Angiotensin II-induced superoxide anion generation in human vascular endothelial cells: Role of membrane-bound NADH-/NADPH-oxidases

Background: Angiotensin II (ANG II) mediated hypertension accelerates ather osclerosis (AS) and thereby increases the incidence of myocardial infarctio n (MI). On the other hand, superoxide anion (O-2(-)) is involved in the mod ification of low density lipoproteins, inhibition of prostacyclin (PGI(2)) formation and breakdown of nitric oxide. These events finally lead to rapid progression of AS and MI. In the present study, we investigate whether ANG II can induce O-2(-) release from human vascular endothelial cells (HVECs) and the possible mechanisms involved. Methods and Results: The expression of ANG receptors subtype-1 (AT-1) and subtype-2 (AT-2) were identified by u sing reverse transcription polymerase chain reaction and sequence analysis. The O-2(-) production was dose-dependently increased in HVECs treated with ANG II (10(-7)-10(-9) M) and with a maximum rate after 1 h of incubation. This event was significantly inhibited by pretreatment of cells with the sp ecific AT-1 blocker losartan (10(-7) M) and to a lesser extent by the speci fic AT-2 receptor blocker PD123319 (10(-7) M). The combined incubation of b oth receptor blockers was even more effective. In addition, our lucigenin-e nhanced chemiluminescence assay showed that the activity of plasma membrane -bound NADH-/NADPH-oxidases derived from ANG II-treated cells was also sign ificantly increased, this effect was reduced in cells pretreated with losar tan or to lesser extent by PD123319. However, the activity of xanthine oxid ase remained unchanged in response to ANG II. Furthermore, the basal O-2(-) release from HVECs was inhibited in cells treated with angiotensin-convert ing enzyme (ACE) inhibitor, Lisinopril (10(-6) M), and this event could be reversed by ANG II. Conclusion: ANG II induces O-2(-) release in HVECs via activation of membrane-bound NADH-/NADPH-oxidases, an effect, that is media ted by both AT-1 and AT-2 receptors. This suggests that acceleration of AS and MI in ANG II-mediated hypertension may at least be due to ANG II-induce d O-2(-) generation from vascular endothelial cells. In this case, the ACE inhibitors and the ANG receptor antagonists may act as causative "antioxida nts". (C) 1999 Elsevier Science B.V. All rights reserved.