Estrogen Activates an Oxidant‐Dependent Signaling Pathway Threatening VEGF Promoter Integrity in Pulmonary Artery Endothelial Cells (Paecs)

Uncertainty about the role of estrogen (E2) in lung vascular disease relates in part to the complex reactive oxygen species (ROS)-dependent signaling pathways used by the hormone. We examined pan-cellular, mitochondrial and nuclear ROS signaling in rat PAECs using fluorescence microscopy of dichlorofluorescein (DCF), MitoTracker CMH2XRos, and nuclear-targeted ro-GFP, respectively. E2 caused time and dose-dependent increases in DCF-detectable ROS burden. While mitochondrial ROS accumulation was minimal, the nuclear ROS burden rose markedly. PCR and ChIP assays showed that E2 caused formation of oxidized bases in, and recruitment of DNA repair enzymes to the E2 responsive element (ERE) of the VEGF promoter. The complex I inhibitor rotenone failed to suppress pan-cellular or nuclear ROS accumulation, but the monoamine oxidase inhibitor, pargyline, attenuated ROS accumulation in the nucleus, prevented oxidized base formation in the ERE of the VEGF promoter, and suppressed E2-mediated induction of VEGF mRNA expression. These findings suggest E2 activates a nuclear ROS signaling pathway in PAECs, possibly linked to gene expression through a DNA bound histone demethylase, that oxidatively threatens a promoter sequence of an E2-inducible nuclear gene critically involved in maintenance of lung vascular structure. Supported by NIH.