Abstract
As a new potential inflammatory mediator, visfatin plays an important role in inflammation and atherosclerosis. The formation of macrophage-derived foam cells occurs at the early stage of atherosclerosis and underlies the visible fatty streak. Recent studies have indicated that visfatin may be associated with the development of foam cells, but its exact effect and molecular mechanism remain unknown. This study aims to study the effect of visfatin on foamy cell formation and its underlying molecular mechanism. Visfatin levels were determined in apolipoprotein E (ApoE) knockout (KO) mice on a western diet for 16 weeks. Effects of visfatin in cholesterol accumulation were studied both in vivo and in vitro. The levels of scavenger receptors located in macrophage surface were measured in RAW264.7 cells after treatment with visfatin. Visfatin levels were much higher in ApoE KO mice than that in the control mice. Meanwhile, oxidized low-density lipoprotein induces both visfatin release from RAW264.7 cells and its cellular levels within 24 h. Visfatin promotes lipid accumulation mainly through excessive cholesterol uptake not only in RAW264.7 cells but also in peritoneal macrophages isolated from ApoE KO mice. Furthermore, visfatin induces the activation of scavenger receptors (SR)-A and cluster of differentiation (CD)36, but not that of SR-BI, ATP-binding cassette transporter (ABC)A1, or ABCG1 in RAW264.7 cells. Both transcriptional and posttranscriptional regulation may work in concert to mediate the expression of SR-A and CD36 in visfatin-treated cells. Visfatin induces cholesterol accumulation in macrophages and accelerates the process of atherosclerosis mainly through modulating the expression of SR-A and CD36.