Angiotensin (Ang) II vasoconstrictor actions are mainly mediated through the AT1 receptor. In contrast, other renin—angiotensin system (RAS) components appear to oppose the classical effects, resulting in vasodilation via the AT2 AngII receptor, or via the Mas receptor of Ang 1—7. Microarray analysis performed by our group in human umbilical vein endothelial cells (HUVEC) exposed to estradiol (E2), suggests E2 regulates RAS activity. Our aim was to check whether E2 mediates nitric oxide (NO) production through Mas receptors.Methods
After 24 hours of HUVEC exposure to E2, mRNA and protein expression of the enzymes implicated in Ang 1—7 production and NO synthesis were measured by RT-PCR and Western blot, respectively. Angiotensin converting enzyme (ACE) activity was measured by EIA. Endothelial NO production was determined by the ISONOP oxide sensor, and using the cell permeable fluorescent detector of NO, DAF2-DA. A799 were used to antagonize Mas receptors. Relaxant responses of mice mesenteric vessels were measured using a small-vessel myograph in isolated mesenteric vessels of Mas-deficient and of wild-type mice.Results
E2 increased ACE activity and expression, and cathepsin A expression. E2 also enhanced the expression of AKT1 kinase and endothelial nitric oxide synthase (eNOS), both enzymes implicated in NO production, and the NO receptor expression, cytosolic guanylate cyclase (cGC). Furthermore, the effect induced of E2 on eNOS and cGC expression was abolished with the presence of A779. NO levels were increased by E2, and decreased with the presence of Mas receptor antagonist. The relaxant response induced by E2 in mesenteric vessels was reduced in Mas-deficient mice.Conclusions
E2 induces a vasodilatation response mediated by Mas receptor activation in HUVEC and mesenteric arteries, since E2, through Mas receptor, has the capacity to up-regulate the gene expression and the protein activated content of the enzymes Akt and eNOS, and to incline the RAS balance to NO production.