Objective: To explore the effects of sirolimus upon endothelial thrombotic function of human umbilical vein endothelial cells (HUVEC).
Methods: Sirolimus was added into the in vitro cultured HUVEC at the concentrations of 0 (control), 0.1, 1 and 10 ng/ml. At 2, 4, 8, 12 and 24 h post-incubation, the cells were harvested for determination of tissue factor (TF), plasminogen activator inhibitor (PAI-1), endothelial nitric oxide synthase (eNOS) and thrombomodulin (TM) expression by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The clotting functions of HUVEC were assayed by an automated coagulation analyzer.
Results: Sirolimus induced the expressions of TF and PAI-1 and inhibited the expressions of eNOS and TM in a concentration-dependent manner. The maximal change of mRNA expression was observed at 8 h and remained up to at least 24 h. And the most marked change of protein expression (65% reduction in eNOS expression, 52% reduction in TM, 1.7-fold increase in PAI-1 and 2.8-fold increase in TF) was at 12 h. The clotting time in sirolimus group (89 s ± 9 s) was significantly shorter than that in control group (152 s ± 17 s, P = 0.005).
Conclusion: Sirolimus induces endothelial antithrombotic dysfunction and shortens the clotting time through an elevated expression of prothrombotic genes TF and PAI-1 and a lowered expression of antithrombotic genes eNOS and TM. It may be one of mechanisms of thrombosis after the implantation of sirolimus-eluting stents.