Modified phosphatidylethanolamines induce different levels of cytokine expression in monocytes and dendritic cells

Abstract

Glycation of phosphatidylethanolamine (PE) is a reaction that is known to occur under the chronic hyperglycemic conditions found in diabetes. Glycated phosphatidylethanolamines were found in plasma and atherosclerotic plaques of diabetic patients, and its presence was correlated with increased oxidative stress. Moreover, upregulation of cytokines and other inflammatory mediators can be observed not only in diabetes, but also under oxidized phosphatidylcholine stimulation. In this study, we evaluate the effect of dipalmitoyl-phosphatidylethanolamine (DPPE) and linoleoyl-palmitoyl-phosphatidylethanolamine (PLPE) structural oxidation, glycation and glycoxidation, on monocyte and myeloid dendritic cell stimulation. Expression of cytokines, IL-1β, IL-6, IL-8, MIP-1β and TNF-α, were determined using flow cytometry after cell stimulations with native PEs, oxidized, glycated and glycoxidized PEs. Native PE, PLPE and DPPE, and all modified PEs were able to increase the stimulation levels of monocytes and mDCs. Generally, in monocytes and mDCs stimulation, GluOxPLPE and GluDPPE were the PLPE/DPPE modifications that induced the most pronounced rise in cytokine production. However, GluOxDPPE was the DPPE modification that produced the lowest stimulation levels of mDCs and monocytes. Our results indicate that glycated PE and glycoxidized PE may have an important contribution to the low-grade systemic inflammation associated with diabetes and to the development of diabetic complications.

Keywords: AGEs; Cytokines; DPPE; ESI; Flow cytometry; GluOxPE; GluPE; Glycation, Oxidation; Glycoxidation; HLA-DR; IFN-γ; IL; LC–MS; LDL; LPS; MFI; MIP; MS/MS; OxPE; PB; PBS; PE; PL; PLPE; Phospholipids; TNF-α; advanced glycated end products; dipalmitoyl-phosphatidylethanolamine; electrospray; glycated phosphatidylethanolamine; glycoxidized phosphatidylethanolamine; human leukocyte antigen; interferon-γ; interleukin; linoleoyl-palmitoyl-phosphatidylethanolamine; lipopolysaccharide; liquid chromatography–mass spectrometry; low density lipoprotein; mDC; macrophage inflammatory protein; mean fluorescence intensity; myeloid dendritic cell; oxPAPC; oxidized 2-arachidonoyl-1-palmitoyl-sn-glycero-3-phosphatidylcholine; oxidized phosphatidylethanolamine; peripheral blood; phosphate-buffered saline; phosphatidylethanolamine; phospholipid; tandem mass spectrometry; tumor necrosis factor-α.