Format

Send to

Choose Destination
J Diabetes Complications. 2018 Jan;32(1):1-10. doi: 10.1016/j.jdiacomp.2017.09.012. Epub 2017 Sep 23.

AGE-albumin enhances ABCA1 degradation by ubiquitin-proteasome and lysosomal pathways in macrophages.

Author information

1
Laboratorio de Lipides, LIM-10, Hospital das Clinicas HCFMUSP, Faculdade de Medicina da Universidade de Sao Paulo, São Paulo, Brazil.
2
Laboratorio de Lipides, LIM-10, Hospital das Clinicas HCFMUSP, Faculdade de Medicina da Universidade de Sao Paulo, São Paulo, Brazil; Universidade São Judas Tadeu, São Paulo, Brazil.
3
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
4
Laboratorio de Carboidratos e Radioimunoinsaio, LIM 18, Hospital das Clinicas HCFMUSP, Faculdade de Medicina da Universidade de Sao Paulo, São Paulo, Brazil; Programa de pós-Graduação em Medicina, Universidade Nove de Julho, São Paulo, Brazil.
5
Bioanalytical Mass Spectrometry Facility, University of New South Wales, Sydney, Australia.
6
School of Chemical Sciences, University of Auckland, Auckland, New Zealand.
7
Lipid Research Group, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, Australia.
8
Nutritional Health Science Research Center at Chubu University, Kasugai, Japan.
9
Laboratorio de Lipides, LIM-10, Hospital das Clinicas HCFMUSP, Faculdade de Medicina da Universidade de Sao Paulo, São Paulo, Brazil. Electronic address: mpassere@usp.br.

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.

KEYWORDS:

ABCA1; Advanced glycation end products; Atherosclerosis; Lysosome; Macrophages; Proteasome

PMID:
29097054
DOI:
10.1016/j.jdiacomp.2017.09.012
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center