BACKGROUND: Biochemical analyses of mechanisms triggered in platelets (PLTs) upon pathogen inactivation (PI) are crucial to further understand the impact of PI on PLT functionality and, subsequently, quality.
STUDY DESIGN AND METHODS: PLT concentrates(PCs) were split into four small illumination bags: 1) untreated control, 2) treated with riboflavin and ultraviolet light (RF/UV), and spiked with 3) solvent control dimethyl sulfoxide and 4) p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 before RF/UV treatment. Flow cytometry was used to monitor PLT mitochondrial potential (DW m ); generation of intracellular reactive oxygen species (ROS); and release of microvesicles (MVs), mitochondria (MT), and MVs containing MT (MVs/ MT). Quantitative polymerase chain reaction (qPCR) was used to quantify extracellular mitochondrial DNA (mtDNA). Translocation of selected mitochondrial proteins was analyzed in subcellular fractions by immunoblot.RESULTS: RF/UV treatment triggered an increased mitochondrial translocation of both Bax and Bid (p < 0.05, Day 7) and cytochrome c release (p < 0.01, Day 7), loss of DW m (p < 0.05, Day 5 and Day 7), and ROS generation (p < 0.01, Day 5 and Day 7) in PCs compared to the untreated control during storage. These PI-triggered changes were inhibited by SB203580 (p < 0.05). The release of MVs, MT, and MVs/MT was increased upon the RF/UV treatment during storage (p < 0.05) and, with the exception of MT, the release was decreased by the inhibitor (p < 0.05). qPCR analysis showed that RF/UV does not trigger mtDNA release during storage.
CONCLUSION:These findings further our understanding of mechanisms in PLTs initiated by the RF/UV treatment, demonstrating that this treatment induces p38 MAPK-dependent mitochondrial signaling and MV release in apheresis PCs. R iboflavin and ultraviolet light (RF/UV) treatment is one of several pathogen inactivation (PI) technologies currently available.1 These treatments aim to target the replication and/or proliferation mechanism of pathogens and to destroy residual white blood cells (WBCs) to improve the safety of blood 14,15,25 The aim of this study was to evaluate the effects of RF/UV treatment on PLT mitochondrial function and signaling, including the recently discovered release of MT by PLTs, and to determine whether p38 is involved in the modulation of these mechanisms.
MATERIALS AND METHODS
MaterialsCommon chemicals were purchased from Sigma-Aldrich or Fisher Scientific. SB203580, a p38 MAPK inhibitor, was purchased from Santa Cruz Biotechnology.
Apheresis PC preparationThis study was approved by the research ethics board of Canadian Blood Services and informed consent was obtained from all healthy volunteers before blood donation. Phlebotomy and plateletpheresis were carried out by the NetCAD development laboratory of Canadian Blood Services (Vancouver, Canada) using a Trima Accel (TerumoBCT).
RF/UV treatment and inhibitor studyThe SB inhibitor stock solution in dimethyl sulfoxide (DMSO) was diluted in phosphate-buffered saline (PBS) and...