Mitochondrial Calcium Uniporter: A Potential Target to Modulate Procoagulant Platelets

Introduction Procoagulant platelets are a subpopulation of highly activated platelets that are generated by strong stimulation and acquire the ability to promote thrombin generation at the site of vascular injury. They exhibit on their surface negatively-charged phosphatidylserine that facilitate the formation of tenase and prothrombinase complexes. In procoagulant platelets, dual stimulation with thrombin and convulxin leads to persistently high levels of cytosolic calcium (Ca 2+ ), whichis transported to the mitochondrial matrix via mitochondrial calcium uniporter (MCU), eventually triggering mitochondrial depolarization and opening of mitochondrial permeability transition pores (mPTP). Several studies including our own have shown MCU as a key regulator of the generation of procoagulant platelets. Therefore, in our current work we target MCU pharmacologically to modulate the formation of procoagulant platelets. Method MCU was inhibited by treating platelets with Ru265. Platelets were then stimulated with increasing concentrations of thrombin (THR) and convulxin (CVX) individually or in combination (THR+CVX). Platelet procoagulant properties were assessed by flow cytometry using immunofluorescent labeling with PAC-1 (binding the activated fibrinigen receptor) and Annexin V (binding negatively-charged phosphotidylserine). Mitochondrial function was assessed by measuring mitochondrial membrane potential using TMRM. Results THR alone (0.5 U/ml) induced: (i) ~80% aggregating platelets (PAC-1+ve), which were slightly reduced (less than 10%) in presence of Ru265; and (ii) ~5% procoagulant platelets (PAC-1 -ve and Annexin-V+ve), with no change in presence of Ru265. CVX alone (500 ng/ml) induced: (i) ~70% aggregating platelets, and (ii) ~10% procoagulant platelets; both activation endpoints showed a trend to slight reduction in presence of Ru265. The combination of THR (0.5 U/ml) and CVX (500 ng/ml) induced: (i) ~40% aggregating platelets and (ii) ~60% procoagulant platelets. Remarkably, in presence of Ru265, aggregating platelets increased (sic!) to ~70% and procoagulant one decreased to ~30%. Ru265 dose-dependently prevented both mitochondrial depolarization and the formation of procoagulant platelets. Conclusion Our data demonstrates that when platelets are activated simultaneously by THR and CVX, MCU inhibition with Ru265 reduces procoagulant platelet formation by preventing calcium-dependent mitochondrial depolarization and thus maintain the platelets in an aggregating activation state. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany