Placental BCRP transporter reduces cadmium accumulation and toxicity in immortalized human trophoblasts

Mycoestrogen Exposure during Pregnancy: Impact of the ABCG2 Q141K Variant on Birth and Placental Outcomes

BACKGROUND

Zearalenone (ZEN) is an estrogenic mycotoxin ("mycoestrogen") that contaminates global grain crops leading to detectable concentrations of ZEN and its metabolites, including the synthetic version α -zearalanol (also called zeranol; ZER), in human populations. Despite in vitro and in vivo animal evidence of endocrine disruption by ZEN, there has been limited investigation in humans.

OBJECTIVES

To examine markers of fetal growth following prenatal exposure to ZEN and evaluate the role of the placental efflux transporter BCRP/ABCG2 in protecting against ZEN's potential fetoplacental toxicity.

METHODS

Placentas were collected from participants (n = 271 ) in the Understanding Pregnancy Signals and Development cohort (Rochester, New York, USA). Placental ZEN and its metabolites were analyzed from tissue samples using HPLC-MS. Birth weights and placental weights were obtained from medical records and direct measurement, respectively; fetoplacental weight ratio (FPR) was calculated by dividing birth weight by placental weight. Covariate-adjusted generalized linear regression models were used to examine ZEN, ZER, and total mycoestrogens (sum of ZEN, ZER, and their metabolites) in relation to birth length, birth weight, placental weight and FPR. We additionally stratified models by infant sex and ABCG2 C421A (Q141K) genotype.

RESULTS

Mycoestrogens were detected in 84% of placentas (median ZEN: 0.010  ng / g ) and total mycoestrogens were associated with lower FPR [- 0.20 ; 95% confidence interval (CI): - 0.32 , - 0.08 ], particularly in female infants (- 0.31 ; 95% CI: - 0.52 , - 0.09 ). Associations with birth weight were inverse and overall nonsignificant. Among the 17% of participants with the reduced function 421A ABCG2 variant (AA or AC), total mycoestrogens were associated with lower birth weight (- 113.5 g ; 95% CI: - 226.5 , - 0.50 ), whereas in wild-type individuals, total mycoestrogens were associated with higher placental weight (9.9; 95% CI: 0.57, 19.2) and reduced FPR (- 0.19 ; 95% CI: - 0.33 , - 0.05 ).

DISCUSSION

Results from this epidemiological study of prenatal mycoestrogen exposure and perinatal health suggest that mycoestrogens may reduce placental efficiency, resulting in lower birth weight, particularly in female and ABCG2 421A infants. https://doi.org/10.1289/EHP14478.

Fetoplacental Disposition and Toxicity of Cadmium in Mice Lacking the Bcrp Transporter

The environmental toxicant cadmium (Cd) impairs the growth of rodents and humans in utero which in turn heightens susceptibility to diseases later in life. We previously demonstrated that the maternal-facing efflux transporter, breast cancer resistance protein (human BCRP/ABCG2, mouse Bcrp/Abcg2) confers resistance against Cd toxicity in human trophoblasts. In the current study, we sought to determine whether the absence of Bcrp alters the fetoplacental disposition and toxicity of Cd in mice. Pregnant female wild-type (WT) and Bcrp-null mice (n = 9-10/group) were administered a single injection of saline (5 ml/kg) or CdCl2 (5 mg/kg) on gestational day (GD) 9. Following Cd treatment, Bcrp-null offspring were shorter and accumulated more Cd in their placentas on GD 17 compared to WT mice. Because Cd can adversely impact placentation and transplacental nutrient delivery in mice, multiple pathways were assessed using morphometrics and immunohistochemistry including placenta zonation, vasculature development, and nutrient transporter expression. Most notably, the placentas of Bcrp-null mice had reduced immunostaining of the cell adhesion marker, β-catenin, and the trophoblast marker, cytokeratin, as well as decreased expression of divalent metal nutrient transporters (Dmt1, Zip14, and ZnT1) following Cd treatment. In summary, the absence of Bcrp expression increased placental concentrations of Cd which was associated with shorter fetal size that may be related to differential changes in molecular patterns of placental development and nutrition.