Loss of the lysophosphatidylcholine effector, G2A, ameliorates aortic atherosclerosis in low-density lipoprotein receptor knockout mice

Abstract

OBJECTIVE - Lysophosphatidylcholine is a major product of low-density lipoprotein (LDL) oxidation and secretory phospholipase A2-mediated lipid hydrolysis within atherosclerotic lesions. The G2A receptor mediates chemotaxis of cultured macrophages and T cells to lysophosphatidylcholine, supporting a pro-atherogenic role for this receptor in vivo. We investigated the ability of G2A to modulate atherosclerosis in mice. METHODS AND RESULTS - We measured atherosclerosis in G2A and G2A LDL receptor knockout (LDLR) mice. Consistent with a previous study, early lesion size at the aortic sinus was unaffected by G2A deficiency. However, G2A deficiency attenuated lesion progression at this site (42% to 44% reduction in average lesion area) and led to robust suppression of atherosclerosis throughout the aorta after short and extended periods of diet intervention (reduction in aortic lesion coverage: 62% to 73% at 9 weeks, 75% to 84% at 20 weeks). In G2ALDLR mice, intimal macrophage accumulation at lesion-prone sites of the aorta was significantly reduced in the absence of any detectable effect on T cell recruitment. Examination of lipoprotein profiles revealed elevated levels of circulating high-density lipoprotein (HDL) cholesterol in G2ALDLR mice compared with their G2ALDLR counterparts after extended periods of diet intervention (54% increase in mean HDL cholesterol concentration). CONCLUSION - G2A provides a pro-atherogenic stimulus in vivo consistent with its chemotactic action but to which a pleiotropy of effects, including modulation of lipoprotein metabolism, may also contribute. © 2006 American Heart Association, Inc.