Macrophage-derived lipoprotein lipase increases aortic atherosclerosis in cholesterol-fed Tg rabbits

Lipoprotein lipase (LPL) produced by macrophages is upregulated in the atherosclerotic lesions; however, it is not fully understood whether increased macrophage-derived LPL is pro-atherogenic. To examine the hypothesis that macrophage-derived LPL in the arterial wall enhances atherosclerotic lesion formation, we generated transgenic (Tg) rabbits that express the human LPL transgene under the control of the human scavenger receptor enhancer/promoter, which drives macrophage-specific expression of the human LPL gene. We fed Tg and non-Tg littermate rabbits a diet containing 0.3% cholesterol for 16 weeks and compared their lipoproteins and aortic atherosclerosis. We found that there was no difference in plasma lipid or lipoprotein profiles between Tg and non-Tg rabbits; however, atherosclerotic lesions were significantly increased in Tg compared to non-Tg rabbits. There was a 1.4-fold increase in total aortic en face lesions and a 2-fold increase in intimal lesions evaluated by image analysis system. Furthermore, immunohistochemical staining revealed that the increased atherosclerotic lesions present in Tg rabbits were characterized by marked accumulation of macrophage-derived foam cells and frequently associated with the deposition of oxidized LDL. These results support the notion that macrophage-derived LPL in the arterial wall is pro-atherogenic, possibly via the enhancement of foam cell formation during atherogenesis.