Identification of environmental chemicals with estrogenic activity using a combination of in vitro assays.

Abstract

Environmental chemicals that function as estrogens have been suggested to be associated with an increase in disease and dysfunctions in animals and humans. To characterize chemicals that may act as estrogens in humans, we have compared three in vitro assays which measure aspects of human estrogen receptor (hER)-mediated estrogenicity. Chemicals were first tested for estrogen-associated transcriptional activity in the yeast estrogen screen (YES). This was created by expressing hER and two estrogen response elements linked to the lacZ gene in yeast. Second, chemicals that were tested in YES were then assayed for direct interaction with hER in a competition binding assay. Third, chemicals were tested in the estrogen-responsive MCF-7 human breast cancer cell line transiently transfected with a plasmid containing two estrogen response elements linked to the luciferase gene. Together, these assays have identified two metabolites of DDT, o,p'-DDD and p,p'-DDD, that have estrogenic activity. Interestingly, previous studies had reported that the DDD metabolites were nonestrogenic in whole animal models. Alachlor, the most frequently used herbicide in the United States, cis-nonachlor, and trans-nonachlor displayed weak estrogenic activity in the combined assays. The antifungal agent benomyl had no estrogenic activity. We propose that a combination of in vitro assays can be used in conjunction with whole animal models for a more complete characterization of chemicals with estrogenic activity.ImagesFigure 1.Figure 2. AFigure 2. BFigure 3.Figure 4.Figure 5.

DDT and its metabolites alter gene expression in human uterine cell lines through estrogen receptor-independent mechanisms.

“…To examine the effects of the ER on AP-1-mediated gene expression by environmental compounds, we generated from Figure 3B). This result and the fact that o,p´-DDD has virtually no ER binding activity (19,21), indicates a non-ER-mediated AP-1 signaling mechanism. p,p´-DDA, a metabolite found in humans, had no effect on AP-1 activity.…”

“…However, this chemical is still used in many developing countries today and exists at high concentrations along with its metabolites and contaminants throughout the world, including the United States, because of long half-lives in soil, water, and the adipose tissue of animals (24,28,30,(75)(76)(77). Although DDT and some of its metabolites bind ERs (16,19,21), induce egg-shell thinning in raptors (78,79), and induce estrogen-like effects in exposed animals and humans (1,22,25), the mechanisms of action of this class of synthetic compounds is still not completely understood. Here we have shown that DDT can directly affect the activity of AP-1, an important cell regulatory factor.…”

“…Organochlorines, such as the pesticide dichlorodiphenyltrichloroethane (DDT) and its metabolites, have been shown to mimic estrogen, binding to and activating the ERs, thereby often producing estrogen-like effects (2,(16)(17)(18)(19)(20)(21). DDT and its metabolites have displayed harmful feminizing effects on wildlife such as birds (22,23), fish (22,24), and reptiles (22,(25)(26)(27), altering endogenous hormone levels (25,26), elevating estrogen-regulated protein levels (24), and reducing male phallus size (25,26).…”

In vitro synergistic interaction of alligator and human estrogen receptors with combinations of environmental chemicals.

“…The insecticide chlordane and the herbicide alachlor did not stimulate the proliferation of breast cancer cells (3). Recently, alachlor was reported to have weak estrogenic activity with the human estrogen receptor (hER) in breast cancer cells and yeast using reporter-gene assays (4).…”

Isolation of Bacterial Strains that Produce the Endocrine Disruptor, Octylphenol Diethoxylates, in Paddy Fields

“…[1][2][3][4] Endocrine disrupters include such degradation products of alkylphenol polyethoxylates (APPEOs) as nonylphenol polyethoxylates (NPPEOs) and octylphenol polyethoxylates (OPPEOs) that are commercially important surfactants. APPEOs are composed of a phenol nucleus that is o, m, and p-substituted with a hydrophobic and branched alkyl moiety, and with a hydrophilic polyethylene glycol chain linked to the phenolic oxygen.…”