Estradiol Regulates Renin–angiotensin System Towards Nitric Oxide Production Through Mas Receptor: Pp.24.462

Objective: The renin–angiotensin system (RAS) plays an important role in the regulation of vascular tone. Vasoconstrictor actions of angiotensin (Ang) II are mainly mediated through the AT1 receptor. In contrast, other components of RAS appear to oppose the classical effects, resulting in vasodilation via the AT2 AngII receptor, or via the Mas receptor of Ang 1–7. Recent microarray analysis performed by our group in human umbilical vein endothelial cells (HUVEC) exposed to estradiol (E2), suggests that E2 regulates RAS activity. Our aim was to check whether E2 mediates nitric oxide (NO) production through RAS pathway regulation. Design and Method: HUVEC were exposed to different concentrations of E2 for 24 hours. mRNA expression of the enzymes implicated in Ang 1–7 production and NO synthesis were measured by RT-PCR. Endothelial NO production was determined by two different methods: in culture medium by the ISONOP oxide sensor, and using the cell permeable fluorescent detector of NO, DAF2-DA. PD123319 and A799 were used to antagonize AT2 and Mas receptors, respectively. Results: E2 increased AngI converting enzyme (ACE) and cathepsin A expression, both enzymes implicated in Ang 1–7 synthesis. E2 also increased AKT1 kinase, endothelial nitric oxide synthase (eNOS) and cytosolic guanylate cyclase (cGC) expression, enzymes implicated in NO production. Furthermore, the effect induced by E2 on eNOS and cGC expression was abolished with the presence of A779 and PD123319. NO levels were increased by E2, and decreased with the presence of Mas receptor antagonist, A779, but not AT2 antagonist, PD123319. Conclusion: E2 increases endothelial RAS proteins. Moreover, Mas receptor mediates in part the stimulatory effect of E2 on NO production. Our study suggests E2 balances RAS activity in HUVEC to the vasodilator way.