Arrhenius temperature dependence ofin vitrotissue plasminogen activator thrombolysis

Abstract

Stroke is a devastating disease and a leading cause of death and disability. Currently, the only FDA approved therapy for acute ischemic stroke is the intravenous administration of the thrombolytic medication, recombinant tissue plasminogen activator (tPA). However, this treatment has many contraindications and can have dangerous side effects such as intra-cerebral hemorrhage. These treatment limitations have led to much interest in potential adjunctive therapies, such as therapeutic hypothermia (T ≤ 35 °C) and ultrasound enhanced thrombolysis. Such interest may lead to combining these therapies with tPA to treat stroke, however little is known about the effects of temperature on the thrombolytic efficacy of tPA. In this work, we measure the temperature dependence of the fractional clot mass loss Δm(T) resulting from tPA exposure in an in vitro human clot model. We find that the temperature dependence is well described by an Arrhenius temperature dependence with an effective activation energy E eff of 42.0 ± 0.9 kJ mole −1 . E eff approximates the activation energy of the plasminogen-to-plasmin reaction of 48.9 kJ mole −1 . A model to explain this temperature dependence is proposed. These results will be useful in predicting the effects of temperature in future lytic therapies.

Ultrasound-enhanced tissue plasminogen activator thrombolysis in an in vitro porcine clot model

“…8 as a function of time demonstrate a square root of time dependence. A similar time dependence has been predicted by a theoretical model of rt-PA thrombolysis developed by Shaw et al [40]. The phenomenon of in vitro rt-PA induced clot lysis is predominantly controlled by plasminogen-and fibrin-specific chemical reactions and, importantly, the diffusion of exogenous rt-PA and plasminogen into the clot sample.…”

Tissue Plasminogen Activator Concentration Dependence of 120 kHz Ultrasound-Enhanced Thrombolysis

“…Others have found similar results for human clots (Francis et al 1995;Kondo et al 1999). In the absence of ultrasound, exogenous tPA diffuses into the clot down the concentration gradient (Blinc et al 1993;Shaw et al 2007) and converts plasminogen to plasmin. The plasmin then cleaves the fibrin, thus lysing the clot.…”

Modulation by the Noble Gas Helium of Tissue Plasminogen Activator: Effects in a Rat Model of Thromboembolic Stroke*

“…Then, after administration of tPA has ended, all rats were given medical air again for a 25-minute period. Because administration of helium at a room temperature of 25°C and below is known to decrease body temperature (16,42), a condition shown by itself to reduce the catalytic, thrombolytic, and proteolytic properties of tPA (37)(38)(39)(40), all rats were maintained normothermic throughout the experiment using a feedback-controlled thermostatic heating pad connected to a rectal probe to assess the effect of helium on tPA-induced thrombolysis independently of hypothermia. After surgery, the polyethylene-10 catheter was removed, and all animals were returned to their home cages with food and water ad libitum before being used for histology.…”