In vitro procoagulant and anticoagulant properties of Naja naja naja venom

A Combined Bioassay and Nanofractionation Approach to Investigate the Anticoagulant Toxins of Mamba and Cobra Venoms and Their Inhibition by Varespladib

Envenomation by elapid snakes primarily results in neurotoxic symptoms and, consequently, are the primary focus of therapeutic research concerning such venoms. However, mounting evidence suggests these venoms can additionally cause coagulopathic symptoms, as demonstrated by some Asian elapids and African spitting cobras. This study sought to investigate the coagulopathic potential of venoms from medically important elapids of the genera Naja (true cobras), Hemachatus (rinkhals), and Dendroaspis (mambas). Crude venoms were bioassayed for coagulant effects using a plasma coagulation assay before RPLC/MS was used to separate and identify venom toxins in parallel with a nanofractionation module. Subsequently, coagulation bioassays were performed on the nanofractionated toxins, along with in-solution tryptic digestion and proteomics analysis. These experiments were then repeated on both crude venoms and on the nanofractionated venom toxins with the addition of either the phospholipase A₂ (PLA₂) inhibitor varespladib or the snake venom metalloproteinase (SVMP) inhibitor marimastat. Our results demonstrate that various African elapid venoms have an anticoagulant effect, and that this activity is significantly reduced for cobra venoms by the addition of varespladib, though this inhibitor had no effect against anticoagulation caused by mamba venoms. Marimastat showed limited capacity to reduce anticoagulation in elapids, affecting only N. haje and H. haemachatus venom at higher doses. Proteomic analysis of nanofractionated toxins revealed that the anticoagulant toxins in cobra venoms were both acidic and basic PLA₂s, while the causative toxins in mamba venoms remain uncertain. This implies that while PLA₂ inhibitors such as varespladib and metalloproteinase inhibitors such as marimastat are viable candidates for novel snakebite treatments, they are not likely to be effective against mamba envenomings.

Evaluation of the merit of the methanolic extract of Andrographis paniculata to supplement anti-snake venom in reversing secondary hemostatic abnormalities induced by Naja naja venom

Increasing evidence suggests a sizable involvement of hemotoxins in the morbidity associated with envenomation by the Indian spectacled cobra, Naja naja (N.N). This study investigates the ability of Indian polyvalent anti-snake venom (ASV), methanolic extract of Andrographis paniculata (MAP) and their combination in reversing the hemostatic abnormalities, viz. activated partial thromboplastin time(aPTT), prothrombin time(PT) and thrombin time(TT) in citrated plasma. These parameters were assessed in 2 groups of experiments. Group 1: Without the prior incubation of plasma with venom and Group 2: With prior incubation of plasma with venom for 90 min at 37°C. Venom caused significant (p < 0.001) prolongation in aPTT (175%), PT (49%) and TT (34%) in Group 1 and ASV could completely bring them back to normal. MAP showed a concentration-dependent reversal in aPTT, normalization of PT and prolongation of TT. When low concentration of ASV was supplemented with MAP, their combined effect in normalizing aPTT and PT improved by 37% and 26% respectively when compared to ASV alone. In Group 2, venom caused significant (p < 0.001) prolongation in aPTT (231%), PT (312%) and TT (245%). ASV had limited effect in reversing aPTT (52%), TT (31%) but completely normalized PT. MAP was marginally effective in reversing the prolonged aPTT and PT but caused further prolongation of TT. Combination of ASV and MAP was more effective than ASV alone in reversing venom-induced increase in aPTT (52%) and PT (29%). The study proved that, a drastic reduction of ASV by 70%, could be effectively supplemented by MAP in combating hemostatic abnormalities induced by NN venom.

Anticoagulant Activity of Naja nigricollis Venom Is Mediated by Phospholipase A2 Toxins and Inhibited by Varespladib

Bites from elapid snakes typically result in neurotoxic symptoms in snakebite victims. Neurotoxins are, therefore, often the focus of research relating to understanding the pathogenesis of elapid bites. However, recent evidence suggests that some elapid snake venoms contain anticoagulant toxins which may help neurotoxic components spread more rapidly. This study examines the effects of venom from the West African black-necked spitting cobra (Naja nigricollis) on blood coagulation and identifies potential coagulopathic toxins. An integrated RPLC-MS methodology, coupled with nanofractionation, was first used to separate venom components, followed by MS, proteomics and coagulopathic bioassays. Coagulation assays were performed on both crude and nanofractionated N. nigricollis venom toxins as well as PLA₂s and 3FTx purified from the venom. Assays were then repeated with the addition of either the phospholipase A₂ inhibitor varespladib or the snake venom metalloproteinase inhibitor marimastat to assess whether either toxin inhibitor is capable of neutralizing coagulopathic venom activity. Subsequent proteomic analysis was performed on nanofractionated bioactive venom toxins using tryptic digestion followed by nanoLC-MS/MS measurements, which were then identified using Swiss-Prot and species-specific database searches. Varespladib, but not marimastat, was found to significantly reduce the anticoagulant activity of N. nigricollis venom and MS and proteomics analyses confirmed that the anticoagulant venom components mostly consisted of PLA₂ proteins. We, therefore, conclude that PLA₂s are the most likely candidates responsible for anticoagulant effects stimulated by N. nigricollis venom.

Can the methanolic extract of Andrographis paniculata be used as a supplement to anti-snake venom to normalize hemostatic parameters: A thromboelastographic study

ETHNOPHARMACOLOGICAL RELEVANCE OF ANDROGRAPHIS PANICULATA

The whole plant (including leaves and roots) is used in traditional Ayurveda and Siddha medicine to treat various clinical conditions such as fever, respiratory tract infections, colic pain, liver disorders, diabetes, hypertension, and inflammation. It is also used as an antidote for snake-bite, poisonous bites of insects and recommended as a dietary supplement to boost immunity.

AIM OF THE STUDY

In-vitro thromboelastographic evaluation of the efficacy of methanolic extract of Andrographis paniculata (MAP) and polyvalent anti-snake venom (ASV) in neutralizing the Naja naja (N.N) venom-induced changes in hemostatic parameters.

MATERIALS AND METHODS

Thromboelastographic evaluation of hemostatic parameters was initiated by adding 3μg N.N venom to citrated whole blood from healthy volunteers. The effect of different concentrations of ASV and MAP in neutralizing the toxicity of N.N venom were studied in two groups. In group 1 experiments, citrated whole blood (340μl) was mixed with N.N venom (3μg), immediately followed by successive addition of ASV (5μl, 8μl and 15μl) or MAP (15μg, 30μg, 60μg and 120 μg) or combination of ASV and MAP (3μl ASV+30μg MAP and 3μl ASV+60μg MAP). In group 2 experiments, N.N venom was incubated with whole blood for 90 minutes at 37°C, followed by successive addition of ASV (5μl, 10μl, and 15μl) or MAP (30μg and 60μg) or combination of ASV and MAP (5μl ASV+30μg MAP and 5μl ASV+60μg MAP).

RESULT

In Group 1 experiments, N.N venom caused significant (p<0.05) increase in R-time, K-time, LY30% and a decrease in angle and MA. Optimum effect on hemostatic parameters was observed at a concentration of 8μl ASV, where all the deleterious effects of the venom were completely reversed. Similarly, the addition of MAP to the assay system could reproduce results as ASV, in reversing the deleterious effects of the venom. This occurred in a concentration-dependent manner, from 15μg-60μg, with the optimum results at 60μg. When ASV concentration was reduced to 3μl and supplemented with MAP (30μg or 60μg), the positive supplementary effect of MAP was demonstrated. In Group 2 experiments, N.N venom caused significant (p<0.05) changes in all TEG parameters, with most deleterious changes observed in MA and LY30% compared to Group 1 experiments. ASV when added in increasing concentrations (5-15μl), had beneficial effects only on K-time, angle, and MA. When added together with ASV, MAP (30μg or 60μg) could significantly (p<0.05) supplement the effect of ASV (5μl) in improving R-time, K-time, and angle.

CONCLUSION

This in-vitro study demonstrates the effectiveness of MAP as a supplement to ASV in combating the deleterious effects of N.N venom on hemostasis. However, further in-vivo experiments in animal models are required to substantiate these effects.

Inhibition of crude viper venom action by silver nanoparticles: A biophysical and biochemical study

This investigation understands the interaction between lyophilized crude Viper snake venom (Doboia russellie) and Silver nanoparticles (SNPs) using biophysical and biochemical approaches. SNPs were synthesized by chemical reduction method and characterized using UV-Visible spectroscopy, Dynamic Light Scattering (DLS) and Transmission electron microscope (TEM). The average hydrodynamic size of SNPs was found to be 52 nm with 0.261 PDI. TEM image revealed the spherical shape of SNP. Interaction of SNPs and viper venom was resulted in the formation of complex which was confirmed by using DLS technique. Spectroscopic results showed an increase in absorbance intensity of venom upon interaction with SNPs which indicated interaction with venom proteins. Fluorescence spectroscopic data revealed the quenching in the fluorescence intensity of viper venom upon incubation with varying concentration of SNPs. The results obtained by biochemical assays (Protease and whole blood clotting test) revealed the inhibition of venom action due to presence of silver nanoparticles. The activity of protease enzyme was found to be decreased (10-13% reduction) in presence of silver nanoparticles. Prolonged clotting time (two fold) of viper venom upon interaction with SNPs compared to native crude viper venom was observed. The overall results confirmed the inhibition action of silver nanoparticles against viper venom.

Proteomic analysis to unravel the complex venom proteome of eastern India Naja naja: Correlation of venom composition with its biochemical and pharmacological properties

The complex venom proteome of the eastern India (EI) spectacled cobra (Naja naja) was analyzed using tandem mass spectrometry of cation-exchange venom fractions. About 75% of EI N. naja venom proteins were <18kDa and cationic at physiological pH of blood. SDS-PAGE (non-reduced) analysis indicated that in the native state venom proteins either interacted with each-other or self-aggregated resulting in the formation of higher molecular mass complexes. Proteomic analysis revealed that 43 enzymatic and non-enzymatic proteins in EI N. naja venom with a percent composition of about 28.4% and 71.6% respectively were distributed over 15 venom protein families. The three finger toxins (63.8%) and phospholipase A₂s (11.4%) were the most abundant families of non-enzymatic and enzymatic proteins, respectively. nanoLC-ESI-MS/MS analysis demonstrated the occurrence of acetylcholinesterase, phosphodiesterase, cholinesterase and snake venom serine proteases in N. naja venom previously not detected by proteomic analysis. ATPase, ADPase, hyaluronidase, TAME, and BAEE-esterase activities were detected by biochemical analysis; however, due to a limitation in the protein database depository they were not identified in EI N. naja venom by proteomic analysis. The proteome composition of EI N. naja venom was well correlated with its in vitro and in vivo pharmacological properties in experimental animals and envenomed human.

BIOLOGICAL SIGNIFICANCE

Proteomic analysis reveals the complex and diverse protein profile of EI N. naja venom which collectively contributes to the severe pathophysiological manifestation upon cobra envenomation. The study has also aided in comprehending the compositional variation in venom proteins of N. naja within the Indian sub-continent. In addition, this study has also identified several enzymes in EI N. naja venom which were previously uncharacterized by proteomic analysis of Naja venom.

Use of Molecular Diagnostic Tools for the Identification of Species Responsible for Snakebite in Nepal: A Pilot Study

Snakebite is an important medical emergency in rural Nepal. Correct identification of the biting species is crucial for clinicians to choose appropriate treatment and anticipate complications. This is particularly important for neurotoxic envenoming which, depending on the snake species involved, may not respond to available antivenoms. Adequate species identification tools are lacking. This study used a combination of morphological and molecular approaches (PCR-aided DNA sequencing from swabs of bite sites) to determine the contribution of venomous and non-venomous species to the snakebite burden in southern Nepal. Out of 749 patients admitted with a history of snakebite to one of three study centres, the biting species could be identified in 194 (25.9%). Out of these, 87 had been bitten by a venomous snake, most commonly the Indian spectacled cobra (Naja naja; n = 42) and the common krait (Bungarus caeruleus; n = 22). When both morphological identification and PCR/sequencing results were available, a 100% agreement was noted. The probability of a positive PCR result was significantly lower among patients who had used inadequate "first aid" measures (e.g. tourniquets or local application of remedies). This study is the first to report the use of forensic genetics methods for snake species identification in a prospective clinical study. If high diagnostic accuracy is confirmed in larger cohorts, this method will be a very useful reference diagnostic tool for epidemiological investigations and clinical studies.

Hemostatic interference of Indian king cobra (Ophiophagus hannah) Venom. Comparison with three other snake venoms of the subcontinent

Unlike Naja naja, Bungarus caeruleus, Echis carinatus, and Daboia/Vipera russellii venoms, Ophiophagus hannah venom is medically ignored in the Indian subcontinent. Being the biggest poisonous snake, O. hannah has been presumed to inject several lethal doses of venom in a single bite. Lack of therapeutic antivenom to O. hannah bite in India makes any attempt to save the victim a difficult exercise. This study was initiated to compare O. hannah venom with the above said venoms for possible interference in hemostasis. Ophiophagus hannah venom was found to actively interfere in hemostatic stages such as fibrin clot formation, platelet activation/aggregation, and fibrin clot dissolution. It decreased partial thromboplastin time (aPTT), prothrombin time (PT), and thrombin clotting time (TCT). These activities are similar to that shown by E. carinatus and D. russellii venoms, and thus O. hannah venom was found to exert procoagulant activity through the common pathway of blood coagulation, while N. naja venom increased aPTT and TCT but not PT, and hence it was found to exert anticoagulant activity through the intrinsic pathway. Venoms of O. hannah, E. carinatus, and D. russellii lack plasminogen activation property as they do not hydrolyze azocasein, while they all show plasmin-like activity by degrading the fibrin clot. Although N. naja venom did not degrade azocasein, unlike other venoms, it showed feeble plasmin-like activity on fibrin clot. Venom of E. carinatus induced clotting of human platelet rich plasma (PRP), while the other three venoms interfered in agonist-induced platelet aggregation in PRP. Venom of O. hannah least inhibited the ADP induced platelet aggregation as compared to D. russellii and N. naja venoms. All these three venoms showed complete inhibition of epinephrine-induced aggregation at varied doses. However, O. hannah venom was unique in inhibiting thrombin induced aggregation.

Hemostatic and toxinological diversities in venom of Micrurus tener tener, Micrurus fulvius fulvius and Micrurus isozonus coral snakes

The coral snake Micrurus tener tener (Mtt) from the Elapidae family inhabits the southwestern United States and produces severe cases of envenomations. Although the majority of Mtt venom components are neurotoxins and phospholipase A₂s, this study demonstrated, by SDS-PAGE and molecular exclusion chromatography (MEC), that these venoms also contain high-molecular-weight proteins between 50 and 150 kDa that target the hemostatic system. The biological aspects of other Micrurus venoms were also studied, such as the LD₅₀s of Micrurus isozonus (from 0.52 to 0.61 mg/kg). A pool from these venoms presented a LD₅₀ of 0.57 mg/kg, Micrurus f. fulvius (Mff) and Mtt had LD₅₀s of 0.32 and 0.78 mg/kg, respectively. These venoms contained fibrino(geno)lytic activity, they inhibited platelet aggregation, as well as factor Xa and/or plasmin-like activities. M. isozonus venoms from different Venezuelan geographical regions inhibited ADP-induced platelet aggregation (from 50 to 68%). Micrurus tener tener venom from the United States was the most active with a 95.2% inhibitory effect. This venom showed thrombin-like activity on fibrinogen and human plasma. Fractions of Mtt showed fibrino(geno)lytic activity and inhibition on plasmin amidolytic activity. Several fractions degraded the fibrinogen Aα chains, and fractions F2 and F7 completely degraded both fibrinogen Aα and Bβ chains. To our knowledge, this is the first report on thrombin-like and fibrino(geno)lytic activity and plasmin or factor Xa inhibitors described in Micrurus venoms. Further purification and characterization of these Micrurus venom components could be of therapeutic use in the treatment of hemostatic disorders.

Comparative study of anticoagulant and procoagulant properties of 28 snake venoms from families Elapidae, Viperidae, and purified Russell's viper venom-factor X activator (RVV-X)

Snake venoms consist of numerous molecules with diverse biological functions used for capturing prey. Each component of venom has a specific target, and alters the biological function of its target. Once these molecules are identified, characterized, and cloned; they could have medical applications. The activated clotting time (ACT) and clot rate were used for screening procoagulant and anticoagulant properties of 28 snake venoms. Crude venoms from Daboia russellii siamensis, Bothrops asper, Bothrops moojeni, and one Crotalus oreganus helleri from Wrightwood, CA, had procoagulant activity. These venoms induced a significant shortening of the ACT and showed a significant increase in the clot rate when compared to the negative control. Factor X activator activity was also measured in 28 venoms, and D. r. siamensis venom was 5-6 times higher than those of B. asper, B. moojeni, and C. o. helleri from Wrightwood County. Russell's viper venom-factor X activator (RVV-X) was purified from D. r. siamensis venom, and then procoagulant activity was evaluated by the ACT and clot rate. Other venoms, Crotalus atrox and two Naja pallida, had anticoagulant activity. A significant increase in the ACT and a significant decrease in the clot rate were observed after the addition of these venoms; therefore, the venoms were considered to have anticoagulant activity. Venoms from the same species did not always have the same ACT and clot rate profiles, but the profiles were an excellent way to identify procoagulant and anticoagulant activities in snake venoms.

Region-specific neutralization of Indian cobra (Naja naja) venom by polyclonal antibody raised against the eastern regional venom: A comparative study of the venoms from three different geographical distributions

Indian cobra (Naja naja) venoms from different geographical locations vary in their composition, biochemical, and pharmacological properties. Venom samples from eastern, western and southern India are compared in this study. The venom from eastern region was found to be the most lethal of the three regional venoms. Monovalent antivenom (NNEV-IgG) prepared against the eastern venom was found to cross-react with the other two regional venoms. NNEV-IgG at an Ag:Ab ratio of 1:25 completely neutralized the lethality of eastern venom. At this ratio, it did not neutralize the other two venoms, but the survival time of experimental mice was extended significantly. Commercially available polyvalent antivenom neutralized the lethality of western venom at an Ag:Ab ratio of 1:60 and increased the survival time of experimental mice injected with eastern and southern venoms marginally. Further, NNEV-IgG neutralized the tested pharmacological and enzymatic activities of all the three venom samples dose dependently, with neutralization potency varying with the geographic origin of the tested venoms. Thus, the present study demonstrates the diversity in the immunological properties of venom from different geographical regions and underscores the importance of developing region-specific antivenoms for therapeutic purpose.

Anticoagulant effect of Naja naja venom 5′nucleotidase: Demonstration through the use of novel specific inhibitor, vanillic acid

The snake venom proteins affect hemostasis by either advancing/delaying blood coagulation. Apart from proteases and phospholipase A(2)s (PLA(2)s), 5'nucleotidase is known to affect hemostasis by inhibiting platelet aggregation. In this study, the possible involvement of Naja naja venom 5'nucleotidase in mediating anticoagulant affect is evaluated. Vanillic acid selectively and specifically inhibited 5'nucleotidase activity among other enzymes present in N. naja venom. It is a competitive inhibitor as evident of inhibition relieving upon increased substrate concentration. Vanillic acid dose dependently inhibited the anticoagulant effect of N. naja venom up to 40%. This partial involvement of 5'nucleotidase in mediating anticoagulant effect is substantiated by concanavalin-A (Con-A) inhibition studies. Con-A, competitively inhibited in vitro protease and 5'nucleotidase activity up to 100%. However, it did not exhibit inhibitory activity on PLA(2). The complete inhibition of anticoagulant effect by Con-A upon recalcification time suggests the participation of both 5'nucleotidase and protease in mediating anticoagulant effect of N. naja venom. Vanillic acid and Con-A inhibition studies together suggest that probably 5'nucleotidase interacts with one or more factors of intrinsic pathway of blood coagulation to bring about anticoagulant effect. Thus, this study for the first time demonstrates the involvement of 5'nucleotidase in mediating N. naja venom anticoagulant effect.

Differential action of proteases from Trimeresurus malabaricus, Naja naja and Daboia russellii venoms on hemostasis

The action of venom proteases and their role in hemostasis has been compared in the venoms of Trimeresurus malabaricus, Daboia russellii and Naja naja from the Southern region of Western Ghats, India. These venoms exhibit varying amounts of proteolytic activity and also influence hemostasis differently. Casein hydrolyzing activity of T. malabaricus venoms was 16 and 24 fold higher than those of N. naja and D. russellii venoms, respectively. With the synthetic substrate TAME, the highest activity was observed in T. malabaricus venom. N. naja venom did not hydrolyze TAME even at higher concentrations. These variations in proteolytic activity also influenced the coagulation process. T. malabaricus and D. russellii venoms are strongly procoagulant and reduce the re-calcification time from 148 to 14 and 12 s, respectively. Similarly, both T. malabaricus and D. russellii venoms reduce the prothrombin time from 12.5 to 6.0 s. On the other hand, N. naja venom is anticoagulant and prolongs re-calcification time to 600 s and prothrombin time to 42 s. In spite of varied effects on hemostasis, all the venoms hydrolyze fibrinogen. T. malabaricus venom hydrolyses both Aalpha and Bbeta subunits. While D. russellii and N. naja venoms hydrolyse only Aalpha. None of these venoms hydrolyze the gamma subunit of fibrinogen. Inhibition studies with specific protease inhibitors revealed that both N. naja and T. malabaricus venoms contain only metalloproteases. D. russellii venom contained both serine and metalloproteases. Only, T. malabaricus venom exhibited thrombin-like activity and induces fibrin clot formation with purified fibrinogen within 58 s. Even though D. russellii venom exhibits procoagulant activity, it did not show thrombin-like activity and may act on other coagulation factors.

Protective immunity against alpha-cobratoxin following a single administration of a genetic vaccine encoding a non-toxic cobratoxin variant

Venomous snakebites result in almost 125,000 deaths per year worldwide. We present a new paradigm for the development of vaccines to protect against snakebite, using knowledge of the structure and action of specific toxins combined with a gene-based strategy to deliver a toxin gene modified to render it non-toxic while maintaining its three-dimensional structure and hence its ability to function as an immunogen. As a model for this approach, we developed a genetic vaccine to protect against alpha-cobratoxin (CTX), a potent, post-synaptic neurotoxin that is the major toxic component of the venom of Naja kaouthia, the monocellate cobra. To develop the vaccine, substitutions in the CTX cDNA were introduced at two residues critical for binding to the nicotinic acetylcholine receptor (Asp27 to Arg, Arg33 to Gly). The mutated CTX expression cassette was delivered in the context of a replication deficient adenovirus vector (AdmCTX). To assess whether expression of the mutated CTX in vivo leads to the development of protective immunity, BALB/c mice were challenged by IV administration of 2 microg of alpha-cobratoxin protein 21 or 63 days after administration of AdmCTX or Ad- Null (as a control; both, 10(9) particle units). Animals receiving AdmCTX but no alpha-cobratoxin challenge suffered no ill effects, but > or =80% of naive animals or those receiving the AdNull control vector died within 10 min from the alpha-cobratoxin challenge. In contrast, 100% of animals receiving a single dose of AdmCTX 21 or 63 days prior to alpha-cobratoxin challenge survived. The data demonstrates that an adenovirus-based vaccine can be developed to protect against lethal challenge with a potent snake venom. The effectiveness of this approach might serve as a basis to consider the development of a global public health program to protect those at risk for death by snakebite.