Lipid mediators in platelet concentrate and extracellular vesicles: Molecular mechanisms from membrane glycerophospholipids to bioactive molecules

Platelets are collected for transfusion to patients with different hematological disorders, and for logistical reasons, platelets are stored as concentrates. Despite the carefully controlled conditions, platelets become activated during storage, and platelet concentrates (PLCs) may cause adverse inflammatory reactions in the recipients. We studied by mass spectrometry the lipidomic changes during storage of the clinical PLCs, the platelets isolated from PLCs, and the extracellular vesicles (EVs) thereof. The release of EVs from platelets increased with the prolonged storage time. The molar percentages of arachidonic acid -containing species were increased during storage especially in the phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine classes of glycerophopholipids. The increase of these species in the membrane glycerophopholipid composition paralleled the production of both proinflammatory and proresolving lipid mediators (LMs) as the amount of the arachidonic acid-derived LMs such as thromboxane B2 and prostaglandin E2 also increased in time. Moreover, several monohydroxy pathway markers and functionally relevant proinflammatory and proresolving LMs were detected in the PLC and the EVs, and some of these clearly accumulated during storage. By Western blot, the key enzymes of these pathways were shown to be present in the platelets and in many cases also in the EVs. Since the EVs were enriched in the fatty acid precursors of LMs, harbored LM-producing enzymes, contained the related monohydroxy pathway markers, and also secreted the final LM products, the PLC-derived EVs appear to have the potential to regulate inflammation and healing, and may thereby aid the platelets in exerting their essential physiological functions.Peer reviewe

hiPSC-derived hepatocytes closely mimic the lipid profile of primary hepatocytes: A future personalised cell model for studying the lipid metabolism of the liver

Peer reviewe

LDL aggregation susceptibility is higher in healthy South Asian compared with white Caucasian men

BACKGROUND: South Asians are more prone to develop atherosclerotic cardiovascular disease (ASCVD) compared with white Caucasians, which is not fully explained by classical risk factors. We recently reported that the presence of aggregation-prone low-density lipoprotein (LDL) in the circulation is associated with increased ASCVD mortality. OBJECTIVE: We hypothesized that LDL of South Asians is more prone to aggregate, which may be explained by differences in their LDL lipid composition. METHODS: In this cross-sectional hypothesis-generating study, LDL was isolated from plasma of healthy South Asians (n = 12) and age- and BMI-matched white Caucasians (n = 12), and its aggregation susceptibility and lipid composition were analyzed. RESULTS: LDL from South Asians was markedly more prone to aggregate compared with white Caucasians. Among all measured lipids, sphingomyelin 24:0 and triacylglycerol 56:8 showed the highest positive correlation with LDL aggregation. In addition, LDL from South Asians was enriched in arachidonic acid containing phosphatidylcholine 38:4 and had less phosphatidylcholines and cholesteryl esters containing monounsaturated fatty acids. Interestingly, body fat percentage, which was higher in South Asians (+26%), positively correlated with LDL aggregation and highly positively correlated with triacylglycerol 56:8, sphingomyelin 24:0, and total sphingomyelin. CONCLUSIONS: LDL aggregation susceptibility is higher in healthy young South Asians compared with white Caucasians. This may be partly explained by the higher body fat percentage of South Asians, leading to sphingomyelin enrichment of LDL. We anticipate that the presence of sphingomyelin-rich, aggregation -prone LDL particles in young South Asians may increase LDL accumulation in the arterial wall and thereby contribute to their increased risk of developing ASCVD later in life. (C) 2019 National Lipid Association. Published by Elsevier Inc.Peer reviewe

Polyunsaturated fatty acids modify the extracellular vesicle membranes and increase the production of proresolving lipid mediators of human mesenchymal stromal cells

Abstract Human mesenchymal stromal/stem cells (hMSCs) are used in experimental cell therapy to treat various immunological disorders, and the extracellular vesicles (hMSC-EVs) they produce have emerged as an option for cell-free therapeutics. The immunomodulatory function of hMSCs resembles the resolution of inflammation, in which proresolving lipid mediators (LMs) play key roles. Multiple mechanisms underlying the hMSC immunosuppressive effect has been elucidated; however, the impact of LMs and EVs in the resolution is poorly understood. In this study, we supplemented hMSCs with polyunsaturated fatty acids (PUFAs); arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which serve as precursors for multiple LMs. We then determined the consequent compositional modifications in the fatty acid, phospholipid, and LM profiles. Mass spectrometric analyses revealed that the supplemented PUFAs were incorporated into the main membrane phospholipid classes with different dynamics, with phosphatidylcholine serving as the first acceptor. Most importantly, the PUFA modifications were transferred into hMSC-EVs, which are known to mediate hMSC immunomodulation. Furthermore, the membrane-incorporated PUFAs influenced the LM profile by increasing the production of downstream prostaglandin E2 and proresolving LMs, including Resolvin E2 and Resolvin D6. The production of LMs was further enhanced by a highly proinflammatory stimulus, which resulted in an increase in a number of mediators, most notably prostaglandins, while other stimulatory conditions had less a pronounced impact after a 48-h incubation. The current findings suggest that PUFA manipulations of hMSCs exert significant immunomodulatory effects via EVs and proresolving LMs, the composition of which can be modified to potentiate the therapeutic impact of hMSCs

Synovial fluid fatty acid profiles are differently altered by inflammatory joint pathologies in the shoulder and knee joints

Abstract Anomalies of fatty acid (FA) metabolism characterize osteoarthritis (OA) and rheumatoid arthritis (RA) in the knee joint. No previous study has investigated the synovial fluid (SF) FA manifestations in these aging-related inflammatory diseases in the shoulder. The present experiment compared the FA alterations between the shoulder and knee joints in patients with end-stage OA or end-stage RA. SF samples were collected during glenohumeral or knee joint surgery from trauma controls and from OA and RA patients (n = 42). The FA composition of SF total lipids was analyzed by gas chromatography with flame ionization and mass spectrometric detection and compared across cohorts. The FA signatures of trauma controls were mostly uniform in both anatomical locations. RA shoulders were characterized by elevated percentages of 20:4n-6 and 22:6n-3 and with reduced proportions of 18:1n-9. The FA profiles of OA and RA knees were relatively uniform and displayed lower proportions of 18:2n-6, 22:6n-3 and total n-6 polyunsaturated FAs (PUFAs). The results indicate location- and disease-dependent differences in the SF FA composition. These alterations in FA profiles and their potential implications for the production of PUFA-derived lipid mediators may affect joint lubrication, synovial inflammation and pannus formation as well as cartilage and bone degradation and contribute to the pathogeneses of inflammatory joint diseases

Increased n-6 polyunsaturated fatty acids indicate pro- and anti-inflammatory lipid modifications in synovial membranes with rheumatoid arthritis

Abstract Emerging evidence suggests that fatty acids (FAs) and their lipid mediator derivatives can induce both beneficial and detrimental effects on inflammatory processes and joint degradation in osteoarthritis (OA) and autoimmune-driven rheumatoid arthritis (RA). The present study characterized the detailed FA signatures of synovial membranes collected during knee replacement surgery of age- and gender-matched OA and RA patients (n = 8/diagnosis). The FA composition of total lipids was determined by gas chromatography and analyzed with univariate and multivariate methods supplemented with hierarchical clustering (HC), random forest (RF)-based classification of FA signatures, and FA metabolism pathway analysis. RA synovium lipids were characterized by reduced proportions of shorter-chain saturated FAs (SFAs) and elevated percentages of longer-chain SFAs and monounsaturated FAs, alkenyl chains, and C20 n-6 polyunsaturated FAs compared to OA synovium lipids. In HC, FAs and FA-derived variables clustered into distinct groups, which preserved the discriminatory power of the individual variables in predicting the RA and OA inflammatory states. In RF classification, SFAs and 20:3n-6 were among the most important FAs distinguishing RA and OA. Pathway analysis suggested that elongation reactions of particular long-chain FAs would have increased relevance in RA. The present study was able to determine the individual FAs, FA groups, and pathways that distinguished the more inflammatory RA from OA. The findings suggest modifications of FA elongation and metabolism of 20:4n-6, glycerophospholipids, sphingolipids, and plasmalogens in the chronically inflamed RA synovium. These FA alterations could have implications in lipid mediator synthesis and potential as novel diagnostic and therapeutic tools

Susceptibility of low-density lipoprotein particles to aggregate depends on particle lipidome, is modifiable, and associates with future cardiovascular deaths

Abstract Aims: Low-density lipoprotein (LDL) particles cause atherosclerotic cardiovascular disease (ASCVD) through their retention, modification, and accumulation within the arterial intima. High plasma concentrations of LDL drive this disease, but LDL quality may also contribute. Here, we focused on the intrinsic propensity of LDL to aggregate upon modification. We examined whether inter-individual differences in this quality are linked with LDL lipid composition and coronary artery disease (CAD) death, and basic mechanisms for plaque growth and destabilization. Methods and results: We developed a novel, reproducible method to assess the susceptibility of LDL particles to aggregate during lipolysis induced ex vivo by human recombinant secretory sphingomyelinase. Among patients with an established CAD, we found that the presence of aggregation-prone LDL was predictive of future cardiovascular deaths, independently of conventional risk factors. Aggregation-prone LDL contained more sphingolipids and less phosphatidylcholines than did aggregation-resistant LDL. Three interventions in animal models to rationally alter LDL composition lowered its susceptibility to aggregate and slowed atherosclerosis. Similar compositional changes induced in humans by PCSK9 inhibition or healthy diet also lowered LDL aggregation susceptibility. Aggregated LDL in vitro activated macrophages and T cells, two key cell types involved in plaque progression and rupture. Conclusion: Our results identify the susceptibility of LDL to aggregate as a novel measurable and modifiable factor in the progression of human ASCVD