孕期缺氧诱导RAS表观遗传修饰改变与胎源性血管功能调节障碍

Recent progress has demonstrated that a variety of adverse factors during pregnancy leading to developmental changes in renin-angiotensin system (RAS), which is linked to cardiovascular diseases in later life. Meanwhile, it has been accepted that the changes in RAS epigenetic modifications are important molecular mechanisms in developmental “programming” of cardiovascular diseases. In fact, a number of adverse intrauterine factors induced abnormal fetal development that could be related to in utero hypoxia. Our preliminary experimental results show that prenatal hypoxia was predisposed to high blood pressure in the offspring rats. However, the underlying "programming" mechanism involved in prenatal hypoxia-induced offspring hypertension is still poorly understood. Meanwhile, we found that hypoxia of vascular endothelial cell indeed changed the expression of RAS in our preliminary experimental results. Therefore, this project will determine the relationship between prenatal hypoxia-induced changes of RAS epigenetic modifications and blood pressure dysregulation in fetal origins. We have established the prenatal hypoxia and cell models. This project will use Real-time PCR, and methylation sensitive PCR method, at the molecules, cells, tissues and in vivo levels to investigate the molecular mechanism on prenatal hypoxia-induced blood pressure dysregulation in fetal origins. This proposed project will provide new information that will contribute to further understanding RAS pathway, as well as adding new information on early prevention of cardiovascular diseases in fetal origins.

近期多项研究证实孕期不良因素诱导胎儿肾素-血管紧张素系统 (RAS) 的发育改变可致出生后患心血管疾病的危险性增加，其中表观遗传调控已被认为是孕期不良因素导致胎源性心血管疾病发生的重要机制，同时孕期不良因素所致胎儿发育障碍与宫内缺血缺氧密切相关。我们预实验结果显示孕期缺氧的子代大鼠易患高血压，同时缺氧也改变了血管内皮细胞中RAS的表达。然而，迄今有关孕期缺氧诱导子代高血压发生的机理知之甚少，有待进一步探讨。因此，我们提出假说：孕期缺氧可能通过诱导RAS表观遗传修饰改变导致子代血管功能、血压调节障碍。为了验证这一假说，我们建立孕鼠及细胞缺氧模型，运用Real-time PCR及甲基化敏感性PCR等实验方法，从分子、细胞、组织及动物整体水平上探讨孕期缺氧导致子代高血压 “程序化”发生的分子机理。本研究成果也将有利于增加对RAS通路调控的新认识，为早期干预心血管性疾病提供新思路。

多项研究证实孕期不良因素诱导胎儿肾素-血管紧张素系统 (RAS) 的发育改变，从而增加出生后患血管疾病的风险。孕期（宫内）缺氧是胎儿发育过程中最为常见不良因素，基于其在围产期的高发性和严重性，宫内缺氧是否影响胎儿及出生后血管功能、血压调节亟待深入探讨。因此，本项目研究内容包括：1）孕期缺氧对胎儿、成年子代RAS表达、血管功能的影响。2）孕期缺氧对成年子代血压调节的影响。3）孕期缺氧诱导RAS组分改变的表观遗传机制。4）孕期缺氧诱导子代高血压的“程序性”的分子机制。本项目重要结果包括：1）孕期缺氧胎儿、成年子代血管功能障碍。在孕期缺氧胎儿血管中，血管紧张素II（Ang II）介导的收缩增强与其受体AT1R表达增加有关。高水平的AT1R通过激活NADPH氧化酶4/活性氧（Nox4/ROS）氧化应激信号通路，从而引起Ang II介导的收缩增强。2）孕期缺氧的成年子代，虽然其血压无明显升高，但Ang II介导的升压反应增加。这与血管中AT1R、蛋白酶C（PKCε）表达升高有关。PKCε表达升高导致磷酸化的巯基蛋白酶抑制剂（p-CPI）增加，从而抑制肌球蛋白轻链磷酸酶（MLCP）酶活，进而血管平滑肌细胞对Ang II敏感性增加。3）不论孕期缺氧胎儿，还是成年子代，其血管对Ang II的收缩反应均增加。虽然它们病理机制有所不同，但其共同点是AT1R表达增强。通过对AT1R 基因启动子区DNA甲基化水平检测，发现孕期缺氧胎儿、子代血管中AT1R基因启动子区域DNA甲基化修饰均明显降低。这说明：孕期缺氧导致从胎儿期到成年期血管功能障碍的“程序化”发生与AT1R基因表观遗传修饰改变有关。本研究成果将有利于增加对血管RAS调控的新认识，为早期干预心血管性疾病提供新思路。