RESUMO
BACKGROUND: Continuous agitation during storage slows down the platelet storage lesions. However, in special circumstances, manual-mixing can be alternatively used to store products for short time periods without compromising platelet quality. Based on this finding, and given the role of shear stress in modulating receptor expression, we were interested in comparing the levels of platelet adhesion receptor, GPVI and platelet adhesion capacity under each storage condition. METHODS: Platelet concentrates (PCs) were divided into three groups: continuously-agitated PCs (CAG-PCs) with or without PP2 (Src kinase inhibitor) and manually-mixed PCs (MM-PCs). Platelet count/MPV, swirling, GPVI and P-selectin expression, GPVI shedding, platelet adhesion/spreading to collagen were examined during 5 days of storage. RESULTS: While MM- and CAG-PCs showed similar levels of P-selectin expression, GPVI expression was significantly elevated in MM-PCs with lower GPVI shedding/expression ratios, enhanced platelet adhesion/spreading and swirling in manually-mixed PCs. Of note, CAG-PCs treated with PP2 also demonstrated lower P-selectin expression and GPVI shedding, higher GPVI expression and attenuated swirling and spreading capability. CONCLUSION: Given the comparable platelet activation state in MM and CAG-PCs as indicated by P-selectin expression, enhanced platelet adhesion/spreading in MM-PCs, along with relatively higher GPVI expression here, supports previous studies demonstrating a role for biomechanical forces in modulating GPVI-dependent function. Thus, lower GPVI expression in CAG-PCs may be due to shear forces induced by agitation, which keeps this receptor down-regulated while also attenuating platelet adhesion/spreading capacities during storage. Low platelet function in PP2-CAG-PCs also highlights the importance of Src-kinases threshold activity in maintaining platelets quality.
RESUMO
BACKGROUND: Platelet storage is often complicated by deleterious changes that are started by reversible activation of the cells and can lead to procoagulant function and apoptosis during longer periods of storage. Given that increasing levels of reactive oxygen species (ROS) generation are associated with platelet activation and apoptosis, our study investigated whether ROS scavenging or the inhibition of ROS production can enhance the viability of stored platelets. METHODS: For this study platelet-rich plasma platelet concentrates (PRP-PCs) were either treated with ROS-reducing agents (1 mM N-acetyl-L -cysteine [NAC] or 30 µM NADPH oxidase [NOX] inhibitor, VAS2870) or kept untreated during storage. P-selectin expression, phosphatidylserine (PS) exposure, levels of microparticle (MP) formation, and intraplatelet caspase activity of PCs were analyzed by flow cytometry during 7 days of storage while the platelet viability was also evaluated by MTT assay. RESULTS: Both NAC- and VAS2870-treated platelets had significantly lower caspase activity, MP formation, and PS exposure during storage while they also showed improved viability. The platelet count and mean platelet volume (MPV) were also better preserved in the presence of NAC. CONCLUSION: Our results confirmed that either the inhibition of ROS generation or the scavenging of these oxidant agents can attenuate platelet apoptosis while improving their viability during storage. In this study, the significant improvement of platelet viability obtained by NAC suggested that its supplementation with a designated safe concentration into PCs may better preserve the quality of these products, especially for longer storage.
