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

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.

Plasma and lipids from stored platelets cause acute lung injury in an animal model.

BACKGROUND: Transfusion of PLT concentrates may cause TRALI, a life-threatening reaction that has been linked to the infusion of anti-WBC immunoglobulins or older, stored PLTs that contain bioactive lipids. We hypothesize that lipids generated during storage of PLTs cause TRALI in a two-event animal model. STUDY DESIGN AND METHODS: Plasma from both whole-blood PLTs (WB-PLTs) and apheresis PLTs (A-PLTs) was isolated on Day 0 (D.0) and Day 5 (D.5) of storage and heat-treated before use. Rats were pretreated with saline or 2 mg per kg endotoxin (LPS), anesthetized, and the lungs were ventilated, isolated, and perfused with saline or 5-percent PLT plasma. Pulmonary artery pressure, pulmonary edema, and leukotriene B4 levels (perfusate) were measured. RESULTS: Plasma from D.5, but not D.0, of the identical WB-PLT and A-PLT units caused injury in lungs from LPS-pretreated rats (LPS/D.5) evidenced by increases in pulmonary edema and leukotriene B4 (p < 0.05). Lipid extracts and purified lipids from D.5 PLT plasma also elicited injury in lungs from LPS-pretreated rats (p < 0.05). Saline/D.5 plasma or lipids or LPS/D.0 did not cause pulmonary edema. Prestorage WBC reduction was ineffective in inhibiting TRALI. CONCLUSION: PLT-induced TRALI may be the result of two events: 1) the clinical condition of the patient and 2) the infusion of lipids in stored PLTs.

A two-insult in vitro model of PMN-mediated pulmonary endothelial damage: requirements for adherence and chemokine release.

Lysophosphatidylcholines (lyso-PCs), generated during blood storage, are etiologic in a two-insult, sepsis-based model of transfusion-related acute lung injury (TRALI). Individually, endotoxin (LPS) and lyso-PCs prime but do not activate neutrophils (PMNs). We hypothesized that priming of PMNs alters their reactivity such that a second priming agent causes PMN activation and endothelial cell damage. PMNs were primed or not with LPS and then treated with lyso-PCs, and oxidase activation and elastase release were measured. For coculture experiments, activation of human pulmonary microvascular endothelial cells (HMVECs) was assessed by ICAM-1 expression and chemokine release. HMVECs were stimulated or not with LPS, PMNs were added, cells were incubated with lyso-PCs, and the number of viable HMVECs was counted. Lyso-PCs activated LPS-primed PMNs. HMVEC activation resulted in increased ICAM-1 and release of ENA-78, GRO alpha, and IL-8. PMN-mediated HMVEC damage was dependent on LPS activation of HMVECs, chemokine release, PMN adhesion, and lyso-PC activation of the oxidase. In conclusion, sequential exposure of PMNs to priming agents activates the microbicidal arsenal, and PMN-mediated HMVEC damage was the result of two insults: HMVEC activation and PMN oxidase assembly.