Search

The aryl hydrocarbon receptor (AhR) is a highly conserved ligand--dependent transcription factor that senses environmental toxins and endogenous ligands, thereby inducing detoxifying enzymes and modulating immune cell differentiation and responses. We hypothesized that AhR evolved to sense not only environmental pollutants but also microbial insults. We characterized bacterial pigmented virulence factors, namely the phenazines from Pseudomonas aeruginosa and the naphthoquinone phthiocol from Mycobacterium tuberculosis, as ligands of AhR. Upon ligand binding, AhR activation leads to virulence factor degradation and regulated cytokine and chemokine production. The relevance of AhR to host defence is underlined by heightened susceptibility of AhR-deficient mice to both P. aeruginosa and M. tuberculosis. Thus, we demonstrate that AhR senses distinct bacterial virulence factors and controls antibacterial responses, supporting a previously unidentified role for AhR as an intracellular pattern recognition receptor, and identify bacterial pigments as a new class of pathogen-associated molecular patterns., The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that senses environmental toxins, notably halogenated and non-halogenated polycyclic aromatic hydrocarbons, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (1). Upon activation, AhR enters [...]

BACKGROUND: Styrene trimers (STs) are polystyrene-container-eluted materials that are sometimes detected in packaged foods. Although the possible endocrine-disrupting effects of STs, such as estrogenic activities, have been reported, their potential [...]

Endogenous activation of the aryl hydrocarbon receptor (AHR) is required for normal vascular development. This biology led us to investigate the interplay between the AHR and vascular physiology by using an in vitro model of fluid shear stress. Using this system, we show that fluid flow induces a robust AHR-mediated increase in CYP1 expression. Furthermore, we demonstrate that incubation with sheared bovine or human sera is sufficient for AHR activation, indicating that direct cellular exposure to shear stress is not required for this response. Fractionation of sera by size and density revealed the AHR-activating factor to be low-density lipoprotein (LDL). Purified LDL (0.1 mg/ml) from sheared sera induces a 6-fold increase in AHR-mediated signaling as compared with LDL purified from static sera. Similar results were obtained by exposing a purified fraction of LDL to fluid flow, suggesting that shear stress is capable of directly modifying LDL structure and/or function. In addition, we show that LDL can be converted to an AHR-activating species by conventional methods of lipoprotein modification, such as NaOCl oxidation. Finally, we demonstrate that an increased level of AHR-activating LDL is present in the sera of AHR null mice as compared with heterozygous littermates, suggesting a role for the Ahr locus in the physiological response to modified LDL in vivo. Overall, these data demonstrate a previously undescribed relationship between LDL modification and AHR biology and provide a potential explanation for the vascular abnormalities observed in AHR null mice. AHR | cyp1a1 | cyp1b1 | shear stress

Most mitochondrial preproteins are maintained in a loosely folded import-competent conformation by cytosolic chaperones, and are imported into mitochondria by translocator complexes containing a pre-protein receptor, termed translocase of the outer membrane of mitochondria (Tom) 20. Using two-hybrid screening, we identified arylhydrocarbon receptor-interacting protein (AIP), an FK506-binding protein homologue, interacting with Tom20. The extreme COOH-terminal acidic segment of Tom20 was required for interaction with tetratricopeptide repeats of AIP. An in vitro import assay indicated that AIP prevents preornithine transcarbamylase from the loss of import competency. In cultured cells, overexpression of AIP enhanced preornithine transcarbamylase import, and depletion of AIP by RNA interference impaired the import. An in vitro binding assay revealed that AIP specifically binds to mitochondrial preproteins. Formation of a ternary complex of Tom20, AIP, and preprotein was observed. Hsc70 was also found to bind to AIP. An aggregation suppression assay indicated that AIP has a chaperone-like activity to prevent substrate proteins from aggregation. These results suggest that AIP functions as a cytosolic factor that mediates preprotein import into mitochondria.

Research has been conducted on biodegradative microbial populations. The effect of nutrients ammendments on these populations has been investigated, and the results are reported.

Research has been conducted on the microbial community activity and composition in soil contaminated with chromium, hydrocarbons and lead. The association between the contaminant's and alteration's levels in this community has been investigated and the details are reported.

Research has been conducted on the crystalline polycyclic aromatic hydrocarbons. The method developed to screen bacterial isolates for the ability to grow on these hydrocarbons has been developed and is described.

Research has been conducted on the soil fungus Cladophialophora sp. strain T1. The ability of this strain to grow on water-soluble gasoline containing benzene, ethylbenzene, toluene, and xylene isomers (BTEX) has been investigated and the results suggest that the soil fungi can contribute to the BTEX pollution biodegradation.

The author reviews the publications on rare-earth complexes containing cyclic aromatic ligands. The topics of interest include lanthanide-arene cations formed in gas-phase reactions of lanthanide metal cations with different hydrocarbons.

Research has been conducted on the polycyclic aromatic hydrocarbon-spiked and aged marine sediments. The effect of these hydrocarbons on the indigenous marine sediment bacteria has been investigated and the details are presented.

Research has been conducted on Rhodococcus opacus PD630 growth and lipid accumulation under nitrogen-limited conditions during cultivation. Results indicate hydrocarbon phenyldecane degradation caused by the monoterminal oxidation and alkyl side-chain beta-oxidation to phenylacetic acid.

Research has been conducted on the nitronyl-substituted hydrocarbon, stilbazulenyl nitrone. The synthesis and antioxidant properties of stilbazulenyl nitrone and their potency as chain breaking antioxidants have been investigated and the details are discussed.

Research has been conducted on the unsaturated hydrocarbons. The hydride donor reactivities of these hydrocarbons have been investigated via benzhydryl cations used as reference electrophiles and the results indicate that the hydride transfer processes' second-rate constants are independent of the solvents.

Research has been conducted on the sulfate-reducing bacteria. The diversity of these bacteria in a petroleum hydrocarbon-contaminated aquifer has been investigated via the use of the activity microscopic measurement and molecular analysis and the results are reported.

Research has been conducted on naphthalene, 2-methylnaphthalene and tetralin. The anaerobic degradation of these compounds has been investigated in a sulfate-reducing enrichment culture from a contaminated aquifer and the results indicate that further degradation occurs via saturated compounds with the cyclohexane ring structure and not via monoaromatic hydrocarbons.

Research has been conducted on the annelated housane. The preparation of the unknown housanes via the Hunig isopyrazole route has been carried out and the study of the rearrangement behavior complexities of the cyclopentadiyl radical cations and cyclopentyl cations is presented.

Research has been conducted on the planar and overcrowded large polycyclic aromatic hydrocarbons, the products of the peri-peri reductive couplings of benzanthrone and naphthanthrone. The results of the ab initio study of the overcrowding motifs of these hydrocarbons are reported.

Research has been conducted on the coordination chemistry of polycyclic aromatic hydrocarbons and silver(I). The production of the double-decker silver(I) coordination polymer with 1-methylpyrene is reported.

Research has been conducted on the direct hydrocarbon oxyfunctionalization under mild conditions. The use of the dioxirane in the regiospecific oxidation of the saturated heptacyclic hydrocarbon Binor S is described.

Research has been conducted on the tetra-n-propyl zirconate. The purification of this compound via the vacuum distillation and the isolation as a moisture-sensitive crystalline solid have been carried out and the results indicate that zirconate is composed of the tetrameric Zr (sub)4 (OPr (super)n ) (sub)16.

Research has been conducted on the beta-cycloalkylnitriles. The synthesis of these compounds has been carried out via the photochemical process starting from the alpha,beta-unsaturated nitriles and cyclic hydrocarbons in the presence of the aromatic ketones and the results are reported.

A study to understand how Drosophila elegans discriminates between potential mates has been carried out. Partial sexual isolation has developed between the brown and black morphs, but body coloration is not used as a sexual cue. Sexual isolation and cuticular hydrocarbons are discussed.

Research has been conducted on the Mycobacterium sp. strain KR20 isolated from the polyacyclic aromatic hydrocarbon. The fluoranthene-degrading capability of this strain, the time course of fluoranthene degradation and the structural data of the metabolites have been investigated.

Research has been conducted on the polycyclic aromatic hydrocarbons. These hydrocarbons have been metabolized to trans-dihydrodiols proximate carcinogens by human epoxide hydrolase and CYP1A1 and the results are discussed.

Research has been conducted on the 4-pentenylketenes and cyclopropylketenes. The generation of these compounds via the photochemical Wolff rearrangements has been carried out and the results of the IR observations indicate that they are long-lived species in hydrocarbon solvents at room temperature.

Research has been conducted on the protonation and methylation. The use of the hydrocarbons and B-N analogues in investigating the energetics of these methylation and protonation is described.

Research has been conducted on the ruthenium(II) surfactants [Ru(bpy) (sub)2 L] (super)2+. The synthesis and characterization of these surfactants carried out via elemental analysis, (super)1 H NMR, UV-vis, luminescence spectroscopy and cyclic voltammetry are reported.

Research has been conducted on the Y-aromaticity which suggests that acyclic conjugated species with pi-electron configuration and branched Y-shaped delocalization have aromatic stability. The results of the ab initio computational study of the acylic hydrocarbon dications with linear and branched pi-conjugation are discussed.