.

  20. Identification of the cytochrome P450 monooxygenase that bridges the clavine and ergoline alkaloid pathways.

    Science.gov (United States)

    Haarmann, Thomas; Ortel, Ingo; Tudzynski, Paul; Keller, Ullrich

    2006-04-01

    Clavines and D-lysergic acid-derived alkaloid amides and alkaloid peptides are two different families of compounds that have the indole-derived tetracyclic metergoline ring system in common. Previous work has shown that D-lysergic acid is biosynthetically derived from clavine alkaloids. Recent cloning and analysis of the ergot alkaloid biosynthesis gene cluster from the D-lysergic acid peptide (ergopeptines)-producing Claviceps purpurea, has shown that it most probably contains all genes necessary for D-lysergic acid synthesis as well as those that encode the assembly of D-lysergic acid peptides, such as ergotamine. To address the role of the oxygenase genes of alkaloid-gene clusters, the only cytochrome P450 monooxygenase gene of this cluster was inactivated by disruption. The resultant mutant accumulated agroclavine, elymoclavine, and chanoclavine in substantial amounts but not ergopeptines. Feeding the mutant with D-lysergic acid restored ergopeptine synthesis; this suggests a block in the conversion of elymoclavine to D-lysergic acid. The gene was designated cloA (for encoding a clavine oxidase, CLOA). Retransformation of the mutant with the intact cloA gene also restored ergopeptine synthesis. These data show that CLOA catalyses the conversion of clavines to D-lysergic acid, it acts as a critical enzyme in the ergot alkaloid gene cluster, and bridges the biosynthesis of the two different families of alkaloids. PMID:16538694