Abstract 1732: Deletion of Fc Receptor Ameliorates Progression of Atherosclerotic Lesions in LDL Receptor Knockout Mice: Protective Role against Vascular Inflammation and Oxidative Stress

Abstract

Background : Vascular endothelial dysfunction through the production of reactive oxygen species (ROS) plays an important role in the initiation and progression of atherosclerosis. Immunoglobulin Fc receptor (FcR) involves the activation of immune and inflammatory reaction, however, the role of FcR in endothelial function, ROS production, and atherogenesis, has not clearly elucidated. To examine the hypothesis that FcR deletion blunts the progression of atherosclerotic lesions via improvements of superoxide production and endothelial dysfunction, we generated FcR/LDL receptor double-knockout (DKO) mice. Methods : Mice (8 weeks) with LDL receptor knockout (LDLR-KO) and DKO were fed a high cholesterol diet for 10 weeks. We examined the endothelium-dependent relaxation of isolated thoracic aorta, superoxide production by dihydroethidium-derived fluorescence (DHE) staining before and after high cholesterol feeding. We also assessed atherosclerotic lesions by Oil Red O-staining, macrophage infiltration, and p22phox expression by immnohistochemical analysis. Results : Vascular endothelial-dependent relaxation induced by high cholesterol diet was significantly higher in DKO mice than in LDLR-KO mice (−53 ± 7% vs −22 ± 9, p < 0.05). Superoxide production was significantly lower in DKO mice than in LDLR-KO mice (13.6 ± 10 vs 38.8 ± 20 ×10 3 μ m 2 p < 0.05). The expression of p22phox in DKO mice was significantly lower than in LDLR-KO mice (90 ± 19 vs 141 ± 42 × 10 3 μm 2 p < 0.05). The area of macrophage infiltration of the vascular wall was significantly lower in DKO mice than LDLR-KO mice (34 ± 5 vs 59 ± 17 × 10 3 μ m 2 p < 0.05). The Oil -Red O staining showed the significant reduction of atherosclerotic lesions in DKO mice than in LDLR-KO mice (73 ± 24 vs 133 ± 31 × 10 4 μ m 2 p < 0.005). Conclusion : Deletion of FcR attenuated the production of ROS, vascular inflammation, and endothelial dysfunction, resulting in prevention of atherosclerotic formation in LDLR-KO mice. These data suggested that FcR might be involved in atherosclerotic process through not only vascular inflammation, but also oxidative stress in vasculature.