Cultured macrophages transfer surplus cholesterol into adjacent cells in the absence of serum or high-density lipoproteins
Cuiwen He, Haibo Jiang, Wenxin Song, Howard Riezman, Peter Tontonoz, Thomas A. Weston, Paul Guagliardo, Paul H. Kim, Rachel S. Jung, Patrick J. Heizer, Loren G. Fong, Stephen G. Young
Abstract
Significance By ingesting apoptotic cells and other cellular debris, macrophages accumulate cholesterol. Some of the cholesterol is esterified and stored in cytosolic lipid droplets, mitigating the toxicity from free cholesterol. Eventually, however, macrophages must unload surplus cholesterol—a process often referred to as “cholesterol efflux.” Cholesterol efflux is an important physiologic process because it would be expected to retard the formation of cholesterol-rich macrophage foam cells in atherosclerotic plaques. Most studies of cholesterol efflux have focused on the ability of ABC transporters to export cholesterol onto high-density lipoproteins. The current study examines another mechanism. We found, using NanoSIMS imaging, that [ 13 C]cholesterol-loaded macrophages unload cholesterol directly into adjacent smooth muscle cells. This mechanism is potentially relevant to cholesterol efflux by tissue macrophages.