<i>Aspergillus fumigatus</i>‐derived gliotoxin impacts innate immune cell activation through modulating lipid mediator production in macrophages

Gliotoxin (GT), a secondary metabolite and virulence factor of the fungal pathogen Aspergillus fumigatus, suppresses innate immunity and supports the suppression of host immune responses. Recently, we revealed that GT blocks the formation of the chemotactic lipid mediator leukotriene (LT)B₄ in activated human neutrophils and monocytes, and in rodents in vivo, by directly inhibiting LTA₄ hydrolase. Here, we elucidated the impact of GT on LTB₄ biosynthesis and the entire lipid mediator networks in human M1- and M2-like monocyte-derived macrophages (MDMs) and in human tissue-resident alveolar macrophages. In activated M1-MDMs with high capacities to generate LTs, the formation of LTB₄ was effectively suppressed by GT, connected to attenuated macrophage phagocytic activity as well as human neutrophil movement and migration. In resting macrophages, especially in M1-MDMs, GT elicited strong formation of prostaglandins, while bacterial exotoxins from Staphylococcus aureus evoked a broad spectrum of lipid mediator biosynthesis in both MDM phenotypes. We conclude that GT impairs functions of activated innate immune cells through selective suppression of LTB₄ biosynthesis, while GT may also prime the immune system by provoking prostaglandin formation in macrophages.