The coagulant action of Russell's viper venom; the use of antivenom in defining its reaction with a serum factor

Russell Viper Venom: A Journey from the Bedside to the Bench and Back to the Bedside

Russell Viper Venom (RVV) is widely used as a diagnostic test for antiphospholipid syndrome (APS). But the history of how this venom came to be discovered is well known. Dr Patrick Russell is responsible for the identification of the venom during his work on snake bites in India while Dr Robert Macfarlane used it to staunch bleeding in persons with haemophilia. The ability to directly activate factor X led RVV to the laboratory diagnosis of APS. More recently, it has come back to clinical world with a potential for an engineered factor X activator from RVV to be used in the treatment of haemophilia.

Aspirin plus tirofiban inhibit the thrombosis induced by Russell's viper venom

Background

Thrombosis and coagulopathy are the commonest hematological manifestations of envenomation of Russell’s viper venom (RVV). Factor X is activated by a factor X-activating enzyme from Russell’s viper venom (RVV-X) to start the coagulation cascade. We established an animal model with local ischemic effects induced by RVV. We tried to treat RVV envenomation with antiplatelets and anticoagulants without recourse to antivenom.

Methods

RVV was injected into the foot pad of mice. We observed the effects at different intervals and compared local changes in ischemia with drug treatment after 30 min.

Results

A combination of aspirin plus tirofiban could prevent the ischemic change induced by RVV. The antithrombotic effects of single-use of aspirin or tirofiban were better than single-use of heparin or clopidogrel.

Conclusion

The aspirin + tirofiban group had a better outcome with respect to prevention of tissue ischemia and gangrene. This indicates that the activation and aggregation of platelets is the major cause of thrombosis induced by RVV.

Snake venom metalloproteinases

Recent proteomic analyses of snake venoms show that metalloproteinases represent major components in most of the Crotalid and Viperid venoms. In this chapter we discuss the multiple activities of the SVMPs. In addition to hemorrhagic activity, members of the SVMP family also have fibrin(ogen)olytic activity, act as prothrombin activators, activate blood coagulation factor X, possess apoptotic activity, inhibit platelet aggregation, are pro-inflammatory and inactivate blood serine proteinase inhibitors. Clearly the SVMPs have multiple functions in addition to their well-known hemorrhagic activity. The realization that there are structural variations in the SVMPs and the early studies that led to their classification represents an important event in our understanding of the structural forms of the SVMPs. The SVMPs were subdivided into the P-I, P-II and P-III protein classes. The noticeable characteristic that distinguished the different classes was their size (molecular weight) differences and domain structure: Class I (P-I), the small SVMPs, have molecular masses of 20-30 kDa, contain only a pro domain and the proteinase domain; Class II (P-II), the medium size SVMPs, molecular masses of 30-60 kDa, contain the pro domain, proteinase domain and disintegrin domain; Class III (P-III), the large SVMPs, have molecular masses of 60-100 kDa, contain pro, proteinase, disintegrin-like and cysteine-rich domain structure. Another significant advance in the SVMP field was the characterization of the crystal structure of the first P-I class SVMP. The structures of other P-I SVMPs soon followed and the structures of P-III SVMPs have also been determined. The active site of the metalloproteinase domain has a consensus HEXXHXXGXXHD sequence and a Met-turn. The "Met-turn" structure contains a conserved Met residue that forms a hydrophobic basement for the three zinc-binding histidines in the consensus sequence.

Biochemical and biological properties of the venom from Russell's viper (Daboia russelli siamensis) of varying ages

Russell's viper (Daboia russelli siamensis) venoms of four different lengths (21-25 cm, 40-60 cm, 81-90 cm and 101-110 cm) were studied by SDS-PAGE electrophoresis and immunoblotting. Studies on biological and biochemical properties of the venom were also carried out. The venom of young snakes (21-60 cm) had a high lethal potency and possessed powerful coagulant and defibrinogenating activities compared to adults (101-110 cm). As snakes aged, these activities decreased. Potent capillary permeability increasing activity was detected in venom of 40-60 cm snakes and was the lowest in the youngest snakes (21-25 cm). SDS-PAGE electrophoresis and immunoblot of venoms showed that venom from the youngest snakes has fewer protein bands; the number of bands increased as the snakes aged. Snakes more than 91 cm long demonstrated no striking differences in the protein pattern.

Neutralization of pathophysiological manifestations of Russell's viper envenoming by antivenom raised against gamma-irradiated toxoid

Rabbits were immunized against gamma-irradiated (100 krads) Russell's viper venom toxoid adsorbed to aluminium phosphate gel. The antivenom (0.1 ml) neutralized 5 LD50, 8 minimum hemorrhagic doses (MHD) and 14 minimum necrotic doses (MND) of venom. The coagulant and protease activities of the viper venom were neutralized more effectively than phospholipase A activity, by the toxoid antivenom.

Haemostatic changes caused by the venoms of South American snakes

Changes in the haemostatic mechanism caused by venoms of Bothrops, Crotalus and Lachesis snakes from Central and South America in human accidents are reviewed. Changes in the blood coagulation mechanism could be found depending on the action of the venom on clotting factors.

An investigation of the coagulant activity of the venom of the saw-scaled viper (Echis carinatus) from Saudi Arabia

Unlike the venom of Echis carinatus from India, Pakistan, Nigeria, Kenya, Iran and Oman, Saudi Arabian E. carinatus venom is a poor activator of prothrombin. However, it possesses similar defibrinogenating activity to the other venoms. This is because the venom from Saudi Arabian snakes contains a calcium-dependent factor X activator. It is suggested that in future studies of the coagulant activity of venoms, the determination of plasma coagulant activity should be carried out in the presence of added calcium ions. This applies particularly to those venoms which do not act on plasma or fibrinogen, but which do cause in vivo defibrinogenation.

Haemostatic disturbances in patients bitten by Russell's viper (Vipera russelli siamensis) in Burma

Patients who are severely envenomed by Russell's viper develop DIC which is frequently associated with spontaneous bleeding and incoagulable blood. These haemostatic disturbances may be responsible for death or organ/tissue damage both through haemorrhage and microvascular occlusion by fibrin thrombi. The most striking laboratory features of the coagulopathy developing after Russell's viper bite in the 42 patients studied were depletion of fibrinogen (mean 0.09 g/l, range 0-0.6), factor V (6.5 u/dl, range 0-17), factor X (35 u/dl, range 1-85), factor XIIIa (57 u/dl, range 15-82), plasminogen (61 u/dl, range 10-92), antiplasmin (36 u/dl, range 14-62). Protein C (49 u/dl, range 15-100) and platelets (104 x 10(9)/l, range 25-197). Intense fibrinolytic activity was detected in all cases with marked elevation of FDPs (1614 micrograms/ml, range 350-3000), a large proportion of which were cross-linked (1058 micrograms/ml, range 38-3000). The monospecific Burmese antivenom appeared to be very effective in neutralizing the venom procoagulants and in restoring blood coagulability. Moreover, the unexpectedly normal level of AT III provides a theoretical basis for the use of heparin to enhance the inactivation of those serine proteases present before antivenom administration.

The anticoagulant effect of Bothrops castelnaudi snake venom (Castelnaud's pit viper)

An inhibitory effect of Bothrops castelnaudi venom was observed on the following systems: prothrombin time, activated partial thromboplastin time, thrombin time, thromboplastin generation time, activation of factor X by Russell's viper venom and Russell's viper venom activated factor X (factor Xa). This effect did not require previous incubation and was prevented by the addition of Bothrops-antivenom. The prolonged activated partial thromboplastin time was not shortened by increased phospholipid concentration (0.5-10 mg/ml), suggesting that the inhibitory effect is not due to an anti-phospholipid activity. No significant fibrinogenolytic activity was detected upon incubation of human fibrinogen with the venom, since physiological levels of thrombin-clottable material were still present. Compared to Bothrops jararaca venom, the proteolytic activity on casein and on azocoll was very low. Thrombin-induced clots of human plasma and fibrinogen were not lysed by the venom within 24 hr. The results indicate that the anticoagulant effect of Bothrops castelnaudi venom is exerted at least at two levels of the blood coagulation mechanism: (1) before prothrombin activation, by inhibiting factor X-activation and factor Xa activity; (2) by direct action on thrombin.

Modulation of fibrin clot formation by human serum amyloid P component (SAP) and heparin

Serum amyloid P-component (SAP) is a normal plasma constituent in man with a circulating concentration of approximately 40 micrograms/ml. Supraphysiological amounts of SAP (150-300 micrograms/ml) have been reported to affect coagulation. We have investigated this further by studying the effect of SAP upon clot times in both the absence and presence of heparin, a suggested ligand for SAP and itself a modulator of coagulation processes. In the absence of heparin, SAP (5-125 micrograms/ml) had no effect on clot times generated by Activated Thrombofax Reagent, brain thromboplastin, Russell's Viper Venom or thrombin when assessed in normal citrated plasma. However, in the presence of amounts of heparin that had only a minor effect upon clot times, SAP (5-40 micrograms/ml) greatly prolonged clot formation, with the thrombin time the most sensitive to SAP. This suggested that the primary effect of SAP was at this distal level of the coagulation pathway. Evaluation by radioimmunoassay revealed that supraphysiological concentrations of SAP (150-300 micrograms/ml) alone reduced by approximately 25% the release of fibrinopeptide A (FPA) from fibrinogen. In the presence of heparin, substantial synergism was observed with maximal reductions of approximately 70% in FPA production requiring only 25-50 micrograms/ml SAP. This inhibition correlated with increased thrombin clot time but was unrelated to any direct modulation in either the activities of anti-thrombin III or activated Factor XIII, and was independent of an alteration in the rate of fibrinolysis. Further, while SAP itself did not interfere with the process of spontaneous fibrin polymerization, in the presence of heparin a prolonged polymerization time (greater than 145%) was observed. We believe that these data reflect the primary mechanisms by which serum amyloid P component influences blood coagulation.

Blood coagulation induced by Bothrops atrox venom: identification and properties of a factor X activator

The coagulating activity of Bothrops atrox venom was investigated in vitro with purified fibrinogen, with normal plasma and with plasma deficient in various factors of the coagulation cascade. This study indicated that Bothrops atrox venom possesses a thrombin-like action caused by one or several serine proteases sensitive to DFP treatment, but that its clotting action is in fact mainly due to components insensitive to DFP which activate prothrombin and factor X (Stuart factor). We partially purified the DFP insensitive activator of factor X from Bothrops atrox venom and found it to be a protein of molecular weight 77,000. Analysis of the purified fraction by electrophoresis on polyacrylamide gel in the presence of SDS showed that it is mainly composed of one heavy polypeptide chain (65,000) and one light doublet (12 - 13,000). This activator is calcium-dependent and catalyzes in vitro the conversion of purified factor X into factor X alpha. By its molecular properties, it resembles the factor X activator from Vipera russellii venom rather than physiological activators.

Effects of Russell's viper venom on blood coagulation, platelets and the fibrinolytic enzyme system

The effects of Russell's viper venom (RVV) on blood coagulation, platelts and fibrinolysis were studied in vivo and in vitro in rabbits and dogs as experimental subjects. RVV was shown to be a strong coagulant, and at the time of manifestation of bleeding due to consumption coagulopathy, the most striking hemostatic abnormalities were fall of fibrinogen level, reduction in platelet count, delayed ADP aggregation of platelets, increased fibrinolytic activity and presence of fibrin degradation products. These findings showed that RVV interfered with blood coagulation, caused abnormalities of platelet function and also activated the fibrinolytic enzyme system.

Purification and characterization of a coagulant protein from the venom of Russell's viper

The coagulant protein from the venom of Russell's viper was purified by means of successive chromatography on Sephadex G-50, DEAE-cellulose and Sephadex G-200. The purified coagulant protein was homogeneous by polyacrylamide gel electrophoresis and ultracentrifugation. The molecular weight was estimated to be about 100 000 by ultracentrifuge analysis and 130 000 by gel filtration. The coagulant protein contains 11.1% carbohydrate which includes 5.1% hexose (galactose: mannose = 1:1), 5% hexosamine (glucosamine), and 1% neuraminic acid (N-acetylneuraminic acid and N-glycolyneuraminic acid). The isoelectric point is pH 6.3. The results of both sodium dodecyl sulfate electrophoresis and gel filtration in 6 M guanidium chloride suggest that it consists of four polypeptide chains. The coagulant protein functions as an enzyme in activating blood coagulation factor X in the presence of Ca2+. N-a-p-Toluenesulfonyl-L-arginine methyl ester hydrolyzing activity in the preparation definitely decreased during purification and it suggests that the clotting activity is not associated with the esterase activity. The clotting activity is inhibited by diisopropyl phosphorofluoridate and by phenylmethylsulfonyl fluoride, suggesting that the coagulant protein is a serine protease. The optimum pH is between pH 7.0 and pH 8.0. At neutral pH the coagulant protein is stable below 50 degrees C, but is rapidly inactivated above 55 degrees C.

The platelet in leukemic reticuloendotheliosis. Functional and morphological evidence of a qualitative disorder

Platelets were studied in a group of 10 patients with typical clinical course, morphological findings, and specific histochemical criteria for leukemic reticuloendotheliosis. In 8 of these, marked qualitative abnormalities were found. These included lack of aggregation following epinephrine stimulation (6 patients), and decreased platelet factor 3 availability following ADP stimulation (4 patients). In addition, platelets in 4 of the 10 patients were studied by electron microscopy. All had granular abnormality, and 1 case showed the presence of rough-surfaced endoplasmic reticulum. The functional and ultrastructural abnormalities of platelets reported here may be responsible for the clinically important bleeding episodes which were not attributable to thrombocytopenia in 2 of our patients. The findings also provide a clue to the basic nature of this histogenetically controversial malignancy.

An investigation of three patients with Christmas disease due to an abnormal type of factor IX

Three patients with Christmas disease whose plasma was shown to have a prolonged one-stage prothrombin time with ox brain thromboplastin have been investigated. These patients have an inhibitor for the reaction between factor X, factor VII, and ox brain extract. The abnormal constituent responsible for this inhibitor appears to be factor IX whuch is functionally inactive but antigenically indistinguishable from normal factor IX. It is proposed that patients might be classified into haemophilia B(+) for patients with this defect (Christmas disease(+)) and haemophilia B(-) (Christmas disease(-)) for patients who have classical Christmas disease.