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Synthesis of platelet-activating factor by polymorphonuclear neutrophils stimulated with interleukin-8
F Bussolino1, M Sironi, E Bocchietto
1Dipartimento di Genetica, Biologia e Chimica Medica, Torino, Italy.
Abstract:
Human interleukin-8 (IL-8) was evaluated for its capability to induce the synthesis and release of platelet-activating factor (PAF) from human polymorphonuclear neutrophils (PMN). IL-8 promotes in a dose-dependent fashion (1-100 ng/ml) a rapid synthesis of PAF, which is only partially released. The synthesis of PAF is preceded by the activation of acetyl-CoA: 1-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyl-transferase, suggesting that IL-8 activates the "remodeling pathway" of PAF synthesis. By thin layer chromatography and reverse-phase high pressure liquid chromatography, we demonstrated that PAF synthesized by human PMN stimulated with IL-8 is heterogeneous: the 2-acetylated phospholipids having the biological and physicochemical characteristics of PAF include the 1-O-alkyl form, which is produced in large extent (51%), and the 1-acyl form (20%). The analysis of the individual molecular species of radyl chain indicated nine peaks, 16:0 and 18:0 being the predominant forms. These results identify PAF as a direct product of IL-8 stimulation in PMN.
Insights
Human interleukin-8 (IL-8) stimulates human neutrophils to synthesize platelet-activating factor (PAF) via the remodeling pathway. This research details the PAF molecular species produced, identifying it as a direct product of IL-8.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Interleukin-8 (IL-8) is a key chemokine involved in inflammatory responses.
- Platelet-activating factor (PAF) is a potent lipid mediator implicated in various physiological and pathological processes.
- Polymorphonuclear neutrophils (PMN) are crucial immune cells that release inflammatory mediators.
Purpose of the Study:
- To investigate the capacity of human IL-8 to induce the synthesis and release of PAF from human PMN.
- To elucidate the specific pathway and molecular characteristics of PAF produced upon IL-8 stimulation.
Main Methods:
- Dose-response evaluation of IL-8 (1-100 ng/ml) on PAF synthesis and release in human PMN.
- Enzyme activity assay for acetyl-CoA: 1-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyl-transferase.
- Thin layer chromatography (TLC) and reverse-phase high-performance liquid chromatography (RP-HPLC) for PAF characterization.
Main Results:
- IL-8 dose-dependently induced rapid PAF synthesis in human PMN, with only partial release.
- Activation of the remodeling pathway enzyme acetyl-CoA: 1-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyl-transferase preceded PAF synthesis.
- Synthesized PAF was heterogeneous, comprising 1-O-alkyl (51%) and 1-acyl (20%) forms, with 16:0 and 18:0 predominant alkyl chains.
Conclusions:
- IL-8 directly stimulates human PMN to synthesize PAF.
- The remodeling pathway is activated by IL-8, leading to PAF production.
- IL-8-induced PAF in PMN is molecularly diverse, with significant 1-O-alkyl species.