The effect of ABCG1 deficiency on atherosclerotic lesion development in LDL receptor knockout mice depends on the stage of atherogenesis

Objective: As ABCG1 plays a role in cholesterol efflux, macrophage ABCG1 expression has been suggested to protect against atherosclerosis. However, we and others observed varying effects of ABCG1 deficiency on atherosclerotic lesion size. The objective of this study was to define the effect of ABCG1 deficiency during atherosclerotic lesion progression in LDL receptor knockout (LDLr-/-) mice. Methods and results: ABCG1(-/-)/LDLr-/- and ABCG1(+/+)/LDLr-/- littermates were fed a Western-type diet for 10 and 12 weeks in order to study the effect of ABCG1 deficiency in the exponential phase of atherosclerotic lesion formation. At 10 weeks of diet feeding, a significant 1.5-fold increase in early atherosclerotic lesion size (130 +/- 12 x 10(3) mu m(2)) was observed in ABCG1(-/-)/LDLr-/- mice compared to ABCG1(+/+)/LDLr-/- mice (88 +/- 11 x 103 mu m(2); p < 0.05). Interestingly, in more advanced lesions, induced by 12 weeks of WTD feeding, ABCG1(-/-)/LDLr-/- mice showed a significant 1.7-fold decrease in atherosclerotic lesion size (160 +/- 20 x 10(3) mu m(2) vs 273 +/- 19 x 10(3) mu m(2) in control mice; p < 0.01), indicating that in the ABCG1(-/-)/LDLr-/- mice progression of lesion formation is retarded as compared to ABCG1(+/+)/LDLr-/- mice. In addition, correlation analysis performed on 7 independent published studies and the current study confirmed that ABCG1 is atheroprotective in early lesions, while the development of advanced lesions is stimulated. Conclusions: It appears that the effect of ABCG1 deficiency on lesion development in LDLr-/- mice depends on the stage of atherogenesis, whereby the absence of ABCG1 leads to increased lesions at sizes < 167 x 10(3) mu m(2) while in more advanced stages of atherosclerosis enhanced apoptosis and/or compensatory mechanisms lead to retarded lesion progression. (C) 2011 Elsevier Ireland Ltd. All rights reserved.