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

Abstract

Endocrine-disrupting organochlorines, such as the pesticide dichlorodiphenyltrichloroethane (DDT), bind to and activate estrogen receptors (ERs), thereby eliciting estrogen-like effects. Although ERs function predominantly through activation of transcription via estrogen-responsive elements, both ERs, alpha and ss, can interact with various transcription factors such as activator protein-1 (AP-1). Additionally, estrogens may regulate early signaling events, suggesting that the biological effects of environmental estrogens may not be mediated through classic ER (alpha and ss) activity alone. We hypothesized that known environmental estrogens, such as DDT and its metabolites, activate AP-1-mediated gene transactivation through both ER-dependent and ER-independent means. Using two Ishikawa human endometrial adenocarcinoma cell line variants that we confirmed to be estrogen responsive [Ishikawa(+)] and estrogen unresponsive [Ishikawa(-)], we generated stably transfected AP-1 luciferase cell lines to identify the role of an estrogen-responsive mechanism in AP-1-mediated gene expression by various stimuli. Our results demonstrate that DDT and dichlorodiphenyldichloroethane (DDD) were the most potent activators of AP-1 activity; 2,2-bis(p-chlorophenyl) acetic acid failed to activate. Although stimulated in both Ishikawa(+) and Ishikawa(-) cells by DDT and its congeners, AP-1 activation was more pronounced in the estrogen-unresponsive Ishikawa(-) cells. In addition, DDT, DDD, and dichlorodiphenyldichloroethylene (DDE) could also stimulate AP-1 activity in the estrogen-unresponsive human embryonic kidney 293 cells using a different promoter context. Thus, our data demonstrate that DDT and its metabolites activate the AP-1 transcription factor independent of ER (alpha or ss) status.

Binding of MCF‐7 cell mitochondrial proteins and recombinant human estrogen receptors α and β to human mitochondrial dna estrogen response elements

“…MCF-10A cells are negative for ERb expression [Lane et al, 1999]. MDA-MB-231 cells express ERb but not ERa [Jiang and Jordan, 1992;Frigo et al, 2002;Chen et al, 2004, in press]. MCF-7 and MDA-MB 231 cells were cultured in phenol red-free IMEM (Biofluids, Bioscience International, Camarilla, CA) and DMEM (Roche), respectively, containing 5% fetal bovine serum (FBS) (Hyclone, Logan, UT) and gentamycin (Roche).…”

Gene expression analysis of estrogenic compounds in the liver of common carp (Cyprinus carpio) using a custom cDNA microarray

“…Yet, estrogenic chemicals can also act upon the cell by interacting with other molecules first, for example, by a metabolic activation or modification by various cytochrome P450 isoforms [7,8]. Furthermore, some xenoestrogens may exert additional (nonestrogenic) effects, independent of the estrogen receptor [9][10][11]. Monitoring the expression of multiple genes, involved in a wide spectrum of cellular processes and signaling pathways, rather than focusing on a single gene (e.g., the ER), is therefore crucial to unravel molecular mechanisms underlying the observed adverse physiological effects of these compounds.…”

Endocrine disruption of oestrogen action and female reproductive tract cancers

“…Interestingly, DDT has been shown to mediate ER-dependent changes in gene expression by binding either ERE or AP-1 binding sites in promoters. In addition, DDT has been shown to activate ER-independent transcription in Ishikawa cells (Frigo et al 2002). DDT and its metabolites have weak binding affinity for ERa and ERb, although o,p 0 -DDT has been reported to activate ERa (Kuiper et al 1998).…”