Mitochondrial-dependent apoptosis in experimental rodent abdominal aortic aneurysms.
OBJECTIVE
While extrinsic mechanisms of apoptosis in abdominal aortic aneurysms (AAAs) are recognized, this project hypothesizes that an intrinsic, mitochondrial-dependent, mechanism of apoptosis also contributes to experimental AAA formation.


METHODS
Rat aortas were perfused with either saline or elastase (N = 5 per group) and harvested 7 days postperfusion. The aortas were placed in gluteraldehyde for subsequent transmission electron microscopy, Bouin's solution for TUNEL, or paraformaldehyde for immunohistochemical staining for caspase-9, caspase-3, and Bid.


RESULTS
Abdominal aortic diameters increased 168 +/- 25% (mean +/- SEM) after elastase perfusion. compared with 30 +/- 5% after saline perfusion (P < .001). Apoptosis of aortic smooth muscle cells, macrophages, and neutrophils was evidenced by transmission electron microscopy and TUNEL in the elastase-perfused aneurysmal aortas. Quantitative analysis of the apoptotic cells revealed a significant (P < .01) increase in the number of total apoptotic cells in the elastase-perfused aortas (12 +/- 3 cells per high-power field), compared with that of saline-infused controls (1.3 +/- 0.2). Caspase-9, the key initiator in the mitochondrial-dependent apoptotic pathway, stained positively in only elastase-perfused aortas. Bid staining was not detected in either the elastase-perfused aortas or the saline controls.


CONCLUSIONS
Apoptosis is evident in multiple cell lines in elastase-perfused aneurysmal aortas, but rarely observed in control aortas. Caspase-9, the key initiator of intrinsic apoptosis, was documented only in elastase-perfused aortas. These results suggest that mitochondrial-dependent apoptosis is associated with abdominal aortic aneurysm formation.
Sinha
Indranil
I
Jobst Vascular Research Laboratories, Section of Vascular Surgery, Department of Surgery, University of Michigan, Ann Arbor, USA.
Sinha-Hikim
Amiya P
AP
Hannawa
Kevin K
KK
Henke
Peter K
PK
Eagleton
Matthew J
MJ
Stanley
James C
JC
Upchurch
Gilbert R
GR
D000818:Animals; D017544:Aortic Aneurysm, Abdominal / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D004789:Enzyme Activation; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008854:Microscopy, Electron; D008928:Mitochondria; D010196:Pancreatic Elastase / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling
D010196:Pancreatic Elastase; C505410:Casp3 protein, rat; C506435:Casp9 protein, rat; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases