Lysophosphatidylcholines prime the NADPH oxidase and stimulate multiple neutrophil functions through changes in cytosolic calcium

Abstract

A mixture of lysophosphatidylcholines (lyso-PCs) are generated during blood storage and are etiologic in models of acute lung injury. We hypothesize that lyso-PCs stimulate polymorphonuclear neutrophils (PMNs) through Ca(2)(+)-dependent signaling. The lyso-PC mix (0.45-14.5 micro M) and the individual lyso-PCs primed formyl-Met-Leu-Phe (fMLP) activation of the oxidase (1.8- to 15.7-fold and 1.7- to 14.8-fold; P<0.05). Labeled lyso-PCs demonstrated a membrane association with PMNs and caused rapid increases in cytosolic Ca(2)(+). Receptor desensitization studies implicated a common receptor or a family of receptors for the observed lyso-PC-mediated changes in PMN priming, and cytosolic Ca(2)(+) functions were pertussis toxin-sensitive. Lyso-PCs caused rapid serine phosphorylation of a 68-kD protein but did not activate mitogen-activated protein kinases or cause changes in tyrosine phosphorylation. With respect to alterations in PMN function, lyso-PCs caused PMN adherence, increased expression of CD11b and the fMLP receptor, reduced chemotaxis, provoked changes in morphology, elicited degranulation, and augmented fMLP-induced azurophilic degranulation (P<0.05). Cytosolic Ca(2)(+) chelation inhibited lyso-PC-mediated priming of the oxidase, CD11b surface expression, changes in PMN morphology, and serine phosphorylation of the 68-kD protein. In conclusion, lyso-PCs affect multiple PMN functions in a Ca(2)(+)-dependent manner that involves the activation of a pertussis toxin-sensitive G-protein.

Lysophospholipids of Different Classes Mobilize Neutrophil Secretory Vesicles and Induce Redundant Signaling through G2A

“…These findings corroborate earlier studies in which lyso-PC enhanced neutrophil superoxide production, adherence, chemotaxis, and degranulation (5,8). Of note, neutrophil responses to lyso-PC appear to depend both on fatty acid chain length (5,7) and on the method of presentation (dissolved in organic solvents or water, or presented on albumin or in liposomes) (2,5).…”

“…2A). This was not evident for the heterologous stimulus, PAF, confirming findings of Silliman et al (5). Several GPCR for lyso-PC have been proposed as follows: G2A, GPR4, and the PAFR (5, 7, 29 -31).…”

“…Given the potential for detergent-like properties of lyso-PLs, and the demonstrated variability of their biological effects in previous publications, the concentration, method of presentation (solvents or carrier proteins), and/or the physical state of the lipid (monomers, micelles, or liposomes) are most likely of critical importance (2,5,17). Using simultaneous staining with propidium iodide to detect permeabilization of the plasma membrane (17), we assessed calcium flux in response to C16:0/OH, C18:0/OH, and C18:1/OH lyso-PC species in human neutrophils.…”

TRALI – Definition, mechanisms, incidence and clinical relevance

“…The second event is transfusion of mediators, such as lipids and cytokines from stored blood products, which can prime or directly activate neutrophils, leading to pulmonary damage. These lipids include lysophosphatidylcholines, which are released from apoptotic white blood cells and platelets and have the capacity to enhance neutrophil function (32).…”

Immunomodulatory Actions of Lysophosphatidylcholine

“…LPC-induced changes in human neutrophils were extensively studied by Silliman et al (2003). In addition to priming formyl-Met-Leu-Phe (fMLP)-induced activation of the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, LPC (0.45-14.5 µM) enhances adhesion of neutrophils to fibrinogen-coated microtiter plates and surface expression of the CD11b and fMLP receptor .…”