Abstract
In recent years, several studies have demonstrated that polyunsaturated fatty acids have strong immunomodulatory properties, altering several functions of macrophages. In the present work, we sought to provide a multi-omic approach combining the analysis of the lipidome, the proteome, and the metabolome of RAW 264.7 macrophages supplemented with phospholipids containing omega-3 (PC 18:0/22:6; ω3-PC) or omega-6 (PC 18:0/20:4; ω6-PC) fatty acids, alone and in the presence of lipopolysaccharide (LPS). Supplementation of macrophages with ω3 and ω6 phospholipids plus LPS produced a significant reprogramming of the proteome of macrophages and amplified the immune response; it also promoted the expression of anti-inflammatory proteins (e.g., pleckstrin). Supplementation with the ω3-PC and ω6-PC induced significant changes in the lipidome, with a marked increase in lipid species linked to the inflammatory response, attributed to several pro-inflammatory signalling pathways (e.g., LPCs) but also to the pro-resolving effect of inflammation (e.g., PIs). Finally, the metabolomic analysis demonstrated that supplementation with ω3-PC and ω6-PC induced the expression of several metabolites with a pronounced inflammatory and anti-inflammatory effect (e.g., succinate). Overall, our data show that supplementation of macrophages with ω3-PC and ω6-PC effectively modulates the lipidome, proteome, and metabolome of these immune cells, affecting several metabolic pathways involved in the immune response that are triggered by inflammation.
Highlights
IntroductionMacrophages are specialised cells of the innate immune system and the mononuclear phagocyte system and are strongly involved in all stages of inflammation [1]
The classic dichotomous classification of ω3-PC as anti-inflammatory and ω6-PC as pro-inflammatory has been challenged by numerous studies, indicating that the impact of these bioactive lipids on immune cells is much more complex
The Griess reaction was used to estimate the total nitric oxide (NO) concentration in the culture medium and to assess the activation/inflammatory state of macrophages triggered by LPS and the modulation caused by ω3 and ω6 PLs supplementation
Summary
Macrophages are specialised cells of the innate immune system and the mononuclear phagocyte system and are strongly involved in all stages of inflammation [1]. Macrophages display a wide range of functions, such as (1) recognition of pathogen-associated molecular patterns (PAMPs) or danger-associated molecular patterns (DAMPs) [2,3]; (2) antigen presentation; (3) phagocytosis of microorganisms, debris, and apoptotic cells; and (4) the secretion of several molecules, including a variety of cytokines, lipid mediators [1,4] and the production of reactive oxygen species (ROS), and reactive nitrogen species (RSN), such as nitric oxide (NO), to eliminate phagocytosed harmful organisms [3]. It is known that a balance between M1-like and M2-like macrophages is crucial for the resolution of inflammation and to ensure homeostasis [7]
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