Uterine ERa epigenetic modifications are induced by the endocrine disruptor endosulfan in female rats with impaired fertility

MILESI MM; VARAYOUD J; RAMOS JG; LUQUE EH

MOLECULAR AND CELLULAR ENDOCRINOLOGY.

ELSEVIER IRELAND LTD

Lugar: Amsterdam; Año: 2017 vol. 454 p. 1 - 11

0303-7207

High ERa activity may disrupt the window of uterine receptivity, causing defective implantation. We investigated whether implantation failures prompted by endosulfan are associated with aberrant ERa uterine expression and DNA methylation status during the pre-implantation period. ERa-dependent target genes that play a crucial role in the uterine receptivity for embryo attachment and implantation were also investigated. Newborn female rats received corn oil (vehicle, Control), 6 ug/kg/d of endosulfan (Endo6) or 600 ug/kg/d of endosulfan (Endo600) on postnatal days (PND) 1, 3, 5, and 7. On PND90, females were made pregnant and on gestational day 5 (GD5, pre-implantation period) uterine samples were collected. ERa expression was assessed at protein and mRNA levels by immunohistochemistry and real time RT-PCR, respectively. ERa transcript variants mRNA containing alternative 5´-untranslated regions (5´UTRs) were also evaluated. We searched for predicted transcription factors binding sites in ERa regulatory regions and assessed their methylation status by Methylation-Sensitive Restriction Enzymes-PCR technique (MSRE-PCR). The expression of the ERa-dependent uterine target genes, i.e. mucin-1 (MUC-1), insulin-like growth factor-1 (IGF-1), and leukemia inhibitory factor (LIF), was assessed by real time RT-PCR. Both doses of endosulfan increased the expression of ERá and its transcript variants ERa-OS, ERa-O, ERa-OT and ERa-E1. Moreover, a decreased DNA methylation levels were detected in some ERá regulatory regions, suggesting an epigenetic up-regulation of it transcription. ERá overexpression was associated with an induction of its downstream genes, MUC-1 and IGF-1, suggesting that endosulfan might alter the uterine estrogenic pathway compromising uterine receptivity. These alterations could account, at least in part, for the endosulfan-induced implantation failures.