Evaluation of estrogenic activity of phthalate esters by gene expression profiling using a focused microarray (estrarray^®)

Abstract

Phthalates are used industrially as plasticizers and are known to contaminate natural environments, mostly as di-ester or mono-ester complexes. Because they are structurally similar to natural estrogens, they could act as endocrine disruptors. Here, we used a DNA microarray containing estrogen responsive genes (EstrArray) to examine gene expression profiles in MCF-7 cells treated with 10 microM butylbenzyl phthalate (BBP), dibutyl phthalate (DBP), diethyl phthalate (DEP), and diisopropyl phthalate (DIP) along with the natural estrogen 17beta-estradiol ([E(2)], 10 nM). The profiles for phthalate esters and E(2) were examined by correlation analysis using correlation coefficients (r-values) and cluster analysis. We found that BBP showed the highest correlation with E(2) (r = 0.85), and DEP and DIP showed moderate r-values (r = 0.52 and r = 0.49, respectively). Dibutyl phthalate exhibited the lowest (but still significant) correlation with E(2) (r = 0.36). Furthermore, among the pairs of chemicals, DEP-DIP and DIP-DBP showed very high correlations (r = 0.90 and r = 0.80, respectively), and the other pairs showed moderate relationships, which reflected how structurally close they are to each other. The analysis of six functional groups of genes (enzymes, signaling, proliferation, transcription, transport, and others) indicated that the genes belonging to the enzyme, transcription, and other functional groups showed common responses to phthalate esters and E(2). Although the effect of BBP was similar to that of E(2), the other phthalate esters showed different types of effects. These results indicate that the structure of estrogenic chemicals is strongly related to their estrogenic activity and can be evaluated by appropriate grouping of the responsive genes by focused microarray analysis.

Transcriptional profiling of Chinese medicinal formula Si-Wu-Tang on breast cancer cells reveals phytoestrogenic activity

“…DNA microarray – based expression profiling has been used as a genomic approach for the characterization of compounds with estrogen-like activities. For examples, a customized DNA microarray containing 172 estrogen-responsive genes have been used to evaluate the effect of multiple well known phytoestrogens including genistein and daidzein [19], and the industrial endocrine disruptors including zearalenone, diethylstilbestrol and dioxin [20-23]. These results obtained using DNA microarrays were consistent with those derived from other bioassays that are used for detecting estrogenic activity, such as ligand-binding and reporter gene assays.…”

Toxicity and Estrogenic Endocrine Disrupting Activity of Phthalates and Their Mixtures

“…To be more specific, BBP, though it caused no estrogenic effect in one ovariectomized Sprague-Dawley rat based an in vivo assay using uterine wet weight and vaginal cell cornification as endpoints [20], it has repeatedly demonstrated estrogenic activity in the present and several previous in vitro studies [15,16,18,20]. DBP that reportedly exhibited estrogenic activity in some in vitro tests [15,16,33], did not induce detectable estrogenic activity signal in the present and other in vitro and in vivo studies [20,34].…”

“…Though studies have been carried out to evaluate the estrogenic endocrine disrupting activity of phthalates, and some phthalates such as DEP, DBP, BBP and DEHP have been reported to possess estrogenic activity in vitro [14,15,16,17,18,19,20], the toxicity and estrogenic endocrine disrupting potency of some phthalates and phthalate mixtures in in vivo systems are still not clear. …”

Expression profiling of the genes responding to zearalenone and its analogues using estrogen‐responsive genes

“…DNA microarrays have opened a new paradigm in toxicology [19], by characterizing the genome‐wide response of gene expression stimulated by endocrine‐disrupting chemicals and by offering a means of understanding the biological effects and mechanisms of estrogenicity on a genome‐wide scale. We have already applied this technology to several chemicals of artificial and natural origins [20–24]. Here, we obtained expression profiles of estrogen‐responsive genes for ZEA and its analogues and attempted to identify specific genes or biological pathways to understand their mode of action.…”