Bisphenol-A exposure alters endometrial progesterone receptor expression in the nonhuman primate

Abstract

Objective: To evaluate the effect of bisphenol-A (BPA), a xenoestrogen endocrine disruptor, on endometrial P receptor (PR) expression in nonhuman primates and human cells.

Design: Controlled trial in primates.

Setting: University.

Animal(s): African green monkeys.

Intervention(s): After oophorectomy, BPA (50 μg/kg/d), E(2), both, or vehicle control were administered. Estradiol and BPA were used in Ishikawa cells.

Main outcome measure(s): Progesterone receptor expression using immunohistochemistry and quantitative polymerase chain reaction.

Result(s): Progesterone receptor expression was increased in E(2)-treated primates compared with controls. Exposure to the combination of E(2) and BPA resulted in decreased PR expression compared with E(2) exposure alone. In Ishikawa cells treated with E(2), PR expression increased 5.1-fold; however, when Ishikawa cells were simultaneously treated with E(2) and BPA, PR expression was decreased to 0.6-fold that of cells treated with E(2) alone.

Conclusion(s): Bisphenol-A alone functions as a weak estrogen. However, when administered with E(2), BPA diminishes E(2)-induced PR expression. The estrogen-like effect of BPA reported in exposed humans may be mediated by PR blockade and a resultant decrease in the estrogen inhibition normally imparted by P. Diminished PR expression may underlie previous reports linking BPA exposure to endometrial dysfunction in humans.

FIGURE 1

A) Endometrial PR expression using immunohistochemcial analysis in the non-human primate. PR immunostaining was nearly absent either the glands or stroma of control animals. BPA treatment had minimal effect on endometrial PR expression. As expected, estradiol treatment led to a large increase in both glandular and stromal PR expression. Treatment with the combination of estradiol and BPA led to decreased glandular and stromal expression compared to treatment with estradiol alone. Representative photomicrographs taken at 400X magnification are shown. B) The effect of estradiol and BPA on endometrial PR protein expression in the non-human primate. H score was used as a semi-quantitative measure of PR expression. Estradiol exposure led to a 49 fold increase in glandular PR expression and an 11 fold increase in stromal PR expression compared to vehicle treated control (*p<0.01). Exposure to a combination of estradiol and BPA decreased glandular PR expression to 62% and decreased stromal PR expression to 50% of the H-score in obtained in endometrium of animals treated with estradiol alone (**p<0.01).

FIGURE 1

A) Endometrial PR expression using immunohistochemcial analysis in the non-human primate. PR immunostaining was nearly absent either the glands or stroma of control animals. BPA treatment had minimal effect on endometrial PR expression. As expected, estradiol treatment led to a large increase in both glandular and stromal PR expression. Treatment with the combination of estradiol and BPA led to decreased glandular and stromal expression compared to treatment with estradiol alone. Representative photomicrographs taken at 400X magnification are shown. B) The effect of estradiol and BPA on endometrial PR protein expression in the non-human primate. H score was used as a semi-quantitative measure of PR expression. Estradiol exposure led to a 49 fold increase in glandular PR expression and an 11 fold increase in stromal PR expression compared to vehicle treated control (*p<0.01). Exposure to a combination of estradiol and BPA decreased glandular PR expression to 62% and decreased stromal PR expression to 50% of the H-score in obtained in endometrium of animals treated with estradiol alone (**p<0.01).

FIGURE 2

Total PR and PR-B mRNA expression in Ishikawa cell line after treatment with estradiol and /or BPA. Real-time PCR results show that total PR and PR-B expression increased 5.2 fold and 4.1 fold, respectively, in cells treated with estradiol compared to the control (*p<0.01). PR and PR-B expression increased 1.7 fold and 1.9 fold, respectively, in cells treated with BPA when compared to the control (*p<0.05). PR and PR-B expression decreased to 0.6 fold and 0.7 fold respectively, in cells treated with a combination estradiol and BPA when compared to those treated with Estradiol alone (** p<0.01 total PR and p<0.05 PR B).