The myeloperoxidase product, hypochlorous acid, reduces thrombus formation under flow and attenuates clot retraction and fibrinolysis in human blood

• Published in: Free radical biology & medicine 2019-09, Vol.141, p.426-437
• Main Authors: Misztal, Tomasz, Golaszewska, Agata, Tomasiak-Lozowska, Maria Magdalena, Iwanicka, Marta, Marcinczyk, Natalia, Leszczynska, Agnieszka, Chabielska, Ewa, Rusak, Tomasz
• Format: Article
• Language: English
• Subjects: Clot architecture; Clot retraction; Dityrosine; Fibrinogen modifications; Fibrinolysis; Hemostasis; HOCl; Hypochlorous acid; Myeloperoxidase; Platelets; Thrombus formation under flow
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2019.07.003

Hypochlorite (HOCl), a strong oxidant and antimicrobial agent, has been proposed to be associated with hemostatic abnormalities during inflammatory response. However, its complex impact on hemostasis is not completely understood. In this report we studied the effect of clinically relevant (micromolar) HOCl concentrations on thrombus formation under flow, kinetics of platelet-fibrin clot formation, its architecture, retraction, and lysis. We found that HOCl (up to 500 µM) did not affect kinetics of coagulation measured in whole blood. HOCl (500-1000 µM) markedly diminished thrombus formation under flow. Clot retraction rate was reduced by HOCl dose-dependently (50-500 µM). HOCl (125-500 µM) inhibited fibrinolysis in whole blood and in platelet-depleted plasma, dose-dependently. Activity of plasmin was reduced by HOCl at concentrations started from 500 µM. HOCl (up to 500 µM) did not reduce plasminogen binding to fibrin under flow. HOCl (125-500 µM) modulated architecture of fibrin- and platelet-fibrin clots towards structures made of thin and densely packed fibers. Exposure of pure fibrinogen to HOCl (10-1000 µM) resulted in formation of dityrosine and was associated with altered fibrin structure derived from such modified fibrinogen. HOCl-altered fibrin net structure was not related with modulation of platelet procoagulant response, thrombin generation, and factor XIII activity. We conclude that, in human blood, clinically relevant HOCl concentrations may inhibit thrombus formation under flow, clot retraction and fibrinolysis. Fibrinolysis and clot retraction seem to be the most sensitive to HOCl-evoked inhibition. HOCl-modified fibrinogen and altered clot structure associated with it are likely to be primary sources of attenuated fibrinolysis. [Display omitted] •Inflammation is associated with formation of large quantities of HOCl.•We tested the hypothesis that HOCl may affect hemostasis in humans.•HOCl inhibited thrombus formation under flow, clot retraction, and fibrinolysis.•Inhibition of fibrinolysis was associated with the formation of denser fibrin net.•HOCl-evoked fibrinogen modifications are likely cause of altered fibrin structure.