The counterregulating role of ACE2 and ACE2-mediated angiotensin 1-7 signaling against angiotensin II stimulation in vascular cells.

To clarify the role of endogenous angiotensin (Ang)-converting enzyme 2 (ACE2) and its cleavage product, Ang 1-7, in the atherogenic stimulation of vascular cells, we investigated the effect of pharmacological inhibition of ACE2 and Mas, an Ang 1-7 receptor, on cellular responses against Ang II stimulation. We measured extracellular signal-regulated kinase (ERK) 1/2 phosphorylation by western blot, smooth muscle cell (SMC) proliferation by WST assay and the adhesion of monocytes labeled with PKH67 to endothelial cells (ECs) by fluorescence microplate reader. Cells were pretreated with Ang 1-7, olmesartan (Ang II type 1 receptor (AT1) blocker), DX600 (ACE2 inhibitor), -Ala7-Ang1-7 (D-Ala; Mas antagonist), or combinations of treatments before the application of Ang II. Treatment with Ang II increased phosphorylated ERK 1/2 of SMC and EC, proliferation of SMC and adhesion of monocyte to EC, which were blocked by olmesartan. Pretreatment with DX600 either did not accelerate or only slightly accelerated these cellular responses. However, when Ang II signaling through AT1 was reduced by olmesartan, the additional treatment with DX600 significantly blunted some of the effect of olmesartan. Similarly, pretreatment with D-Ala reduced the inhibitory effect of olmesartan in response to Ang II stimulation. Endogenous ACE2 in vascular cells may contribute to counteracting the Ang II-mediated cellular response partly by upregulating the Ang 1-7 signaling through Mas.