| Research Abstract |
To investigate the role of the renin angiotensin system (RAS) in oxidative stress-induced endothelial cell (EC) apoptosis, we examined the effects of RAS modulation and the underlying mechanism using the rat model and cultured EC. EC apoptosis was induced by a 5-minute exposure of hydrogen peroxide (H2O2) into the rat carotid artery. ACE activities in arterial homogenates were not increased by H2O2 treatment, rather were decreased at 24 hours in parallel with EC denudation. At 24 hours after H2O2 treatment, apoptotic EC were counted by evaluating the chromatin staining of enface specimens with Hoechst33342 fluorescent dye. Administration of an ACE inhibitor, temocapril or an AT1 receptor blocker, olmesartan for 3 days before H2O2 treatment inhibited EC apoptosis. Conversely, angiotensin II administration augmented H2O2-induced EC apoptosis. Furthermore, administration of temocapril before H2O2 treatment inhibited neointima formation that occurred 2 weeks later, suggesting the causal influence of EC apoptosis on neointima formation. Next, cultured EC derived from the bovine carotid artery were treated with H2O2 to induce apoptosis. Again, EC apoptosis was inhibited by addition of temocapril or olmesartan, but was not affected by an AT2 receptor blocker, PD123319. Nitric oxide synthase inhibitor, L-NAME did not influence the effects of temocapril on EC apoptosis. H2O2 treatment stimulated the activities of ERK, JNK, p38 MAP kinase and Akt peaking at 30min. Temocapril inhibited the activities of a proapoptotic serin/ threonine kinase, p38 MAP kinase but not of others. Taken together, it is concluded that angiotensin II-AT1 receptor signaling augments EC apoptosis and the resulting vascular lesion formation in the process of oxidative stress-induced vascular injury.
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