OBJECTIVETo investigate the in vitro effects of immune inhibitor tacrolimus on platelet function.

METHODSFresh venous blood was collected from healthy volunteers at ages of 18-25 years old, who are not taking antiplatelet drugs within two weeks. The platelets were isolated from the blood and incubated with different concentrations of tacrolimus (0.06, 0.6, 6, 60, 120, 240 μmol/L) at 37 °C for 2 hours, and then the changes of mitochondrial membrane potential and P-selection of platelets were detected by flow cytometry, the expression of apoptosis related protein by Western Blot, and the change of the platelet aggregation function by platelet aggregation analyzer.

RESULTSTacrolimus at concentration of 0.06 μmol/L could promote collagen induced platelet aggregation, inhibit thrombin induced platelet aggregation, have no effect on ristocetin and vWF induced platelet aggregation function. Tacrolimus at concentration of 120 μmol/L and 240 μmol/L could reduce the platelet mitochondrial membrane potential and induce the expression of apoptosis protein caspase-3.

CONCLUSIONIn vitro experimental results showed that high concentration of tacrolimus could lead to platelet apoptosis. But the current therapeutic dose of tacrolimus at 0.06 μmol/L (which is equivalent to 50 ng/ml blood concentration) could have different effects on platelet aggregation function according to different stimulating agents.