Brief report: Accelerated atherosclerosis in low-density lipoprotein receptor-deficient mice lacking the membrane-bound complement regulator CD59

Objective - Whereas studies in humans and animal models have suggested a role for complement activation in atherosclerosis, there has been little analysis of the importance of complement regulators. We tested the hypothesis that the terminal pathway inhibitor CD59 plays an essential role in limiting the proinflammatory effects of complement activation. Methods and Results - CD59 gene targeted mice (CD59a(-/-)) mice were crossed with low-density lipoprotein receptor deficient (Ldlr(-/-)) mice. CD59-deficient Ldlr(-/-) mice had significantly more extensive en face Sudan IV staining of thoracoabdominal aorta than Ldlr(-/-) single knock-outs, both after a low-fat diet (6.51 +/- 0.36% versus 2.63 +/- 0.56%, P<0.001) or a high-fat diet (17.05 +/- 2.15% versus 7.69 +/- 1.17%, P < 0.004). Accelerated lesion formation in CD59a (-/-)/Ldlr(-/-) mice on a high-fat diet was associated with increased lesional vascular smooth muscle cell (VSMC) number and fibrous cap formation. Conclusion - Our data show that CD59 deficiency accelerates the development of lesions and increases plaque VSMC composition. Assuming that the main function of CD59 is to prevent the development of C5b-9 membrane attack complexes, our observations are consistent with the terminal complement pathway having proatherogenic potential in the Ldlr(-/-) mouse model, and highlight the importance of complement regulation.