Regulation of platelet-leukocyte interaction in simulated ECC: attenuation with heparin surface modification

Background

Blood exposure to artificial surfaces results in blood cell activation. The present study analyses the impact of heparin immobilisation in a model of simulated extracorporeal circulation SECC on leukocyte and platelet activation, expression of surface markers and adhesion receptors, as well as on leukocyte-platelet interaction.

Methods

Fresh heparinized human blood was recirculated in in vitro cardiopulmonary bypass circuits (untreated: n = 10; coated n = 10; randomized, blinded for group affiliation). Samples were taken before and 15, 30, 60, 120, and 180 min after commencement of circulation. By means of flow cytometry neutrophil activation (respiratory burst; expression of CD11b), platelet activation (GpIb and GMP140 expression), as well as numbers of monocytes/PMNs binding platelets were assessed.

Results

Blood cell activation and interaction demonstrated ECC-dependent dynamics. SECC produced significant PMN activation and platelet GMP140 expression. Monocytes bound more platelets and at an faster rate than PMNs. In the group with heparin-coated surfaces PMN activation was significantly reduced, GMP140 expression less upregulated and leukocyte-platelet adhesion diminished.

Conclusions

Heparin coating in SECC reduces neutrophil and platelet activation and attenuates leukocyte-platelet adhesion. These studies indicate that there are cross-links between hemostatic and inflammatory disorders associated with ECC.