Macrophage scavenger receptor CD36 is the major receptor for LDL modified by monocyte-generated reactive nitrogen species
Eugene A. Podrez, … , Henry F. Hoff, Stanley L. Hazen
Eugene A. Podrez, … , Henry F. Hoff, Stanley L. Hazen
Published April 15, 2000
Citation Information: J Clin Invest. 2000;105(8):1095-1108. https://doi.org/10.1172/JCI8574.
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Article

Macrophage scavenger receptor CD36 is the major receptor for LDL modified by monocyte-generated reactive nitrogen species

Abstract

The oxidative conversion of LDL into an atherogenic form is considered a pivotal event in the development of cardiovascular disease. Recent studies have identified reactive nitrogen species generated by monocytes by way of the myeloperoxidase-hydrogen peroxide-nitrite (MPO-H2O2-NO2–) system as a novel mechanism for converting LDL into a high-uptake form (NO2-LDL) for macrophages. We now identify the scavenger receptor CD36 as the major receptor responsible for high-affinity and saturable cellular recognition of NO2-LDL by murine and human macrophages. Using cells stably transfected with CD36, CD36-specific blocking mAbs, and CD36-null macrophages, we demonstrated CD36-dependent binding, cholesterol loading, and macrophage foam cell formation after exposure to NO2-LDL. Modification of LDL by the MPO-H2O2-NO2– system in the presence of up to 80% lipoprotein-deficient serum (LPDS) still resulted in the conversion of the lipoprotein into a high-uptake form for macrophages, whereas addition of less than 5% LPDS totally blocked Cu2+-catalyzed LDL oxidation and conversion into a ligand for CD36. Competition studies demonstrated that lipid oxidation products derived from 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine can serve as essential moieties on NO2-LDL recognized by CD36. Collectively, these results suggest that MPO-dependent conversion of LDL into a ligand for CD36 is a likely pathway for generating foam cells in vivo. MPO secreted from activated phagocytes may also tag phospholipid-containing targets for removal by CD36-positive cells.

Authors

Eugene A. Podrez, Maria Febbraio, Nader Sheibani, David Schmitt, Roy L. Silverstein, David P. Hajjar, Peter A. Cohen, William A. Frazier, Henry F. Hoff, Stanley L. Hazen

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Figure 9

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Effect of various competitors on the binding of NO2-LDL to CD36- transfe...
Effect of various competitors on the binding of NO2-LDL to CD36- transfected cells. [125I]LDL was modified by isolated MPO, a H2O2-generating system, and NO2– as described for the complete system in Figure 2a. [125I]-labeled lipoproteins ([125I]NO2-LDL, 5 μg/mL) were then incubated with vector-transfected cells (hatched bar) (a) or CD36-expressing 293 cells (filled bars) (a) and (b), for 3 hours at 4°C either in the absence (NA) or presence of the indicated competitors. Cellular binding of lipoproteins was subsequently determined as described in Methods. Liposomes generated from lipid extracts of native LDL (LDL lipids) and NO2-LDL (NO2-LDL lipids) were prepared as described in Methods. NO2-LDL protein was prepared as described in Methods. BSA was exposed to the same MPO-H2O2-NO2– system as LDL (NO2-BSA) and used as a competitive ligand as well. (a) The final concentrations of competitors used were 200 μg protein/mL for LDL, NO2-LDL, NO2-LDL protein, BSA, and NO2-BSA. The concentration of LDL lipids and NO2-LDL lipids used was equivalent to that present in 200 μg LDL protein/mL. Synthetic tri-peptides were used at 200 μM final concentration. (b) The concentration of intact LDL and LDL lipids used was equivalent to the amount present in the indicated amount of LDL (μg protein/mL). Data represent the mean ± SD of triplicate determinations (a) or means of triplicate determinations (b) of a representative experiment that was performed 3 times. AP < 0.001 for comparison versus control (NA).