Increased Production of Leukocyte Microparticles with Enhanced Expression of Adhesion Molecules from Activated Polymorphonuclear Leukocytes in Severely Injured Patients

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Abstract
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. MP 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 (≥ or < 1.0 μm). 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 (O2−) 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 μm 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.