AhR和VitA/RA途径在二噁英诱发腭裂中的相互作用

The dioxin produces teratogenic effect by binding with aromatic hydrocarbon receptor (AhR). Retinoic acid (RA), an oxidative metabolite, is a physiological activity form of vitamin A. Our previous study showed that the dioxin exposure significantly reduced the storage of vitamin A in the livers of mothers and fetus and cause 100% incidence of cleft palate. RA treatment increased the protein level of AhR in fetus’ palatal tissue. Dioxins enhanced RA-induced transactivation of the RARE (Retinoic Acid Response Elements) luciferase report gene. Based on these previous data and related literatures, we proposed a hypothesis: there is an interplay between AhR and VitA/RA pathway in dioxin-induced cleft palate, which may play an important role in regulating the fusion of bilateral palatal shelf, such as the degradation of medial epithelial seam, the fusion of bilateral palates, the proliferation, differentiation and secretion of mesenchymal cells. To reveal the mechanism of dioxin-induced cleft palate through VitA/RA pathway and the interaction between AhR and VitA/RA pathway from different aspects and angles, the development of secondary palate in Wistar rat will be chosen as the experimental starting point, various models of cleft palate study will be established and modern pathology and molecular biology technology will be used to study palatal morphogenesis, growth, and fusion during the induction of left palate by dioxin through VitA/RA pathway. These reseach can provide theoretical guidance for prenatal care.

二噁英通过与芳香烃受体AhR结合而发挥其致畸效应。视黄酸(RA)是维生素A(VitA)的生理活性形式。我们在前期工作中发现，二噁英抑制并降低VitA在母体和仔体肝脏中的储存水平，从而导致100%仔鼠发生腭裂；RA可促进胎鼠腭组织中AhR的表达水平；二噁英能显著增强RA的生物学活性。这些前期工作和文献复习促使我们提出本立项的科学假说：AhR和VitA/RA途径在二噁英诱发腭裂中存在相互作用，并对腭突融合可能具有重要调节作用。为阐释这一科学问题，我们拟以Wistar大鼠次生腭发育期为切入点，借助现代组织病理学技术和分子生物学方法，选用多种腭裂研究模型，从不同层面和角度，揭示二噁英经VitA/RA途径诱发腭裂的作用机制，阐明AhR和VitA/RA途径间的交互作用模式，以及这种交互作用对中嵴缝降解、腭突融合、腭间充质组织细胞增殖、分泌和分化等的调节机制。研究资料可为围产期保健提供理论指导。

我们在前期工作中发现，二噁英抑制并降低VitA在母体和仔体肝脏中的储存水平，从而导致100%仔鼠发生腭裂；RA可促进胎鼠腭组织中AhR的表达水平；二噁英能显著增强RA的生物学活性。这些前期工作和文献复习促使我们提出本立项的科学假说：AhR和VitA/RA途径在二噁英诱发腭裂中存在相互作用，并妨害腭突融合。为阐释这一科学问题，本课题借助现代组织病理学技术和分子生物学方法，选用多种腭裂研究模型，从不同层面和角度，揭示了二噁英经VitA/RA途径诱发腭裂的作用机制。研究结果表明TCDD抑制中嵴缝中上皮细胞的迁移和凋亡，并诱导间充质组织细胞发生凋亡；Western blot结果显示，TCDD抑制RARβ和RARγ蛋白表达水平，并对VitA/RA信号途径中一些关键酶(CYP1A1、CYP26A、RALDH)及调节基因(AhR、RARs、CRBP) 的表达量有显著影响；体内实验结果表明，TCDD/AhR和VitA/RA途径中的关键信息分子间(如AhR、CYP1A1、CYP26A、RALDH和CRBP)的在间充质和上皮组织中均存在时空交叠模式，但TCDD对EMT进程中的增殖和分泌无调节作用。结论：在次生腭发育过程中，左右腭突的接触、粘附和融合对于腭器官的正常发育起着重要作用，TCDD通过影响VitA/RA信号途径，妨害腭的发育，致使腭不能融合，形成腭裂。这些研究资料对临床围产期保健具有重要指导意义。