Lipid-Free Apolipoprotein A-I and Discoidal Reconstituted High-Density Lipoprotein Differentially Inhibit Glucose-Induced Oxidative Stress in Human Macrophages
Objective—The goal of this study was to investigate the mechanisms by which apolipoprotein (apo) A-I, in the lipid-free form or as a constituent of discoidal reconstituted high-density lipoprotein ([A-I]rHDL), inhibits high-glucose–induced redox signaling in human monocyte-derived macrophages (HMDM).
Methods and Results—HMDM were incubated under normal (5.8 mmol/L) or high-glucose (25 mmol/L) conditions with native high-density lipoprotein (HDL) lipid-free apoA-I from normal subjects and from subjects with T2D or (A-I)rHDL. Superoxide (O2−) production was measured using dihydroethidium fluorescence. NADPH oxidase activity was assessed using lucigenin-derived chemiluminescence and a cyotochrome c assay. p47phox translocation to the plasma membrane, Nox2, superoxide dismutase 1 (SOD1), and SOD2 mRNA and protein levels were determined by real-time polymerase chain reaction and Western blotting. Native HDL induced a time-dependent inhibition of O2− generation in HMDM incubated with 25 mmol/L glucose. Lipid-free apoA-I and (A-I)rHDL increased SOD1 and SOD2 levels and attenuated 25 mmol/L glucose-mediated increases in cellular O2−, NADPH oxidase activity, p47 translocation, and Nox2 expression. Lipid-free apoA-I mediated its effects on Nox2, SOD1, and SOD2 via ABCA1. (A-I)rHDL-mediated effects were via ABCG1 and scavenger receptor BI. Lipid-free apoA-I from subjects with T2D inhibited reactive oxygen species generation less efficiently than normal apoA-I.
Conclusion—Native HDL, lipid-free apoA-I and (A-I)rHDL inhibit high-glucose–induced redox signaling in HMDM. The antioxidant properties of apoA-I are attenuated in T2D.
- Received December 20, 2010.
- Accepted February 4, 2011.
- © 2011 American Heart Association, Inc.