Abstract
Soybean oil (SO)-, SO medium-chain triglyceride (MCT)-, olive oil (OO)-, and fish oil (FO)-based lipid emulsions are generally applied in clinical practice via intravenous injection for patients with nutritional requirements. The function of lipid emulsions on immune modulation remains inconsistent, and their effects on macrophages are limited. In the present study, we used a model of S. aureus-infected mouse RAW264.7 macrophages to determine the influence of three different compositions of lipid emulsions (Lipofundin, ClinOleic, and Omegaven) on reactive oxygen species (ROS) production, phagocytosis, and bacterial survival. The three individual lipid emulsions similarly enhanced bacterial survival but reduced S. aureus-stimulated ROS, phagocytosis of S. aureus bioparticles conjugate, polymerization of F-actin, and phosphorylation of AKT, JNK, and ERK. Compared with the JNK and ERK inhibitors, the PI3K inhibitor markedly suppressed the phagocytosis of S. aureus bioparticles conjugate and the polymerization of F-actin, whereas it significantly increased the bacterial survival. These results suggest that the three lipid emulsions diminished ROS production and phagocytosis, resulting in increased bacterial survival. PI3K predominantly mediated the inhibitory effects of the lipid emulsions on the phagocytosis of mouse RAW264.7 macrophages.
Highlights
Accepted: 25 November 2021Lipid emulsions for clinical use are usually injected intravenously for nutrition for critically ill patients [1]
The time kinetics of the S. aureus-stimulated total reactive oxygen species (ROS) is shown in Figure 2a, and the peak value occurred at 5 min
We further demonstrated that the phosphatidylinositol 3-kinase (PI3K) inhibitor obviously suppressed the phagocytosis of S. aureus bioparticles conjugate and the polymerization of F-actin, which were similar to the effect of cytochalasin D, a polymerization inhibitor of actin used to block phagocytosis
Summary
Lipid emulsions for clinical use are usually injected intravenously for nutrition for critically ill patients [1]. The immune modulation activity of lipid emulsions used in clinical applications is still controversial [2,3,4]. Different compositions of fatty acids in lipids influence several features of immune cells, including the cell membrane structure, production of bioactive substances, intracellular signaling pathways, regulation of gene expression, and immune modulation [2,4]. Phagocytes are innate immune cells that are involved in protection against infection [5,6]. One of their major functions, phagocytosis, is an important mechanism to remove pathogens and cell debris. Enzymes and reactive oxygen species (ROS) digest the pathogen [6]
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