Differential effects of apolipoprotein A-I-mimetic peptide on evolving and established atherosclerosis in apolipoprotein E-null mice.

BACKGROUND Apolipoprotein (apo) A-I and apoA-I-mimetic peptides showed promise to prevent atherosclerosis development. Using a bypassed vein graft model in apoE-null mice, we evaluated the effects of oral or intraperitoneal administration of an apoA-I-mimetic peptide on evolving atherosclerotic lesions in the vein graft and compared such effects on the established atherosclerotic lesions in aortic sinus in the same mice. METHODS AND RESULTS We used apoE-null mice in which a segment of inferior vena cava was grafted into the right carotid artery at 16 weeks of age. Native aortic atherosclerotic lesions (established atherosclerosis) and vein-graft atherosclerotic lesions (evolving atherosclerosis) were assessed 4 weeks after daily oral (0.3 mg/mL) or intraperitoneal (50 microg in 200 microL saline) administration of an apoA-I-mimetic peptide, D4F. Mice receiving saline or water without D4F served as controls. Both oral and intraperitoneal administration of D4F reduced vein-graft atherosclerotic (evolving lesions) plaque size by 43% and 42%, plaque lipid by 70% and 49%, and macrophage immunoreactivity by 63% and 62%, respectively, compared with controls. In contrast, D4F had no effect on the native aortic sinus atherosclerotic lesions (established lesions). CONCLUSIONS Oral and intraperitoneal administration of the apoA-I-mimetic peptide D4F significantly reduced rapidly evolving atherosclerotic lesions in vein grafts but not established atherosclerotic lesions in aortic sinus. These observations suggest that the type of atherosclerotic lesions and the time of initiation during the course of lesion evolution modulate the beneficial effects of apoA-I-mimetic peptides on atherosclerosis.