ANGIOTENSIN-II INDUCES APOPTOSIS OF HUMAN ENDOTHELIAL-CELLS - PROTECTIVE EFFECT OF NITRIC-OXIDE

Angiotensin II (Ang II) importantly contributes to the pathobiology of atherosclerosis. Since endothelial injury is a key event early in the pathogenesis of atherosclerosis, we tested the hypothesis that Ang II may injure endothelial cells by activation of cellular suicide pathwa ys leading to apoptosis. Human umbilical venous endothelial cells (HUV ECs) were incubated with increasing doses of Ang II for 18 hours. Apop tosis of HUVECs was measured by ELISA specific for histone-associated DNA fragments and confirmed by DNA laddering and nuclear staining. Ang II dose-dependently induced apoptosis of HUVECs. Simultaneous blockad e of both the AT(1) and AT(2) receptor prevented Ang II-induced apopto sis, whereas each individual receptor blocker alone was not effective. Selective agonistic stimulation of the AT(2) receptor also dose-depen dently induced apoptosis. Ang II-mediated as well as selective AT(2) r eceptor stimulation-mediated apoptosis was associated with the activat ion of caspase-3, a central downstream effector of the caspase cascade executing the cell death program. Specific inhibition of caspase-3 ac tivity abrogated Ang II-induced apoptosis. In addition, the NO donors sodium nitroprusside and S-nitrosopenicillamine completely inhibited A ng II-induced apoptosis and eliminated caspase-3 activity. Thus, Ang I I induces apoptosis of HUVECs via activation of the caspase cascade, t he central downstream effector arm executing the cell death program. N O completely abrogated Ang II-induced apoptosis by interfering with th e activation of the caspase cascade.