Expression of CD36 in Cultured Human Aortic Smooth Muscle Cells (HASMCs)

Abstract

CD36, a family of scavenger receptor class B (SR-B), is believed to possess multiple functions in vivo. We have reported that CD36 is one of the major receptors for oxidized low density lipoproteins (OxLDL) in vivo by the study with genetic CD36 deficiency. Although it was reported that other SR, SR class A (SR-A), is expressed in vascular smooth muscle cells (VSMCs), one of the major components in the atherosclerotic lesions, it is still unknown whether these cell types do express CD36 or not. In the current study, we have found that cultured human aortic SMCs (HASMCs) from five donors out of eight did express CD36 mRNA with variable levels, determined by RNase protection assay and RT-PCR. Protein expression was confirmed by fluorescence flow cytometry with the specific antibody against human CD36, OKM5. Confocal laser microscopy demonstrated that CD36 immunoreactive mass was detected in the cell surface. The expression was markedly up-regulated by the addition of oxidized LDL(Ox-LDL) and/or troglitazone, a ligand for peroxisome proliferator activator receptor -gamma (PPAR-β). CD36-positive (CD36 (+)) HASMCs have CD36-specific binding for 125I-labeled OxLDL and accumulation of intracellular cholesterol ester (CE). The current study demonstrated that many of VSMCs express CD36 and uptake OxLDL via CD36. We propose that CD36 (+) HASMCs might be one of the origins of foam cells observed in the intima of atherosclerotic lesions.