Increased endothelial ACE is a risk factor for cardiovascular disease. Little is known about the regulation of ACE in endothelial cells, but protein levels are regulated by the AMPK and the miR-143/145-cluster in other cells. Thus, we determined the effect of AMPK and/or miR-143/145 on endothelial ACE expression.

Application of shear-stress decreased ACE levels in human endothelial cells, an effect prevented by downregulating (siRNA) the AMPKα2 (but not AMPKα1) subunit. Higher ACE levels were also found in vivo in different vascular beds from AMPKα2^-/- (not AMPKα1^-/-) mice. Consequently, AMPKα2^-/- mice were more sensitive to the hypotensive effect of an ACE-inhibitor and demonstrated an impaired bradykinin-induced hindlimb vasodilatation. The latter was also evident in endothelial cell specific AMPKα2^-/- animals. In endothelial cells from miR-143/145-deficient LacZ-reportergene mice ACE levels were decreased, a finding that could be confirmed in human cells treated with specific AntagomiRs. Shear-stress increased mature and pre-miR-143/145 levels while AMPKα2 deletion (siRNA, AMPKα2^-/-) decreased them. However, shear-stress did not affect pri-miR-143/145 levels or the activity of the miR-143/145-promoter (LacZ reportergene), indicating a post-transcriptional upregulation of miRs. p53 is known to affect miR levels via post-transcriptional regulation, and we demonstrated p53 phosphorylation(Ser15) by AMPKα2 in response to shear-stress. Moreover, p53 deletion (siRNA) decreased miR-143/145 levels, accompanied by an increase in ACE-expression and prevention of its shear-stress-induced downregulation.

AMPKα2 suppresses endothelial ACE expression via post-transscriptional upregulation of miR-143/145 by p53. Since AMPK/p53-dysregulation is associated with several diseases (e.g. diabetes, cancer), their effect on miR and ACE levels might underlie disease-associated cardiovascular disorders.