Retinoic Acid-Stimulation of VEGF Secretion from Human Endometrial Stromal Cells Is Mediated by Production of Reactive Oxygen Species.

Abstract

Non-technicalsummary Vascular endothelial growth factor (VEGF) is an angiogenic factor that plays a primary role in blood vessel development in uterine endometrial tissue during embryo implantation and early growth. Previously, we determined that retinoic acid (RA) can act as a co-factor to rapidly induce VEGF secretion from human endometrial stromal cells. We show here that stimulation of VEGF by RA is directly mediated by increased production of reactive oxygen species (ROS) in these cells. These findings predict a ROS-mediated mechanism for RA regulation of localized VEGF secretion in the human endometrium that may be necessary for the successful establishment of pregnancy. The results obtained may provide new targets for therapeutic intervention. Abstract It is widely accepted that vascular endothelial growth factor (VEGF) is involved in angiogenic functions that are necessary for successful embryonic implantation. We have shown that retinoic acid (RA), which is known to play a necessary role in early events in pregnancy, can combine with transcriptional activators of VEGF (e.g. TPA, TGF-β ,I L-1β) to rapidly induce VEGF secretion from human endometrial stromal cells through a translational mechanism of action. We have now determined that this stimulation of VEGF by RA is mediated through an increased production of cellular reactive oxygen species (ROS). Results indicated that RA, but not TPA or TGF-β, directly increases ROS production in endometrial stromal cells and that the co-stimulating activity of RA on VEGF secretion can be mimicked by direct addition of H2O2. Importantly, co-treatment of RA with TPA or TGF-β further stimulated ROS production in a fashionthatpositivelycorrelatedwithlevelsofVEGFsecretion.TheantioxidantsN-acetylcysteine andglutathionemonoethylesterinhibitedbothRA +TPAandRA +TGF-β-stimulatedsecretion of VEGF, as well as RA-induced ROS production. Treatment of cells with RA resulted in a shift in the glutathione (GSH) redox potential to a more oxidative state, suggesting that the transduction pathwayleadingtoincreasedVEGFsecretionisatleastpartiallymediatedthroughtheantioxidant capacity of GSH couples. The specificity of this action on GSH-sensitive signalling pathways is suggested by the determination that RA had no effect on the redox potential of thioredoxin. Together, these findings predict a redox-mediated mechanism for retinoid regulation of localized VEGFsecretioninthehumanendometriumthatmaybenecessaryforthesuccessfulestablishment of pregnancy.