Human lactoferrin interacts with soluble CD14 and inhibits expression of endothelial adhesion molecules, E-selectin and ICAM-1, induced by the CD14-lipopolysaccharide complex

Lipopolysaccharides (LPS), either in the free form or complexed to CD14, a LPS receptor, are elicitors of the immune system. Lactoferrin (Lf), a LPS-c helating glycoprotein, protects animals against septic shock Since optimal protection requires administration of Lf prior to lethal doses of LPS, we h ypothesized that interactions between Lf and soluble CD14 (sCD14) exist. In a first step, human sCD14 and human Lf (hLf) were used to determine the ki netic binding parameters of hLf to free sCD14 in an optical biosensor. The results demonstrated that hLf bound specifically and with a high affinity ( K-d = 16 +/- 7 nM) to sCD14. Affinity chromatography studies showed that hL f interacted not only with free sCD14 but also, though with different bindi ng properties, with sCD14 complexed to LPS or lipid A-2-keto-3-deoxyoctonic acid-heptose. In a second step, we have investigated whether the capacity of hLf to interact with sCD14 could modulate the expression of endothelial- leukocyte adhesion molecule 1 (E-selectin) or intercellular adhesion molecu le 1 (ICAM-1) induced by the sCD14-LPS complex on human umbilical vein endo thelial cells (HUVEC). Our experiments show that hLf significantly inhibite d both E-selectin and ICAM-1 expressions at the surface of HUVEC. In conclu sion, these observations suggest that the anti-inflammatory effects of hLf are due not only to the ability of the molecule to chelate LPS but also to its ability to interact,vith sCD14 and with the sCD14 complexed to LPS, thu s modifying the activation of endothelial cells.