Structural Transition of Lipopolysaccharide and Reduction in the Biological Activity by Amphiphilic Lipid with Cationic Amino Acid

Abstract

Abstract Lipopolysaccharide (LPS), the endotoxin of Gram-negative bacteria, is a strong elicitor in the immune system by interacting with lipopolysaccharide-binding protein and CD14 with high specificity. The removal of LPS contamination in protein drug products expressed by bacteria is essential in pharmaceutical products for human use. Although polymyxin B (PMB)-immobilized columns are mainly used for removal of LPS, there are some problems, such as high production cost, and the toxicity of ligands. We synthesized aromatic lipids bearing lysine or arginine at the headgroup. These lipids form a complex with LPS through electrostatic interaction between cationic amino acids and phosphate groups in the lipid A backbone. The resultant complexes induce the structural transition of LPS from a cylindrical structure to a vesicle. Addition of amino-lipid/LPS complexes to RAW264.7 cells, a macrophage-like cell line, decrease the LPS activity. The efficiencies are higher than commonly used cationic compounds, such as dioleoyltrimethylammoniumpropane (DOTAP) and PMB. These results show that amphiphilic lipids with cationic amino acids can be used for deactivation of LPS.