Tirofiban potentiates agonist-induced platelet activation and degranulation, despite effectively inhibiting aggregation

Abstract

We aimed to investigate the effects of integrin αIIbβ3 inhibitor tirofiban on hallmarks of platelet activation, degranulation, and aggregation during its use to analyze activated but non-complexed platelets via flow cytometry. To do so, we used washed platelets from healthy human donors. We combined aggregometry, an assay of platelet functionality, with flow cytometry and ELISA to detect and correlate, respectively, platelet aggregation, activation, and granule release. While tirofiban effectively inhibited agonist-induced platelet aggregation (thrombin receptor-activating peptide 6 (TRAP), convulxin (CVX), U46619 and IV.3), the surface expression of P-selectin and CD63 and granule release of RANTES were significantly increased, indicating that tirofiban enhances degranulation, uncoupled from aggregation. The results show that tirofiban alters the activation phenotype of platelets, something that should be considered when using tirofiban to enable flow cytometric analysis of activated but unaggregated platelet suspensions.

Keywords:

• platelet activation
• platelet aggregation
• platelet degranulation
• platelet inhibition
• tirofiban

Acknowledgement

We would like to thank Prof Ruland and Linda Bachmann (TUM, Munich) for kindly providing access to flow cytometry instrumentation FACSCanto II.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/09537104.2022.2078489

Additional information

Funding

This work was supported by the Austrian Science Fund (FWF) [UE10207024_07]; Gesellschaft für Thrombose- und Hämostaseforschung [Rudolf-Marx Stipendium]; Literar Mechana [Doktoratsfertigstellungsstipendium]; Universität zu Lübeck [Clinician Scientist Program]; Deutsche Forschungsgemeinschaft (DFG) CRU-303 Project 7 and CRC-1526 Project A5 (both to A.V.).