Regulation of NADPH Oxidase by Angiotensin II-Role in Myometrial Hypertrophy

描述（由申请人提供）：子宫肥大是妊娠期发生的一种生理过程，以适应胎儿生长和分娩时收缩的需要。已知生长因子、性激素和细胞因子在正常妊娠或纤维化期间刺激子宫平滑肌生长。血管紧张素II是一种有据可查的血管平滑肌生长因子。然而，血管紧张素II在子宫生长中的作用尚未明确，尽管事实上其浓度增加，并且在妊娠妇女中子宫肌层受体亚型向1型血管紧张素II受体有显著转变。NADPH氧化酶亚型通过产生活性氧，已被证明负责血管紧张素II的生长促进作用，其由血管平滑肌和心肌细胞中的1型受体介导。我们在人子宫肌层和人子宫平滑肌细胞系中鉴定了几种NADPH氧化酶亚型。我们还发现，NADPH氧化酶抑制剂阻断血管紧张素II诱导的活性氧的产生以及子宫平滑肌蛋白质的合成。因此，我们假设血管紧张素II通过激活NADPH氧化酶在妊娠期间子宫肌层生长中起重要作用，NADPH氧化酶依赖于1型血管紧张素II受体和下游信号通路。我们进一步假设NADPH氧化酶定位于细胞膜小窝并被激活，在细胞膜小窝中发现了一个信号转导途径的几个元件，包括血管紧张素II 1型受体、NADPH氧化酶亚型1（Nox 1）的催化单位、G蛋白和表皮生长因子受体。我们将采用分子生物学、细胞生物学和生物化学方法相结合的方法，在子宫平滑肌细胞系中研究以下特定目标：1）血管紧张素II在子宫平滑肌细胞中NADPH氧化酶表达和激活的调节作用; 2）NADPH氧化酶在血管紧张素II受体介导的子宫平滑肌生长（肥大）和信号传导中的作用。目前，活性氧在产科病理学中的作用引起了人们极大的兴趣。众所周知，许多早产病例与感染有关，其中细胞因子诱导活性氧产生。活性氧簇的过度产生导致收缩失败、僵硬和钙超载。因此，我们预测血管紧张素Ⅱ-NADPH氧化酶-活性氧途径在分娩过程中也发挥作用。

DESCRIPTION (provided by applicant): Uterine hypertrophy is a physiological process occurring in pregnancy to accommodate fetal growth and the need for contraction at delivery. Growth factors, sex hormones and cytokines are known to stimulate uterine smooth muscle growth during normal pregnancy or fibrosis. Angiotensin II is a well documented vascular smooth muscle growth factor. However, the role of angiotensin II in uterine growth is not well defined, despite the fact that its concentration is increased and there is a significant switch in myometrial receptor subtype towards the type 1 angiotensin II receptor in pregnant women. NADPH oxidase isoforms, via generation of reactive oxygen species, have been shown to be responsible for the growth promoting effect of angiotensin II which is mediated by type 1 receptor in vascular smooth muscle and cardiac myocytes. We have identified several NADPH oxidase isoforms in human myometrium and in a human uterine smooth muscle cell line. We also found that a NADPH oxidase inhibitor blocked angiotensin ll-induced production of reactive oxygen species as well as uterine smooth muscle protein synthesis. Therefore, we hypothesize that angiotensin II plays an important role in myometrial growth during pregnancy via activation of NADPH oxidase, which is dependent on the type 1 angiotensin II receptor and downstream signaling pathways. We further hypothesize that NADPH oxidase is localized and activated in caveolae, the plasma membrane structures where several elements of a proposed signal transduction pathway were found. These include angiotensin II type 1 receptor, the catalytic unit of NADPH oxidase isoform 1 (Nox1), G proteins, and epidermal growth factor receptor. We will employ a combination of molecular biology, cell biology, and biochemical methods to study, in the uterine smooth muscle cell line, the following specific aims: 1) The role of angiotensin II in regulation of NADPH oxidase expression and activation in myometrial smooth muscle cells; and 2) The role of NADPH oxidase in angiotensin II receptor-mediated myometrial growth (hypertrophy) and signaling. Currently there is a great deal of interest in the role of reactive oxygen species in obstetric pathologies. It is known that many cases of preterm delivery are associated with infection where cytokines induce reactive oxygen species production. Excessive generation of reactive oxygen species contributes to contractile failure, rigor and calcium overload. Thus we predict that the angiotensin II-NADPH oxidase-reactive oxygen species pathway plays a role in labor process as well.