Abstract
Background: Adrenaline is believed to play a role in thrombosis and hemostasis. The complex effect of its clinically relevant concentrations on thrombus formation, coagulation and fibrinolysis in human blood has never been specifically studied.Methods: Confocal microscopy was used to study thrombus formation under flow, exposure of phosphatidylserine (PS) in adhered platelets, to evaluate clots density, and to measure kinetics of fibrin formation and external fibrinolysis under flow. Flow cytometry was utilized to assess PS exposure in non-adhered platelets. Kinetics of clot formation and internal fibrinolysis was evaluated by thromboelastometry. Platelet aggregation was measured by optical aggremometry. Kinetics of clot retraction was assessed by using digital camera.Results: We found that adrenaline (1–10 nM) is able to enhance platelet activation evoked by subthreshold collagen (150 ng/ml), resulting in augmentation of platelet aggregation, thrombus formation under arterial flow conditions, platelet PS exposure, and formation of platelet-fibrin clots. The development of platelet procoagulant response evoked by adrenaline + low collagen was associated with the formation of denser platelet-fibrin clots and the decrease in rate of fibrinolysis despite whether lysis was initiated inside (internal fibrinolysis) or outside the clot (external fibrinolysis). The above phenomena were abolished by the α2-adrenergic receptor antagonist, rauwolscine. Adrenaline-collagen synergism, expressed as PS exposure, was significantly reduced by cyclooxygenase inhibitor (acetylsalicic acid), GPIIb/IIIa receptor blocker (tirofiban), and P2Y12 receptor antagonist (PSB 0739).Conclusion: Clinically relevant concentrations of adrenaline may significantly augment responses of human platelets in the presence of subthreshold concentrations of collagen, which should be considered during therapies involving adrenaline infusion. Routinely used antiplatelet drugs may reduce the prothrombotic state evoked by adrenaline-collagen synergism.
Highlights
Adrenaline is a catecholamine hormone engaged in a broad spectrum of human physiology, released into the bloodstream after the stimulation of sympathetic nervous system (Goldstein, 2010)
To investigate whether adrenaline may modulate platelet adhesion in a shear-dependent manner, we recorded platelet accumulation on collagen under flow conditions corresponding with two arterial shear rates (1,000 and 1,600 s−1)
At a shear rate 1,600 s−1 adrenaline (1 nM) enhanced platelet adhesion to collagen; this effect was reduced by rauwolscine (Figure 1B)
Summary
Adrenaline (epinephrine) is a catecholamine hormone engaged in a broad spectrum of human physiology, released into the bloodstream after the stimulation of sympathetic nervous system (Goldstein, 2010). The concentration of adrenaline in human blood has been estimated to vary from below 1 nM up to 20 nM during severe stress reaction (Dimsdale and Moss, 1980; Seiss et al, 1982; Ardlie et al, 1985). The research points to the involvement of Na+/H+ exchanger (Steen et al, 1989), arachidonic acid cascade (Cameron and Ardlie, 1982), and PI-3K kinase (Selheim et al, 2000) in adrenaline-evoked platelet activation. The complex effect of its clinically relevant concentrations on thrombus formation, coagulation and fibrinolysis in human blood has never been studied
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