Resistin increases lipid accumulation by affecting class A scavenger receptor, CD36 and ATP-binding cassette transporter-A1 in macrophages
Journal
Life Sciences
Journal Volume
84
Journal Issue
3/4
Pages
97-104
Date Issued
2009
Author(s)
Lin C.-Y.
Tsai J.-Y.
Wu Y.-L.
Su K.-H.
Lu K.-Y.
Hsiao S.-H.
Pan C.-C.
Kou Y.R.
Hsu Y.-P.
Ho L.-T.
Abstract
Aims: Resistin promotes macrophage-foam cell formation, but the mechanisms are unclear. In macrophages, lipid uptake is regulated by scavenger receptors (SR-A and CD36), while the cholesterol efflux is regulated by SR-BI, ATP-binding cassette transporter-A1 (ABCA1) and ABCG1. We investigated the mechanisms underlying the dysregulation by resistin of these regulators leading to promotion of lipid accumulation in bone marrow-derived macrophages. Main methods: Western blotting, real-time PCR and oil red O staining were performed. Key findings: Resistin exacerbated lipid accumulation in oxLDL-treated macrophages. Resistin treatment of oxLDL-untreated macrophages showed increased SR-A and CD36 mRNA and protein levels, and decreased ABCA1 protein level, while having no effect on SR-BI or ABCG1 expression. Up-regulation of SR-A and CD36 by resistin resulted from activation of AP-1 and PPARγ, respectively, and this was confirmed by the lack of activation of either after AP-1 inhibition using curcumin or SP600125, or PPARγ inhibition using GW9662, respectively. The down-regulation of ABCA1 by resistin was not accompanied by a reduced mRNA level or an activation of LXRα/RXR, but resulted from enhanced protein degradation as revealed by the abolition of the down-regulation after inhibition of the proteasome pathway using ALLN or MG-132. A combined inhibition by SP600125, GW9662 and ALLN prevented resistin-induced exacerbation of lipid accumulation in oxLDL-treated macrophages. Significance: Resistin promotes foam cell formation via dysregulation of SR-A, CD36 and ABCA1. SR-A and CD36 are transcriptionally up-regulated by resistin through AP-1 and PPARγ, respectively, whereas ABCA1 is down-regulated by resistin through proteasome-mediated enhancement of protein degradation. © 2008 Elsevier Inc. All rights reserved.
Type
journal article