Global gene expression and morphological alterations in the mammary gland after gestational exposure to bisphenol A, genistein and indole-3-carbinol in female Sprague-Dawley offspring

Abstract

This study aimed to evaluate the modifying effects of dietary genistein (GEN) and indole-3-carbinol (I3C) on early mammary gland development in female Sprague-Dawley offspring born to mothers exposed to BPA during gestation. Pregnant rats were treated with BPA25 or 250 μg/kg bw/day from gestational days 10 to 21 with or without dietary intake of GEN (250 mg/kg chow) or I3C (2000 mg/kg chow). At post-natal day (PND) 21, female offspring from different litters were euthanized for mammary gland development and gene expression analyses. Our results indicated that prenatal exposure to BPA25 and 250 did not modify the ductal elongation of the mammary gland tree or the estrogen receptor alpha (ER-α) expression in terminal end buds (TEBs). However, BPA25exposed offspring had a higher number of terminal structures (TEBs + TDs) and an increased mammary branching and cell proliferation index in TEBs. Besides that, BPA25 and 250 modulated the expression of several genes in the immature mammary gland that were not changed in a dose dependent manner and involved different clusters of up-and down-regulated genes. Furthermore, BPA25 and BPA250 + I3C-treated groups also had a higher number of enriched functional gene categories. In addition, maternal dietary GEN and I3C in association with BPA exposure produced specific gene expression alterations in the mammary gland and overcome the adverse effect of BPA25, decreasing the branching of the mammary gland. In conclusion, prenatal BPA exposure induced both morphological and gene expression modifications on the mammary gland that dietary intake of GEN and I3C reverted on BPA25-exposed animals.

Re‐evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs

“…Delayed ductal growth was observed at PND30 after s.c. application of 250 μg/kg bw per day (equal to 8,925 μg/kg bw per day, GD7–23, Kass et al, 2015 [RefID 3402]). In another study, increased branching score and number of terminal ducts (TDs) and TEB+TDs are induced by 25 μg/kg bw per day (but not at 250 μg/kg bw per day) on PND21 after exposure from GD10 until GD21 (Grassi et al., 2016 [RefID 2387]). This finding is supported by a Tier 3 study (Leung et al, 2017 [RefID 3990]) showing also increased numbers of TEBs at 2.5 and 25 μg/kg bw per day.…”

“…For histological effects in this exposure period seven studies were identified, i.e. one Tier 1 study in mice (Tucker et al, 2018 [RefID 13275]), five Tier 1 studies in rats (Grassi et al, 2016 [RefID 2387]; Kass et al, 2015 [RefID 3402]; Mandrup et al, 2016 [RefID 4831]; NTP Clarity Report, 2018/Camacho et al, 2019 [RefID 11370]; Montévil et al, 2020 [RefID 13788]) and one Tier 3 study in rats (Leung et al., 2017 [RefID 3990]).…”

“…Additionally, in Kass et al ( 2015 ) [RefID 3402] male pups were exposed to BPA by s.c. injection of 25 and 250 μg/kg bw per day (converted to the correspondent oral doses 892.5 and 8,925 μg/kg bw per day) from GD9 until GD23, resulting in an increased ductal growth at PND5 (transient effect) and a delay in ductal growth when assessed on PND30, both at the higher dose. No changes in ductal length were observed at PND21 in female rats when exposed to 25 or 250 μg/kg bw per day from GD10–GD21 (Grassi et al, 2016 [RefID 2387]). No changes in longitudinal growth at PND20 or in lobuloalveolar hyperplasia at 8 and 14 months were reported in female mice exposed to high doses (500, 5,000 or 50,000 μg/kg bw per day) during gestation (Tucker et al, 2018 [RefID 13275]).…”

Implementation of the evidence‐based risk assessment for the re‐evaluation of Bisphenol A: preparatory work on Mode of Action studies in mammalian, human and/or in vitro models.

“…Three studies within the mammalian stream were concerned with mammary gland development. Grassi et al (2016) [RefID #2387] aimed to evaluate the modifying effects of gestational BPA on early mammary gland development in female rat offspring. Prenatal BPA exposure induced both morphological and epigenetic gene expression modifications on the mammary gland with alterations in several genes occurring at a low BPA dose.…”

“…this cluster were concerned with the development of mammary gland. These are studies reported byGrassi et al (2016) [RefID #2387], Kas et al (2015) [RefID #3402] and Tucker et al (2018) [RefID #13275] and all have been summarised in Section 3.8.5 'Proliferative changes to the mammary gland'. (vii) Neuronal development Several studies in this cluster were concerned with neurological development.…”