DNA Demethylation and BKca Channel Expression and Function in Uterine Arteries

 描述(由申请人提供)：怀孕期间子宫血流量的显著增加对于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发育异常。大电导钙激活钾通道(BKCa)在调节妊娠子宫血流中起着重要作用。最近在绵羊身上的研究表明，妊娠和类固醇激素导致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。然而，其分子机制仍不清楚。我们的初步研究表明，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。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。这些发现导致了一项非常新的机制的研究，该机制验证了类固醇激素介导的DNA甲基化和去甲基化的动态变化在调节BKCa通道在子宫血管适应妊娠中的表达和功能中起关键作用的假说。两个特定的目标将决定：1)类固醇激素介导的启动子去甲基化和BKCaTET1基因上调是否在妊娠子宫动脉β通道功能增强中起因果作用；2)类固醇激素介导的TET1-3上调在妊娠中活性β去甲基化和TET1基因上调中起因果作用。这项研究是一项重大突破和范式转换的研究重点，旨在揭示激素介导的DNA去甲基化在调节子宫血管和血管平滑肌功能基因表达模式方面的高度新颖的表观遗传学机制。这项研究的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和妊娠并发症的病理生理机制的理解。由于BKCa通道功能在调节几乎所有血管床的血管张力和压力中起着至关重要的作用，而BKCa通道在血管平滑肌中的表达和活性的表观遗传调控方面的知识极其有限，因此本研究将在生理学和病理生理学上对BKCa通道活性和血管功能调节的分子机制的全面理解产生更广泛的影响。

 DESCRIPTION (provided by applicant): The striking increase of uterine blood flow during pregnancy 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 development abnormality. Large-conductance Ca2+-activated K+ (BKCa) channels play a critical role in regulating uterine blood flow in pregnancy. Recent 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. Yet the molecular mechanisms remain unknown. Our preliminary studies 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. Recent studies suggest a robust mechanism of ten-eleven translocation 1-3 (TET1-3) proteins in active DNA demethylation. Preliminary studies suggested that pregnancy and steroid hormones increased TET1-2 expression in uterine arteries. These findings lead to the proposed studies of a highly novel mechanism testing the hypothesis that steroid hormone-mediated dynamic changes of DNA methylation and demethylation play a key role in regulating expression and function of BKCa channels in uterine vascular adaptation to pregnancy. Two specific aims will determine whether: 1) steroid hormone-mediated promoter demethylation and BKCa β1 gene up- regulation play a causal role in increased BKCa channel function in uterine arteries in pregnancy, and 2) steroid hormone-mediated up-regulation of TET1-3 plays a causal role in active DNA demethylation and the β1 gene up-regulation in pregnancy. The proposed study presents a major breakthrough and paradigm-shifting focus of research aiming at unraveling highly novel epigenetic mechanisms of hormone-mediated DNA demethylation in regulating gene expression patterns in uterine vasculature in particular, and in vascular smooth muscle function in general. The outcome of the proposed study will significantly advance our knowledge in molecular mechanisms of uteroplacental adaptation to pregnancy and improve our understanding of pathophysiological mechanisms underlying maladaptation of uteroplacental circulation and pregnancy complications. Because of the vital importance of BKCa channel function in regulating vascular tone and pressure in virtually all vascular beds, and the extremely limited knowledge in epigenetic regulation of BKCa channel expression and activity in vascular smooth muscle, the proposed study will indeed have a much broad impact in comprehensive understanding of molecular mechanisms in regulating BKCa channel activity and vascular function in physiology and pathophysiology.