Chemical cross-linking alters high-density lipoprotein to be recognized by a scavenger receptor in rat peritoneal macrophages.

Rat peritoneal macrophages possess a surface receptor for high-density lipoprotein (HDL). To obtain the functional aspect of the HDL receptor, the present study was undertaken to modify HDL with three different cross-linkers; dimethylsuberimidate, disuccinimidylsuberate and dithiobissuccinimidylpropionate (DSP) and determine their effect on the ligand activity for the HDL receptor. Upon modification at a low reagent concentration, DSP was found to be most effective in cross-linking of HDL apolipoproteins. The ligand activity of DSP-HDL for the HDL receptor was reduced by greater than 60%. Experiments with these macrophages at 37 degrees C showed; (i) the amounts of the cell-associated [125I]DSP-HDL as 3.5-fold higher than [125I]HDL; (ii) the cell-association of [125I]DSP-HDL was effectively (greater than 70%) inhibited by unlabeled DSP-HDL, whereas HDL showed a partial inhibition (30%); (iii) [125I]DSP-HDL underwent chloroquine-sensitive intracellular degradation; and (iv) DSP-HDL induced a 3-fold increase in the incorporation of [14C]oleic acid into cholesteryl oleate when compared with unmodified HDL. Experiments at 0 degrees C showed that the cellular binding of [125I]DSP-HDL was competed by acetylated low-density lipoprotein and dextran sulfate. These findings indicate that DSP-HDL is recognized as a ligand by a scavenger receptor of rat peritoneal macrophages, a notion consistent with HDL modified with tetranitromethane (Kleinherenbrink-Stins, M.F. et al. (1989) J. Lipid Res. 39, 511-520).