High ACE-levels are associated with cardiovascular disease development, but little is known about its expressional regulation. ACE is a target of the miR143/145-cluster in murine vascular smooth muscle cells and can also be affected by AMPK activation in monocytes. Since shear stress activates AMPK in endothelial cells, we determined whether flow alters ACE expression and the involvement of AMPK and miR143/145.

Shear stress decreased ACE expression in human endothelial cells, an effect prevented by downregulating (siRNA) the AMPKa2 subunit, but not AMPKa1. Pharmacological AMPK activation also suppressed endothelial ACE expression and AMPKa2^-/- (not AMPKa1^-/-) mice expressed significantly higher ACE levels in different arteries than wild-type littermates. While basal blood pressure was comparable in AMPKa2^+/+ and AMPKa2^-/- mice, AMPKa2^-/- mice were more sensitive to the hypotensive effect of the ACE-inhibitor ramipril and demonstrated an impaired bradykinin-induced hindlimb-vasodilatation. The suppressive effect of the miR-143/145-cluster on human endothelial ACE was confirmed by overexpression of pre-miR143/145 and AMPKa2 downregulation decreased miR143/145-levels. Since flow increased mature and pre-miR-143/145 levels, but not pri-miR143/145 levels, we focused on the post-transcriptional regulation of miR143/145 by AMPK via p53. Indeed, p53 expression and phosphorylation (Ser15) increased in response to shear stress, and were sensitive to treatment with AMPKa2 (but not AMPKa1) siRNA.

The data indicate that AMPKa2 suppresses endothelial ACE expression via p53 activation and upregulation of miR143/145. Since AMPK (and p53) dysregulation is associated with several diseases (e.g. diabetes, cancer), their effect on miRNA143/145 and ACE might mediate disease-associated cardiovascular disorders.