Endocrine disrupting chemicals and the mammary gland

Subacute tributyltin exposure alters the development and morphology of mammary glands in association with CYP19A1 expression in female rats

Tributyltin (TBT) is an endocrine-disrupting chemical (EDC) related to reproductive dysfunctions. However, few studies have investigated the effects of TBT exposure on mammary gland development. Thus, we assessed whether subacute TBT exposure causes irregularities in mammary gland development. We administered TBT (100 and 1,000 ng/kg/day for 30 days) to female rats from postnatal day (PND) 25 to PND 55, and mammary gland development, morphology, inflammation, collagen deposition, and protein expression were evaluated. Abnormal mammary gland development was observed in both TBT groups. Specifically, TBT exposure reduced the number of terminal end buds (TEBs), type 1 (AB1) alveolar buds, and type 2 (AB2) alveolar buds. An increase in the lobule and differentiation (DF) 2 score was found in the mammary glands of TBT rats. TBT exposure increased mammary gland blood vessels, mast cell numbers, and collagen deposition. Additionally, both TBT rats exhibited intraductal hyperplasia and TEB-like structures. An increase in estrogen receptor alpha (ERα), progesterone receptor (PR), and cytochrome P450 family 19 subfamily A member 1 (CYP19A1) - positive cells was observed in the mammary glands of TBT rats. A strong negative correlation was observed between CYP19A1- positive cells and TEB number. In addition, CYP19A1 - positive cells were positively correlated with mammary gland TEB-like structure, ductal hyperplasia, inflammation, and collagen deposition. Thus, these data suggest that TBT exposure impairs mammary gland development through the modulation of CYP19A1 signaling pathways in female rats.

Effects of a TAML catalyst on mice exposed during pregnancy and lactation

Tetra-amido macrocyclic ligands (TAMLs) are catalysts designed to mimic endogenous peroxidases that can degrade pollutants. Before TAMLs gain widespread use, it is first important to determine if they have endocrine disrupting properties. In this study, we evaluated the effects of the iron TAML, NT7, on hormone-sensitive outcomes in mice exposed during pregnancy and lactation, and on their litters prior to weaning. We administered NT7 at one of three doses to mice via drinking water prior to and then throughout pregnancy and lactation. Two hormonally active pharmaceuticals, ethinyl estradiol (EE2) and flutamide (FLUT), a known estrogen receptor agonist and androgen receptor antagonist, respectively, were also included. In the females, we measured pre- and post-parturition weight, length of pregnancy, organ weights at necropsy, and morphology of the mammary gland at the end of the lactational period. We also quantified maternal behaviors at three stages of lactation. For the offspring, we measured litter size, litter weights, and the achievement of other developmental milestones. We observed only one statistically significant effect of NT7, a decrease in the percentage of pups with ear opening at postnatal day 5. This contrasts with the numerous effects of EE2 on both the mother and the litter, as well as several modest effects of FLUT. The approach taken in this study could provide guidance for future studies that aim to evaluate novel compounds for endocrine disrupting properties.

Causes of Low Milk Supply: The Roles of Estrogens, Progesterone, and Related External Factors

Low milk supply (LMS) poses a significant challenge to exclusive and continued breastfeeding, affecting ∼10% to 15% of mothers. Milk production is intricately regulated by both endocrine and autocrine control mechanisms, with estrogens and progesterone playing pivotal roles in this process. In addition to endogenously produced hormones, external substances capable of interfering with normal hormonal actions, including phytoestrogens, mycoestrogens, synthetic estrogens, and hormonal contraceptives, can influence milk production. The effects of these extrinsic hormones on milk production may vary based on maternal body mass index. This comprehensive review examines the multifaceted causes of LMS, focusing on the involvement of estrogens, progesterone, and related external factors in milk production. Furthermore, it investigates the interplay between hormonal factors and obesity, aiming to elucidate the endocrine mechanisms underlying obesity-associated LMS. Insights from this review provide valuable perspectives for developing interventions to improve milk production and address the challenges associated with LMS.

The regulation of endocrine-disrupting chemicals to minimize their impact on health

Endocrine-disrupting chemicals (EDCs) are substances generated by human industrial activities that are detrimental to human health through their effects on the endocrine system. The global societal and economic burden posed by EDCs is substantial. Poorly defined or unenforced policies can increase human exposure to EDCs, thereby contributing to human disease, disability and economic damage. Researchers have shown that policies and interventions implemented at both individual and government levels have the potential to reduce exposure to EDCs. This Review describes a set of evidence-based policy actions to manage, minimize or even eliminate the widespread use of these chemicals and better protect human health and society. A number of specific challenges exist: defining, identifying and prioritizing EDCs; considering the non-linear or non-monotonic properties of EDCs; accounting for EDC exposure effects that are latent and do not appear until later in life; and updating testing paradigms to reflect 'real-world' mixtures of chemicals and cumulative exposure. A sound strategy also requires partnering with health-care providers to integrate strategies to prevent EDC exposure in clinical care. Critical next steps include addressing EDCs within global policy frameworks by integrating EDC exposure prevention into emerging climate policy.

Hormonal regulation of mammary gland development and lactation

Lactation is critical to infant short-term and long-term health and protects mothers from breast cancer, ovarian cancer and type 2 diabetes mellitus. The mammary gland is a dynamic organ, regulated by the coordinated actions of reproductive and metabolic hormones. These hormones promote gland development from puberty onwards and induce the formation of a branched, epithelial, milk-secreting organ by the end of pregnancy. Progesterone withdrawal following placental delivery initiates lactation, which is maintained by increased pituitary secretion of prolactin and oxytocin, and stimulated by infant suckling. After weaning, local cytokine production and decreased prolactin secretion trigger large-scale mammary cell loss, leading to gland involution. Here, we review advances in the molecular endocrinology of mammary gland development and milk synthesis. We discuss the hormonal functions of the mammary gland, including parathyroid hormone-related peptide secretion that stimulates maternal calcium mobilization for milk synthesis. We also consider the hormonal composition of human milk and its associated effects on infant health and development. Finally, we highlight endocrine and metabolic diseases that cause lactation insufficiency, for example, monogenic disorders of prolactin and prolactin receptor mutations, maternal obesity and diabetes mellitus, interventions during labour and delivery, and exposure to endocrine-disrupting chemicals such as polyfluoroalkyl substances in consumer products and other oestrogenic compounds.

Environmental chemical TCPOBOP disrupts milk lipid homeostasis during pregnancy and lactation

Humans are exposed to different kinds of environmental contaminants or drugs throughout their lifetimes. The widespread presence of these compounds has raised concerns about the consequent adverse effects on lactating women. The constitutive androstane receptor (CAR, Nr1i3) is known as a xenobiotic sensor for environmental pollution or drugs. In this study, the model environmental chemical 1, 4-bis [2-(3, 5-dichloropyridyloxy)] benzene, TCPOBOP (TC), which is a highly specific agonist of CAR, was used to investigate the effects of exogenous exposure on lactation function and offspring health in mice. The results revealed that TC exposure decreased the proliferation of mammary epithelial cells during pregnancy. This deficiency further compromised lobular-alveolar structures, resulting in alveolar cell apoptosis, as well as premature stoppage of the lactation cycle and aberrant lactation. Furthermore, TC exposure significantly altered the size and number of milk lipid droplets, suggesting that TC exposure inhibits milk lipid synthesis. Additionally, TC exposure interfered with the milk lipid metabolism network, resulting in the inability of TC-exposed mice to efficiently secrete nutrients and feed their offspring. These findings demonstrated that restricted synthesis and secretion of milk lipids would indirectly block mammary gland form and function, which explained the possible reasons for lactation failure and retarded offspring growth.

New insights into the effect of bisphenol AF exposure on maternal mammary glands at various stages of gestation in mice

Bisphenol AF (BPAF) is the most estrogenic compound among BPA analogs. Mammary glands (MDs) are special organs that undergo repeated cycles of structural development, metabolism, and functional differentiation. Gestation is a sensitive window for MDs. In the present study, plug-positive CD-1 mice were exposed to vehicle (Veh) or 300 μg/kg BPAF through oral gavage every second day during gestation, and maternal MDs were collected from different developmental windows at 9.5, 13.5, and 18.5 d of gestation (gestation day [GD]9.5, GD13.5 and GD18.5). The results showed that gestational BPAF exposure induced a significantly elevated MD density at GD18.5. Non-target metabolomics analysis was used to screen for tyrosine, valine, ornithine, proline, threonine, phenylalanine and asymmetrical dimethylarginine (ADMA) amino acids, which changed significantly at all time points. Furthermore, the mRNA expression levels of genes related to these amino acids also changed significantly. Additionally, amino acid levels in BPAF-treated MGs at GD18.5 were related to the serum ammonia concentration of the corresponding offspring. These results provide a comprehensive view of the adverse effects of BPAF exposure during gestation on the maternal MG structure and function, which may affect milk components during lactation. Moreover, higher amino acids content may lead to amino acid imbalance or hyperammonemia in newborns.

Exposure to Low Doses of Oxybenzone During Perinatal Development Alters Mammary Gland Stroma in Female Mice

Mammary stroma is a prominent modulator of epithelial development, and a complex set of interactions between these tissue compartments is essential for normal development, which can be either permissive or restrictive in tumor initiation and progression. During perinatal development, exposures of mice to oxybenzone, a common UV filter, environmental pollutant and endocrine disruptor, induce alterations in mammary epithelium. Our prior research indicates that oxybenzone alters mammary epithelial structures at puberty and in adulthood. We had also previously observed changes in the expression of hormone receptors at puberty (e.g., oxybenzone induced a decrease in the number of epithelial cells positive for progesterone receptor) and in adulthood (e.g., oxybenzone induced a decrease in the number of estrogen receptor-positive epithelial cells), and increased body weight in adulthood. Here, we investigated mammary stromal changes in BALB/c animals exposed during gestation and perinatal development to 0, 30, or 3000 μg oxybenzone/kg/day. In mice exposed to 30 μg/kg/day, we observed morphological changes in adulthood (e.g., a thicker periductal stroma and adipocytes that were considerably larger). We also observed an increased number of mast cells in the mammary stroma at puberty which may represent a transient influence of oxybenzone exposure. These results provide additional evidence that even low doses of oxybenzone can disrupt hormone sensitive outcomes in the mammary gland when exposures occur during critical windows of development, and some of these effects manifest in later life.