Activated platelets enhance microparticle formation and platelet-leukocyteinteraction in severe trauma and sepsis

Background: activated platelets have been recently reported to produce plat elet microparticles and to enhance platelet-leukocyte interaction. The prec ise role of platelets in systemic inflammatory response syndrome (SIRS) has not been clarified. The objective of this study was to evaluate microparti cle formation acid platelet-leukocyte interaction in severe trauma and seps is. Methods: Twenty-six patients with severe SIRS (SIRS criteria and serum C-re active protein > 10 mg/dL) and 12 healthy volunteers were studied. The seve re SIRS was caused by trauma in 12 patients and sepsis in 14, Microparticle formation, P-selectin expression on platelets, platelet-monocyte binding, and platelet-polymorphonuclear leukocyte (PMNL) binding were measured by fl ow cytometry in the presence or absence of ionomycin, N-formyl-methionyl-le ucyl-phenylalanine, or anti-CD62p monoclonal antibody. Soluble P-selectin, thrombomodulin, neopterin, and PMNL elastase in blood were also measured. Results: Microparticle formation, P-selectin expression on platelets, plate let-monocyte binding with or without ionomycin, and platelet-PMNL binding w ith ionomycin significantly increased in patients with severe SIRS in compa rison with values in normal volunteers. The increased platelet-leukocyte bi nding in severe SIPS patients was markedly inhibited by P-selectin blockade and was not enhanced by N-formyl-methionyl-leucyl-phenylalanine, Soluble P -selectin, thrombomodulin, neopterin, and PMNL elastase in blood also incre ased in these patients. Conclusion: Activated platelets enhance microparticle formation and platele t-leukocyte interaction in severe trauma and sepsis, Enhanced platelet-leuk ocyte interaction is dependent on P-selectin expression and may be involved in the systemic inflammatory response after severe inflammatory insult.