Differences in the effect of angiotensin-converting enzyme inhibitors on the rate of endothelial cell apoptosis: in vitro and in vivo studies.

AIM: An imbalance between endothelial apoptosis and regeneration is one of the initiating events in atherosclerosis. Angiotensin-converting enzyme (ACE) inhibition corrects the endothelial dysfunction observed in coronary artery disease, and this could be the consequence of a reduction in the rate of endothelial apoptosis. The aim of this study was to investigate the effect of different ACE inhibitors on endothelial apoptosis. METHODS: We examined the effect of five ACE inhibitors (enalapril, perindopril, quinapril, ramipril, and trandolapril) on the rate of endothelial apoptosis, either in vitro in human umbilical vein endothelial cells (HUVECs), using a serum deprivation method to induce apoptosis, or in vivo in rats, inducing apoptosis via endotoxic shock with Escherichia coli lipopolysaccharides (LPS). RESULTS: We were unable to detect any significant effect of ACE inhibition on the rate of in vitro endothelial apoptosis at concentrations ranging from 5 x 10(-8) to 10(-6) M. In contrast, chronic in vivo administration of ACE inhibitors to rats at dosages that had similar hypotensive effects reduced the rate of LPS-induced apoptosis significantly for perindopril (P < 0.001) and nonsignificantly for the other ACE inhibitors. The order of potency of the ACE inhibitors tested was perindopril > ramipril >> quinapril = trandolapril = enalapril, with significant differences between perindopril and quinapril (P < 0.01), trandolapril (P < 0.001), and enalapril (P < 0.001). The difference between perindopril and ramipril did not reach significance. CONCLUSION: Our experiments suggest differences between ACE inhibitors in terms of inhibition of endothelial apoptosis in vivo.

Therapeutic modulation of the nitric oxide: all ace inhibitors are not equivalent.

The properties of the angiotensin-converting enzyme (ACE) inhibitors have largely been attributed to a class effect. However, this opinion is now increasingly challenged in view of the findings from recent clinical trials, which have demonstrated differential effects of ACE inhibitors, in particular with respect to secondary cardiovascular prevention outcomes. In this experimental study, Sprague-Dawley rats were treated with five different ACE inhibitors (enalapril, perindopril, quinapril, ramipril, and trandolapril) at equihypotensive doses. All ACE inhibitors increased endothelial nitric oxide synthase (eNOS) protein expression and activity in the aorta (both P<0.0001 versus vehicle) and in cardiac myocytes (both P<0.05 versus vehicle). A highly significant effect was observed with perindopril when compared with vehicle in the modulation of eNOS protein expression and activity in aorta (22.52+/-1.09 versus 9.12+/-0.57 AU microg(-1) protein and 1.59+/-0.03 versus 0.77+/-0.02 pmol l(-1) citrulline min(-1)mg protein(-1), respectively) and in cardiac myocytes (17.64+/-0.94 versus 11.30+/-0.59 AU microg(-1) protein and 0.93+/-0.02 versus 0.62+/-0.03 pmol l(-1) citrulline min(-1)mg protein(-1), respectively). On the basis of the eNOS protein expression in the rat aorta, the other ACE inhibitors had similar, but lower effects. Indeed, the rank of potency - based both on eNOS protein expression and activity - was perindopril>trandolapril approximately quinapril approximately ramipril approximately enalapril (P<0.05 perindopril versus trandolapril and ramipril and P<0.01 perindopril versus enalapril, respectively). Levels of circulating nitrite/nitrate, the end-metabolites of nitric oxide, were also significantly affected by ACE inhibition, with the same order of potency. Our findings provide further evidence in favor of differential effects associated with ACE inhibitor therapy and suggest that the clinical benefits associated with these drugs may not solely reflect a class effect extending their benefit beyond blood pressure-lowering effect.