Profiling changes triggered during maturation of dendritic cells: a lipidomic approach

Lipids are important in several biological processes because they act as signalling and regulating molecules, or, locally, as membrane components that modulate protein function. This paper reports the pattern of lipid composition of dendritic cells (DCs), a cell type of critical importance in inflammatory and immune responses. After activation by antigens, DCs undergo drastic phenotypical and functional transformations, in a process known as maturation. To better characterize this process, changes of lipid profile were evaluated by use of a lipidomic approach. As an experimental model of DCs, we used a foetal skin-derived dendritic cell line (FSDC) induced to mature by treatment with lipopolysaccharide (LPS). The results showed that LPS treatment increased ceramide (Cer) and phosphatidylcholine (PC) levels and reduced sphingomyelin (SM) and phosphatidylinositol (PI) content. Mass spectrometric analysis of a total lipid extract and of each class of lipids revealed that maturation promoted clear changes in ceramide profile. Quantitative analysis enabled identification of an increase in the total ceramide content and enhanced Cer at m / z 646.6, identified as Cer(d18:1/24:1), and at m / z 648.6, identified as Cer(d18:1/24:0). The pattern of change of these lipids give an extremely rich source of data for evaluating modulation of specific lipid species triggered during DC maturation.