Adipocyte-derived plasma protein, adiponectin, suppresses lipid accumulation and class A scavenger receptor expression in human monocyte-derived macrophages.
BACKGROUND
Excessive lipid accumulation in macrophages plays an important role in the development of atherosclerosis. Recently, we discovered an adipocyte-specific plasma protein, adiponectin, that is decreased in patients with coronary artery disease. We previously demonstrated that adiponectin acts as a modulator for proinflammatory stimuli and inhibits monocyte adhesion to endothelial cells. The present study investigated the effects of adiponectin on lipid accumulation in human monocyte-derived macrophages.


RESULTS
Human monocytes were differentiated into macrophages by incubation in human type AB serum for 7 days, and the effects of adiponectin were investigated at different time intervals. Treatment with physiological concentrations of adiponectin reduced intracellular cholesteryl ester content, as determined using the enzymatic, fluorometric method. The adiponectin-treated macrophages contained fewer lipid droplets stained by oil red O. Adiponectin suppressed the expression of the class A macrophage scavenger receptor (MSR) at both mRNA and protein levels by Northern and immunoblot analyses, respectively, without affecting the expression of CD36, which was quantified by flow cytometry. Adiponectin reduced the class A MSR promoter activity, as measured by luciferase reporter assay. Adiponectin treatment dose-dependently decreased class A MSR ligand binding and uptake activities. The mRNA level of lipoprotein lipase as a marker of macrophage differentiation was decreased by adiponectin treatment, but that of apolipoprotein E was not altered. Adiponectin was detected around macrophages in the human injured aorta by immunohistochemistry.


CONCLUSIONS
The adipocyte-derived plasma protein adiponectin suppressed macrophage-to-foam cell transformation, suggesting that adiponectin may act as a modulator for macrophage-to-foam cell transformation.
Department of Internal Medicine and Molecular Science, Graduate School of Medicine, Osaka University, Osaka, Japan. ouchi@imed2.med.osaka-u.ac.jp
N
N
Ouchi
S
S
Kihara
Y
Y
Arita
M
M
Nishida
A
A
Matsuyama
Y
Y
Okamoto
M
M
Ishigami
H
H
Kuriyama
K
K
Kishida
H
H
Nishizawa
K
K
Hotta
M
M
Muraguchi
Y
Y
Ohmoto
S
S
Yamashita
T
T
Funahashi
Y
Y
Matsuzawa
D017667:Adipocytes / Q000737:chemistry*; D052242:Adiponectin; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism; D001798:Blood Proteins / Q000494:pharmacology; D018955:CD36 Antigens / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism; D005487:Foam Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D050356:Lipid Metabolism; D008071:Lipoprotein Lipase / Q000235:genetics / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D009000:Monocytes / Q000166:cytology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011971:Receptors, Immunologic / Q000096:biosynthesis*; D051116:Receptors, Scavenger; D051117:Scavenger Receptors, Class A
D052242:Adiponectin; D001057:Apolipoproteins E; D001798:Blood Proteins; D018955:CD36 Antigens; D002788:Cholesterol Esters; D036341:Intercellular Signaling Peptides and Proteins; D008077:Lipoproteins, LDL; C495139:MSR1 protein, human; D010446:Peptide Fragments; D011506:Proteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D051116:Receptors, Scavenger; D051117:Scavenger Receptors, Class A; C032629:acetyl-LDL; C117630:apolipoprotein E (141-155); D008071:Lipoprotein Lipase