Identification of lipids that accumulate during the routine storage of prestorage leukoreduced red blood cells and cause acute lung injury

Abstract

BACKGROUND Lipids accumulate during the storage of red blood cells (RBCs), prime neutrophils (PMNs), and have been implicated in transfusion-related acute lung injury (TRALI). These lipids are composed of two classes: nonpolar lipids and lysophosphatidylcholines based on their retention time on separation by high-pressure liquid chromatography. Prestorage leukoreduction significantly decreases white blood cell and platelet contamination of RBCs; therefore, it is hypothesized that prestorage leukoreduction changes the classes of lipids that accumulate during storage, and these lipids prime PMNs and induce acute lung injury (ALI) as the second event in a two-event in vivo model. STUDY DESIGN AND METHODS RBC units were divided: 50% was leukoreduced (LR-RBCs), stored, and sampled on Day 1 and at the end of storage, Day 42. Priming activity was evaluated on isolated PMNs, and the purified lipids from Day 1 or Day 42 were used as the second event in the in vivo model. RESULTS The plasma and lipids from RBCs and LR-RBCs primed PMNs, and the LR-RBC activity decreased with longer storage. Unlike RBCs, nonpolar lipids comprised the PMN-priming activity from stored LR-RBCs. Mass spectroscopy identified these lipids as arachidonic acid and 5-, 12-, and 15-hydroxyeicsotetranoic acid. At concentrations from Day 42, but not Day 1, three of four of these lipids individually, and the mixture, primed PMNs. The mixture also caused ALI as the second event in a two-event model of TRALI. CONCLUSION We conclude that the nonpolar lipids that accumulate during LR-RBC storage may represent the agents responsible for antibody-negative TRALI.

Experimental prestorage filtration removes antibodies and decreases lipids in RBC supernatants mitigating TRALI in vivo

“…37 The PMN priming activity that accumulates in the supernatant during LR-RBC storage is almost totally composed of lipophilic compounds, which were significantly decreased by experimental filtration. 8,20 Experimental filtration for RBC units represents a possible method for TRALI mitigation via antibody removal, which to date has not been implemented in most blood centers. Washing of RBC units removes proinflammatory activity, including both antibodies and lipids, and ALI may be mitigated in high-risk populations by washing of cellular components.…”

“…6 Experimental filtration decreased (1) the accumulation of PMN priming activity in the day 42 RBC supernatant, (2) the lipid priming activity in the day 42 RBC supernatant, and (3) the concentration of 5-HETE in comparison with leukoreduced control RBCs. 8,20 These filters were constructed to remove immunoglobulins and do passively bind lipophilic compounds and a number of enzymes and other cofactors. The decrease in 5-HETE accumulation without any decrease in AA, the most common precursor, is likely attributable to removal of the enzyme(s) responsible for its conversion.…”

“…Removal of leukocytes and platelets has been shown to reduce: (1) HLA antigen exposure; (2) febrile, nonhemolytic transfusion reactions; (3) levels of cytokine accumulation during routine RBC storage; (4) sCD40L accumulation; and (5) cytomegalovirus exposure. 8,[17][18][19][20] The majority of RBC units in most countries are prestorage leukoreduced either by filtration or buffy coat removal. TRALI in a susceptible host has been related to the infusion of donor antibodies against the HLA antigens of the recipient, which may reside on either the recipient's leukocytes or endothelial cells, or the infusion of lipids or sCD40L.…”

“…25 Lipids were isolated from these samples using a 1:1:1 chloroform:methanol:water 0.2% acetic acid extraction. 20,25 The lipids were solubilized with 1.25% fatty-acid-free human albumin, and PMNs were incubated with albumin or the lipids for 5 minutes at 37°C. The PMNs were then activated with 1 mM fMLF, and O 2 2 was measured.…”

Immunoregulatory Effects of Stored Red Blood Cells

“…11 Leukoreduction of RBC concentrates after collection results in the removal of WBCs by greater than 3 logs and a decrease in platelets by 4 to 5 logs, as well as marked reduction in some but not all lipids, although it did not prevent neutrophil priming or the ability to induce TRALI in a mouse model. 12 Similarly, removal of WBCs by filtration and/or inactivation by gamma irradiation is associated with reduction but not elimination of immunologic adverse events consequences, although leukoreduction appears to reduce the percentage of hemolysis by almost half after RBC storage. 13 …”