Abstract 973: Angiotensin II Up-Regulates Soluble Epoxide Hydrolase in Vascular Endothelial Cells
Epoxyeicosatrienoic acids (EETs) can hyperpolarize vascular smooth muscle, induce dilation of coronary arteries, and decrease the expression of adhesion molecules, thus, may be endogenous mediators protecting vascular wall from hypertension and atherosclerosis. Because EETs are degraded by soluble epoxide hydrolase (sEH), pharmacological inhibition of sEH is a potential therapeutic approach to enhance the EET-mediated vascular functions. Recently, we reported that laminar flow augmented cellular levels of EETs but decreased the levels of sEH in vascular endothelial cells (ECs). However, the molecular basis underlying sEH regulation is largely unknown. Because of the close correlation between EETs and vascular tone regulation, we investigated the regulation of sEH by Angiotensin II (Ang II) in ECs and the underlying mechanism. Treating human umbilical vein ECs or bovine aortic ECs with Ang II for 24 hrs increased sEH expression at both mRNA and protein levels. Further studies revealed that Ang II up-regulates sEH in a time- and dose-dependent manner. To study the transcriptional regulation of sEH by AngII, we cloned three different lengths of the human sEH promoter (2.1 kb, 1.1kb and 660bp) and constructed these fragments into a luciferase reporter system. Transient transfection of these promoter constructs into ECs showed that the activities of 1.1kb and 660bp were significantly increased after the treatment of Ang II. Sequence analysis of the sEH promoter found the existence of one NF-κB binding site (−306) and two putative AP-1 binding motifs (−213, −494). Overexpression of c-Jun and c-Fos activated sEH promoter while overexpression of p65 had little induction effect. These results suggested the involvement of AP-1, but not NF-κB, in the sEH regulation. We further confirmed that Ang II treatment increased the activity of AP-1-driven luciferase in ECs. Furthermore, western blotting showed that levels of sEH protein in the intima of spontaneously hypertensive rat aorta were higher than that in Wistar rats. Our results suggested that AP-1 is involved in the transcriptional up-regulation of sEH by Ang II. The clinical implication of the current study is that Ang II-induced hypertension is mediated in part by the up-regulation of sEH in endothelium.