CD137-CD137L Interaction Regulates Atherosclerosis via Cyclophilin A in Apolipoprotein E-Deficient Mice

BACKGROUND Our previous studies showed that increased levels of cyclophilin A (CyPA) may be a valuable marker for predicting the severity of acute coronary syndromes and that interruption of CD137-CD137L interactions diminished the formation and progression of atherosclerosis in apolipoprotein E-deficient (ApoE-/-) mice. Here, we sought to determine whether the proinflammatory factor CyPA is involved in atherosclerosis regulated by CD137-CD137L interactions. METHODS AND RESULTS A constrictive collar was placed around the right carotid arteries of ApoE-/- mice that were fed a high-fat diet to induce atherosclerotic plaque formation. After that, the mice were intraperitoneally injected with anti-CD137 or anti-CD137L in the presence or absence of the recombinant lentiviral vectors LVTHM-CyPA or pGC-FU-CyPA, respectively. Interestingly, activation of CD137-CD137L was negatively correlated with CyPA expression in vivo and in vitro. Stimulating CD137-CD137L interaction significantly increased CyPA, which was concurrent with the upregulation of proinflammatory cytokines, chemokines and matrix metalloproteinases and resulted in the promotion of atherosclerosis in ApoE-/- mice. Silencing CyPA could eliminate these effects, and restoration of CyPA effectively and consistently attenuated the atherosclerotic suppression phenotypes elicited by the blockade of CD137-CD137L. CONCLUSION These observations suggest that CD137-CD137L interactions mediated via regulation of CyPA contribute to the progression of atherosclerosis.