Scavenger receptor pathway for lipopolysaccharide binding to Kupffer and endothelial liver cells in vitro

We have investigated the interaction of Salmonella minnesota R595 lipopolysaccharide (ReLPS) depleted of Ca2+ and Mg2+ with both Kupffer and endothelial liver cells under serum-free conditions. Specific and saturable binding levels of 125I-ReLPS were similar in both types of cells with respect to divalent cation independence, susceptibility to proteases, and concanavalin A inhibition. By using partial structures of ReLPS, it was demonstrated that acidic 3-deoxy-D-manno-octulosonic acid residues and phosphoryl groups on lipid A are of primary importance in ReLPS binding. The role of ionic interactions in LPS recognition by the cells was further confirmed by susceptibility of the binding to competitive inhibition by polyanions. Both ReLPS and ReLPS partial structures inhibited the specific cellular binding of acetylated low-density lipoprotein (Ac-LDL) by Kupffer cells and Ac-LDL- and formaldehyde-treated albumin by endothelial cells whose cellular accumulation is mediated by a different type(s) of scavenger receptor(s). In contrast, 125I-ReLPS binding to Kupffer and endothelial cells was not competed by Ac-LDL or formaldehyde-treated albumin. Our results indicate the scavenger pathway of LPS uptake by Kupffer and endothelial cells and the primary role of LPS anionic properties in this process.