A secreted soluble form of LR11, specifically expressed in intimal smooth muscle cells, accelerates formation of lipid-laden macrophages.
OBJECTIVE
Macrophages play a key role in lipid-rich unstable plaque formation and interact with intimal smooth muscle cells (SMCs) in early and progressive stages of atherosclerosis. LR11 (also called sorLA), a member of low-density lipoprotein receptor family, is highly and specifically expressed in intimal SMCs, and causes urokinase-type plasminogen activator receptor-mediated degradation of extracellular matrices. Here we investigated whether the secreted soluble form of LR11 (solLR11) enhances adhesion, migration, and lipid accumulation in macrophages using animal models and cultured systems.


RESULTS
Immunohistochemistry showed solLR11 expression in thickened intima of balloon-denuded rat artery. Macrophage infiltration into the cuff-injured artery was markedly reduced in LR11-deficient mice. In vitro functional assays using THP-1-derived macrophages showed that solLR11 (1 microg/mL) significantly increased acetylated low-density lipoprotein uptake by THP-1 cells and cell surface levels of scavenger receptor SR-A 1.7- and 2.8-fold, respectively. SolLR11 dose-dependently increased the migration activity of THP-1 macrophages and adhesion to extracellular matrices 2.0- and 2.1-fold, respectively, at 1 microg/mL. These effects of solLR11 were almost completely inhibited by a neutralizing anti-urokinase-type plasminogen activator receptor antibody.


CONCLUSIONS
SolLR11, secreted from intimal SMCs, regulates adhesion, migration, and lipid accumulation in macrophages through activation of urokinase-type plasminogen activator receptor. The formation of lipid-laden macrophages in atherosclerotic plaques possibly is regulated by SolLR11 of intimal SMCs.
Ohwaki
Kenji
K
Department of Clinical Cell Biology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
Bujo
Hideaki
H
Jiang
Meizi
M
Yamazaki
Hiroyuki
H
Schneider
Wolfgang J
WJ
Saito
Yasushi
Y
D000818:Animals; D015153:Blotting, Western; D020212:Carotid Artery Injuries / Q000378:metabolism / Q000473:pathology; D017536:Carotid Artery, Common / Q000378:metabolism / Q000473:pathology; D002448:Cell Adhesion / Q000502:physiology*; D002465:Cell Movement; D002478:Cells, Cultured; D006801:Humans; D007150:Immunohistochemistry; D008077:Lipoproteins, LDL / Q000378:metabolism; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000096:biosynthesis*; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins; D051381:Rats; D017208:Rats, Wistar; D011973:Receptors, LDL / Q000096:biosynthesis*; D017539:Tunica Intima / Q000378:metabolism* / Q000473:pathology
D008077:Lipoproteins, LDL; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D011973:Receptors, LDL; C491167:Sorl1 protein, rat; C032629:acetyl-LDL