1. AGE-albumin enhances ABCA1 degradation by ubiquitin-proteasome and lysosomal pathways in macrophages.
- Author
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Iborra RT, Machado-Lima A, Okuda LS, Pinto PR, Nakandakare ER, Machado UF, Correa-Giannella ML, Pickford R, Woods T, Brimble MA, Rye KA, Lu R, Yokoyama S, and Passarelli M
- Subjects
- Albumins metabolism, Animals, Atherosclerosis metabolism, Atherosclerosis pathology, Cells, Cultured, Cholesterol metabolism, Diabetes Mellitus metabolism, Diabetes Mellitus pathology, Glycation End Products, Advanced metabolism, Humans, Hypercholesterolemia metabolism, Hypercholesterolemia pathology, Lipid Metabolism drug effects, Lysosomes metabolism, Macrophages drug effects, Macrophages metabolism, Mice, Proteasome Endopeptidase Complex metabolism, Proteolysis drug effects, Ubiquitin metabolism, Up-Regulation drug effects, ATP Binding Cassette Transporter 1 metabolism, Albumins pharmacology, Glycation End Products, Advanced pharmacology, Lysosomes drug effects, Proteasome Endopeptidase Complex drug effects, Ubiquitination drug effects
- Abstract
Background and Aims: Advanced glycation end products (AGEs) induce cellular oxidative/endoplasmic reticulum stress and inflammation. We investigated its underlying mechanisms for atherogenesis focusing on regulation of ABCA1 protein decay in macrophages., Methods: The ABCA1 decay rate was evaluated in macrophages after treatment with LXR agonist and by incubation with control (C) or AGE-albumin concomitant or not with cycloheximide, MG-132, ammonium chloride and calpain inhibitors were utilized to inhibit, respectively, proteasome, lysosome and ABCA1 proteolysis at cell surface. ABCA1 was determined by immunoblot and the protein decay rate calculated along time by the slope of the linear regression. Ubiquitination level was determined in ABCA1 immunoprecipitated from whole cell lysate or bulk cell membrane. AGE effect was also analyzed in THP-1 cells transfected with siRNA-RAGE. Carboxymethyllysine (CML) and pyrraline (PYR) were determined by LC/MS. One-way ANOVA and Student t test were utilized to compare results., Results: CML and PYR-albumin were higher in AGE-albumin as compared to C. AGE-albumin reduced ABCA1 in J774 and THP-1 macrophages (20-30%) and induced a higher ABCA1 ubiquitination and a faster protein decay rate that was dependent on the presence of AGE during the kinetics of measurement in the presence of cycloheximide. Proteasomal inhibition restored and lysosomal inhibition partially recovered ABCA1 in cells treated with AGE-albumin. Calpain inhibition was not able to rescue ABCA1. RAGE knockdown prevented the reduction in ABCA1 elicited by AGE., Conclusions: AGE-albumin diminishes ABCA1 by accelerating its degradation through the proteasomal and lysosomal systems. This may increase lipid accumulation in macrophages by diminishing cholesterol efflux via RAGE signaling contributing to atherosclerosis in diabetes mellitus., (Copyright © 2017 Elsevier Inc. All rights reserved.)
- Published
- 2018
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