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Here, we examined phytoestrogens, isoflavones (genistein, daidzein, glycitein, biochanin A and ipriflavone), flavones (chrysin, luteolin and apigenin), flavonols (kaempferol and quercetin), and a coumestan, a flavanone and a chalcone (coumestrol, naringenin and phloretin, respectively) by means of a DNA microarray assay. A total of 172 estrogen responsive genes were monitored with a customized DNA microarray and their expression profiles for the above phytoestrogens were compared with that for 17β-estradiol (E2) using correlation coefficients, or R values, after a correlation analysis by linear regression. While R values indicate the similarity of the response by the genes, we also examined the genes by cluster analysis and by their specificity to phytoestrogens (specific to genistein, daidzein or glycitein) or gene functions. Several genes were selected from p53-related genes (CDKN1A, TP53I11 and CDC14), Akt2-related genes (PRKCD, BRCA1, TRIB3 and APPL), mitogen-activated protein kinase-related genes (RSK and SH3BP5), Ras superfamily genes (RAP1GA1, RHOC and ARHGDIA) and AP-1 family and related genes (RIP140, FOS, ATF3, JUN and FRA2). We further examined the extracts from two local crops of soy beans (Kuro-daizu or Mochi-daizu) by comparing the gene expression profiles with those of E2 or phytoestrogens as a first step in utilizing the expression profiles for various applications.

Proper epidemiological, risk assessment and exposure analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related halogenated aromatic hydrocarbons (HAHs) requires accurate measurements of these chemicals both in the species of interest and in various exposure matrices (i.e. biological, environmental, food and feed). High-resolution instrumental analysis techniques are established for these chemicals, however, these procedures are very costly and time-consuming and as such, they are impractical for large scale sampling studies (i.e. for epidemiological studies and assessment of areas with widespread contamination). Accordingly, numerous bioanalytical methods have been developed for the detection of these chemicals in extracts from a variety of matrices, the majority of which take advantage of the ability of these chemicals to activate the aromatic hydrocarbon receptor (AhR) and the AhR signal transduction pathway. Here we review the currently available in vitro AhR-based cell bioassay systems with a focus on recent recombinant reporter gene cell lines that have been developed for detection and relative quantitation of TCDD and related HAHs. Comparison of the relative sensitivities of the various cell bioassays and examples of their use in screening and analysis of environmental, biological, and food and feed samples are presented. Currently available experimental results and validation studies demonstrate the utility of these cell bioassay systems to provide a relatively rapid, accurate, and cost effective screening approach for the detection of TCDD and related HAHs in a variety of environmental, biological, food and feed samples. The availability of these cell bioassay systems will not only facilitate the large scale sampling studies needed for accurate assessment of contamination and exposure to these environmental chemicals, but they provide avenues for the identification of novel classes of TCDD-like chemicals.

The effects of culture medium and serum components on immunoglobulin (Ig) production by mouse splenocytes were examined. In this study, we showed that culture medium containing charcoal-dextran-treated fetal bovine serum (CDFBS) supported Ig production more efficiently than culture medium containing FBS. In addition, RPMI 1640 medium supported Ig production more efficiently than Dulbecco modified Eagle medium. In addition, an increase in medium IgA production was observed with the increase in both CDFBS and FBS concentrations, whereas an increase in IgM level was observed in the presence of 5% and 10% FBS and 10% CDFBS. Dose-dependent effects of estrogenic compounds on Ig production were also examined. We found that 17beta-estradiol induced increases in IgM and IgE levels, but diethylstilbestrol enhanced only the IgE level. On the other hand, tamoxifen and bisphenol A enhanced medium IgM level at physiological concentrations. Among flavonoids, daidzein enhanced IgM and IgE levels at concentrations above 10 microM, and genistein induced a decrease in IgM level and an increase in IgE level at concentrations above 10 microm. In addition, quercetin and luteolin enhanced medium IgE level at all concentrations tested, whereas IgA, IgG, and IgM levels were not affected. These results suggest that environmental estrogens affect Ig production of mouse Splenocytes in a complex and class-specific manner.

In this study, we have compared the time and dose response curves for TCDD using the pGudLuc1.1-chemically activated luciferase expression (CALUX) cell bioassay and two new recombinant cell lines that contain a stably transfected mutated form of firefly luciferase reporter gene (pGudLuc6.1) or enhanced green fluorescent protein (EGFP) reporter gene (pGreen1.1). The time course of induction with pGudLuc1.1-containing H1L1.1c2 cells is transient, with maximal activity observed at 4 hours after treatment with 1 nM TCDD. In contrast, expression of luciferase from the pGudLuc6.1-containing H1L6.1c2 cells and the pGreen1.1-containing H1G1.1c3 cells progressively increases with time, with luciferase activity increasing at a significant faster rate than that of EGFP. Dose response analysis with each cell line at optimal analysis times reveal similar relative dose response curves and EC50s for H1L6.1c2 and H1G1.1c3 cells, while the EC50 for TCDD in the H1L1.1c2 cells was about 7-fold lower. In addition, these bioassay systems respond to halogenated and/or polycyclic aromatic hydrocarbons in a dose-specific manner. Given the above differences between cell lines and reporters, the choice of which cell line to use will certainly be dependent on the specific questions and issues being examined.

Indirubin, a bis-indole obtained from various natural sources, is responsible for the reported antileukemia activity of a Chinese Medicinal recipe, Danggui Longhui Wan. However, its molecular mechanism of action is still not well understood. In addition to inhibition of cyclin-dependent kinases and glycogen synthase kinase-3, indirubins have been reported to activate the aryl hydrocarbon receptor (AhR), a cotranscriptional factor. Here, we confirm the interaction of AhR and indirubin using a series of indirubin derivatives and show that their binding modes to AhR and to protein kinases are unrelated. As reported for other AhR ligands, binding of indirubins to AhR leads to its nuclear translocation. Furthermore, the apparent survival of AhR-/- and +/+ cells, as measured by the MTT assay, is equally sensitive to the kinase-inhibiting indirubins. Thus, the cytotoxic effects of indirubins are AhR-independent and more likely to be linked to protein kinase inhibition. In contrast, a dramatic cytostatic effect, as measured by actual cell counts and associated with a sharp G1 phase arrest, is induced by 1-methyl-indirubins, a subfamily of AhR-active but kinase-inactive indirubins. As shown for TCDD (dioxin), this effect appears to be mediated through the AhR-dependent expression of p27(KIP1). Altogether these results suggest that AhR activation, rather than kinase inhibition, is responsible for the cytostatic effects of some indirubins. In contrast, kinase inhibition, rather than AhR activation, represents the main mechanism underlying the cytotoxic properties of this class of promising antitumor molecules.