Effects of Rapamycin on the Differentiation and Function of Macrophages In Vitro

Fusogenic pH sensitive liposomal formulation for rapamycin: improvement of antiproliferative effect

CONTEXT

Liposomes are increasingly employed to deliver chemotherapeutic agents, antisense oligonucleotides, and genes to various therapeutic targets.

OBJECTIVE

The present investigation evaluates the ability of fusogenic pH-sensitive liposomes of rapamycin in increasing its antiproliferative effect on human breast adenocarcinoma (MCF-7) cell line.

MATERIALS AND METHODS

Cholesterol (Chol) and dipalmitoylphosphatidylcholine (DPPC) (DPPC:Chol, 7:3) were used to prepare conventional rapamycin liposomes by a modified ethanol injection method. Dioleoylphosphatidylethanolamine (DOPE) was used to produce fusogenic and pH-sensitive properties in liposomes simultaneously (DPPC:Chol:DOPE, 7:3:4.2). The prepared liposomes were characterized by their size, zeta potential, encapsulation efficiency percent (EE%), and chemical stability during 6 months. The antiproliferative effects of both types of rapamycin liposomes (10, 25, and 50 nmol/L) with optimized formulations were assessed on MCF-7 cells, as cancerous cells, and human umbilical vein endothelial cells (HUVEC), as healthy cells, employing the diphenyltetrazolium bromide (MTT) assay for 72 h.

RESULTS AND DISCUSSION

The particle size, zeta potential, and EE% of the liposomes were 165 ± 12.3 and 178 ± 15.4 nm, -39.6 ± 1.3, and -41.2 ± 2.1 mV as well as 76.9 ± 2.6 and 76.9 ± 2.6% in conventional and fusogenic pH-sensitive liposomes, respectively. Physicochemical stability results indicated that both liposome types were relatively stable at 4 °C than 25 °C. In vitro antiproliferative evaluation showed that fusogenic pH-sensitive liposomes had better antiproliferative effects on MCF-7 cells compared to the conventional liposomes. Conversely, fusogenic pH-sensitive liposomes had less cytotoxicity on HUVEC cell line.

Influence of sirolimus-loaded nanoparticles on physiological functions of native human polymorphonuclear neutrophils

Sirolimus (SRL) is an immunosuppressive agent of high clinical relevance that has been associated with serious side effects. Biodegradable, SRL-loaded poly(d,l-lactide) nanoparticles (SRL-PLA-NPs) are being investigated as a drug delivery system to improve drug targeting. Polymorphonuclear neutrophils (PMNs) are phagocytes for particulate xenobiotics and also important trigger cells of the primary immune response. Therefore, the effects of SRL, SRL-PLA-NPs, and plain PLA-NPs on the viability of human PMNs, their essential functions, and the secretion of relevant cytokines were determined and evaluated with respect to the intracellular concentrations assessed by liquid chromatography-mass spectrometry ultra-trace analysis. For the first time to our knowledge, incorporation of NPs into PMNs was monitored by flow cytometry using fluorescence-labeled NPs. SRL accumulated intracellularly, exceeding therapeutic blood levels by a factor of two to four. Phagocytic activity was promptly reduced but recovered within 3 hours. No other parameters of the PMNs were affected. Hence, PLA-NPs appear suitable as drug carriers for SRL, allowing for better control of drug release.

FROM THE CLINICAL EDITOR

This team of authors describe the incorporation of sirolimus loaded florescent NPs into polymorphonuclear neutrophils, a process that has been monitored by flow cytometry utilizing the fluorescent properties of the polymeric NPs. SRL accumulated intracellularly, exceeding therapeutic blood levels by a factor of two to four, resulting in reduced phagocytic activity that recovered within 3 hours.