Abstract 105: 20-HETE: An Inducer of ACE in Human Microvascular Endothelial Cells (HMVEC).

Abstract

20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 derived arachidonic acid metabolite, is manufactured in the microcirculation and shown to sensitize the smooth muscle to constrictor stimuli and cause endothelial activation and dysfunction. Increased vascular production of 20-HETE promotes hypertension that is dependent, in part, on the renin angiotensin system. Microarray analysis of endothelial cells treated with 20-HETE revealed a five-fold upregulation of angiotensin converting enzyme (ACE). In cultured human microvascular endothelial cells (HMVEC), 20-HETE (5 nM) induced ACE mRNA by 3.1-fold (± 0.16 p<0.05), increased ACE protein levels by 4.2-fold (±0.99 p<0.05) and ACE activity by 2-fold (±0.23 p<0.05). These effects were abrogated by co-treatment with 20-HEDE, a 20-HETE antagonist. 20-HETE induction of ACE mRNA was abolished by inhibitors of EGFR-tyrosine kinase, MAPK and IKKβ activation but was not affected by PKC inhibition. Moreover, transfection of cells with IKKβ siRNA prevented 20-HETE from inducing ACE mRNA. Collectively, theses results suggest a role for 20-HETE as a regulator of endothelial ACE. This regulatory activity impacts vascular function since downregulation of ACE in endothelial cells treated with siRNA exogenous 20-HETE from inhibiting NO synthesis and stimulating O 2 - production. This study demonstrates that induction of ACE expression and activity is critical to the actions of 20-HETE on endothelial cell function, further implicating the induction of ACE and activation of RAS as a key mechanism by which excessive production of 20-HETE within the vasculature leads to hypertension.