Oxidized type IV hypertriglyceridemic VLDL-remnants cause greater macrophage cholesteryl ester accumulation than oxidized LDL.
We have previously shown that very low density lipoproteins (VLDL, Sf 60-400) from subjects with type IV hyperlipoproteinemia (HTG-VLDL) will induce appreciable cholesteryl ester accumulation in cultured macrophages (J774A.1). The present study examined whether copper-mediated oxidative modification of HTG-VLDL and their remnants would further enhance cholesteryl ester accumulation in J774A.1 cells. Incubation with oxidized VLDL-remnants caused the greatest increase in cellular cholesteryl ester concentrations (54-fold) relative to control cells (P = 0.001). HTG-VLDL and VLDL-remnants each induced similar increases in cholesteryl ester levels (32.3- and 35.8-fold, respectively; both P = 0.001), whereas incubation with oxidized HTG-VLDL brought about only a 20.6-fold increase in cholesteryl ester concentrations (P = 0.014). The increase in cellular cholesteryl ester concentrations induced by oxidized VLDL-remnants was significantly higher (P < or = 0.04) than that induced by all other lipoproteins tested including low density lipoprotein (LDL) and oxidized LDL which caused a 6.7- and a 35.1-fold increase (P < or = 0.0002 for both), respectively. Unlike HTG-VLDL and to a lesser extent VLDL-remnants, uptake of oxidized VLDL and oxidized VLDL-remnants did not require catalytically active, cell secreted lipoprotein lipase. Co-incubation with polyinosine, which blocks binding to the type I scavenger receptor, completely inhibited the cholesteryl ester accumulation induced by oxidized HTG-VLDL, oxidized VLDL-remnants and oxidized LDL (P < or = 0.02). We conclude that oxidation of VLDL-remnants significantly enhances macrophage cholesteryl ester accumulation compared to either HTG-VLDL, VLDL-remnants, or oxidized LDL. Uptake of oxidized VLDL and oxidized VLDL-remnants does not require catalytically active lipoprotein lipase, and involves a receptor that can be competed for by polyinosine.
Whitman
S C
SC
Department of Medicine, Robarts Research Institute at The University of Western Ontario, London, Canada.
Sawyez
C G
CG
Miller
D B
DB
Wolfe
B M
BM
Huff
M W
MW
D000818:Animals; D002417:Cattle; D002460:Cell Line; D002788:Cholesterol Esters / Q000378:metabolism*; D006801:Humans; D006953:Hyperlipoproteinemia Type IV / Q000378:metabolism*; D008071:Lipoprotein Lipase / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008892:Milk / Q000201:enzymology
D002788:Cholesterol Esters; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; C099252:oxidized low density lipoprotein; C108132:oxidized very low density lipoprotein; D008071:Lipoprotein Lipase