title: Intrinsic pathway-mediated apoptosis in elastase-induced aneurysms in rabbits.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: R
authors.initials: R
authors.lastname: Kadirvel
authors.forename: Y H
authors.initials: YH
authors.lastname: Ding
authors.forename: D
authors.initials: D
authors.lastname: Dai
authors.forename: D A
authors.initials: DA
authors.lastname: Lewis
authors.forename: D F
authors.initials: DF
authors.lastname: Kallmes
mesh_terms: D000818:Animals; D017209:Apoptosis; D002532:Intracranial Aneurysm / Q000139:chemically induced / Q000503:physiopathology*; D010196:Pancreatic Elastase / Q000008:administration & dosage; D011817:Rabbits
chemical_list: D010196:Pancreatic Elastase