Epigenetic mechanisms of uterine vascular adaptation to pregnancy and hypoxia

 描述(由申请人提供)：怀孕期间子宫血流量显著增加，这对胎儿的最佳发育和母亲的心血管健康都是必不可少的。妊娠期子宫胎盘循环适应不良与临床并发症的高发生率有关，包括先兆子痫和胎儿宫内生长受限。大电导钙激活钾(BKCa)通道在调节妊娠子宫血流中起着重要作用。血管平滑肌中的BKCa通道含有通道形成的α亚基和最多四个辅助β1亚基，它们增强了BKCa通道对钙的敏感性。以往对绵羊的研究表明，妊娠和类固醇激素引起子宫动脉BKcaβ1亚基显着增加，导致β1：α亚基化学计量比增加，子宫动脉BKCa通道活动增强。重要的是，妊娠期间的慢性缺氧消除了这些变化。然而，其分子机制仍不清楚。我们最近的研究表明，妊娠和类固醇激素导致β1基因启动子上的甲基化减少。DNA甲基化是表观遗传抑制基因表达模式的主要机制，最近的研究表明10-11易位1-3(TET1-3)蛋白在活跃的DNA去甲基化中具有强大的机制。我们的初步研究表明，妊娠和类固醇激素增加了子宫动脉中TET1-2的表达。此外，初步数据表明，妊娠期间的慢性低氧导致子宫动脉中针对TET1mRNA3‘非编码区的microRNA210(MiR210)显著增加，并负调控其翻译。有了这些令人兴奋的发现和许多非常新颖的线索，我们准备通过启动一个新的和范式转换的研究重点来显著推动该领域的发展，并测试这一假设，即miR210与Tet介导的DNA去甲基化相互作用的分子和表观遗传机制在调节BKCa通道的表达和功能方面发挥关键作用，使子宫血管适应妊娠和慢性缺氧。三个特定的目标将决定：1)在子宫动脉对妊娠的适应中，类固醇激素是否上调Tet基因的表达，导致DNA去甲基化和BKcaβ1基因的表达增加；2)妊娠期的慢性低氧增加miR210抑制Tet基因的翻译并取消类固醇激素介导的子宫动脉BKcaβ1基因的表达上调；3)确定miR210和Tet介导的去甲基化在子宫动脉对妊娠和低氧适应中调节BKca通道功能的因果作用。这些结果将极大地提高我们对子宫胎盘适应妊娠的分子机制的认识，并提高我们对子宫胎盘循环适应不良以及与慢性低氧相关的妊娠并发症的病理生理机制的理解。它们也将在生理学和病理生理学中对调节BKCa通道活性和血管功能的分子机制的理解产生广泛的影响。

 DESCRIPTION (provided by applicant): Uterine blood flow increases significantly during pregnancy, which is essential both for optimal growth of the fetus and cardiovascular well-being of the mother. Maladaptation of the uteroplacental circulation during gestation is associated with high incidence of clinical complications including preeclampsia and fetal intrauterine growth restriction. Large-conductance Ca2+-activated K+ (BKca) channels play a critical role in regulating uterine blood flow in pregnancy. The BKca channel in vascular smooth muscle contains the channel-forming α subunit and up to four accessory β1 subunits that enhance the Ca2+ sensitivity of BKca channels. Previous studies in sheep demonstrated that pregnancy and steroid hormones caused a significant increase in BKCa β1 subunit resulting in increased β1: α subunit stoichiometry and heightened BKCa channel activity in uterine arteries. Of importance, chronic hypoxia during gestation abrogated these changes. Yet the molecular mechanisms remain unknown. Our recent study showed that pregnancy and steroid hormones caused a decrease in DNA methylation at the β1 gene promoter. DNA methylation is a chief mechanism in epigenetic repression of gene expression patterns, and recent studies suggest a robust mechanism of ten-eleven translocation 1-3 (TET1-3) proteins in active DNA demethylation. Our preliminary studies suggested that pregnancy and steroid hormones increased TET1-2 expression in uterine arteries. Furthermore, the preliminary data demonstrated that chronic hypoxia during gestation resulted in a significant increase in microRNA 210 (miR210) in uterine arteries, which targeted TET1 mRNA 3'UTR and negatively regulated its translation. With these exciting findings and many highly novel leads, we are positioned to move the field forward significantly in a manner by launching a new and paradigm-shifting focus of research and to test the hypothesis that molecular and epigenetic mechanisms of miR210 interacting with TET-mediated DNA demethylation play a key role in regulating expression and function of BKca channels in uterine vascular adaptation to pregnancy and chronic hypoxia. Three specific aims will determine whether: 1) steroid hormones upregulate TET gene expression leading to DNA demethylation and increased BKca β1 gene expression in uterine arterial adaptation to pregnancy, 2) chronic hypoxia during gestation increases miR210 inhibiting TET mRNA translation and abrogates steroid hormone-mediated upregulation of BKca β1 gene expression in uterine arteries, and 3) determine the causal effect of miR210 and TET-mediated demethylation in regulating BKca channel function in uterine arterial adaptation to pregnancy and hypoxia. The results will significantly advance our knowledge in molecular mechanisms of uteroplacental adaptation to pregnancy and improve our understanding of pathophysiological mechanisms underlying maladaptation of the uteroplacental circulation and pregnancy complications associated with chronic hypoxia. They also will have a broad impact in the understanding of molecular mechanisms in regulating BKca channel activity and vascular function in general in physiology and pathophysiology.