Synthetic retinoid Am80 reduces scavenger receptor expression and atherosclerosis in mice by inhibiting IL-6

Background - Macrophage scavenger receptors facilitate the uptake of modified low-density lipoprotein (LDL), formation of foam cells, and development of atherosclerosis. Given that proinflammatory cytokines, including IL-6, can modulate the macrophage foaming process, the aim of the present study was to determine whether the synthetic retinoic acid receptor-alpha/beta-specific agonist Am80, which is also an IL-6 inhibitor, can modulate macrophage lipid accumulation and foam cell formation. Methods and Results - Am80 suppressed IL-6 production induced by 12-myristate13-acetate (PMA) or angiotensin II in mouse Raw264 macrophages. It also suppressed expression of the 2 major scavenger receptors ( scavenger receptor-A [SR-A] and CD36), in part by inhibiting IL-6, and inhibited macrophage foam cell formation. Systemic administration of Am80 led to reductions in the areas of atherosclerotic lesions and foam cell accumulation in the aortas of apolipoprotein E ( apoE)- deficient mice and reduced serum concentrations of IL-6 and IL-1 beta without affecting body weights, serum lipid profiles or IL-10 levels. Conclusions - Am80 suppresses scavenger receptor expression and macrophage foam cell formation in vitro and prevents atherogenesis in apoE-deficient mice in vivo. This suggests Am80 is a novel candidate agent that could be highly useful in the prevention and treatment of atherosclerosis.