Platelet-derived microparticles induce polymorphonuclear leukocyte-mediated damage of human pulmonary microvascular endothelial cells

BackgroundPlatelets (PLTs) stored at 22 degrees C accumulate microparticles and biologic response modifiers (BRMs) that induce inflammatory reactions in transfusion recipients. However, soluble BRMs are fully diluted in the recipient's blood circulation. The mechanisms by which BRMs exert their effects have not been elucidated. The objectives of this study were to determine the effect of PLT microparticles (PMPs) on polymorphonuclear leukocyte (PMN)-mediated human pulmonary microvascular endothelial cell (HMVEC) damage and determine the role of soluble CD40 ligand (sCD40L). Study Design and MethodsPMPs were isolated from apheresis PLT concentrates. We used a two-insult in vitro model of HMVEC damage to investigate the effects of PMP and sCD40L and role of apocynin, an inhibitor of PMN respiratory burst. Their priming activities were measured using hydrogen peroxide production. The expression of intercellular cell adhesion molecule-1 (ICAM-1) and integrin M (CD11b) were also determined. ResultsLipopolysaccharide (LPS)-activated HMVEC damage and PMN respiratory burst depend on the presence of PMP and the concentration of sCD40L. PMP-induced PMN-mediated HMVEC damage was significantly reduced by apocynin-treated PMNs (p<0.05). The surface expression of ICAM-1 on HMVEC was increased by LPS stimulation. The expression of CD11b on PMNs was increased by PMP priming. Blocking ICAM-1 with a monoclonal antibody (MoAb) CD54 significantly reduced HMVEC damage (p<0.05). The treatment of endothelial cells but not PMN with a MoAb targeting CD40 failed to prevent the HMVEC damage caused by PMPs (p>0.05). ConclusionPMPs carry a concentrated CD40L signal, promote PMN-mediated HMVEC damage, and may affect the development of transfusion-related acute lung injury.