Stored platelets alter glycerophospholipid and sphingolipid species, which are differentially transferred to newly released extracellular vesicles.

BACKGROUND: Stored platelet concentrates (PLCs) for transfusion develop a platelet storage lesion (PSL), resulting in decreased platelet (PLT) viability and function. The processes leading to PSL have not been described in detail and no data describe molecular changes occurring in all three components of stored PLCs: PLTs, PLC extracellular vesicles (PLC-EVs), and plasma. STUDY DESIGN AND METHODS: Fifty PLCs from healthy individuals were stored under standard blood banking conditions for 5 days. Changes in cholesterol, glycerophospholipid, and sphingolipid species were analyzed in PLTs, PLC-EVs, and plasma by mass spectrometry and metabolic labeling. Immunoblots were performed to compare PLT and PLC-EV protein expression. RESULTS: During 5 days, PLTs transferred glycerophospholipids, cholesterol, and sphingolipids to newly formed PLC-EVs, which increased corresponding lipids by 30%. Stored PLTs significantly increased ceramide (Cer; +53%) and decreased sphingosine-1-phosphate (-53%), shifting sphingolipid metabolism toward Cer. In contrast, plasma accumulated minor sphingolipids. Compared to PLTs, fresh PLC-EVs were enriched in lysophosphatidic acid (60-fold) and during storage showed significant increases in cholesterol, sphingomyelin, dihydrosphingomyelin, plasmalogen, and lysophosphatidylcholine species, as well as accumulation of apolipoproteins A-I, E, and J/clusterin. CONCLUSION: This is the first detailed analysis of lipid species in all PLC components during PLC storage, which might reflect mechanisms active during in vivo PLT senescence. Stored PLTs reduce minor sphingolipids and shift sphingolipid metabolism toward Cer, whereas in the plasma fraction minor sphingolipids increase. The composition of PLC-EVs resembles that of lipid rafts and confirms their role as carriers of bioactive molecules and master regulators in vascular disease.

Lipidomic analysis of platelet senescence.

BACKGROUND: A hallmark of platelet (PLT) storage lesion is the loss of PLT lipids. Due to technical limitations a detailed lipidomic analysis of plateletpheresis products during storage was so far not available. STUDY DESIGN AND METHODS: Fifty plateletpheresis products were stored for 5 days at 22°C under agitation. Each day plasma and PLTs were isolated by gel filtration and lipid species analyzed by electrospray ionization tandem mass spectrometry. RESULTS: During 5 days of storage the total lipid content decreased by 10% in PLTs and increased by 5% in plasma. We observed the following changes in lipid class fractions during storage relative to the day of preparation: increases of 69% ceramide (Cer), 32% lysophosphatidylcholine (LPC), and 49% cholesteryl esters (CE) and a decrease of 10% free cholesterol (FC) in PLTs and elevation of 43% LPC and 14% CE and a decline of 20% phosphatidylcholine (PC) and 24% FC in plasma. Significant lipid species shifts were observed for phosphatidylserine, Cer, and LPC. Correlation analysis of lipid changes in plasma indicated that lecithin-cholesterol-acyltransferase (LCAT) activity may be responsible for the shift in plasma lipid composition. These lipid changes correlated between plasma and PLTs for LPC, FC, and CE fractions. CONCLUSIONS: This study presents for the first time detailed lipid species profiles of PLTs and plasma during storage of PLT concentrates. These data provide clear evidence for LCAT-mediated esterification of FC and LPC generation in the plasma of PLT concentrates. Moreover, we showed evidence that these changes also impact PLT lipid composition.

Metabolism and atherogenic disease association of lysophosphatidylcholine.

Lysophosphatidylcholine (LPC) is a major plasma lipid that has been recognized as an important cell signalling molecule produced under physiological conditions by the action of phospholipase A(2) on phosphatidylcholine. LPC transports glycerophospholipid components such as fatty acids, phosphatidylglycerol and choline between tissues. LPC is a ligand for specific G protein-coupled signalling receptors and activates several second messengers. LPC is also a major phospholipid component of oxidized low-density lipoproteins (Ox-LDL) and is implicated as a critical factor in the atherogenic activity of Ox-LDL. Hence, LPC plays an important role in atherosclerosis and acute and chronic inflammation. In this review we focus in some detail on LPC function, biochemical pathways, sources and signal-transduction system. Moreover, we outline the detection of LPC by mass spectrometry which is currently the best method for accurate and simultaneous analysis of each individual LPC species and reveal the pathophysiological implication of LPC which makes it an interesting target for biomarker and drug development regarding atherosclerosis and cardiovascular disorders.