Conjugation and Deconjugation Reactions within the Fetoplacental Compartment in a Sheep Model: A Key Factor Determining Bisphenol A Fetal Exposure
作者:Tanguy Corbel、Elisabeth Perdu、Véronique Gayrard、Sylvie Puel、Marlène Z. Lacroix、Catherine Viguié、Pierre-Louis Toutain、Daniel Zalko、Nicole Picard-Hagen
DOI:10.1124/dmd.114.061291
日期:2015.4
The widespread human exposure to bisphenol A (BPA), an endocrine disruptor targeting developmental processes, underlines the need to better understand the mechanisms of fetal exposure. Animal studies have shown that at a late stage of pregnancy BPA is efficiently conjugated by the fetoplacental unit, mainly into BPA-glucuronide (BPA-G), which remains trapped within the fetoplacental unit. Fetal exposure to BPA-G might in turn contribute to in situ exposure to bioactive BPA, following its deconjugation into parent BPA at the level of fetal sensitive tissues. The objectives of our study were 1) to characterize the BPA glucurono- and sulfoconjugation capabilities of the ovine fetal liver at different developmental stages, 2) to compare hepatic conjugation activities in human and sheep, and 3) to evaluate the extent of BPA conjugation and deconjugation processes in placenta and fetal gonads. At an early stage of pregnancy, and despite functional sulfoconjugation activity, ovine fetuses expressed low hepatic BPA conjugation capabilities, suggesting that this stage of development represents a critical window in terms of BPA exposure. Conversely, the late ovine fetus expressed an efficient detoxification system that metabolized BPA into BPA-G. Hepatic glucuronidation activities were quantitatively similar in adult sheep and humans. In placenta, BPA conjugation and BPA-G deconjugation activities were relatively balanced, whereas BPA-G hydrolysis was systematically higher than BPA conjugation in gonads. The possible reactivation of BPA-G into BPA could contribute to an increased exposure of fetal sensitive tissues to bioactive BPA in situ.
双酚 A(BPA)是一种针对发育过程的内分泌干扰物,人类广泛接触双酚 A,这突出表明有必要更好地了解胎儿接触双酚 A 的机制。动物研究表明,在妊娠晚期,双酚 A 会被胎盘有效结合,主要转化为双酚 A-葡萄糖醛酸内酯(BPA-G),并滞留在胎盘中。反过来,胎儿接触 BPA-G 又可能导致其在胎儿敏感组织水平上解聚成母体双酚 A 后,在原位接触到生物活性双酚 A。我们的研究目的是:1)描述绵羊胎儿肝脏在不同发育阶段的双酚A葡糖醛酸和磺酸结合能力;2)比较人和绵羊肝脏的结合活性;3)评估胎盘和胎儿性腺中双酚A结合和脱结合过程的程度。在妊娠早期,尽管有功能性的磺化结合活性,但绵羊胎儿肝脏对双酚 A 的结合能力很低,这表明这一发育阶段是接触双酚 A 的关键窗口期。相反,晚期绵羊胎儿表现出高效的解毒系统,可将双酚 A 代谢为双酚 A-G。成年绵羊和人类的肝脏葡萄糖醛酸化活性在数量上相似。在胎盘中,双酚 A 结合和双酚 A-G 解结合活性相对平衡,而在性腺中,双酚 A-G 水解活性系统性地高于双酚 A 结合活性。双酚 A-G 可能重新活化为双酚 A,这可能会增加胎儿敏感组织在原位暴露于生物活性双酚 A 的机会。