Effects of Caspase Inhibitor on Angiotensin II-Induced Abdominal Aortic Aneurysm in Apolipoprotein E-Deficient Mice

Objective-The presence of apoptotic markers is a prominent histological feature of abdominal aortic aneurysm. To understand the role of apoptosis in the pathogenesis of this common vascular disease, we tested the effect of the pan-caspase inhibitor quinoline-Val-Asp-difluorophenoxymethylketone (Q-VD-OPh) on aneurysm formation using a mouse angiotensin II (Ang II) model. Methods and Results-Ang II in apolipoprotein E-deficient mice significantly induced medial cell apoptosis 3 days after infusion at the aortic region, eventually becoming aneurismal. A daily administration of 20 mg/kg per day Q-VD-OPh starting 6 hours before Ang II infusion reduced aneurysm incidence from 83.3% to 16.7% and maximal aortic diameter from 2.43 +/- 0.29 mm to 1.58 +/- 0.18 mm. The caspase inhibitor treated mice showed profoundly diminished levels of medial apoptosis and inflammation. In contrast, administration of Q-VD-OPh starting 7 days after Ang II infusion had no significant impact on aneurysm development. In vitro, media conditioned by Ang II-treated smooth muscle cells (SMCs) stimulated macrophage chemotaxis in a caspase-dependent manner. Inhibition of monocyte chemoattractant protein-1 (MCP-1) in the conditioned media via a neutralizing antibody completely blocked the ability of conditioned media to attract macrophages. Conclusion-These results indicate that medial SMC apoptosis may contribute to vascular inflammation and thus aneurysm formation, in part through production of MCP-1. (Arterioscler Thromb Vasc Biol. 2010; 30: 702-707.)