To determine whether procarboxypeptidase B (pCPB)
mice are susceptible to accelerated abdominal aortic aneurysm (AAA) development secondary to unregulated OPN-mediated mural inflammation in the absence of CPB inhibition.
Methods and Results—
Thrombin/thrombomodulin cleaves thrombin-activatable pCPB or thrombin-activatable fibrinolysis inhibitor, activating CPB, which inhibits the generation of plasmin and inactivates proinflammatory mediators (complement C5a and thrombin-cleaved osteopontin [OPN]). Apolipoprotein E
mice are protected from experimental AAA formation. Murine AAAs were created via intra-aortic porcine pancreatic elastase (PPE) infusion. Increased mortality secondary to AAA rupture was observed in pCPB
mice at the standard PPE dose. At reduced doses of PPE, pCPB
mice developed larger AAAs than wild-type controls (1.01±0.27 versus 0.68±0.05 mm;
=0.02 [mean±SD]). C5
mice were not protected against AAA development. Treatment with tranexamic acid inhibited plasmin generation and abrogated enhanced AAA progression in pCPB
This study establishes the role of CPB in experimental AAA disease, indicating that CPB has a broad anti-inflammatory role in vivo. Enhanced AAA formation in the PPE model is the result of increased plasmin generation, not unregulated C5a- or OPN-mediated mural inflammation.