Fetal Hypoxemia and Endothelium Derived Nitric Oxide

描述（由申请人提供）：胎儿缺氧是胎儿发病和死亡的主要原因。胎儿适应缺氧应激的能力对其生存至关重要。一氧化氮（NO）作为冠状动脉血流和心肌收缩力的重要调节剂，在心脏保护中起重要作用，并且NO合酶（NOS）的基因表达是缺氧敏感的。我们推测，慢性缺氧上调NOS途径在胎儿心脏诱导心脏保护通过增加eNOS衍生的NO在冠状动脉循环和心肌损伤的iNOS衍生的NO在心室的心肌细胞。为了验证这一点，将妊娠豚鼠暴露于慢性缺氧（10.5%O_2，持续14天），胎儿心脏将在5个特定目的中进行检查：目的1）验证慢性缺氧增加胎豚鼠心脏中的冠状动脉和心脏NOS基因表达和血管生成的假设。将定量NOS/cGMP/PKG途径的基因/蛋白表达，并使用免疫荧光法在常氧（NMX）和缺氧（HPX）胎心中定位蛋白。目的2）探讨慢性缺氧对胎鼠心脏的损伤作用。将对细胞凋亡（Bax/Bcl 2表达，TUNEL）和冠状动脉血管生成（VEGF、VEGFR 1、VEGFR 2、Ang 1、Ang 2表达）进行定量，并在离体胎心制备物中测量冠状动脉血流和收缩力的功能反应。目的3）验证宫内抑制iNOS源性NO和ROS的产生对胎儿心脏缺氧损伤的保护作用。NOS和ROS抑制剂将给予妊娠母亲，并测量对胎儿心脏基因表达和冠状动脉/收缩功能的子宫内影响。目的4）验证iNOS源性NO刺激离体胎儿心肌细胞（FCM）产生ROS的假说。将在来自NMX和HPX胎心的培养的FCM中研究iNOS衍生的NO刺激ROS的机制。目的5）验证产前缺氧通过诱导型一氧化氮合酶（iNOS）途径升高子代豚鼠动脉血压的假说。将测量年龄匹配后代的血压和心脏基因表达/心脏功能反应的无线电遥测。我们建议，缺氧改变NOS在胎儿心脏的表达有助于适应和适应不良的反应，出生前和出生后。这将鉴定iNOS衍生的NO合成作为胎儿存活的靶途径。

DESCRIPTION (provided by applicant): Fetal hypoxia is a leading cause of fetal morbidity and mortality. The ability of the fetus to adapt to hypoxic stress is critical for its survival. Nitric oxide (NO) plays an important role in cardioprotection as an important modulator of both coronary flow and cardiac contractility, and gene expression of NO synthase (NOS) is hypoxia-sensitive. We hypothesize that chronic hypoxia upregulates the NOS pathway in fetal hearts inducing cardioprotection by increasing eNOS-derived NO in the coronary circulation and cardiac injury by iNOS-derived NO in the cardiomyocytes of the ventricle. To test this, pregnant guinea pigs will be exposed to chronic hypoxia (10.5%O2 for 14d duration) and hearts of fetuses will be examined in 5 specific aims: Aim 1) To test the hypothesis that chronic hypoxia increases coronary and cardiac gene expression of NOS and angiogenesis in the fetal guinea pig heart. Gene/protein expression of the NOS/cGMP/PKG pathway will be quantified and proteins localized using immunofluorescence in normoxic (NMX) and hypoxic (HPX) fetal hearts. Aim 2) To test the hypothesis that chronic hypoxia induces cardiac injury in the fetal guinea pig heart. Apoptosis (Bax/Bcl2 expression, TUNEL) and coronary angiogenesis (VEGF, VEGFR1, VEGFR2, Ang1, Ang2 expression) will be quantified and functional responses of coronary flow and contractile force measured in isolated fetal heart preparations. Aim 3) To test the hypothesis that in utero inhibition of iNOS-derived NO and ROS generation protects the fetal heart from hypoxia-induced injury. NOS and ROS inhibitors will be administered to pregnant mothers and the in utero effect on fetal heart gene expression and coronary/contractile function measured. Aim 4) To test the hypothesis that iNOS-derived NO stimulates ROS generation in isolated fetal cardiomyocytes (FCM). The mechanism of iNOS-derived NO in stimulating ROS will be studied in cultured FCM derived from NMX and HPX fetal hearts. Aim 5) To test the hypothesis that prenatal hypoxia increases arterial blood pressure in the guinea pig offspring via the iNOS pathway. Radiotelemetry of blood pressure and cardiac gene expression/functional responses of hearts of age-matched offspring will be measured. We propose that hypoxia alters NOS expression in the fetal heart contributing to adaptive and maladaptive responses, both pre- and postnatally. This will identify iNOS-derived NO synthesis as a target pathway for fetal survival.