Epigenetic mechanisms of uterine vascular adaptation to pregnancy and hypoxia

 描述（由申请人提供）：妊娠期间子宫血流量显著增加，这对胎儿的最佳生长和母亲的心血管健康至关重要。妊娠期子宫胎盘循环的适应不良与临床并发症的高发生率相关，包括先兆子痫和胎儿宫内生长受限。大电导钙激活钾通道（BKca）在妊娠期子宫血流调节中起着重要作用。血管平滑肌中的BKca通道包含通道形成α亚基和多达四个辅助β1亚基，其增强BKca通道的Ca 2+敏感性。先前在绵羊中的研究表明，妊娠和类固醇激素导致BKCa β1亚基显著增加，导致子宫动脉中β1：α亚基化学计量增加和BKCa通道活性升高。重要的是，妊娠期间的慢性缺氧消除了这些变化。然而，分子机制仍然未知。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DNA甲基化降低。DNA甲基化是基因表达模式表观遗传抑制的主要机制，最近的研究表明TET 1 - 3蛋白在主动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子宫动脉TET 1 -2的表达。此外，初步数据表明，妊娠期间慢性缺氧导致子宫动脉中microRNA 210（miR 210）显著增加，其靶向TET 1 mRNA 3 'UTR并负调控其翻译。有了这些令人兴奋的发现和许多高度新颖的线索，我们将通过启动一个新的和范式转移的研究重点，并测试miR 210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子宫血管适应妊娠和慢性缺氧的BKca通道的表达和功能中发挥关键作用的假设，从而显著地推动该领域的发展。三个具体目标将决定：1）类固醇激素上调泰特基因表达，导致DNA去甲基化和子宫动脉适应妊娠中BKca β1基因表达增加，2）妊娠期间慢性缺氧增加miR 210抑制泰特mRNA翻译，并消除类固醇激素介导的子宫动脉中BKca β1基因表达上调，以及3）确定miR 210和TET介导的去甲基化在子宫动脉适应妊娠和缺氧中调节BKca通道功能的因果作用。结果将显着推进我们的知识，子宫胎盘适应妊娠的分子机制，提高我们的理解的病理生理机制的子宫胎盘循环和妊娠并发症与慢性缺氧相关的适应不良。他们也将在生理学和病理生理学中调节BKca通道活性和血管功能的分子机制的理解中产生广泛的影响。

 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.