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AJNR - American Journal of Neuroradiology

Published ahead of print on September 12, 2009
doi: 10.3174/ajnr.A1781

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American Journal of Neuroradiology 31:165-169, January 2010
© 2010 American Society of Neuroradiology

INTERVENTIONAL

Intrinsic Pathway–Mediated Apoptosis in Elastase-Induced Aneurysms in Rabbits

R. Kadirvel^a, Y.H. Ding^a, D. Dai^a, D.A. Lewis^a and D.F. Kallmes^a

^aFrom the Department of Radiology, Mayo Clinic, Rochester, Minnesota.

Please address correspondence to: David F. Kallmes, MD, Department of Radiology, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905; e-mail: Kallmes.david{at}mayo.edu

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.