Estrogen Upregulates Endothelial Nitric Oxide Synthase Gene Expression in Fetal Pulmonary Artery Endothelium

Abstract

NO, produced by endothelial NO synthase (eNOS), is a key mediator of pulmonary vasodilation during cardiopulmonary transition at birth. The capacity for NO production is maximal at term because pulmonary eNOS expression increases during late gestation. Since fetal estrogen levels rise markedly during late gestation and there is indirect evidence that the hormone enhances nonpulmonary NO production in adults, estrogen may upregulate eNOS in fetal pulmonary artery endothelium. Therefore, we studied the direct effects of estrogen on eNOS expression in ovine fetal pulmonary artery endothelial cells (PAECs). Estradiol-17beta caused a 2.5-fold increase in NOS enzymatic activity in PAEC lysates. This effect was evident after 48 hours, and it occurred in response to physiological concentrations of the hormone (10(-10) to 10(-6) mol/L). The increase in NOS activity was related to an upregulation in eNOS protein expression, and eNOS mRNA abundance was also enhanced. Estrogen receptor antagonism with ICI 182,780 completely inhibited estrogen-mediated eNOS upregulation, indicating that estrogen receptor activation is necessary for this response. In addition, immunocytochemistry revealed that fetal PAECs express estrogen receptor protein. Furthermore, transient transfection assays with a specific estrogen-responsive reporter system have demonstrated that the endothelial estrogen receptor is capable of estrogen-induced transcriptional transactivation. Thus, estrogen upregulates eNOS gene expression in fetal PAECs through the activation of PAEC estrogen receptors. This mechanism may be responsible for pulmonary eNOS upregulation during late gestation, thereby optimizing the capacity for NO-mediated pulmonary vasodilation at birth.

Estrogen-Mediated, Endothelial Nitric Oxide Synthase–Dependent Mobilization of Bone Marrow–Derived Endothelial Progenitor Cells Contributes to Reendothelialization After Arterial Injury

“…23 In this context, it is interesting to note that estradiol has also been shown to activate Akt signaling, suggesting one possible mechanism for modulation of EPCs. 33 Given the above findings, the central role of Akt signaling in eNOS activity and the regulation of eNOS and NO by estradiol, 34,35 we considered the possibility that EPC mobilization by estradiol might require NO-mediating signaling. We evaluated reendothelialization and EPC kinetics after the injury in eNOS Ϫ/Ϫ mice and found that the absence of eNOS essentially nullified estradiol-induced mobilization of EPCs and blocked the acceleration of endothelial recovery seen in wild-type mice treated with estradiol.…”

Postnatal Estradiol Up-regulates Lung Nitric Oxide Synthases and Improves Lung Function in Bronchopulmonary Dysplasia

“…Having previously shown that estrogen up-regulation of eNOS expression is ER dependent (33), and that estrogen modifies ERa and ERb abundance in primary fetal pulmonary artery endothelial cells (34), the impact of E 2 on lung estrogen receptor expression was assessed by immunoblot analysis (see Figure E5). ERb protein was detected in 125 days gestation control lung, and the level of expression did not change between 125 days and 140 days gestation; ERa protein was not detected (data not shown).…”

Estrogen is a modulator of vascular inflammation

“…Estrogen can activate eNOS through a PI3K and Akt mediated nongenomic pathway, causing rapid generation of NO, with beneficial effects on the vasculature (10). Prolonged estrogen exposure also upregulates the expression of eNOS through a genomic pathway, ensuring long-term NO availability (11). Apart from being a potent vasodilator, NO exerts an antiinflammatory role on the endothelium, as manifested by decreased leukocyte recruitment and scavenging of reactive oxygen species (ROS) (12).…”