Modified LDLs induce and bind to membrane ruffles on macrophages

• Published in: The Anatomical record 1999-05, Vol.255 (1), p.44-56
• Main Authors: Jones, Nancy L., Allen, Nina S., Willingham, Mark C., Lewis, Jon C.
• Format: Article
• Language: English
• Subjects: AcLDL; Animals; AVEC‐DIC; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Cells, Cultured; Columbidae; correlative microscopy; Foam Cells - cytology; Foam Cells - metabolism; IVEM; Lipoproteins, LDL - metabolism; Lipoproteins, VLDL - metabolism; membrane ruffling; Microscopy, Electron, Scanning; Microscopy, Video; Microvilli - ultrastructure; Monocytes - metabolism; OxLDL; Space life sciences; Time Factors
• ISSN: 0003-276X; 1097-0185
• DOI: 10.1002/(SICI)1097-0185(19990501)255:1<44::AID-AR6>3.0.CO;2-7

Macrophage foam cell formation in vitro requires uptake of modified low density lipoproteins (LDL) such as acetylated LDL (AcLDL) and moderately oxidized LDL (OxLDL), or beta‐migrating very low density lipoprotein (βVLDL), a naturally occurring lipoprotein. Incubation of macrophages with AcLDL and OxLDL resulted in stimulation of membrane ruffle formation, while βVLDL primarily resulted in increased numbers of microvilli. Time‐lapse Allen video enhanced contrast differential interference contrast (AVEC‐DIC) light microscopy and correlative whole mount intermediate‐voltage transmission electron microscopy (IVEM) was used to examine the dynamics of AcLDL stimulated membrane ruffling and membrane ruffle ultrastructure. Stereo 3D surface replicas confirmed that AcLDL bound to these AcLDL‐induced membrane ruffles. Quantification of the plasma membrane surface area after incubation with AcLDL, βVLDL or LDL confirmed that AcLDL stimulated membrane ruffling, while βVLDL and LDL stimulated microvilli formation. These studies suggest that modified LDLs induce circular membrane ruffles and modified LDLs bind to these ligand‐induced membrane ruffles. Anat Rec 255:44–56, 1999. © 1999 Wiley‐Liss, Inc.