| Abstract |
Recently, liposomal formulations that target macrophages have been used to treat lung diseases. However, the detailed mechanism of the cellular uptake must be elucidated to identify a formulation with excellent cellular uptake efficiency to treat non-tuberculous mycobacterial lung disease. We studied the effect of lipid composition on the cellular uptake of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/cholesterol (Chol) liposomes with a size of approximately 200 nm into THP-1-derived macrophages. The amount of DPPC/Chol liposomes (80/20 mol%) was greater than that of DPPC/Chol (60/40 mol%) and DPPC/Chol (67/33 mol%) liposomes. The anisotropy of 1,6-diphenyl-1,3,5-hexatriene indicated that the membrane fluidity of the DPPC/Chol (80/20 mol%) liposomes was higher than that of the other two liposomes. DPPC/Chol (80/20 mol%) and DPPC/Chol (67/33 mol%) liposomes were taken up via clathrin- and caveolae-mediated endocytosis and phagocytosis. However, proteins involved in cellular uptake through ligand-receptor interactions were adsorbed to a greater extent on DPPC/Chol (80/20 mol%) liposomes than on DPPC/Chol (67/33 mol%) liposomes. Pretreatment of cells with antibodies against the low-density lipoprotein receptor and scavenger receptor type B1 largely inhibited the uptake efficiency of DPPC/Chol (80/20 mol%) liposomes. Our results indicate that the membrane fluidity of DPPC/Chol liposomes, which is controlled by the Chol ratio, is an important factor in controlling protein adsorption and the subsequent uptake efficiency of liposomes.
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