Devil and angel in the renin-angiotensin system: ACE-angiotensin II-AT1 receptor axis vs. ACE2-angiotensin-(1-7)-Mas receptor axis

Recent studies have established a new regulatory axis in the renin-angiotensin system (RAS). In this axis, angiotensin (Ang)-(1-7) is finally produced from Ang I or Ang II by the catalytic activity of angiotensin-converting enzyme 2 (ACE2). Ang-(1-7) shows actions different from those of AT(1) receptor stimulation, such as vasodilatation, natriuresis, anti-proliferation and an increase in the bradykinin - NO ( nitric oxide) system. As the catalytic efficiency of ACE2 is approximately 400-fold higher with Ang II as a substrate than with Ang I, this axis is possibly acting as a counter-regulatory system against the ACE/Ang II/AT(1) receptor axis. The signaling pathway of the ACE2 - Ang-( 1 - 7) axis has not yet been totally and clearly understood. However, a recent report suggests that the Mas oncogene acts as a receptor for Ang-( 1 - 7). Intracellular signaling through Mas is not clear yet. Several factors such as Akt phosphorylation, protein kinase C activation and mitogen-activated protein ( MAP) kinase inhibition seem to be involved in this signaling pathway. Further investigations are needed to clarify the regulation and mechanism of action of ACE2 and Ang-( 1 - 7). However, this second axis through ACE2 and Ang-( 1 - 7) in RAS can be an important target for the therapy of cardiovascular and metabolic disorders. Hypertension Research (2009) 32, 533 - 536; doi:10.1038/hr.2009.74; published online 22 May 2009