Macrophage degradation of LDL extracted from human aortic plaques: effect of isolation conditions.
Several laboratories have recently reported on the structural and functional characteristics of an LDL fraction isolated from atherosclerotic lesions, designated A-LDL. Given the wide variety of tissue sources and isolation conditions that have been employed, we have addressed whether several procedures currently used affect the interaction of A-LDL with macrophages, and, if so, by what mechanisms. We isolated A-LDL from human aortic plaques by ultracentrifugation and gel filtration chromatography. Although some differences in the chromatographic elution profiles on gel filtration were apparent between homogenized and nonhomogenized extracts, A-LDL isolated from the same pool of plaque minces with or without homogenization showed no differences in macrophage degradation or inhibition of this degradation by excess acetyl-LDL. A-LDL isolated from plaques obtained at surgery or at autopsy less than 12 hr after death also showed no major differences in macrophage recognition, suggesting that post-mortem changes were probably not affecting cell recognition. However, A-LDL particles underwent aggregation when subjected to concentration, when stored for periods of 2 weeks or more, or when subjected to vortexing. The aggregated A-LDL was degraded more readily by macrophages than unaggregated A-LDL, and inhibition of degradation of aggregated A-LDL by excess acetyl-LDL was less than for unaggregated A-LDL. Collectively, these studies show that although post-mortem changes and tissue homogenization do not appreciably affect the interaction of A-LDL with macrophages in culture, other isolation and preparation conditions have dramatic effects which could explain some of the diversity of A-LDL metabolism reported in the literature.
Hoff
H F
HF
Department of Vascular Cell Biology and Atherosclerosis, Cleveland Clinic Foundation, Ohio 44195.
O'Neil
J
J
Cole
T B
TB
D000818:Animals; D001011:Aorta / Q000378:metabolism; D001055:Apolipoproteins B / Q000378:metabolism; D001161:Arteriosclerosis / Q000378:metabolism* / Q000473:pathology; D001344:Autopsy; D002469:Cell Separation / Q000379:methods; D002478:Cells, Cultured; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006801:Humans; D066298:In Vitro Techniques; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D013997:Time Factors
D001055:Apolipoproteins B; D008077:Lipoproteins, LDL