Increased production of leukocyte microparticles with enhanced expression of adhesion molecules from activated polymorphonuclear leukocytes in severely injured patients

Background: Polymorphonuclear leukocyte (PMNL)-derived microparticles (MPs) have been recently reported as activators of vascular endothelium in vitro; The objectives of the present study were to evaluate the production of MPs in severely injured patients and to clarify the role of these MPs. Methods: Thirty severely injured patients (mean Injury Severity Score of 27 +/- 11) and 21 healthy volunteers participated in the study. Blood samples were obtained serially at three time points: days 0 to 1, days 2 to 5, and days 6 to 12 after the trauma event. NIP production, CD11b and CD62L expression on MPs, and oxidative activity in PMNLs were measured by flow cytometry in both the presence and absence of formylmethionyl-leucyl-phenylalanine. Expressions of CD11b and CD62L were differentially evaluated according to the size of the MPs (greater than or equal to or < 1.0 mum). Soluble E-selectin and thrombomodulin levels in blood, variables representative of systemic vascular endothelial damage, were also measured. Results: Production of MPs with and without formylmethionyl-leucyl-phenylalanine and the oxidative activity in PMNLs (O-2(-)) were prominently increased on days 2 to 5 after trauma. CD62L expression was enhanced on MPs at all three time points, and CD11b expression was enhanced on MPs < 1.0 mum in diameter at all three time points. Soluble E-selectin and thrombomodulin in blood did not change significantly between time points. Conclusion: Activated PMNLs enhance production of PMNL-derived MPs with increased adhesion molecule expression on days 2 to 5 after severe trauma. This response per se, however, may not progress to systemic vascular endothelial damage.