The neurorepellent, Slit2, prevents macrophage lipid loading by inhibiting CD36-dependent binding and internalization of oxidized low-density lipoprotein

Abstract

Atherosclerosis is characterized by retention of modified lipoproteins, especially oxidized low density lipoprotein (oxLDL) within the sub-endothelial space of affected blood vessels. Recruited monocyte-derived and tissue-resident macrophages subsequently ingest oxLDL by binding and internalizing oxLDL via scavenger receptors, particularly CD36. The secreted neurorepellent, Slit2, acting through its transmembrane receptor, Roundabout-1 (Robo-1), was previously shown to inhibit recruitment of monocytes into nascent atherosclerotic lesions. The effects of Slit2 on oxLDL uptake by macrophages have not been explored. We report here that Slit2 inhibits uptake of oxLDL by human and murine macrophages, and the resulting formation of foam cells, in a Rac1-dependent and CD36-dependent manner. Exposure of macrophages to Slit2 prevented binding of oxLDL to the surface of cells. Using super-resolution microscopy, we observed that exposure of macrophages to Slit2 induced profound cytoskeletal remodeling with formation of a thick ring of cortical actin within which clusters of CD36 could not aggregate, thereby attenuating binding of oxLDL to the surface of cells. By inhibiting recruitment of monocytes into early atherosclerotic lesions, and the subsequent binding and internalization of oxLDL by macrophages, Slit2 could represent a potent new tool to combat individual steps that collectively result in progression of atherosclerosis.