Liquid chromatography-coupled mass spectrometry analysis of glutathione conjugates of oxygenated polyunsaturated fatty acids.

Glutathione (GSH) conjugates of oxygenated polyunsaturated fatty acids comprise a group of pro-inflammatory and pro-resolving lipid mediators formed in immunocompetent cells. While the pro-inflammatory conjugates such as the cysteinyl leukotrienes (cys-LTs), eoxins (EXs) and five-oxo-GSH conjugate (FOG7) derive from arachidonic acid (AA), the group of conjugates in tissue regeneration (CTRs) such as maresin CTRs (MCTRs), protectin CTRs (PCTRs) and resolvin CTRs (RCTRs) are biosynthesized from docosahexaenoic acid (DHA). Here, we present a gradient UPLC-MS/MS method for the analysis of pro-inflammatory and pro-resolving GSH conjugates using positive electrospray ionization (ESI(+)) and collision-induced fragmentation for unambiguous identification and structural information, and a negative ionization (ESI(-)) mode for quantification of the GSH conjugates. The method was employed to detect GSH conjugates in human platelets and macrophages. MCTRs were detected in platelets upon addition of exogenous docosahexaenoic acid (DHA) and the biosynthesis was independent on leukotriene C4 (LTC4) synthase activity. Pathogenic bacteria stimulated the formation of EXs and PCTRs in M2 macrophages, whereas Ca2+-ionophore activated the biosynthesis of LTC4 in M1 and M2 macrophage phenotypes. Together, our methodology covers the qualitative and quantitative analysis of GSH conjugates and gives an analytical basis for the detection and structural elucidation of cysteinyl-containing lipid mediators.