Simvastatin enhances oxidized-low density lipoprotein-induced macrophage autophagy and attenuates lipid aggregation

Abstract

Macrophage autophagy exerts a protective effect in advanced atherosclerosis. It has previously been reported that oxidized low-density lipoprotein (ox-LDL) induces autophagy in endothelial cells, and simvastatin enhances autophagy in coronary arterial myocytes. However, it is currently unknown whether ox-LDL induces autophagy in macrophages, or whether simvastatin affects macrophage autophagy in atherosclerosis. The present study demonstrated that ox-LDL induced lipid accumulation in the J774A.1 macrophage cell line, in a dose-dependent manner, as determined by oil red O staining. Ox-LDL also induced autophagy in the J774A.1 cells, by converting microtubule-associated protein 1 light chain 3 (LC3) I to LC3 II, which is a well-known autophagy marker. Notably, treatment of the cells with simvastatin elevated ox-LDL-induced macrophage autophagy, this was detected through the conversion of LC3 I to LC3 II and the increased expression of Beclin1, another autophagy marker. Furthermore, it was shown that stimulation with ox-LDL led to the redistribution of green fluorescent protein (GFP) -LC3 from diffusion distribution, to the formation of puncta in the J774A.1 cells. Simvastatin promoted the ox-LDL-induced formation of GFP-LC3 puncta, as detected by confocal laser scanning microscopy. Simvastatin was also shown to inhibit ox-LDL-induced cholesterol accumulation in the J774A.1 cells, as observed by oil red O staining and CHOD-PAP assay. These results suggest that simvastatin may enhance ox-LDL-induced macrophage autophagy and attenuate lipid aggregation.