Reversal of the anticoagulant and anti-hemostatic effect of low molecular weight heparin by direct prothrombin activation

Abstract

Lopap, found in the bristles of Lonomia obliqua caterpillar, is the first exogenous prothrombin activator that shows serine protease-like activity, independent of prothrombinase components and unique lipocalin reported to interfere with hemostasis mechanisms. To assess the action of an exogenous prothrombin activator reversing the anticoagulant and antihemostatic effect induced by low molecular weight heparin (LMWH), male New Zealand rabbits (N = 20, weighing 3.8-4.0 kg) allocated to 4 groups were anticoagulated with 1800 IU/kg LMWH (iv) over 2 min, followed by iv administration of saline or recombinant Lopap (rLopap) at 1 µg/kg (LG1) or 10 µg/kg (LG10), 10 min after the injection of LMWH, in a blind manner. Control animals were treated only with saline. The action of rLopap was assessed in terms of activated partial thromboplastin time (aPTT), prothrombin fragment F1+2, fibrinogen, and ear puncture bleeding time (BT) at 5, 10, 15, 17, 20, 30, 40, 60, and 90 min after initiation of LMWH infusion. LG10 animals showed a decrease of aPTT in more than 50% and BT near to normal baseline. The level of prothrombin fragment F1+2 measured by ELISA had a 6-fold increase with rLopap treatment (10 µg/kg) and was inversely proportional to BT in LMWH-treated animals. Thus, Lopap, obtained in recombinant form using E. coli expression system, was useful in antagonizing the effect of LMWH through direct prothrombin activation, which can be a possible strategy for the reversal of bleeding and anticoagulant events.

Accident involving a 2-year-old child and Lonomia obliqua venom: clinical and coagulation abnormalities

“… 7 Injecting L. obliqua venom in rats increased the expression of endothelial E-selectin, and vascular cell adhesion protein 1 and caused the activation of leukocyte, and the induction of necrosis factor kappa-β, cyclooxygenase-2, heme oxygenase-1and inducible nitric oxide synthase. 8 Lopap and Losac also play a role in the up-regulation of the expression of pro-inflammatory molecules such as interleukin 8, and intercellular adhesion molecule-1. 4 …”

Exogenous Procoagulant Factors as Therapeutic and Biotechnological Tools

“…This toxin also triggers various responses in endothelial cells and displays antiapoptotic activity. Recently our research group have shown that rLopap is able to reverse the bleeding induced by LMWH in vivo [9,46,47].…”

“…In addition, research on possible antidotes for the currently available anticoagulants should also be an interesting issue, especially in the cases of bleeding risk and surgical procedures. Recent studies have showed the recombinant form of the prothrombin activator isolated from Lonomia obliqua (rLopap), [4] as a first exogenous prothrombin activator capable of reversing bleeding induced by LMWH [9]. Table 2 shows some exogenous procoagulant factors as diagnostic test reagents and therapeutic drugs.…”

“…Based on their specific activities, exogenous factors can be used as reagents in diagnostic kits to detect hemostatic disturbances and deficiencies of a clotting factor, or even be used as components for kits to monitor hemostatic parameters [7]. In addition, exogenous factors have been suggested as therapeutic agents for various disturbances that involve unbalanced hemostasis, such as thrombosis, arthrosclerosis, stroke, clotting factor deficiencies, cancer and bleeding reverser [8,9].…”

Toxins from Lonomia obliqua — Recombinant Production and Molecular Approach

“…A recent study suggests that exogenous procoagulant proteins could also be considered for therapeutic use to manage bleeding complications caused by anticoagulation therapy. Treatment with Lopap was able to reduce the bleeding time of rabbits anticoagulated with low molecular weight heparin, through direct prothrombin activation, bypassing factor Xa inhibition [112]. Patent information about those applications can be consulted in Table 3.…”