Characterization of the interaction of acetylated LDL and oxidatively modified LDL with human liver parenchymal and Kupffer cells in culture.

The interaction of acetylated low density lipoprotein (Ac-LDL) and oxidatively modified low density lipoprotein (Ox-LDL) with cultured human liver parenchymal cells and human Kupffer cells was investigated to define, for humans, the presence of scavenger receptors in the liver. A direct comparison of the capacity of Kupffer and parenchymal cells to interact with Ac-LDL and Ox-LDL indicated that the capacity of Kupffer cells per milligram of cell protein to degrade Ac-LDL and Ox-LDL is 14-fold and sixfold higher, respectively, than that of parenchymal cells. The degradation of both Ac-LDL and Ox-LDL by parenchymal cells and Kupffer cells could be inhibited by chloroquine and ammonium chloride, indicating that degradation occurs in the lysosomes. Competition studies showed that unlabeled Ox-LDL competed efficiently with the cell association and degradation of 125I-labeled Ac-LDL by human parenchymal cells and human Kupffer cells. However, unlabeled Ac-LDL did not compete (parenchymal cells) or only partially competed (40% in Kupffer cells) with the cell association and degradation of 125I-labeled Ox-LDL. Polyinosinic acid completely blocked the cell association and degradation of Ac-LDL and Ox-LDL with Kupffer cells while no significant effect on parenchymal cells was noted. It is concluded that human liver parenchymal cells contain a scavenger receptor that interacts with Ac-LDL and Ox-LDL and an additional recognition site that recognizes Ox-LDL specifically.(ABSTRACT TRUNCATED AT 250 WORDS)