TY - JOUR T1 - Intrinsic Pathway−Mediated Apoptosis in Elastase-Induced Aneurysms in Rabbits JF - American Journal of Neuroradiology JO - Am. J. Neuroradiol. SP - 165 LP - 169 DO - 10.3174/ajnr.A1781 VL - 31 IS - 1 AU - R. Kadirvel AU - Y.H. Ding AU - D. Dai AU - D.A. Lewis AU - D.F. Kallmes Y1 - 2010/01/01 UR - http://www.ajnr.org/content/31/1/165.abstract N2 - BACKGROUND AND OBJECTIVES: The pathophysiology of saccular aneurysms is complex and multifactorial. The aim of the present study was to understand the mechanism of apoptosis in an elastase-induced aneurysm model in rabbits. MATERIALS AND METHODS: Elastase-induced saccular aneurysms were created at the origin of the right common carotid artery in 20 rabbits. Aneurysm samples were harvested at 2 and 12 weeks after creation. Expression of apoptosis-associated proteins, including caspases and bcl-2 proteins, were assessed by Western blot analysis (n = 5 at both time points). Terminal deoxynucleotidyltransferase–mediated dUTP nick end-labeling (TUNEL) staining, which indicates the presence of apoptosis, was performed in tissue sections (n = 5 at both time points). The unoperated contralateral common carotid artery was used as a control. RESULTS: Expression of active caspase-3, the final executioner of apoptosis, and caspase-9, the mediator of the intrinsic mitochondrial pathway, was observed in aneurysms at 2 weeks, whereas the expression of activated caspase-8, the mediator of the extrinsic death receptor pathway, was absent at both time points. Expression of antiapoptotic proteins, Bcl-2 and phospho-Bad, was down-regulated in aneurysms compared with controls at 2 weeks. None of these proteins were differentially expressed at 12 weeks. These results were confirmed by the presence of TUNEL-positive cells in some aneurysms at the early time point. CONCLUSIONS: In this study of elastase-induced aneurysms in a rabbit model, activation of apoptosis is mediated predominantly by the Bcl-2-mediated intrinsic pathway through the activation of caspase-9. ER -