Cholesteryl esters of aggregated LDL are internalized by selective uptake in human vascular smooth muscle cells.
OBJECTIVE
Low-density lipoprotein (LDL) receptor-related protein (LRP1) mediates the internalization of aggregated LDL (agLDL)-LDL trapped in the arterial intima bound to proteoglycans-into human vascular smooth muscle cells (VSMC). LRP1-mediated agLDL uptake induces high-intracellular cholesteryl ester (CE) accumulation. The aim of this study was to characterize the mechanism of agLDL internalization in human VSMC.


RESULTS
The lipidic component of LDL was labeled with [3H] and the apolipoprotein component with [(125)I]. We found that >90% of intracellular CE derived from agLDL uptake was not associated with apoB100 degradation but was selectively taken up from agLDL. The inhibition of LRP1 expression by small interfering RNA treatment led to a decrease of 80+/-0.05% in agLDL-CE selective uptake. AgLDL induced intracellular CE accumulation without a concomitant CE synthesis. Cytosolic and cytoskeletal proteins were not required for CE transport. Electron and confocal microscopy experiments indicate that CE derived from agLDL accumulated in adipophilin-stained lipid droplets that were not removable by high-density lipoprotein.


CONCLUSIONS
Taken together, these results demonstrate that LRP1 mediates the selective uptake of CE from agLDL and that CE derived from agLDL is not intracellularly processed but stored in lipid droplets in human VSMC.
Llorente-Cortés
Vicenta
V
Cardiovascular Research Center, CSIC-ICCC, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
Otero-Viñas
Marta
M
Camino-López
Sandra
S
Costales
Paula
P
Badimon
Lina
L
D000962:Antimalarials / Q000494:pharmacology; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000493:pharmacokinetics; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D002788:Cholesterol Esters / Q000493:pharmacokinetics*; D008076:Cholesterol, HDL / Q000378:metabolism; D008078:Cholesterol, LDL / Q000493:pharmacokinetics*; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007457:Iodine Radioisotopes; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D014316:Tritium
D000962:Antimalarials; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D002788:Cholesterol Esters; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004791:Enzyme Inhibitors; D007457:Iodine Radioisotopes; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D047428:Protein Kinase Inhibitors; D014316:Tritium; D002738:Chloroquine