Role of prolylcarboxypeptidase in angiotensin II type 2 receptor-mediated bradykinin release in mouse coronary artery endothelial cells

Abstract

Activation of angiotensin II type 2 receptors (AT2R) causes the release of kinins, which have beneficial effects on the cardiovascular system. However, it is not clear how AT2R interact with the kallikrein-kinin system to generate kinins. Prolylcarboxypeptidase is an endothelial membrane-bound plasma prekallikrein activator that converts plasma prekallikrein to kallikrein, leading to generation of bradykinin from high-molecular-weight kininogen. We hypothesized that AT2R-induced bradykinin release is at least in part mediated by activation of prolylcarboxypeptidase. Cultures of mouse coronary artery endothelial cells were transfected with an adenoviral vector containing the AT2R gene (Ad-AT2R) or green fluorescent protein only (Ad-GFP) as control. We found that overexpression of AT2R increased prolylcarboxypeptidase mRNA by 1.7-fold and protein 2.5-fold compared with Ad-GFP controls. AT2R overexpression had no effect on angiotensin II type 1 receptor mRNA. Bradykinin release was increased 2.2-fold in AT2R-transfected cells. Activation of AT2R by CGP42112A, a specific AT2R agonist, increased bradykinin further in AT2R-transfected cells. These effects were diminished or abolished by AT2R blockade or a plasma kallikrein inhibitor. Furthermore, blocking prolylcarboxypeptidase with a small interfering RNA partially but significantly reduced bradykinin release by transfected AT2R cells either at the basal condition or when stimulated by the AT2R agonist CGP42112A. These findings suggest that overexpression of AT2R in mouse coronary artery endothelial cells increases expression of prolylcarboxypeptidase, which may contribute to kinin release. © 2010 American Heart Association, Inc.