Recombinant thrombomodulin (rTM) suppresses the activity of extracellular histones.

(A) Binding assays with a quartz crystal microbalance (QCM) twin sensor system. Two channels of a sensor chip were coated with either histones (1 mg/ml) or BSA (1 mg/ml). The sensor chip was placed into the NAPiCOS Auto and then perfused with rTM (1 mg/ml). The interaction between molecules was recognized as the change in frequency of a quartz crystal resonator. (B) Inhibition of histone H4-mediated platelet aggregation by rTM. Washed platelets were stimulated with histone H4 (5 µg/ml) preincubated with rTM (5-25 µg/ml) or BSA (25 µg/ml). rTM, but not BSA, inhibited histone-induced platelet aggregation (n = 3-7 per group, mean ± S.D.). (C) Inhibition of histone H3-induced platelet aggregation by rTM. Washed platelets were stimulated with histone H3 (25 µg/ml) or collagen (1.44 µg/ml) in the presence or absence of rTM (15 µg/ml). rTM inhibited histone-induced platelet aggregation, but not collagen-induced platelet aggregation. Representative data of three independent experiments are shown. ** P < 0.01 compared with the histone-alone group.