Bioactive lipids accumulate in stored red blood cells despite leukoreduction: a targeted metabolomics study.

BACKGROUND: Accumulation of bioactive lipids during red blood cell (RBC) storage has been identified as a potential source of posttransfusion sequelae in vulnerable populations. Typically, white blood cells (WBCs) have been implicated in the generation of bioactive lipids, and leukoreduction has been seen as a solution to this issue. STUDY DESIGN AND METHODS: We developed a targeted metabolomics approach with isotope dilution to quantify a panel of bioactive lipids in both leukoreduced (LR) and nonleukoreduced (NLR) RBC units over the course of storage. RESULTS: Leukoreduction greatly attenuated the production of 12-hydroxyeicosatetraenoic acid (HETE), 12-hydroxyeicosapentaenoic acid, and 14-hydroxydocosahexaenoic acid (HDoHE), all three of which are mediated by 12-lipoxygenase present in WBCs and platelets. However, despite leukoreduction, micromolar levels of linoleic acid (LA), arachidonic acid (AA), and docosahexaenoic acid (DHA) were observed in the RBC units stored for 42 days. These major polyunsaturated fatty acids (PUFAs) and their oxidation products (oxylipins) also significantly increased with storage time, including 5-, 8-, 9-, 11-, 12-, and 15- HETEs from AA; 9- and 13-hydroxyoctadecadienoic acid (HODE); 9-, 10-, and 12,13-dihydroxyoctadecenoic acids from LA; and 14-, 16-, and 17-HDoHEs from DHA. The majority of PUFAs and oxylipins accumulated in the supernatant fraction. Large donor-to-donor variations were observed in both LR-RBC and NLR-RBC units. CONCLUSION: While the exact role the accumulation of PUFAs and oxylipins plays in RBC unit quality and transfusion medical outcomes remains undetermined, the analytes of interest in this study may serve as biomarkers for lipid degradation and oxidation during storage and may induce changes in human physiology upon transfusion.

Metabolites in stored platelets associated with platelet recoveries and survivals.

BACKGROUND: Transfusion of platelets (PLTs) is a common therapy in a number of clinical settings. However, it is well understood that there is substantial donor-to-donor variation in how well PLTs store and thus the quality of the products that are transfused. The basis of such variation is poorly understood, and there are limited metrics by which units of PLTs can be assessed for their posttransfusion performance. It has repeatedly been demonstrated that myriad biologic changes take place during PLT storage; however, which of the changes correlate with quality of the stored PLTs and/or are mechanistically involved in PLT function remains undetermined. STUDY DESIGN AND METHODS: The current study tested stored PLTs from 21 normal subjects, combining high-resolution metabolomics of stored PLTs with in vivo PLT recoveries and survivals. Both individual analytes and metabolic pathways that correlate with posttransfusion PLT viability were identified. RESULTS: Caffeine metabolites were associated with poor PLT recovery; caffeine metabolism was not ongoing in the PLT bag and remained at prestorage levels. Acylcarnitines, particular fatty acid metabolites, and oxidized fatty acids were associated with poor PLT survivals. Of the myriad metabolic changes during PLT storage, these are the first reported metabolic findings to begin distinguishing which changes are of functional importance regarding posttransfusion PLT performance. CONCLUSIONS: Together, these findings provide novel mechanistic insights into the functional biology of the PLT storage lesion as well as identifying potential targets for modifying donor environment (e.g., caffeine consumption) and also metrics of quality assessment for stored human PLTs.

Aquatic photochemistry of isoflavone phytoestrogens: degradation kinetics and pathways.

Isoflavones are plant-derived chemicals that are potential endocrine disruptors. Although some recent studies have detected isoflavones in natural waters, little is known about their aquatic fates. The photochemical behaviors of the isoflavones daidzein, formononetin, biochanin A, genistein, and equol were studied under simulated solar light and natural sunlight. All of these phytoestrogens were found to be photolabile under certain conditions. Daidzein and formononetin degraded primarily by direct photolysis. Their expected near-surface summer half-lives in pH 7 water at 47° latitude are expected to be 10 and 4.6 h, respectively. Biochanin A, genistein, and equol degraded relatively slowly by direct photolysis at environmentally realistic pH values, though they showed significant degradation rate enhancements in the presence of natural organic matter (NOM). The indirect photolysis rates for these compounds scaled with NOM concentration, and NOM from microbial origin was found to be a more potent photosensitizer than NOM from terrestrial sources. Mechanistic studies were performed to determine the indirect photolysis pathways responsible for the rate enhancements. Results of these studies implicate reaction with both singlet oxygen and excited state triplet NOM. Environmental half-lives for biochanin A, genistein, and equol are expected to vary on the basis of pH as well as NOM source and concentration.