YC-1 inhibits lipid droplet accumulation and induces lipolysis in lipid-laden RAW264.7 macrophages

Macrophage foam cells play a central role in the initiation and progression of atherosclerosis. The present study investigates the effect of YC-1, a synthetic benzylindazole compound, on lipid metabolism in macrophage-derived foam cells. Foam cell formation was induced by incubating cultured RAW264.7 macrophages with oleic acid (OA) or cobalt chloride (CoCl2) (a hypoxia mimetic). Morphological observation showed several Nile red-positive lipid droplets in the cytoplasm of OA-treated RAW264.7 macrophages. Pretreatment with 60 mu M YC-1 could inhibit lipid accumulation. Co-incubation with OA and YC-1 also attenuated lipid accumulation due to the decrease in surface area of lipid droplets. Post-treatment with YC-1 induced lipolysis and free fatty acid release in lipid-laden macrophages in both dose- and time-dependent manners. In addition, ODQ, a soluble guanynyl cyclase (sGC) inhibitor, could not reverse the inhibitory effect of YC-1 on lipid accumulation, or block the lipolytic effect of YC-1 in lipid-laden macrophages. Neither another nitric oxide-independent sGC activator (BAY 41-2272) nor dibutyryl cGMP (db-cGMP) could mimic the effects of YC-1. Both intracellular sGC activity and the cGMP level remained unchanged following YC-1 incubation. These results suggested that the mechanism of YC-1-mediated lipid metabolism was via an sGC/cGMP-independent signal transduction pathway in RAW264.7 macrophages. In addition, YC-1 significantly attenuated CoCl2-induced lipid droplets accumulation. Our results demonstrated that YC-1 could mediate lipid metabolism in macrophage and reduce foam cell formation, and it could be regarded as a potential drug for the prevention or therapy of atherosclerosis.