Chronic exposure to BPA impairs steroid hormone signalling in the mouse uterus, and may contribute to the pathogenesis of uterine hyperplasia and cancer. - GreenMedInfo Summary

Uterine epithelial proliferation is regulated in a paracrine manner by a complex interplay between estrogen (E) and progesterone (P) signaling, wherein E stimulates proliferation and P inhibits it. Perturbation of steroid hormone signaling within the uterine milieu could contribute to the development of endometrial hyperplasia and cancer. It is well established that bisphenol-A (BPA) is an endocrine disrupting chemical with weak estrogenic effects, although little is known about how it impacts steroid hormone signaling in the adult uterus. Because BPA acts as a weak estrogen, we hypothesized that chronic exposure to BPA would create an imbalance between E and P signaling and cause changes in the uterus, such as aberrant epithelial proliferation. Indeed, exposure to an environmentally relevant dose of BPA had a uterotrophic affect. BPA treated mice showed increased proliferation, notably in the glandular epithelium, which are sites of origin for endometrial hyperplasia and cancer. Increased proliferation appeared to be mediated through a similar mechanism as E-induced proliferation, via activation of the fibroblast growth factor receptor pathway and phosphorylation of the ERK1/2 mitogen-activated protein kinases in the epithelium. Interestingly, BPA reduced expression of HAND2, a known mediator of the anti-proliferative effects of P. BPA also increased methylation of a CpG island in the Hand2 gene promoter, suggesting that BPA may promote epithelial proliferation through epigenetic silencing of anti-proliferative factors like HAND2. Collectively, these findings establish that chronic exposure to BPA impairs steroid hormone signaling in the mouse uterus, and may contribute to the pathogenesis of uterine hyperplasia and cancer.