Selective triggering of platelet apoptosis, platelet activation or both

Abstract

SummaryAnucleate platelets perform two fundamental processes, activation and apoptosis. We elaborated an approach for selective and concurrent stimulation of platelet apoptosis and/or activation, processes important in haemostasis and platelet clearance. Human platelets were treated with BH3 mimetic ABT-737, thrombin, calcium ionophore A23187 and matched diluents. Apoptosis was determined as mitochondrial inner membrane potential (DΨm) depolarization and activation as P-selectin exposure. At optimal treatment conditions (90-180 min, 37°C), ABT-737 predominantly induced apoptosis, when 77-81% platelets undergo only DΨm depolarization. The ABT-737 impact on DΨm depolarization is strongly time-and temperature-dependent, and much higher at 37°C than at room temperature. In contrast, when platelets were treated with thrombin for 15-90 min at either temperature, activation-only was predominantly (79-85%) induced, whereas A23187 triggers both apoptosis and activation (73-81%) when platelets were treated for 15-60 min at 37°C or 15-90 min at room temperature. These data demonstrate that, depending on the triggering stimulus, platelets predominantly undergo DΨm depolarization-only, P-selectin exposure-only, or both responses, indicating that platelet apoptosis and activation are different phenomena driven by different mechanisms. The described model provides a basis for studying differential pharmacological manipulation of platelet apoptosis and activation and their role in haemostasis, thrombosis and platelet clearance.

Riboflavin and UV light treatment of platelets: a protective effect of platelet additive solution?

“…Despite the fact that a rise in CD62P expression and annexin A5 binding are almost always seen together, in our study we find a decoupling of the two processes, which has been described recently in vitro using different stimuli. 27 As reviewed in detail elsewhere, 28 mitochondrial depolarization and annexin A5 positivity are linked through an apoptosis pathway: apoptosis is triggered by, for example PRT; this lowers the membrane potential which in turn activates caspases, which ultimately lead to phosphatidylserine exposure, which is measured by annexin A5 binding. Thus, PLT metabolism and apoptosis are not always linked to degranulation and activation, although they might be synergistic or happen together when other pathways are performing at full power.…”

Enhanced platelet apoptosis in chronic uremic patients

“…PS exposure is assumed to be a typical event in both platelet activation and apoptosis. 22 However, the signaling pathways leading to PS exposure are quite different between these two processes. For the sake of distinguishing platelet apoptosis from platelet activation, P-selectin was analyzed parallelly and the data excluded the possibility of platelet activation (p ¼ 0.14).…”

Role of mitochondrial membrane permeabilization and depolarization in platelet apoptosis

“…Mitochondrial membrane permeabilization and dissipation of mitochondrial transmembrane potential (DΨm depolarization) are frequently used as markers of apoptosis in nucleated cells (Appendix S1, references 2-5) and in anucleate platelets (Leytin, 2012;Gyulkhandanyan et al, 2013Gyulkhandanyan et al, , 2014Gyulkhandanyan et al, , 2015. Two pathways of mitochondrial permeabilization have been reported in nucleated cells.…”