Reduction of monocyte-platelet interaction and monocyte activation in patients receiving antiplatelet therapy after coronary stent implantation

Background. Monocyte activation induces different procoagulant and proadhesive inflammatory responses and thus may play a role in thrombotic complications after coronary interventions. Monocyte-platelet interaction may trigger these effects inducing monocyte activation. Aims. To characterize the effect of antiplatelet vs anticoagulation therapy on monocyte-platelet interaction and monocyte function after intracoronary stenting. Methods and Results. Immediately before, and during the first 12 days after successful coronary stenting, monocyte-platelet conjugates and monocyte function were assessed by flow cytometric detection of GPIIb/IIIa (CD41) on monocytes and by monocyte surface exposure of Mac-1 (CD11b/CD18) and L-selectin (CD62L). Twenty patients receiving combined antiplatelet therapy (ticlopidine, aspirin) were compared to 20 patients with standard anticoagulation (phenprocoumon, overlapping heparin, aspirin). Before stenting, monocyte-platelet conjugates and Mac-1 surface expression in both groups were significantly increased, while L-selectin was significantly diminished. Anticoagulation did not change these variables significantly during the subsequent 12 days. In contrast, antiplatelet therapy reduced platelet-monocyte conjugates by 46 ± 9.3% (mean ± SEM, P = 0.0019) within 4 days, which was associated with a decrease in Mac-1 expression (28 ± 6.7%, P = 0.0013) and an increase in L-selectin (56 ± 15.0%, P = 0.0061). Conclusion. After intracoronary stenting, combined antiplatelet therapy, but not anticoagulation, causes reduction of monocyte-platelet interaction, which is associated with monocyte deactivation. This may contribute to decreased risk for thrombotic events.