Assessment of xenoestrogens using three distinct estrogen receptors and the zebrafish brain aromatase gene in a highly responsive glial cell system

The brain cytochrome P450 aromatase (Aro-B) in zebrafish is expressed in radial glial cells and is strongly stimulated by estrogens (E2); thus, it can be used in vivo as a biomarker of xenoestrogen effects on the central nervous system. By quantitative real-time polymerase chain reaction, we first confirmed that the expression of Aro-B gene is robustly stimulated in juvenile zebrafish exposed to several xenoestrogens. To investigate the impact of environmental estrogenic chemicals on distinct estrogen receptor (ER) activity, we developed a glial cell-based assay using Aro-B as the target gene. To this end, the ER-negative glial cell line U251-MG was transfected with the three zebrafish ER subtypes and the Aro-B promoter linked to a luciferase reporter gene. E2 treatment of U251-MG glial cells cotransfected with zebrafish ER-alpha and the Aro-B promoter-luciferase reporter resulted in a 60- to 80-fold stimulation of luciferase activity. The detection limit was <0.05 nM, and the EC50 (median effective concentration) was 1.4 nM. Interestingly, in this glial cell context, maximal induction achieved with the Aro-B reporter was three times greater than that observed with a classical estrogen-response-element reporter gene (ERE-tk-Luc). Dose-response analyses with ethynylestradiol (EE2), estrone (E1), alpha-zeralenol, and genistein showed that estrogenic potency of these agents markedly differed depending on the ER subtype in the assay. Moreover, the combination of these agents showed an additive effect according to the concept of concentration addition. This confirmed that the combined additive effect of the xenoestrogens leads to an enhancement of the estrogenic potency, even when each single agent might be present at low effect concentrations. In conclusion, we demonstrate that our bioassay provides a fast, reliable, sensitive, and efficient test for evaluating estrogenic potency of endocrine disruptors on ER subtypes in a glial context.

Health effects and time course of particulate matter on the cardiopulmonary system in rats with lung inflammation

Recent epidemiological studies associate health effects and particulate matter in ambient air. Exacerbation of the particle-induced inflammation can be a mechanism responsible for increased hospitalization and death due to cardiopulmonary events in high-risk groups of the population. Systems regulating blood pressure that depend on lung integrity can be involved in progression of cardiovascular diseases. This study focused on the expression levels of various genes involved in cardiovascular and pulmonary diseases to assess their role in the onset of cardiovascular problems due to ambient particulate matter and compared these with the corresponding products. Rats with ozone-induced (1600 microg/m(3); 8 h) pulmonary inflammation were exposed to 0.5 mg, 1.5 mg, or 5 mg of particulate matter (PM) from Ottawa Canada (EHC-93) by intratracheal instillation. mRNA levels of various genes and their products were measured 2, 4, and 7 d after instillation. At 2 d after exposures to PM, tumor necrosis factor (TNF)-alpha levels in bronchoalveolar lavage fluid (BALF) were elevated approximately 4 times for the highest EHC-93 dose. MIP-2 protein levels in BALF were elevated approximately three times during the entire time period studied, whereas IL-6 levels were not affected compared to control groups. The MIP-2 mRNA levels revealed a similar pattern of induction. A twofold increase in endothelin (ET)-1 levels at d 2 and a 20% decrease in angiotensin-converting enzyme (ACE) activity at d 7 were measured in plasma. A 60% decrease of ACE and ET-1 mRNA levels suggested a possible endothelial damage in the lung blood vessels. Inducible nitric oxide synthase (iNOS) mRNA was found to be increased 3.5 times 2 d after instillation of the particles. Therefore, the endothelial damage could have been caused by large amounts of the free radical NO. Also, plasma levels of fibrinogen were elevated (20%), which could presumably increase blood viscosity, leading to decreased tissue blood flow. These changes in hematological and hemodynamic parameters observed in our study are in line with heart failure in high-risk groups of the population after high air pollution episodes.

Assessment of polystyrene extract for estrogenic activity in the rat uterotrophic model and an in vitro recombinant receptor reporter gene assay

The purpose of the study was to determine whether polystyrene used in food-contact applications would elicit an estrogenic response when extracts simulating exaggerated conditions of use were subjected to in vivo and in vitro tests. A sample of polystyrene was subjected to extraction conditions that simulate, or exaggerate, the actual food-contact uses of polystyrene to maximize the amount of low molecular weight polystyrene extractables. The food-simulating solvent and the time and temperature conditions recommended by the Food and Drug Administration (FDA) were selected to maximize the level of extractable components from polystyrene. The extract was examined for its estrogenic response in vivo using the immature rat uterotrophic assay and in vitro using an estrogen receptor (ER)-mediated recombinant receptor reporter gene assay. In vivo, the uterine weights of juvenile female Sprague Dawley rats (10 rats/group) were determined after oral gavage exposure to the extract (two dosage levels: one represents the maximum potential daily human exposure to polystyrene extractables and the other represents one-tenth of the maximum exposure level), vehicle control (sesame oil), or positive control [diethylstilbestrol (DES), at 200 micrograms/kg body weight]. In addition, five treatment groups were dosed by subcutaneous injection of either estradiol (1, 50, and 500 micrograms/kg body weight) or DES (2 and 200 micrograms/kg body weight). Dosing began on postnatal day (pnd) 21 and continued daily through pnd 23. Body weights were collected at study initiation (pnd 21) and at necropsy (pnd 24). Body weights were not different statistically between treatment groups at study initiation or at necropsy. Uterine wet weights and uterine weights relative to body weights were significantly increased (p < 0.05) for estradiol at 50 and 500 micrograms/kg, DES at 2 and 200 micrograms/kg, and DES at 200 micrograms/kg (oral) over vehicle control. The polystyrene extract had no effect on uterine wet weight or uterine weights relative to body weights at either level tested. An in vitro recombinant estrogen receptor/reporter gene assay that involved transiently transfecting MCF-7 human breast cancer cells with the chimeric human ER, Ga14-HEGO, consisting of the yeast Ga14 DNA binding domain linked to the ligand binding domain of the human ER and a Ga14 response element (17mer)-regulated reporter gene (17m5-G-Luc) was employed. Dose-dependent induction of the reporter gene, 17m5-G-Luc, was observed with the positive control, 17 beta-estradiol (E2). Induction of greater than 100-fold was obtained following incubation of transfected MCF-7 cells with 10 nM E2 for 24 hours. No induction of reporter gene activity was observed with the polystyrene extracts dissolved in dimethylsulfoxide (0.01, 0.1 or 0.01 mg/ml) using the same assay conditions. These results indicate that polystyrene extract does not elicit ER-mediated activity using the Ga14-HEGO/17m5-G-Luc recombinant receptor/reporter gene assay. In conclusion, extracts from polystyrene produced no estrogenic response in either the rat uterotrophic assay or the MCF-7 cell assay for estrogen receptor-mediated activity.