Dioxins and other polycyclic aromatic compounds formed during the combustion of waste and fossil fuels represent a risk to human health, as well as to the well being of our environment. The primary sequence and structure of AhR 3 in different species have been highly conserved during the course of evolution, suggesting that this receptor, which belongs to the family of basic helix-loop-helix nuclear transcription factors, plays an important physiological role(s) in homeostatic processes (1, 2). However, despite intensive studies, this physiological role and the endogenous activators of the AhR remain to be elucidated (3). At the cellular level, activated AhR interacts with various signal transduction pathways; induces biotransformation enzymes; alters the cell cycle, cell adhesion, and migration; and causes apoptosis or aberrant cell growth (4 -7). In vivo, the AhR plays significant roles in connection with development, immunological and reproductive functions, and adaptive responses to light and xenobiotics (8 -11). Compounds of this nature exert carcinogenic and endocrinedisrupting effects in experimental animals by binding to the orphan aryl hydrocarbon receptor (AhR). Understanding the mechanism of action of these pollutants, as well as the physiological role(s) of the AhR, requires identification of the endogenous ligand(s) of this receptor. We reported earlier that activation of AhR by ultraviolet radiation is mediated by the chromophoric amino acid tryptophan (Trp), and we suggested that a new class of compounds derived fromThe AhR protein has been shown to bind the compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as well as similar highly lipophilic halogenated and non-halogenated hydrocarbons leading to cardiovascular, carcinogenic, and endocrine effects (12-16). Consequently, most studies designed to explore the functions of this receptor have been performed with TCDD. One remarkable feature of activation of AhR by dioxinlike compounds is sustained induction of both cytochromes P450 and other metabolizing enzymes, whereas other agonists cause only transient induction of these enzymes. It seems likely that for purposes of regulation, endogenous ligands of AhR are metabolized rapidly, so that the use of persistent xenobiotics such as dioxins to investigate this receptor might be inappropriate. A striking discrepancy between the effects of different types of AhR activators was made evident in two recent studies (17,18). The authors showed that FICZ, the suggested physiologic AhR ligand, boosted T H 17-cell differentiation and worsened the experimentally induced autoimmune encephalomyelitis, whereas TCDD increased levels of T reg and suppressed the pathological effects in myelin-immunized mice.* This work was supported by Swedish Research Council (Formas), the Swedish Radiation Safety Authority, Karolinska Institutet, and the Sven and Lily Lawskis Fund. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertiseme...

A very sensitive and specific analytical procedure for determining nonionic polyethoxylate surfactants, such as aliphatic ethoxylate alcohols (AEOs) and nonylphenol polyethoxylates (NPEOs), in aqueous environmental samples using electrospray liquid chromatography/mass spectrometry is presented, This procedure involves passing 10, 100, 1000, and 4000 mt of raw sewage, treated sewage, river water, and drinking water samples,respectively, through a 1-g graphitized carbon black (GCB) extraction cartridge, By exploiting the presence of positively charged active centers on the GCB surface, we succeeded in isolating AEOs and NPEOs from both surfactants and biointermediates acidic in nature by differential elution, Recoveries of the analytes ranged between 85 and 97%, irrespective of the aqueous matrix in which they were dissolved. Chromatography was adjusted for eluting all the oligomers of NPEO and of the various AEO homologues as single peaks, This chromatographic condition enhances detection levels and simplifies quantification of the analytes. The limit of detection (signal-to-noise ratio = 3) was estimated to be about 20 pg/component injected into the column or 0.6, 0.02, 0.002, and 0.0002 mu g/L of each analyte in the influents and effluents of sewage treatment plants, river water, and drinking water, respectively, This procedure was employed for assessing the concentrations of the analytes in seven influent and seven effluent samples of three mechanical-biological treatment plants, The analysis of a municipal water sample revealed the presence of the analytes at parts-per-trillion levels

Nonylphenol polyethoxylates (A(9)PEs) are complex mixtures of isomers and oligomers widely used as surfactants. The weakly estrogenic effects of the A(9)PE breakdown products are impelling reformulation of many commercial products and have made "A(9)PE free" products an industry trend. Initial A(9)PE biotransformation is known to produce metabolites with shortened ethoxy chains, mainly A(9)PE(2), and carboxylated ethoxy chains, mainly A(9)PE(2)C. Very little is known on the ultimate fate of the branched alkyl side chain. We have used liquid chromatography-electrospray-mass spectrometry to elucidate structures of species generated from biotransformation of the branched alkyl chain. According to an OECD protocol, a laboratory A(9)PE biodegradation experiment was conducted. After about two weeks from the beginning of the experiment, relevant amounts of species having both side chains oxidized (CAPECs) and 3-8 carbons in the residual alkyl chain appeared in the test solution. These species were presumably generated from less extensively alkyl branched A(9)PEC isomers by various oxidative mechanisms. The unreacted most extensively alkyl branched A(9)PEC isomers disappeared from the test liquor after more than 3 months by an unknown mechanism. Less abundant, metabolites having only the alkyl chain carboxylated (CAPEs) were also formed. With time, these species were slowly transformed to CAPECs. Apart from a very slow conversion of CAPE(2)Cs to CAPE(1)Cs, this metabolite class was extremely recalcitrant to further biotransformation, as they persisted in the test liquor even more than 5 months after their generation. Analysis of a sewage treatment plant effluent showed CAPECs, as a total, were present at concentration of 58 mu g/L, accounting for 63% of the total AgPE metabolites leaving the plant

Evidence indicates that lipoxygenases (LO) may play a role in cancer cell survival. We show that human malignant pleural mesothelial (MM) cells, but not normal mesothelial (NM) cells, express a catalytically active 5-LO. Pharmacological or genetic inhibition of MM cell 5-LO determined nucleosome formation and induced a DNA fragmentation pattern typical of apoptosis. This was completely reversed by exogenously added 5(S)-HETE but not by 12(S)-, 15(S)-HETE, or leukotriene (LT)B4. A 5-LO antisense oligonucleotide potently and time-dependently reduced vascular endothelial growth factor (VEGF) mRNA and constitutive VEGF accumulation in the conditioned media of MM cells. When NM cells were transfected with a 5-LO cDNA, basal and arachidonic acid-induced VEGF formation increased consistently by 6- and 12-fold, respectively. This was associated with a significant increase in DNA synthesis that was counteracted by a specific anti-VEGF antibody. Arachidonic acid and 5(S)-HETE also potently stimulated the activity of a VEGF promoter construct. Thus, 5-LO is a key regulator of MM cell proliferation and survival via a VEGF-related circuit.

The simplicity and flexibility of solid-phase microextraction have been combined with the selectivity of molecularly imprinted polymers (MIPs). Silica fibers were coated reproducible with a 75-microm layer of methacrylate polymer either nonimprinted or imprinted with clenbuterol to compare their extraction characteristics under various conditions. Although the template molecule could be removed effectively from the imprinted polymer, structural analogues of clenbuterol were used for evaluation. The influence of pH on the extractability of brombuterol was investigated. Extraction yields up to approximately 80% were obtained when both types of fibers were used to extract brombuterol from phosphate buffer (pH 7.0). In contrast, yields of about 75 and <5% were obtained when extraction was performed from acetonitrile with imprinted and nonimprinted polymers, respectively, which demonstrates the selectivity of the MIP-coated fiber. Time sorption profiles were measured for the extraction of brombuterol from buffer and acetonitrile at the 10 and 100 ng/mL level with both types of fibers in order to compare extraction characteristics. Equilibrium times of about 30 and 90 min were found for the extraction of brombuterol from acetonitrile and buffer, respectively. The MIP-coated fibers were capable of extracting five structural analogues of clenbuterol from both buffer and acetonitrile, which suggests that the amine alcohol part of these molecules is responsible for interaction with the imprinted polymer. To achieve selective extraction of brombuterol from human urine, MIP-coated fibers were washed with acetonitrile after the extraction. Clean extracts and yields of approximately 45% were obtained, demonstrating the suitability of MIP-coated fibers for the analysis of biological samples.