Lysophosphatidylcholine modulates neutrophil oxidant production through elevation of cyclic AMP.
Lysophosphatidylcholine (LPC) is an oxidized phospholipid present in micromolar concentrations in blood and inflamed tissues. The effects of LPC on neutrophil functions remain incompletely understood, because conflicting reports exist for its stimulatory and inhibitory roles. We report in this study that LPC inhibits superoxide generation in fMLP- and PMA-stimulated neutrophils without affecting fMLP-induced Ca(2+) mobilization and cell viability. This effect was observed with LPC dissolved in ethanol, but not with LPC stock solutions prepared in water or in BSA-containing aqueous solution with sonication. Under the same experimental conditions, platelet-activating factor primed neutrophils for superoxide generation. The inhibitory effect of LPC was observed within 30 s after its application and was maximal at LPC concentrations between 0.1 and 1 muM. Inhibition of superoxide generation was accompanied by a 2.5-fold increase in the intracellular cAMP concentration. In addition, LPC reduced fMLP-stimulated phosphorylation of ERK and Akt and membrane translocation of p67(phox) and p47(phox). The protein kinase A inhibitors H-89 and adenosine 3'5'-cyclic monophosphorothioate Rp-isomer (Rp-cAMP) partially restored superoxide production in LPC-treated neutrophils, indicating involvement of protein kinase A in LPC-mediated inhibition. Using an ex vivo mouse lung perfusion model that measures lung weight change and capillary filtration coefficient, we found that LPC prevented lung vascular injury mediated by fMLP-activated neutrophils. Taken together, these results suggest that LPC-induced elevation of intracellular cAMP is partially responsible for its inhibition of neutrophil NADPH oxidase activation. A similar mechanism of inhibition may be used for the control of neutrophil-mediated tissue injury.
Lin
Phoebe
P
Department of Pharmacology, University of Illinois College of Medicine, Chicago, IL 60612, USA.
Welch
Emily J
EJ
Gao
Xiao-Pei
XP
Malik
Asrar B
AB
Ye
Richard D
RD
D000818:Animals; D039481:CD11b Antigen / Q000096:biosynthesis / Q000378:metabolism; D002199:Capillary Permeability / Q000276:immunology; D000242:Cyclic AMP / Q000096:biosynthesis / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008168:Lung / Q000098:blood supply / Q000276:immunology / Q000473:pathology; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D051379:Mice; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D019255:NADPH Oxidases; D018375:Neutrophil Activation / Q000187:drug effects / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D016877:Oxidants / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010972:Platelet Activating Factor / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
D039481:CD11b Antigen; D008244:Lysophosphatidylcholines; D016877:Oxidants; D010750:Phosphoproteins; D010972:Platelet Activating Factor; D011518:Proto-Oncogene Proteins; C079789:neutrophil cytosol factor 67K; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; D000242:Cyclic AMP; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D013755:Tetradecanoylphorbol Acetate