Thrombolytic properties of Desmodus rotundus (vampire bat) salivary plasminogen activator in experimental pulmonary embolism in rats

Abstract

rDSPA alpha 1 (recombinant Desmodus salivary plasminogen activator alpha 1) is a recombinant protein corresponding to a natural plasminogen activator from the vampire bat Desmodus rotundus. The thrombolytic properties of rDSPA alpha 1 and tissue-type plasminogen activator (t-PA) were compared in a rat model of pulmonary embolism. Whole blood clots, produced in vitro and labeled with 125I-fibrinogen, were embolized into the lungs of anesthetized rats. Thrombolysis was calculated from the difference between initial clot radioactivity and that remaining in the lungs at 60 minutes. Blood was sampled for gamma counting, measurement of hemostatic factors, and plasminogen activator antigen levels. Thrombolysis at 3, 10, 30, and 100 nmol/kg intravenously (10% bolus, 90% over 60 minutes) amounted to 30% +/- 2%, 51% +/- 4%, 85% +/- 4%, 98% +/- 0% for rDSPA alpha 1 and 30% +/- 3%, 41% +/- 3%, 57% +/- 6%, 93% +/- 2% for t-PA (controls: 29% +/- 2%; mean +/- SEM, n greater than or equal to 6). t-PA at 100 nmol/kg significantly decreased fibrinogen, plasminogen, and alpha 2- antiplasmin levels by 33% +/- 7%, 38% +/- 8%, and 61% +/- 9%, whereas rDSPA alpha 1 at 100 nmol/kg only lowered alpha 2-antiplasmin significantly (by 29% +/- 6%). Compared with t-PA, rDSPA alpha 1 is the more potent and more clot selective (fibrin specific) thrombolytic agent. These results suggest that rDSPA alpha 1 may be safer and more efficacious than currently used thrombolytics.

Structural Biology and Protein Engineering of Thrombolytics

“…Thrombolytic properties of desmoteplase were observed already in 1932, but it took another 34 years to identify that this factor is an activator of plasminogen [304]. Thanks to its enormous fibrin specificity, an absence of neurotoxicity, and a highly prolonged half-life of more than 2 h, desmoteplase represents a promising activator with the potential for the treatment of cardiovascular diseases [116,[305], [306], [307], [308], [309]]. Although these beneficial properties were not observed during randomized clinical trials, further clinical tests are in progress [310,311].…”

Desmoteplase: discovery, insights and opportunities for ischaemic stroke

“…Rabbit (Muschick et al ., 1993), rodent (Witt et al ., 1992) and canine (Witt et al ., 1994) models of thrombosis were used to compare the efficacy of desmoteplase with recombinant t‐PA. In a model of myocardial infarction in dogs, desmoteplase, when delivered at 25, 50 or 100 µg·kg −1 resulted in 100% incidence of patency after 37, 23 and 18 min, respectively, while t‐PA administered at 63 and 125 µg·kg −1 recanalized arteries in 33% and 50% of cases within 40 min (Witt et al ., 1994).…”

“…In a model of myocardial infarction in dogs, desmoteplase, when delivered at 25, 50 or 100 µg·kg −1 resulted in 100% incidence of patency after 37, 23 and 18 min, respectively, while t‐PA administered at 63 and 125 µg·kg −1 recanalized arteries in 33% and 50% of cases within 40 min (Witt et al ., 1994). In a rat model of pulmonary embolism, desmoteplase‐induced thrombolysis was achieved faster than with t‐PA (Witt et al ., 1992). Moreover, t‐PA but not desmoteplase was shown to cause a reduction in levels of fibrinogen and plasminogen.…”

Molecular requirements for safer generation of thrombolytics by bioengineering the tissue-type plasminogen activator A chain

“…Current experimental strategies to improve safer thrombolysis include the use of a plasminogen activator inhibitor-1-derived hexapeptide to inactivate the proneurotoxicity of t-PA [13], and a soluble annexin A2 to improve the efficacy of t-PA-induced fibrinolysis [14]. Desmodus rotundus plasminogen activator (DSPA), a serine protease secreted by the D. rotundus salivary glands, shares 66% identity with human t-PA, but lacks a kringle domain as compared with t-PA. DSPA [15] was developed as a third-generation thrombolytic devoid of the above mentioned side-effects of t-PA. Indeed, a number of studies have emphasized the absence of excitotoxicity of this exclusively single-chain serine protease [16][17][18].…”

“…Desmodus rotundus plasminogen activator (DSPA), a serine protease secreted by the D. rotundus salivary glands, shares 66% identity with human t‐PA, but lacks a kringle domain as compared with t‐PA. DSPA was developed as a third‐generation thrombolytic devoid of the above mentioned side‐effects of t‐PA. Indeed, a number of studies have emphasized the absence of excitotoxicity of this exclusively single‐chain serine protease .…”