Ah receptor-mediated deregulation of lactogenesis

描述（由申请人提供）：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-p-二恶英（TCDD或二恶英）的新毒性作用。具体而言，怀孕期间的接触会损害乳腺发育，抑制乳蛋白的协调诱导，导致泌乳受损和新生儿死亡。 目的/假设：拟议研究的目的是（1）进一步表征这一新发现，（2）确定暴露于二恶英对催乳调节途径的不利影响。这些研究的假设是，妊娠期间AhR激活破坏了指导妊娠相关乳腺发育和乳蛋白基因表达的正常信号传导，导致上皮细胞分化和泌乳受损。具体目标：1）.为了确定乳汁生成的缺陷是否由对乳腺组织的直接影响引起，我们将交叉移植来自野生型和AhR缺失小鼠的乳腺组织。2)要确定受损的牛奶生产的机制，我们将确定是否暴露于TCDD失调的NF-κ B-，STATSa-和C/EB β-介导的乳腺上皮细胞的信号通路的激活。3)为了确定是否发育不良的腺体发育在怀孕期间的结果从失调的增殖，分化，凋亡或缺陷的多个途径，我们将进一步表征暴露于TCDD对这些过程中的乳腺细胞在怀孕期间的影响。4)为了确定额外的分子途径，是放松管制后，暴露于TCDD，我们将比较的表达因子，已知调节腺体分化和泌乳的腺体来自车辆和TCDD治疗的怀孕小鼠使用基因表达谱和免疫细胞化学方法相结合。将使用来自AhR缺失小鼠的乳腺组织来区分直接由AhR介导的缺陷与由于上游病变引起的缺陷。意义：拟议的研究涉及临床相关但很少受到关注的领域。据估计，每年有300万至600万名活婴的母亲不能或很难开始母乳喂养。这一问题的原因尚不清楚，并且对暴露于环境污染物对泌乳的影响知之甚少。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，并且暴露于AhR配体会破坏其他组织中上皮细胞的增殖和分化，因此这些研究的结果将具有广泛的生物学意义，并将帮助我们更好地了解二恶英类化学物质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.