Key Points
- To determine how the thrombin receptors PAR1 and PAR4 differentially regulate human platelet aggregation at agonist concentrations typical of local thrombus formation.
- Examined human platelet aggregation, Rap1 activation, and GPIIbIIIa activation following stimulation with thrombin, PAR1, and PAR4 agonists.
- Evaluated platelet responses under conditions of dual inhibition targeting calcium mobilization and the P2Y12 receptor at high agonist concentrations.
- Dual inhibition of the P2Y12 receptor and calcium mobilization completely blocked PAR4-mediated aggregation, whereas it had no inhibitory effect on PAR1- or thrombin-mediated aggregation.
- Both PAR1- and PAR4-mediated aggregation operated independently of calcium mobilization alone.
- P2Y12 receptor activation was dispensable for PAR-mediated aggregation at elevated agonist levels and was only partially required for downstream Rap1 and GPIIbIIIa activation.
Structured PICO
PPopulationHuman platelets
IInterventionDual inhibition of the P2Y12 receptor and calcium mobilization
OOutcomePlatelet aggregationsurrogate
At high local concentrations of thrombin, platelet aggregation is signaled through PAR4 rather than PAR1 and may be regulated through purinergic feedback, identifying a potential target for therapeutic intervention.