Meeting Abstract
74.4 Monday, Jan. 6 08:45 Membrane progesterone receptor alpha (mPRα) mediates the non-genomic action of progesterone to increase nitric oxide production by human umbilical vein endothelial cells PANG, Y.*; DONG, J.; THOMAS, P.; University of Texas at Austin; University of Texas at Austin; University of Texas at Austin yfpang@utexas.edu
Although the beneficial effects of progesterone (P4) on the human cardiovascular system through increasing cellular nitric oxide (NO) production in vascular endothelial cells are well recognized, but the receptors mediating these effects of P4 remain unclear. Using human umbilical vein endothelial cells (HUVECs) as a model, we show that P4 binds to plasma membrane of HUVECs with the characteristics of membrane progesterone receptors (mPRs). The selective mPRα agonist, Org OD 02-0 (02-0) displayed high binding affinity for membrane progesterone receptor, whereas the nuclear PR agonist R5020 had low binding affinity. Immunocytochemistry and Western blotting confirmed that mPRα is expressed in HUVECs and localized on the plasma membrane. P4 activated an inhibitory G protein in HUVECs, in agreement with previous findings with mPRα expressed in other cell types. P4 and 02-0, but not R5020, significantly increased the activity of endothelial nitric oxide synthase (eNOS) as well as the phosphorylation of eNOS and activation of ERK, Akt; resulting in elevation of cellular NO levels in HUVECs. These progestin effects were abolished when the cells were co-treated with ERK and Akt inhibitors. P4 and 02-0 treatments also decreased cellular cAMP levels, but the cAMP response action and the progestin-induced increase of cellular NO levels were attenuated by co-treatment with an adenylyl cyclase inhibitor. Knockdown of mPRα expression in HUVECs by treatment with antisense siRNA oligos blocked the stimulatory progestin effects on NO production and phosphorylation of eNOS. Taken together, the results provide convincing evidence that the protective effects of P4 on NO production by HUVECs are largely mediated through mPRα.
