Ah receptor-mediated deregulation of lactogenesis

描述(申请人提供)：背景：我们最近发现了芳烃受体(AhR)配体2，3，7，8-四氯二苯并对二恶英(TCDD或二恶英)的新毒性作用。具体地说，怀孕期间的暴露会损害乳腺发育，抑制乳蛋白的协调诱导，导致哺乳障碍和新生儿死亡。 目的/假设：拟议研究的目的是(1)进一步描述这一新发现和(2)确定暴露于二恶英的不利影响的产乳调节途径。这些研究的假设是，怀孕期间AhR的激活扰乱了指导与怀孕相关的乳房发育和乳蛋白基因表达的正常信号，导致上皮细胞分化和哺乳期受损。具体目的：1)为了确定乳汁生成缺陷是否直接影响乳腺组织，我们将野生型和AhR基因缺失的小鼠的乳房组织进行交叉移植。2)为了确定产奶量下降的机制，我们将确定暴露于TCDD是否会放松对乳腺上皮细胞中NF-kappaB-、STATSa-和C/EBbeta介导的信号通路的激活。3)为了确定妊娠期腺发育迟缓是由于细胞增殖、分化、凋亡或多个途径的缺陷引起的，我们将进一步研究TCDD对妊娠期乳腺细胞这些过程的影响。4)为了确定暴露在TCDD后的其他分子途径，我们将使用基因表达谱和免疫细胞化学方法相结合的方法，比较已知的调节腺体分化和乳汁生成的因子在赋形剂和TCDD处理的怀孕小鼠腺体中的表达。来自AhR缺失小鼠的乳房组织将被用来区分直接由AhR介导的缺陷和由上游病变引起的缺陷。意义：拟议的研究解决了一个与临床相关但很少受到关注的领域。据估计，每年有300万至600万活婴儿的母亲无法或有很大困难开始母乳喂养。这一问题的原因尚不清楚，对暴露在环境污染物中对产乳的影响也知之甚少。此外，由于控制乳汁生成的机制也调节其他器官的增殖和分化，而暴露于AhR配体会扰乱其他组织中的上皮细胞的增殖和分化，因此这些研究结果将具有广泛的生物学意义，并将有助于我们更好地了解二恶英类化合物对全身上皮细胞产生不利影响的机制。

DESCRIPTION (provided by applicant): Background: We have recently discovered a new toxic effect of the aryl hydrocarbon receptor (AhR) ligand 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD or dioxin). Specifically, exposure during pregnancy impairs mammary gland development and suppresses the coordinated induction of milk proteins, resulting in impaired lactation and neonatal mortality. Objectives/Hypothesis: The objectives of the proposed studies are (1) to further characterize this novel finding and (2) to identify the lactogenic regulatory pathways adversely affected by exposure to dioxin. The hypothesis for these studies is that AhR activation during pregnancy disrupts the normal signaling that directs pregnancy-associated mammary development and milk protein gene expression, resulting in impaired epithelial cell differentiation and lactation. Specific Aims: 1).To determine whether defects in lactogenesis result from direct effects on mammary tissue, we will cross-transplant mammary tissue from wild-type and AhR-null mice. 2) To identify the mechanism underlying impaired milk production, we will determine whether exposure to TCDD deregulates the activation of NF-kappaB-, STATSa- and C/EBbeta-mediated signalling pathways in mammary epithelial cells. 3) To determine whether stunted glandular development during pregnancy results from deregulation of proliferation, differentiation, apoptosis or defects in multiple pathways, we will further characterize the effects of exposure to TCDD on these processes in mammary cells during pregnancy. 4) To identify additional molecular pathways that are deregulated following exposure to TCDD, we will compare the expression of factors known to regulate to glandular differentiation and lactogenesis in glands derived from vehicle- and TCDD-treated pregnant mice using a combination of gene expression profiling and immunocytochemical methods. Mammary tissue from AhR-null mice will be used to distinguish defects that are directly AhR-mediated from defects that arise due to an upstream lesion. Significance: The proposed studies address an area that is clinically-relevant but has received very little attention. An estimated 3-6 million mothers of live infants annually are either unable to or have significant difficulty initiating breastfeeding. The causes of this problem are not clear, and very little is known about the effects of exposure to environmental contaminants on lactogenesis. Furthermore, since the mechanisms that control lactogenesis also regulate proliferation and differentiation in other organs, and exposure to AhR ligands disrupts the proliferation and differentiation of epithelial cells in other tissues, findings from these studies will have broad biological significance, and will help us better understand the mechanisms by which dioxin-like chemicals adversely affect epithelial cells throughout the body.