Epigenetic disruption of estrogen receptor alpha following perinatal exposure to a glyphosate-based herbicide

GUERRERO SCHIMPF ML; LUQUE EH; LORENZ V; VARAYOUD J; MILESI MM

Congreso; Reunión conjunta de sociedades de Biociencias; 2017

Previously, we showed that perinatal (in utero and lactational) exposure to a glyphosate based herbicide (GBH) produced subfertility associated with implantation failures in female rats. Implantation process is regulated by endocrine signaling pathways in which ERA is one of the primary mediators. Five promoters (E1, OT, O, ON, and OS) control the ERA transcription initiation, yielding different transcripts with alternative 5´ untranslated regions (5?UTRs). This work investigates whether a low dose of a GBH modifies uterine ER expression and induces epigenetic modifications in its regulatory regions during the pre-implantation period. Pregnant rats (F0) were orally exposed to 200 mg of glyphosate/kg/day (NOAEL, EPA) through food, from gestational day (GD) 9 until weaning (lactational day 21). When F1 females reach the sexual maturity, they were pregnant and uterine samples were collected on GD5 (pre-implantation period). ERA expression was determined using RT-qPCR. ERA mRNA levels of transcript variants containing alternative 5´UTRs were also evaluated. Then we in silico evaluated the presence of CpG islands and specific restriction sites (for MaeII and BstUI) to analyze the methylation status using Methylation-Sensitive Restriction Enzymes-PCR technique. Post-translational changes of histones were also studied by chromatin immunoprecipitation assay. GBH treatment increased total ERA mRNA expression mediated by an increased expression of ERA-O variant. GBH rats exhibited a decreased DNA methylation in one of the three sites evaluated in the O promoter. In addition, we detected a higher level of histone 3 (H3) acetylation and a decreased level of H3 methylation at Lys 27. All these epigenetic changes are in accordance with the higher transcriptional activity of ER in GBH treated rats. We detected that low-dose perinatal GBH exposure induces lasting epigenetic disruption in the uterus possible related with the implantation failures.