Differential Immunomodulating Effects of Pegylated Liposomal Doxorubicin Nanoparticles on Human Macrophages

Abstract

The pegylated liposomal doxorubicin (PLD) has been widely accepted in treatment of various cancers. However, the composition of two currently marketed PLD nanoparticles differs in structure and composition of lipids, and their differential effects remain unknown. Macrophages of the mononuclear phagocyte system are pivotal in determining PLD clearance in vivo. The aim of this study was to compare the effect of these two PLDs on drug uptake, cell viability, morphology and immune function of human macrophages. Two PLD nanoparticles were used in this study. The major difference between PLD-D and PLD-H is that their phospholipid bilayers are composed of distearoyl phosphatidylcholine (DSPC) and hydrogenated soybean phosphatidylcholine (HSPC), respectively. Human CD14+ monocytes were isolated from peripheral blood to prepare macrophages. Comparative assays included: flow cytometry for detection of doxorubicin penetration into cells, MTT for cell viability, Trypan blue exclusion for cell membrane integrity, Liu's stain for morphologic evaluation, and inactivated yeast co-culture for phagocytosis. The uptake of PLD-H was rapidly detected at 10 min and kept increasing to 4 h followed by a decline thereafter, whereas that of PLD-D had similar profile with much less doxorubicin fluorescence detected, indicating a greater amount of doxorubicin retention of PLD-H. PLD-H, at higher concentration, decreased the viability and impaired cell membrane integrity of macrophages with an extent greater than PLD-D. The morphological observation showed a more extensive necrosis in PLD-H-treated macrophages. The phagocytosis function of macrophage was inhibited with a greater extent in PLD-H-treated macrophages. The PLD containing HSPC may cause retention of doxorubicin with greater amount and longer period in human macrophages than that containing DSPC. This effect was accompanied by greater toxicity and more profound dysfunction. The correlation of this differential effect to clinical outcome remains to be extensively investigated by performing in vivo experiments or conducting clinical trials.