Abstract 3717: Receptor for Advanced Glycation End Products (RAGE) Plays an Integral Role in Non-Diabetic Atherosclerosis and Oxidized LDL Stimulation
Background: RAGE is a multifunctional receptor which identifies AGE, S100/calgranulins and HMGB-1 as the ligands. An AGE/RAGE axis plays a central role in the pathogenesis in diabetic vascular remodeling. However, the issue that hyperlipidemia associated with oxidized LDL mediates vascular responses via RAGE remains to be elucidated. In this study, we attempted to clarify the role of RAGE in non-diabetic atherosclerosis and oxidized LDL (ox-LDL) stimulation.
Methods and Results: We used the aortic and coronary atherosclerotic lesions of Watanabe heritable hyperlipidemic (WHHL) rabbits at ages of 1 to 14 months, which had high concentrations of serum ox-LDL independent of aging. Immunohistochemistry demonstrated the significant expression of RAGE as early as at age of 1 month with the stronger expression at 3 and 7 months, which was diminished at ages of 14 months. The major original sources of RAGE expression were macrophages and endothelial cells, as well as smooth muscle cells. The concentrations of serum AGE did not alter significantly with aging, while there was no difference in serum AGE level between WHHL rabbits and control New Zealand White rabbits. These data suggest the integral role of RAGE in the initiation and progression of non-diabetic atherosclerosis associated with hyperlipidemia. We further investigated the relevance of RAGE expression in a monocyte/macrophage lineage. Fluorescent immunohistochemistry and Western blotting showed the expression of RAGE on plasma membrane in isolated human peripheral monocytes, with the stronger expression in cultured monocyte-derived macrophages. Inhibition of RAGE by siRNA suppressed AGE-induced MCP-1, MMP-9 and PAI-1 expression in cultured human macrophages. Inhibition of RAGE did not significantly suppress the incorporation of DiI-labeled oxidized LDL in monocyte-derived macrophage by fluorescent study. However, oxidized LDL- triggered MCP-1, MMP-9 and PAI-1 expression was attenuated by inhibition of RAGE.
Conclusions: Our in vivo and in vitro study shows that RAGE plays an integral role in the initiation and development of atherosclerosis independent of diabetes and that ox-LDL mediates vascular responses via RAGE.