Several studies have elucidated the role of these drug classes on the modulation of the ACE2/Ang1-7/Mas axis. Mouse peritoneal macrophages treated in vitro with aldosterone, demonstrated significantly increased ACE activity as well as ACE mRNA and significantly reduced ACE2. However, in mouse peritoneal macrophages treated with nicotinamide adenine dinucleotide phosphate oxidase inhibitor, aldosterone could not increase ACE or decrease ACE2, which suggested these effects were mediated in part by nicotinamide adenine dinucleotide phosphate oxidase (42). These effects were also attenuated with treatment with an MRA (eplerenone) (42). Human monocyte-derived macrophages obtained from patients with heart failure before and after 1 month of treatment with another MRA (spironolactone; 25 mg/day) showed 47% reduction in ACE activity and 53% reduction in ACE mRNA expression. At the same time, ACE2 activity increased by 300% and ACE2 mRNA expression increased by 654% (42). In mice treated for 2 weeks with eplerenone, cardiac ACE2 activity increased 2-fold and was paralleled by increased ACE2 activity in macrophages (42). This study demonstrated that the MRA reduced oxidative stress, decreased ACE activity, and increased ACE2 activity and/or expression, which suggested the protective role played by increased generation of Ang 1-7 and decreased formation of Ang II. Overall, aldosterone decreased ACE2 transcription through a nicotinamide adenine dinucleotide phosphate oxidase−mediated pathway (42), and in vascular smooth muscle cells, potentiated Ang II signaling with increased phosphorylation of ERK1/2 and c-Jun kinase, which are also dependent on reactive oxygen species generation (43). Thus, the beneficial effects of MRAs are likely associated with reduction of oxidative stress and differential control of these angiotensinases. MRAs appeared to promote membrane ACE2 expression and suppress the peripheral effects of Ang II; however, the effect of MRAs on soluble ACE2 remains unclear.