Altered activation of integrin ɑIIbβ3 on platelets irradiated with ultraviolet C from pathogen-reducing xenon flash

Irradiation of platelets with filtered xenon (fXe) flash for pathogen inactivation increases PAC-1 binding, but does not cause discernible aggregation. We aimed to determine whether PAC-1-positive platelets irradiated with fXe flash can bind to fibrinogen. Apheresis-collected platelets (Aph-PLTs) were irradiated with fXe flash (fXe-PLTs). Activation of integrin αIIbβ3 was determined by the binding of PAC-1, fibrinogen Alexa Fluor 488-conjugate (fibrinogen-AF488), and anti-fibrinogen antibody (clone 9F9) using flow cytometry under resting or ADP-stimulated conditions. PAC-1 binding to fXe-PLTs increased in an fXe flash dose-dependent manner. The fraction of PAC-1 binding to fXe-PLTs suspended in either phosphate-buffered saline (PBS) or plasma was larger than that to Aph-PLTs in a resting state. However, no difference of fibrinogen-AF488 binding between fXe-PLTs and Aph-PLTs in PBS was observed under either resting or ADP-stimulated conditions. The binding of anti-fibrinogen to fXe-PLTs in plasma was marginally increased compared with Aph-PLTs, but the magnitude of the positive fraction was significantly smaller than that of PAC-1. Pathogen-inactivating fXe irradiation per se did not induce fibrinogen binding to platelets, while PAC-1 binding was increased in a resting state. On the other hand, the fraction of fibrinogen binding was equivalent to that of PAC-1 under ADP-stimulated conditions.