ABSTRACT
A bulk of cholesteryl esters accumulation in macrophage foam cells drives the occurrence and development of atherosclerosis. Evidence now shows that autophagy plays key roles in the degradation of intracellular lipid droplets via autolysosome, and also in the release of intracellular lipids via cholesterol efflux. In this study, we identified that a mitochondria-targeted antioxidant, Mito-Tempol, has protective effects against cholesteryl esters accumulation by activating autophagy. Mito-Tempol was shown to ameliorate the lipid burden for atherosclerosis, both in vitro and in vivo. In the established in vitro foam cell formation system using oxidized low-density lipoprotein (ox-LDL)-loaded THP-1 macrophages, Mito-Tempol prevented intracellular oxidative stress and attenuated lipid accumulation. Mito-Tempol rescued ox-LDL-impaired autophagic flux, thereby facilitating autophagy-mediated lipid degradation in THP-1 macrophages. Meanwhile, Mito-Tempol also increased the efflux of cholesterol via autophagy-dependent ABCA1 and ABCG1 up-regulation. The classical autophagy pathway of mTOR may be one of the effector for the autophagy restoration of Mito-Tempol. Our findings give the first insight that cardiovascular system disease may benefits more from the treatment of Mito-Tempol for its impact of reversing atherosclerosis via autophagy.
Subject(s)
Antioxidants/pharmacology , Atherosclerosis/drug therapy , Autophagy/genetics , Cyclic N-Oxides/pharmacology , Hypertension/drug therapy , Mitochondria/drug effects , ATP Binding Cassette Transporter 1/agonists , ATP Binding Cassette Transporter 1/genetics , ATP Binding Cassette Transporter 1/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 1/agonists , ATP Binding Cassette Transporter, Subfamily G, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 1/metabolism , Animals , Atherosclerosis/genetics , Atherosclerosis/metabolism , Atherosclerosis/pathology , Autophagy/drug effects , Cell Differentiation/drug effects , Cholesterol Esters/metabolism , Foam Cells/drug effects , Foam Cells/metabolism , Foam Cells/pathology , Gene Expression Regulation , Humans , Hypertension/genetics , Hypertension/metabolism , Hypertension/pathology , Lipoproteins, LDL/pharmacology , Male , Mitochondria/metabolism , Oxidative Stress , Rats , Rats, Inbred SHR , Rats, Inbred WKY , Signal Transduction , Spin Labels , THP-1 Cells , TOR Serine-Threonine Kinases/genetics , TOR Serine-Threonine Kinases/metabolism , Tetradecanoylphorbol Acetate/pharmacologyABSTRACT
Cholesterol efflux from macrophages is a key process in reverse cholesterol transport and, therefore, might inhibit atherogenesis. 9-cis-ß-carotene (9-cis-ßc) is a precursor for 9-cis-retinoic-acid (9-cis-RA), which regulates macrophage cholesterol efflux. Our objective was to assess whether 9-cis-ßc increases macrophage cholesterol efflux and induces the expression of cholesterol transporters. Enrichment of a mouse diet with ßc from the alga Dunaliella led to ßc accumulation in peritoneal macrophages. 9-cis-ßc increased the mRNA levels of CYP26B1, an enzyme that regulates RA cellular levels, indicating the formation of RA from ßc in RAW264.7 macrophages. Furthermore, 9-cis-ßc, as well as all-trans-ßc, significantly increased cholesterol efflux to high-density lipoprotein (HDL) by 50% in RAW264.7 macrophages. Likewise, food fortification with 9-cis-ßc augmented cholesterol efflux from macrophages ex vivo. 9-cis-ßc increased both the mRNA and protein levels of ABCA1 and apolipoprotein E (APOE) and the mRNA level of ABCG1. Our study shows, for the first time, that 9-cis-ßc from the diet accumulates in peritoneal macrophages and increases cholesterol efflux to HDL. These effects might be ascribed to transcriptional induction of ABCA1, ABCG1, and APOE. These results highlight the beneficial effect of ßc in inhibition of atherosclerosis by improving cholesterol efflux from macrophages.
