High density lipoprotein mediates selective reduction in cholesteryl esters from macrophage foam cells

Cross‐linking of apolipoproteins is involved in a loss of the ligand activity of high density lipoprotein upon Cu2+‐mediated oxidation

“…Among several modifications tested, treatment with tetranitromethane (TNM) [12,:3] and chemical cross-linkers [14,15] successfully led to a loss of the ligand activity. Oar previous experiments using rat macrophage foam cells showed that the capacity of HDL to reduce cellular CE was markedly weakened upon treatment with TNM or a chemical cross-linker, dithiobissuceinimidyl propionate, suggesting a functional link of the specific binding to the HDL-mediated cholesterol efflux [11].…”

“…Cells were first converted to foam cells by incubating for 12 h with 50 /~g/ml acetyl-LDL. After a 6-h equiEhration w~th buffer A, cells were further incubated for 24 h with 250/.tg/ml or HDL, oxidized IIDL or TNM-HDL, and c¢llulal lipids were extracted as described [11,15]. The hpid extracts were determined both for CE and total cholesterol mass levels by a modification [11] of the enzymic fluoromemc method of He~der and Boyett [18l.…”

“…After a 6-h equiEhration w~th buffer A, cells were further incubated for 24 h with 250/.tg/ml or HDL, oxidized IIDL or TNM-HDL, and c¢llulal lipids were extracted as described [11,15]. The hpid extracts were determined both for CE and total cholesterol mass levels by a modification [11] of the enzymic fluoromemc method of He~der and Boyett [18l. The cells after lipid extraction were d~s-solved in 0,I M NaOH to determine ¢cll proteins [11],…”

“…The hpid extracts were determined both for CE and total cholesterol mass levels by a modification [11] of the enzymic fluoromemc method of He~der and Boyett [18l. The cells after lipid extraction were d~s-solved in 0,I M NaOH to determine ¢cll proteins [11],…”

“…Although the HDL receptor is being characterized [6][7][8], the most crucial issue is whether the receptor, or the specific iigand binding is functionally correlated with the cholesterol efflux phenomenum [9][10][11]. To an-swer this, chemically modified HDLs with no or a reduced [igand activity for the HDL receptor would be desirable.…”