Abstract 4919: Contradictive Estrogen Effects on BMP Signaling in Pulmonary Artery Depend on Oxygen Concentration
Epidemiologic studies have shown that the female predominance in the morbidity of Idiopathic PAH (pulmonary arterial hypertension) in the world, which suggests a role of female sex hormones in the pathogenesis of PAH. Our previous study demonstrated the contradictory effects of estrogen on pulmonary arterial endothelial cells (PAEC) via BMP (Bone Morphogenetic Protein) signaling depend on cellular oxygen environment. This study is to investigate the mechanism of the contradictory effect of β-estradiol (E2) upon BMP signaling in PAEC.
<MATERIALS and METHODS> Human and rat PAEC were cultured and the expression of BMPR2, Smad1/5/8, and Id1 were examined under 21%O2 (normoxic; N) or 1%O2 (hypoxic; H) condition in the presence of E2. We investigated the effect of estrogen receptor antagonist (ICI 182.780.) and searched for an evidence of binding interaction between estrogen receptor (ER) and Smad. In the presence of E2 (10−7M), the expression of BMPR2, phosphorylated Smad (p-Smad)1/5/8 proteins, Id1 mRNA was augmented under N and suppressed under H. We confirmed same phenomena by using Id1 promoter assay. These alterations of BMPR signal expression were inhibited by ICI182.780. An Immunoprecipitation experiment demonstrated a direct binding interaction between ER and p-Smad1/5/8 proteins only under H, whereas estrogen response activity measured by luciferase assay was increased by E2 only under N. In addition, HIF-1α augmentation by cobalt chloride suppressed BMP signaling, whereas HIF-1α inhibition by YC-1 augmented those expression. By inhibiting de novo synthesis by administration of cycloheximide, p-Smad1/5/8 were suppressed under N, but could not change under H. We demonstrated that the alteration of BMP signaling in PAEC under different O2 condition was associated with HIF-1α expression and the presence of E2. This alteration may also relate to an interaction between BMP signaling and receptor-mediated estrogen pathway under hypoxia, and to de novo synthesis under normoxia. Our observations provide the new mechanism how sex hormone affects on BMP signaling, a key signal pathway for PAH, which can offer novel therapeutic targets in the treatment of PAH.