Endogenous Tissue Plasminogen Activator Enhances Fibrinolysis and Limits Thrombus Formation in a Clinical Model of Thrombosis

Abstract

Objective-Using a clinical model of deep arterial injury, we assessed the ability of exogenous and endogenous tissue plasminogen activator (t-PA) to limit acute in situ thrombus formation. Approach and Results-Ex vivo thrombus formation was assessed in the Badimon chamber at low and high shear rates in 2 double-blind randomized cross-over studies of 20 healthy volunteers during extracorporeal administration of recombinant t-PA (0, 40, 200, and 1000 ng/mL) or during endogenous t-PA release stimulated by intra-arterial bradykinin infusion in the presence or absence of oral enalapril. Recombinant t-PA caused a dose-dependent reduction in thrombus area under low and high shear conditions (P<0.001 for all). Intra-arterial bradykinin increased plasma t-PA concentrations in the chamber effluent (P<0.01 for all versus saline) that was quadrupled in the presence of enalapril (P<0.0001 versus placebo). These increases were accompanied by an increase in plasma D-dimer concentration (P<0.005 for all versus saline) and, in the presence of enalapril, a reduction in thrombus area in the low shear (16±5; P=0.03) and a trend toward a reduction in the high shear chamber (13±7%; P=0.07). Conclusions-Using a well-characterized clinical model of coronary arterial injury, we demonstrate that endogenous t-PA released from the vascular endothelium enhances fibrinolysis and limits in situ thrombus propagation. These data support a crucial role for the endogenous fibrinolytic system in vivo and suggest that continued exploration and manipulation of its therapeutic potential are warranted.

PAR4 Antagonism in Patients With Coronary Artery Disease Receiving Antiplatelet Therapies

“…Assessments of thrombus formation were measured in conditions of high and low shear stress in a validated ex vivo model of acute arterial injury. 18,[23][24][25][26] Participants were cannulated with a 17-G peripheral venous catheter in the antecubital fossa at the beginning of each visit. A motorized pump set at a constant rate of 10 mL/min was used to draw blood from the antecubital vein through 3 perfusion chambers maintained at 37 °C in a water bath.…”

“Going with the flow” in modeling fibrinolysis

“…Release of fluorescent fibrin degradation products over time is directly proportional to the rate of lysis. Plasminogen activators at endogenous concentrations (29) can also be incorporated during thrombus formation under flow, however, the formation time must be decreased to account for simultaneous ongoing fibrinolysis (30). This system is also sensitive to detecting the influence of pharmacological agents on the susceptibility to lysis (31).…”

“…The influence of antithrombotic therapy on thrombus formation can be monitored as thrombus size and release of D-dimer, as a marker of fibrinolysis (41,42). The nature of this model also allows the direct study of endogenous tPA release from the endothelium after bradykinin infusion (29). Alternatively, fluorescently labeled fibrinogen and exogenous tPA can be administrated via a calibrated syringe-driver into the extracorporeal circuit.…”

“…Alternatively, fluorescently labeled fibrinogen and exogenous tPA can be administrated via a calibrated syringe-driver into the extracorporeal circuit. Fibrinolysis can be quantified as fluorescence release after removing the porcine aorta strips, with thrombi attached, and placing in tPA bathing fluid and/or as the concentration of fibrinolytic proteins quantified in effluents (29,30).…”

Features of changes in anticoagulant hemostasis system in patients with hypertensive disease with concomitant hyperuricemia

“…Крім того система ПС бере участь у регуляції проникності ендотелію та процесів запалення. Реакція посилення внутрішнього шляху згортання крові контролюється АТ ІІІ і ПС [2,3]. Активація ПС, дія АТ ІІІ, фібринолітичної системи крові направлена на обмеження надмірного збільшення фібринового тромбу, що забезпечує не лише обмеження його зростання, а й видалення тромботичних мас з судинного русла після того, як фібриновий тромб виконав свою гемостатичну функцію.…”