Adipocyte differentiation-related protein is induced by LRP1-mediated aggregated LDL internalization in human vascular smooth muscle cells and macrophages

V Llorente-Cortés,T Royo,O Juan-Babot,L Badimon

doi:10.1194/jlr.m700039-jlr200

V Llorente-Cortés, T Royo + Show 2 more

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https://doi.org/10.1194/jlr.m700039-jlr200

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Abstract

Aggregated LDL (agLDL) is internalized by LDL receptor-related protein (LRP1) in vascular smooth muscle cells (VSMCs) and human monocyte-derived macrophages (HMDMs). AgLDL is, therefore, a potent inducer of massive intracellular cholesteryl ester accumulation in lipid droplets. The adipocyte differentiation-related protein (ADRP) has been found on the surface of lipid droplets. The objectives of this work were to analyze whether agLDL uptake modulates ADRP expression levels and whether the effect of agLDL internalization on ADRP expression depends on LRP1 in human VSMCs and HMDMs. AgLDL strongly upregulates ADRP mRNA (real-time PCR) and protein expression (Western blot) in human VSMCs (mRNA: by 3.06-fold; protein: 8.58-fold) and HMDMs (mRNA: by 3.5-fold; protein: by 3.71-fold). Treatment of VSMCs and HMDMs with small anti-LRP1-interfering RNA (siRNA-LRP1) leads to specific inhibition of LRP1 expression. siRNA-LRP1 treatment significantly reduced agLDL-induced ADRP overexpression in HMDMs (by 69%) and in VSMCs (by 53%). Immunohystochemical studies evidence a colocolocalization between ADRP/macrophages and ADRP/VSMCs in advanced lipid-enriched atherosclerotic plaques. These results demonstrate that agLDL-LRP1 engagement induces ADRP overexpression in both HMDMs and human VSMCs and that ADRP is highly expressed in advanced lipid-enriched human atherosclerotic plaques. Therefore, LRP1-mediated agLDL uptake might play a pivotal role in vascular foam cell formation.

Highlights

Aggregated LDL is internalized by LDL receptor-related protein (LRP1) in vascular smooth muscle cells (VSMCs) and human monocyte-derived macrophages (HMDMs)
Our results demonstrate that: 1) there is a colocalization of adipocyte differentiation-related protein (ADRP) with both VSMCs and macrophages in advanced lipid-enriched human atherosclerotic plaque; 2) Aggregated LDL (agLDL) induces ADRP mRNA and protein overexpression in both macrophages and VSMCs; and 3) agLDL-induced ADRP overexpression depends on LRP1 expression in VSMCs and macrophages
Strong differences in cholesteryl ester (CE) levels induced by native LDL (nLDL) or agLDL internalization were observed in both VSMCs and HMDMs (Table 1)

Summary

Introduction

Aggregated LDL (agLDL) is internalized by LDL receptor-related protein (LRP1) in vascular smooth muscle cells (VSMCs) and human monocyte-derived macrophages (HMDMs). Adipocyte differentiation-related protein is induced by LRP1-mediated aggregated LDL internalization in human vascular smooth muscle cells and macrophages. Unlike native LDL (nLDL), aggregated LDL (agLDL) is a potent inducer of massive intracellular CE accumulation in both macrophages [6,7,8] and vascular smooth muscle cells (VSMCs) [9,10,11,12,13]. We have previously demonstrated that large lipid vacuoles filled with CE derived from LRP1mediated agLDL-selective uptake colocalize with adipose differentiation-related protein (ADRP) in human VSMCs [13]. This article is available online at http://www.jlr.org

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