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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2000;20:1968.)
© 2000 American Heart Association, Inc.

Atherosclerosis and Lipoproteins

Expression of Class A Scavenger Receptor Inhibits Apoptosis of Macrophages Triggered by Oxidized Low Density Lipoprotein and Oxysterol

Hai-Sun Liao; Tatsuhiko Kodama; Yong-Jian Geng

From the Cardiovascular and Pulmonary Research Institute (H.-S.L., Y.-J.G.), Allegheny General Hospital, Pittsburgh, Pa; Molecular Biology and Medicine (T.K.), University of Tokyo, Tokyo, Japan; and the Cardiology Division (Y.-J.G.), Department of Internal Medicine, University of Texas School of Medicine at Houston.

Correspondence to Yong-Jian Geng, MD, PhD, Cardiology Division, Department of Internal Medicine, University of Texas School of Medicine at Houston, 6431 Fannin St, MSB 1.240, Houston, TX 77030. E-mail ygeng{at}heart.med.uth.tmc.edu

Abstract—The class A macrophage scavenger receptor (MSR-A) is a multifunctional trimeric glycoprotein involved in innate immune response as well as the development of lipid-laden foam cells during atherosclerosis. The MSR ligand, oxidized low density lipoprotein (oxLDL), is known to be cytotoxic to macrophages and other cell types. This study examined whether MSR mediates or modulates oxLDL-induced apoptosis. Treatment with oxLDL and its cytotoxic oxysterol, 7-ketocholesterol (7-KC), reduced viability and increased DNA fragmentation in human THP-1 cells, Chinese hamster ovary cells, and mouse peritoneal macrophages. However, cell death and DNA fragmentation were markedly diminished in the phorbol ester–differentiated MSR-expressing THP-1 cells and Chinese hamster ovary cells, with stable expression of MSR-AI after cDNA transfection when exposed to the same concentrations of oxLDL and 7-KC. Moreover, treatment with oxLDL and 7-KC induced much greater death and DNA fragmentation in MSR-A–deficient peritoneal macrophages compared with wild-type macrophages. Thus, MSR-A does not act as a receptor responsible for the apoptotic effect of oxLDL, and instead, expression of this receptor confers resistance of macrophages to the apoptotic stimulation by oxLDL and its cytotoxic lipid component. These results suggest that by preventing apoptosis, MSR-A may contribute to the long-term survival of macrophages and macrophage-derived lipid-laden foam cells in atherosclerotic lesions.

Key Words: macrophages • scavenger receptors • atherosclerosis • lipoproteins • cell death

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