Progesterone promotes endothelial nitric oxide synthase expression through enhancing nuclear progesterone receptor-SP-1 formation

Progesterone exerts antihypertensive actions partially by modulating endothelial nitric oxide synthase (eNOS) activity. Here, we aimed to investigate the effects and mechanisms of progesterone on eNOS expression. First, human umbilical vein endothelial cells (HUVECs) were exposed to progesterone and then the eNOS transcription factor specificity protein-1 (SP-1) and Progesterone Receptor (PR_A/B) expression were assessed by Western blotting and qRT-PCR. The interaction between SP-1 and PR_A/B was next determined through coimmunoprecipitation assay. The chromatin immunoprecipitation assay and luciferase assay were used to investigate the relationship of PR_A/B, SP-1, and eNOS promoter. At last, rats were intraperitoneally injected with Progesterone Receptor antagonist RU-486, and then the expression of eNOS and vasodilation function in thoracic aorta and mesenteric artery were measured. The results showed that progesterone could increase eNOS expression in HUVECs. Further study showed that progesterone increased PR_A-SP-1 complex formation and facilitated PR_A/B and SP-1 binding to eNOS promoter. Mutating SP-1 or PR-binding motif on eNOS promoter abolished the effect of progesterone on eNOS gene transcription. We also observed that Progesterone Receptor antagonist RU-486 reduced eNOS expression and impaired vasodilation in rats. Those results suggest that progesterone modulates eNOS expression through promoting PR_A-SP-1 complex formation, and progesterone antagonist attenuates eNOS expression, leading to the loss of vascular relaxation.NEW & NOTEWORTHY Progesterone directly upregulated endothelial nitric oxide synthase (eNOS) expression in human endothelial cells. Progesterone augmented eNOS promoter activity through a Progesterone Receptor A- and specificity protein-1-dependent manner. Antagonism of the Progesterone Receptor reduced eNOS expression and impaired vasodilation in rats.