Prenatal Exposure to Environmentally Relevant Low Dosage Dibutyl Phthalate Reduces Placental Efficiency in CD-1 Mice

Abstract

Introduction: Dibutyl phthalate (DBP), a phthalate congener, is widely utilized in consumer products and medication coatings. Women of reproductive age have a significant burden of DBP exposure through consumer products, occupational exposure, and medication. Prenatal DBP exposure is associated with adverse pregnancy/fetal outcomes and cardiovascular diseases in the offspring. However, the role of fetal sex and the general mechanisms underlying DBP exposure-associated adverse pregnancy outcomes are unclear. We hypothesize that prenatal DBP exposure at an environmentally relevant low dosage adversely affects fetal-placental development and function during pregnancy in a fetal sex-specific manner.

Methods: Adult female CD-1 mice (8-10wks) were orally treated with vehicle (control) or with environmentally relevant low DBP dosages at 0.1 μg/kg/day (refer as DBP0.1) daily from 30 days before pregnancy through gestational day (GD) 18.5. Dam body mass composition was measured non-invasively using the echo-magnetic resonance imaging system. Lipid disposition in fetal labyrinth and maternal decidual area of placentas was examined using Oil Red O staining.

Results: DBP0.1 exposure did not significantly affect the body weight and adiposity of non-pregnant adult female mice nor the maternal weight gain pattern and adiposity during pregnancy in adult female mice. DBP0.1 exposure does not affect fetal weight but significantly increased the placental weight at GD18.5 (indicative of decreased placental efficiency) in a fetal sex-specific manner. We further observed that DBP0.1 significantly decreased lipid disposition in fetal labyrinth of female, but not male placentas, while it did not affect lipid disposition in maternal decidual.

Conclusions: Prenatal exposure to environmentally relevant low-dosage DBP adversely impacts the fetal-placental efficiency and lipid disposition in a fetal sex-specific manner.

Keywords: Dibutyl phthalate; Fetal Sex; Lipid Disposition; Placenta; Prenatal Exposure.

Figure.1

Adult female CD-1 mice weight gain compared to control over 30 days of DBP exposure at (A) 100, 10, and (B) 0.1 μg/kg/day. Data expressed as median ± standard error of mean. DBP100: 100μg/kg/day (n=8); DBP10: 10μg/kg/day (n=8); DBP0.1: 0.1μg/kg/day (n=8); Control: Vehicle only (n=14). *: Differ from Control (P<0.05). ^Δ: Differ between DBP100 and DBP10 (P<0.05).

Figure.2

Effect of DBP0.1 exposure on female fertility parameters in control (CT) and DBP0.1 treated CD-1 mice. (A) Pregnancy rate (n=18 for each group), (B) litter size (CT: n=12; DBP0.1: n=14), (C) male/female fetus ratio per litter (CT: n=12; DBP0.1: n=14), and (D) pups to CLs ratio (CT: n=9; DBP0.1: n=13) in CT and DBP0.1 treated CD-1 mice. *: Differ between CT and DBP0.1 groups (P<0.05). Each data point represents the data from an individual dam.

Figure.3

Effect of DBP0.1 exposure on weight gain patterns of pregnant dams. (A) Daily weight gain (CT: n=15; DBP0.1: n=14), (B) adiposity (body fat %; n=6 for each group), and the weight of maternal (C) heart, (D) lung, (E) kidney, (F) liver at GD18.5 in CD-1 mice (C-F: CT group: n=12; DBP0.1 group: n=14). (A) Data expressed as median ± standard deviation. (B-F) Each data point represents the data from an individual dam.

Figure.4

Effect of DBP0.1 exposure on fetal and placental weight at GD18.5. DBP0.1 exposure did not alter fetal weight (A), while it significantly increased placental weight (B) in female (F) and male (M) fetuses in CD-1 mice by GD18.5 (CT-F: n=12; CT-M: n=12; DBP0.1-F: n=14; DBP0.1-M: n=14). *:Differ between CT and DBP0.1 group within the same fetal sex; ^Δ:Differ between F and M fetuses within the same treatment group (P <0.05). Median value of all female or male fetuses from the same dam was shown as a single data point in figures.

Figure.5

Lipid disposition in (A) fetal labyrinth and (B) maternal decidual of mice placental tissues from CT and DBP0.1 groups. *: Differ between CT and DBP0.1 within the same fetal sex; ^Δ: Differ between female and male fetuses within the same treatment group (P <0.05 Two-way ANOVA). The median value of all images from the same placenta was shown as a single data point (CT-F: n=15; DBP0.1-F: n=10; CT-M: n=8); DBP0.1-M: n=11).