Macrophage ATP-Binding Cassette Transporter 1 Overexpression Inhibits Atherosclerotic Lesion Progression in Low-Density Lipoprotein Receptor Knockout Mice

Background—ATP-binding cassette transporter 1 (ABCA1) is a key regulator of cellular cholesterol and phospholipid transport. Previously, we have shown that inactivation of macrophage ABCA1 induces atherosclerosis in low-density lipoprotein receptor knockout (LDLr / ) mice. However, the possibly beneficial effects of specific upregulation of macrophage ABCA1 on atherogenesis are still unknown. Methods and Results—Chimeras that specifically overexpress ABCA1 in macrophages were generated by transplantation of bone marrow from human ABCA1 bacterial artificial chromosome (BAC) transgenic mice into LDLr / mice. Peritoneal macrophages isolated from the ABCA1 3 LDLr / chimeras exhibited a 60% (P 0.0006) increase in cholesterol efflux to apolipoprotein AI. To induce atherosclerosis, the mice were fed a Western-type diet containing 0.25% cholesterol and 15% fat for 9, 12, and 15 weeks, allowing analysis of effects on initial lesion development as well as advanced lesions. No significant effect of macrophage ABCA1 overexpression was observed on atherosclerotic lesion size after 9 weeks on the Western-type diet (245 36 10 m in ABCA1 BAC 3 LDLr / mice versus 210 20 10 m in controls). However, after 12 weeks, the mean atherosclerotic lesion area in ABCA1 BAC 3 LDLr / mice remained only 164 15 10 m (P 0.0008) compared with 513 56 10 m in controls (3.1-fold lower). Also, after 15 weeks on the diet, lesions in mice transplanted with ABCA1 overexpressing bone marrow were still 1.6-fold smaller (393 27 10 m compared with 640 59 10 m in control transplanted mice; P 0.0015). Conclusion—ABCA1 upregulation in macrophages inhibits the progression of atherosclerotic lesions. (Arterioscler Thromb Vasc Biol. 2006;26:000-000.)