PB0875 - Mechanosensitive Ion Channels Piezo1 in Red Blood Cells are Involved in Platelet-Driven Blood Clot Contraction

Background: Piezo1 is a mechanosensitive cationic channel expressed in many cell types, including blood cells. Piezo1 opens in response to mechanical perturbation of the plasma membrane, resulting in a boost of intracellular [Ca2+]i. Since platelet-driven contraction of blood clots is followed by compression of red blood cells (RBCs), it is conceivable that mechanical activation of Piezo1 in RBCs followed by Ca2+ influx can change cell deformability and/or platelet contractility, thus modulating clot contraction.

Aims: To reveal if Piezo1 channels in RBCs and platelets play a role in the contraction of blood clots.

Methods: Effects of a Piezo1 agonist, Yoda1 (5 μM), and antagonist, GsMTx-4 (1 μM), on clot contraction in vitro were studied in fresh human blood anticoagulated with a corn trypsin inhibitor to keep the physiological [Ca2+]. Clot formation and contraction were induced by thrombin (1 U/ml) either in whole blood or in platelet-rich plasma, and the clot shrinkage was followed using an optical tracking system.

Results: Adding the Piezo1 agonist Yoda1 to whole blood before clotting increased the rate and extent of clot contraction significantly compared to control (p=0.025). In platelet-rich plasma Yoda1 caused the opposite effect, with a moderate decrease in the rate and extent of clot contraction (p=0.06), perhaps by competing with the natural Piezo1 activation in distorted platelets. Adding the Piezo1 antagonist, GsMTx-4, caused a marked decrease in the rate and extent of clot contraction relative to control both in whole blood and in platelet-rich plasma (p=0.0006 and p=0.01, respectively).

Conclusion(s): Activation of Piezo1 channels in RBCs enhances contraction of blood clots, likely mimicking the mechanical activation of Piezo1 in compressed RBCs during platelet-induced clot shrinkage. The subsequent Ca2+ influx in RBCs could affect their rigidity and promote platelet contractility via biomechanical feedback, ATP/ADP release or cause phosphatidylserine exposure followed by enhanced thrombin generation.