Encapsulation of the thrombolytic enzyme, brinase, in photosensitized erythrocytes: a novel thrombolytic system based on photodynamic activation

In order to circumvent many of the problems associated with the systemic administration of agents used in thrombolytic therapy, it was decided to investigate the possibility of using erythrocytes as carriers and delivery vehicles for these agents. The enzyme brinase, a fibrinolytic enzyme produced by Aspergillus oryzae, was loaded into rabbit erythrocytes using electroporation. The loading index for this enzyme was found to be 60% and incorporation appeared to be relatively stable over a period of 4 h. In order to facilitate the predetermined release of the loaded component from the erythrocytes, they were photosensitized using haematoporphyrin derivative (HPD) and release was demonstrated within 5 min of photoactivation. Inclusion of the loaded, photosensitized system into clotting blood and subsequent exposure to light demonstrated almost complete lysis of the clot. We believe that this system exhibits potential for use in thrombolytic therapy.

Degradation of amyloid proteins with protease I from Aspergillus oryzae. In vivo increase in SAA clearance rate after enzyme infusion

The effect of the thrombolytic enzyme protease I from Aspergillus oryzae (brinase) on the amyloid protein AA was investigated. The effect of the enzyme on purified, low molecular weight protein AA was very high. Protein AA in intact amyloid fibrils suspended in neutral buffer was also degraded by the enzyme, although at a much lower rate. Amyloid fibrils in tissue sections could also be attacked and removed, leaving the tissue structure fairly intact. The in vivo effect of brinase on protein SAA was demonstrated in rabbits by an increase in the clearance rate of SAA after enzyme infusion.

Influence of brinase on fibrinogen: fibrin transition in vitro and in vivo studies. II. Induction of fibrin deposits by brinase in the kidneys of rats with inhibited fibrinolysis

The influence of brinase on fibrinogen levels, ethanol gelation test (EGT), fibrin content of lungs and kidneys (125I-fibrinogen) and brinase inhibitor capacity was investigated in the rat. The animals were either treated with i.v. infusions of brinase (4 mg/kg), tranexamic acid (AMCA) + brinase or heparin + AMCA + brinase. A control group was given i.v. saline, a reference group AMCA + thrombin. Brinase caused a decrease in fibrinogen levels and an increase in the incidence of positive EGT, deposition of fibrin was not observed. Infusion of brinase into rats with inhibition fibrinolytic system (AMCA), caused a more pronounced decrease in fibrinogen levels, a further increase in the incidence of positive EGT and also fibrin deposition in the kidneys. In rats treated with AMCA + thrombin a similar decrease in fibrinogen levels was recorded, the EGT was positive in all animals, and extensive fibrin deposits were observed in the kidneys and lungs of the animals. Heparinization before infusion of AMCA + brinase antagonized the lowering in fibrinogen levels and the increase in incidence of positive EGT and, moreover, fibrin deposits were no longer observed.

Relief of chronic arterial obstruction using intravenous brinase. A control study

A therapeutic trial using placebo or the thrombolytic enzyme brinase was carried out in a group of patients with chronic arterial obstruction. The patients were observed for 3 months before receiving six intravenous infusions of either saline or brinase over a period of 2 weeks. Ankle blood pressure, Doppler ultrasound scanning, and arteriography were used to establish diagnosis in the patients. No changes were observed during the 3-month pre-observation period. After six brinase infusions, recanalization of 17 out of 27 obstructed arterial segments was recorded and the number of patent segments increased from 11 to 27. No improvement was observed in the placebo-treated patients. The differences between brinase and placebo treatment was statistically significant.

Effect of brinolase on corneal endothelium

We investigated Brinolase, a substance producing enzymatic zonulysis, for effects on the physiological and anatomical function of the corneal endothelium in the specular microscope. Concentrations of 100 C2 units/ml perfused for ten minutes did not appear to damage the corneal endothelium. Longer perfusions or higher concentrations possibly produced alterations in the physiological functions of the endothelium, but no significant anatomic change was demonstrated. Longer perfusion times with high concentrations (1,600 C2 units/ml) resulted in the formation of holes which perforated the corneal stroma.

Dosage of i.v. brinase in man based on brinase inhibitor capacity and coagulation studies

In 17 patients a total of 148 brinase infusions were given. All patients but two had anticoagulant treatment (dicoumarol or heparin) during the brinase series. Dosage of brinase was based on determination of brinase inhibitor capacity in plasma (azocollagen technique) prior to infusion of the enzyme. Iv infusion of brinase lowered inhibitors in plasma. Good correlation was found between expected lowering and measured inhibitor values after brinase infusion. The stipulated safety margin for brinase inhibitor capacity could be maintained. alpha 1-antitrypsin showed irregular changes and alpha 2-macroglobulin values were decreased by iv infusions of brinase. Fibrinogen values were somewhat lowered after iv brinase infusion. Values for fibrinogen degradation products increased and the ethanol gelation test became positive. Thrombotest values were lowered and the activated partial thromboplastin time was prolonged in patients receiving dicoumarol and iv heparin respectively. Changes in other coagulation parameters were insignificant. In two patients transient renal failure was recorded, laboratory data indicated intravascular coagulation as a possible cause. None of these two patients were on anticoagulant treatment. One patient developed a haematoma of the forefoot during massive iv heparin treatment during a series of iv infusions of brinase. Bleeding complications due to brinase treatment were not observed.