Cyclophilin A enhances vascular oxidative stress and development of angiotensin II-induced aortic aneurysms

Inflammation and oxidative stress are pathogenic mediators of many diseases, but therapeutic targets remain elusive. In the vasculature, abdominal aortic aneurysm (AAA) formation critically involves inflammaton and matrix degradation. Cyclophilin A (CyPA, encoded by Ppia) is highly expressed in vascular smooth muscle cells (VSMC), is secreted in response to reactive oxygen species (ROS), and promotes inflammation. Using the angiotensin II (AngII)-induced AAA model in Apoe(−/−) mice, we show that Apoe(−/−)Ppia(−/−) mice were completely protected from AngII–induced AAA formation, in contrast to Apoe(−/−)Ppia(+/+) mice. Apoe(−/−)Ppia(−/−) mice showed decreased inflammatory cytokine expression, elastic lamina degradation, and aortic expansion. These features were not altered by reconstitution of bone marrow cells from Ppia(+/+) mice. Mechanistic studies demonstrated that VSMC-derived intracellular and extracellular CyPA were required for ROS generation and matrix metalloproteinase-2 activation. These data define a novel role for CyPA in AAA formation and suggest CyPA is a new target for cardiovascular therapies.