Effects of endocrine disruptors on steroidogenic enzymes gene expression and on aromatase activity in two human cell lines

Abstract

Endocrine disruptors are chemicals that can alter functions of the endocrine system by several ways. In the present study, we have evaluated the effects of several endocrine disruptors and of some of their metabolites on the last step of steroidogenesis in two cell line models. Two enzymes are implicated in this step: aromatase (CYP19A1), which plays a central role by catalyzing the irreversible conversion of androgens to estrogens, and 17beta-hydroxysteroid dehydrogenase (HSD17B), which catalyses the conversion of inactive sexual hormones to active ones in different steroidogenic organs. We have screened the selected chemicals for their ability to modulate the expression of steroidogenic enzymes and aromatase activity in the human choriocarcinoma JEG-3 cell line and in the human adrenocortical H295R cell line after both short (4 h) and long exposure (24 h). All chemicals were tested at concentrations that did not cause cytotoxicity after 24h of exposure, as tested by the MTT viability assay. Gene expression profile was assessed by real-time RT-PCR and aromatase activity was assessed by the method of tritiated water. Treatments of JEG-3 cells by atrazine, methoxychlor and the vinclozolin metabolite M2 resulted in an increase of CYP19A1 mRNA levels. In contrast, Bisphenol-A and the methoxychlor metabolite HPTE down-regulated the expression of CYP19A1 mRNA. Methoxychlor and HPTE decreased the amount of HSD17B1 mRNAs. In H295R cells, atrazine up-regulated CYP19A1 mRNA expression, HPTE increased HSD17B1 mRNA levels and methoxychlor increased HSD17B1 and HSD17B5 mRNA levels. Concerning the aromatase activity, treatment of H295R cells by atrazine induced aromatase activity. Furthermore, exposure of these cells to either bisphenol A or HPTE inhibited aromatase activity. In JEG-3 cells, which display higher basal aromatase expression than H295R cells, the pattern of aromatase activity regulation was similar but less pronounced. Taken together, these initial results contribute to a better characterization of the action of endocrine disrupting chemicals and their metabolites on the steroidogenic pathways, which needs to be considered when assessing their effects on human health.