Effects of snake venoms on hemostasis

Tiny but Mighty: Vipera ammodytes meridionalis (Eastern Long-Nosed Viper) Ontogenetic Venom Variations in Procoagulant Potency and the Impact on Antivenom Efficacies

The Eastern Long-Nosed Viper (Vipera ammodytes meridionalis) is considered one of the most venomous snakes in Europe. However, it is unknown whether ontogenetic variation in venom effects occurs in this subspecies and how this may impact antivenom efficacy. In this study, we compared the procoagulant activities of V. a. meridionalis venom on human plasma between neonate and adult venom phenotypes. We also examined the efficacy of three antivenoms-Viperfav, ViperaTAb, and Inoserp Europe-across our neonate and adult venom samples. While both neonate and adult V. a. meridionalis venoms produced procoagulant effects, the effects produced by neonate venom were more potent. Consistent with this, neonate venom was a stronger activator of blood-clotting zymogens, converting them into their active forms, with a rank order of Factor X >> Factor VII > Factor XII. Conversely, the less potent adult venom had a rank order of FXII marginally more activated than Factor VII, and both much more so than Factor X. This adds to the growing body of evidence that activation of factors besides FII (prothrombin) and FX are significant variables in reptile venom-induced coagulopathy. Although all three examined antivenoms displayed effective neutralization of both neonate and adult V. a. meridionalis venoms, they generally showed higher efficacy on adult venom than on neonate venom. The ranking of antivenom efficacy against neonate venom, from the most effective to the least effective, were Viperfav, Inoserp Europe, ViperaTAb; for adult venom, the ranking was Inoserp Europe, Viperfav, ViperaTAb. Our data reveal ontogenetic variation in V. a meridionalis, but this difference may not be of clinical concern as antivenom was effective at neutralizing both adult and neonate venom phenotypes. Regardless, our results highlight a previously undocumented ontogenetic shift, likely driven by the documented difference in prey preference observed for this species across age classes.

Prospects and Challenges of Developing Plant-Derived Snake Antivenin Natural Products: A Focus on West Africa

Snakebite envenomation (SBE) is an important public health issue that is now receiving renewed attention following its reclassification as a Neglected Tropical Disease (NTD). Most incidences occur in rural areas of resource-limited countries, as such, timely and appropriate medical care for SBE is often inaccessible. The administration of anti-snake venom serum (ASV) is the only effective definitive treatment of SBE, but treatment failure to available ASVs is not uncommon. Emerging evidence highlights the potential of small-molecule compounds as inhibitors against toxins of snake venom. This presents an encouraging prospect to develop an alternative therapeutic option for the treatment SBE, that may be amenable for use at the point of care in resource-constraint settings. In view of the pivotal role of natural products in modern drug discovery programmes, there is considerable interest in ethno-pharmacological mining of medicinal plants and plant-derived medicinal compounds toward developing novel snake venom-neutralising therapeutics. In this review, we compile a collection of medicinal plants used in the treatment of SBE in West Africa and highlight their promise as potential botanical drugs or as sources of novel small-molecule compounds for the treatment of SBE. The challenges that must be surmounted to bring this to fruition including the need for (sub) regional collaboration have been discussed.

Moringa oleifera Extract Extenuates Echis ocellatus Venom-Induced Toxicities, Histopathological Impairments and Inflammation via Enhancement of Nrf2 Expression in Rats

Echis ocellatus snakebite causes more fatalities than all other African snake species combined. Moringa oleifera reportedly possesses an antivenom property. Therefore, we evaluated the effectiveness of M. oleifera ethanol extract (MOE) against E. ocellatus venom (EOV) toxicities. Thirty male rats were grouped as follows (n = 5): Group 1 (normal control received saline), groups 2 to 6 were administered intraperitoneally, 0.22 mg/kg (LD50) of EOV. Group 2 was left untreated while group 3 to 6 were treated post-envenoming with 0.2 mL of polyvalent antivenom, 200, 400, and 600 mg/kg of MOE respectively. MOE significantly (p < 0.05) normalized the altered haematological indices and blood electrolytes profiles. MOE attenuated venom-induced cellular dysfunctions, characterized by a significant increase in NRF2, and concomitant downregulation of increased antioxidant enzymes (SOD and CAT) activities in the serum and heart of the treated rats. MOE normalized the elevated TNF-α and IL-1β in serum and heart tissues. Furthermore, the IgG titre value was significantly (p < 0.5) higher in the envenomed untreated group compared to the MOE-treated groups. Hemorrhagic, hemolytic and coagulant activities of the venom were strongly inhibited by the MOE dose, dependently. Lesions noticed on tissues of vital organs of untreated rats were abolished by MOE. Our findings substantiate the effectiveness of MOE as a potential remedy against EOV toxicities.

Model-Based Inference of Punctuated Molecular Evolution

In standard models of molecular evolution, DNA sequences evolve through asynchronous substitutions according to Poisson processes with a constant rate (called the molecular clock) or a rate that can vary (relaxed clock). However, DNA sequences can also undergo episodes of fast divergence that will appear as synchronous substitutions affecting several sites simultaneously at the macroevolutionary timescale. Here, we develop a model, which we call the Relaxed Clock with Spikes model, combining basal, clock-like molecular substitutions with episodes of fast divergence called spikes arising at speciation events. Given a multiple sequence alignment and its time-calibrated species phylogeny, our model is able to detect speciation events (including hidden ones) cooccurring with spike events and to estimate the probability and amplitude of these spikes on the phylogeny. We identify the conditions under which spikes can be distinguished from the natural variance of the clock-like component of molecular substitutions and from variations of the clock. We apply the method to genes underlying snake venom proteins and identify several spikes at gene-specific locations in the phylogeny. This work should pave the way for analyses relying on whole genomes to inform on modes of species diversification.

Crotamine in Crotalus durissus: distribution according to subspecies and geographic origin, in captivity or nature

Background:

Crotalus durissus is considered one of the most important species of venomous snakes in Brazil, due to the high mortality of its snakebites. The venom of Crotalus durissus contains four main toxins: crotoxin, convulxin, gyroxin and crotamine. Venoms can vary in their crotamine content, being crotamine-negative or -positive. This heterogeneity is of great importance for producing antivenom, due to their different mechanisms of action. The possibility that antivenom produced by Butantan Institute might have a different immunorecognition capacity between crotamine-negative and crotamine-positive C. durissus venoms instigated us to investigate the differences between these two venom groups.

Methods:

The presence of crotamine was analyzed by SDS-PAGE, western blotting and ELISA, whereas comparison between the two types of venoms was carried out through HPLC, mass spectrometry analysis as well as assessment of antivenom lethality and efficacy.

Results:

The results showed a variation in the presence of crotamine among the subspecies and the geographic origin of snakes from nature, but not in captive snakes. Regarding differences between crotamine-positive and -negative venoms, some exclusive proteins are found in each pool and the crotamine-negative pool presented more phospholipase A₂ than crotamine-positive pool. This variation could affect the time to death, but the lethal and effective dose were not affected.

Conclusion:

These differences between venom pools indicate the importance of using both, crotamine-positive and crotamine-negative venoms, to produce the antivenom.

Delineating the venom toxin arsenal of Malabar pit viper (Trimeresurus malabaricus) from the Western Ghats of India and evaluating its immunological cross-reactivity and in vitro cytotoxicity

The venom protein components of Malabar pit viper (Trimeresurus malabaricus) were identified by combining SDS-PAGE and ion-exchange chromatography pre-fractionation techniques with LC-MS/MS incorporating Novor and PEAKS-assisted de novo sequencing strategies. Total 97 proteins that belong to 16 protein families such as L-amino acid oxidase, metalloprotease, serine protease, phospholipase A2, 5'-nucleotidase, C-type lectins/snaclecs and disintegrin were recognized from the venom of a single exemplar species. Of the 97 proteins, eighteen were identified through de novo approaches. Immunological cross-reactivity assessed through ELISA and western blot indicate that the Indian antivenoms binds less effectively to Malabar pit viper venom components compared to that of Russell's viper venom. The in vitro cell viability assays suggest that compared to the normal cells, MPV venom induces concentration dependent cell death in various cancer cells. Moreover, crude venom resulted in chromatin condensation and apoptotic bodies implying the induction of apoptosis. Taken together, the present study enabled in dissecting the venom proteome of Trimeresurus malabaricus and revealed the immuno-cross-reactivity profiles of commercially available Indian polyvalent antivenoms that, in turn, is expected to provide valuable insights on the need in improving antivenom preparations against its bite.

Analysis of snake venom metalloproteinases from Myanmar Russell's viper transcriptome

Snake venom metalloproteinases (SVMPs) are the key enzymes in Russell's viper (RV) venom which target all important components of haemostasis, such as clotting factors, platelets, endothelial cells and basement membrane. The structural diversity of SVMPs contributes to the broad spectrum of biological activities. The aim of the study was to investigate the SVMP transcript profile to gain better insights into the characteristic clinical manifestations of the Myanmar Russell's viper (MRV) bites that distinguish it from the RVs of other habitats. Next generation sequencing (RNA-Seq) of mRNA from MRV venom glands (2 males and 1 female) was performed on an Illumina HiSeq2000 platform and then de novo assembled using Trinity software. A total of 59 SVMP contigs were annotated through a Blastn search against the serpent nucleotide database from NCBI. Among them, disintegrins were the most abundant transcripts (75%) followed by the P-III class SVMPs (25%). The P-II SVMPs were scarce (0.002%), while no P-I SVMPs were detectable in the transcriptome. For detailed structural analysis, contigs were conceptually translated and compared with amino acid sequences from other RVs and other vipers using Clustal Omega. The RTS-disintegrin (jerdostatin homolog) was the most abundant among transcripts corresponding to 5 disintegrin isoforms. From 10 isoforms of SVMPs, RVV-X, and Vipera lebetina apoptosis-inducing protease (VLAIP) homolog, hereby termed Daboia siamensis AIP (DSAIP), were found to be highly expressed. Venom protein analysis using SDS-PAGE followed by mass spectrometry revealed that the disintegrin was scarce, while the latter two SVMPs were abundant. These two proteins can contribute to severe clinical manifestations caused by MRV envenomation.

Identification and phylogeny of Arabian snakes: Comparison of venom chromatographic profiles versus 16S rRNA gene sequences

Identification of snake species is important for various reasons including the emergency treatment of snake bite victims. We present a simple method for identification of six snake species using the gel filtration chromatographic profiles of their venoms. The venoms of Echis coloratus, Echis pyramidum, Cerastes gasperettii, Bitis arietans, Naja arabica, and Walterinnesia aegyptia were milked, lyophilized, diluted and centrifuged to separate the mucus from the venom. The clear supernatants were filtered and chromatographed on fast protein liquid chromatography (FPLC). We obtained the 16S rRNA gene sequences of the above species and performed phylogenetic analysis using the neighbor-joining method. The chromatograms of venoms from different snake species showed peculiar patterns based on the number and location of peaks. The dendrograms generated from similarity matrix based on the presence/absence of particular chromatographic peaks clearly differentiated Elapids from Viperids. Molecular cladistics using 16S rRNA gene sequences resulted in jumping clades while separating the members of these two families. These findings suggest that chromatographic profiles of snake venoms may provide a simple and reproducible chemical fingerprinting method for quick identification of snake species. However, the validation of this methodology requires further studies on large number of specimens from within and across species.

Naja naja karachiensis envenomation: biochemical parameters for cardiac, liver, and renal damage along with their neutralization by medicinal plants

Naja naja karachiensis envenomation was found to hit more drastically heart, liver, and kidneys. 400 μg/kg of venom-raised moderate serum levels of ALT (72 ± 4.70 U/L, 0.1 > P > 0.05), AST (157 ± 24.24 U/L, 0.1 > P > 0.05), urea (42 ± 3.08 mg/dL, 0.05 > P > 0.02), creatinine (1.74 ± 0.03 mg/dL, 0.01 > P > 0.001), CK-MB (21 ± 1.5 U/L, 0.05 > P > 0.02), and LDH (2064 ± 15.98 U/L, P < 0.001) were injected in experimental rabbits. However, lethality was enhanced with 800 μg/kg of venom in terms of significant release of ALT (86 ± 5.0 U/L, 0.05 > P > 0.02), AST (251 ± 18.2 U/L, 0.01 > P > 0.001), urea (57.6 ± 3.84 mg/dL, 0.02 > P > 0.01), creatinine (2.1 ± 0.10 mg/dL, 0.02 > P > 0.01), CK-MB (77 ± 11.22 U/L, 0.05 > P > 0.02), and LDH (2562 ± 25.14 U/L, P ≪ 0.001). Among twenty-eight tested medicinal plant extracts, only Stenolobium stans (L.) Seem was found the best antivenom (P > 0.5) compared to the efficacy of standard antidote (ALT = 52.5 ± 3.51 U/L, AST = 69.5 ± 18.55 U/L, urea = 31.5 ± 0.50 mg/dL, creatinine = 1.08 ± 0.02 mg/dL, CK-MB = 09 ± 0.85 U/L, and LDH = 763 ± 6.01 U/L). Other plant extracts were proved less beneficial and partly neutralized the toxicities posed by cobra venom. However, it is essential in future to isolate and characterize bioactive compound(s) from Stenolobium stans (L.) Seem extract to overcome the complications of snake bite.

Anti-cobra venom activity of plant Andrographis paniculata and its comparison with polyvalent anti-snake venom

Background:

To investigate the anti-cobra venom effect of alcoholic extract of Andrographis paniculata.

Materials and Methods:

After calculating the LD₉₉ of snake venom, the venom-neutralizing ability of plant extract at the dose 1 g/kg and 2 g/kg was determined using in vitro and in vivo methods. The alleviation in the mean survival time of the animals were used to infer the antivenom property of the drug after challenging with LD₉₉ of snake venom.

Results:

The ethanolic extract of plant A. paniculata significantly increases mean survival time and the protection fold, but could not protect animals from death when used alone. The higher dose, i.e., 2 g/kg was found better than that of the lower. ASV was found more effective than the plant extract. When ASV was given along with plant extract, it potentiates its effect.

Conclusion:

The observation demonstrates the anti-cobra venom activity of ethanolic extract of A. paniculata which is comparable with ASV.

Sequence and phylogenetic analysis of viper venom serine proteases

Snakebites are a major neglected tropical disease responsible for as many as 95000 deaths every year worldwide. Viper venom serine proteases disrupt haemostasis of prey and victims by affecting various stages of the blood coagulation system. A better understanding of their sequence, structure, function and phylogenetic relationships will improve the knowledge on the pathological conditions and aid in the development of novel therapeutics for treating snakebites. A large dataset for all available viper venom serine proteases was developed and analysed to study various features of these enzymes. Despite the large number of venom serine protease sequences available, only a small proportion of these have been functionally characterised. Although, they share some of the common features such as a C-terminal extension, GWG motif and disulphide linkages, they vary widely between each other in features such as isoelectric points, potential N-glycosylation sites and functional characteristics. Some of the serine proteases contain substitutions for one or more of the critical residues in catalytic triad or primary specificity pockets. Phylogenetic analysis clustered all the sequences in three major groups. The sequences with substitutions in catalytic triad or specificity pocket clustered together in separate groups. Our study provides the most complete information on viper venom serine proteases to date and improves the current knowledge on the sequence, structure, function and phylogenetic relationships of these enzymes. This collective analysis of venom serine proteases will help in understanding the complexity of envenomation and potential therapeutic avenues.

Isolation and characterisation of a kallikrein-like enzyme from Agkistrodon halys pallas snake venom

BACKGROUND

Viper snake venoms contain a great variety of toxic proteins. These components mediate their toxicity by either stimulating or inhibiting the haemostatic system of human victims or experimental animals, resulting in common clinical complications of blood clotting or uncontrolled haemorrhage. Therefore it is deemed important to isolate the active component(s) from snake venom with kallikrein-like activity.

RESULTS

A kallikrein-like proteinase of Agkistrodon halys pallas snake venom, designated AHP-Ka, was purified by anion exchange chromatography and affinity chromatography. Physicochemical studies showed that the purified enzyme was a 34 kDa monomeric glycoprotein, the molecular weight of which decreased to 26 kDa after deglycosylation with peptide N-glycosidase F (PNGase F). Sequence studies on the NH(2) -terminal region of the protein indicated that AHP-Ka shared a high degree of sequence homology with other serine proteinases from snake venoms. AHP-Ka showed high catalytic activity and kallikrein-like activity on substrates such as arginine esterase BAEE and chromogenic H-D-Pro-Phe-Arg-pNA·2HCl (S-2302) and was inhibited by protease inhibitor phenylmethylsulfonyl fluoride (PMSF).

CONCLUSION

The results showed that AHP-Ka isolated from A. halys pallas snake venom and purified by anion exchange chromatography and affinity chromatography is in fact a kallikrein-like enzyme.

Structural and functional comparison of proteolytic enzymes from plant latex and snake venoms

This work describes classification, functions, location, inhibition, activation, and therapeutic applications of proteases from snake venoms and vegetables. Snake venoms and vegetables can present toxins that unchain necrosis or proteolysis due to the direct cytotoxic action of venom proteases. These proteases are potential tools in the development of drugs for the prevention and treatment of several illnesses. We report herein mainly fibrinogenolytic metallo proteases and serine proteases ("thrombin-like"). These enzymes are extensively used in the treatment and prevention of thrombotic disorders, since they serve as defibrinogenating agents. The therapeutic uses of fibrin(ogen)olytic metallo proteases hold promise for clinical application due to potential in reversing the effects of thrombosis; this has been shown to be an alternative approach to the prevention and treatment of cardiovascular disorders, which are among the most prominent causes of mortality around the world. Plant proteases can be utilized for many cellular and molecular activities, in antibacterial and anticancer therapies, and in the treatment of snakebites, inhibiting snake venom activities such as blood-clotting, defibrinogenation, and fibrin(ogen)olytic and hemorrhagic actions. These toxins also display potential for clinical use in the treatment of hemostatic disorders.

The effect of different snake venoms and anti-venoms on thrombin clotting time in human plasma

BACKGROUND

Crotaline snake species, or pit vipers, are distributed throughout Asia and America. While much is known about the clinical effect of these snake venoms, there is a lack of evidence related to the various anti-venoms available and their effectiveness in reversing the effect of different venoms.

AIM

This study aimed to determine the interaction of the venoms of the following species: Crotalus unicolor, Crotalus adamanteus, Crotalus vegrandis, Trimeresurus spp, Calloselasma rhodostoma, Bothriechis schlegelii and Agkistrodon and the following anti-venoms: Anticrotalico, Antivipmyn, Antibotropico, Antifidico and SAIMR by evaluating their effect on the thrombin clotting time in human plasma.

METHOD

The interactions of venoms and anti-venoms were evaluated using thrombin clotting time in human plasma.

RESULTS

The results demonstrate that Anticrotalico anti-venom was most effective for the Crotalid species (Crotalus unicolor, Crotalus adamanteus, Crotalus vegrandis). Anticrotalico extended the time to clot formation 2.7 fold for Crotalus Unicolor, 3 fold for Crotalus Adamanteus and 4.6 fold for Crotalus Vegrandis. The anti-venoms most efficient in reversing the effect of the Trimeresurus spp venom, were Anticrotalico, Antivipmyn, Antibotropico and Antifidico anti-venoms, which all completely reversed the effect of clot formation as evident by no clot formation within the 999 seconds measurement limit. Bothriechis schlegelii venom was neutralized by all anti-venoms tested. Calloselasma rhodostoma venom was neutralized by Antifidico as well as Anticrotalico. The most efficient anti-venoms against the Agkistrodon venom were Anticrotalico and Antibotropico. In general, monovalent anti-venoms had improved efficiency for their corresponding snake species, depending highly on the composition of the snake venom. This study confirms the importance of considering the choice of anti-venom in a clinical setting, to reverse the effect of specific snake venoms. In addition, this study suggests that some anti-venoms can be considered for use against a variety of snake-venoms.

Purification and functional characterisation of rhinocerase, a novel serine protease from the venom of Bitis gabonica rhinoceros

Background

Serine proteases are a major component of viper venoms and are thought to disrupt several distinct elements of the blood coagulation system of envenomed victims. A detailed understanding of the functions of these enzymes is important both for acquiring a fuller understanding of the pathology of envenoming and because these venom proteins have shown potential in treating blood coagulation disorders.

Methodology/Principal Findings

In this study a novel, highly abundant serine protease, which we have named rhinocerase, has been isolated and characterised from the venom of Bitis gabonica rhinoceros using liquid phase isoelectric focusing and gel filtration. Like many viper venom serine proteases, this enzyme is glycosylated; the estimated molecular mass of the native enzyme is approximately 36kDa, which reduces to 31kDa after deglycosylation. The partial amino acid sequence shows similarity to other viper venom serine proteases, but is clearly distinct from the sequence of the only other sequenced serine protease from Bitis gabonica. Other viper venom serine proteases have been shown to exert distinct biological effects, and our preliminary functional characterization of rhinocerase suggest it to be multifunctional. It is capable of degrading α and β chains of fibrinogen, dissolving plasma clots and of hydrolysing a kallikrein substrate.

Conclusions/Significance

A novel multifunctional viper venom serine protease has been isolated and characterised. The activities of the enzyme are consistent with the known in vivo effects of Bitis gabonica envenoming, including bleeding disorders, clotting disorders and hypotension. This study will form the basis for future research to understand the mechanisms of serine protease action, and examine the potential for rhinocerase to be used clinically to reduce the risk of human haemostatic disorders such as heart attacks and strokes.

Bioassay-directed purification of an acidic phospholipase A(2) from Agkistrodon halys pallas venom

Relying on ex vivo and in vitro platelet anti-aggregation assays, a tail bleeding time assay, and an anti-thrombotic assay, we have purified the fraction of venom from Agkistrodon halys pallas which, in all of these assays, is the most active. There were two major steps in the purification: gel filtration chromatography on Sephadex G-100, and ion exchange chromatography on DEAE Sephadex A-50. Sequencing of the most active fraction by mass spectrometry revealed that it is a known acidic phospholipase A(2). Prior expectations by others about the in vivo anti-thrombotic activity of this enzyme are confirmed.

Quantitative analysis of snake venoms using soluble polymer-based isotope labeling

We present the design and synthesis of a new quantitative strategy termed soluble polymer-based isotope labeling (SoPIL) and its application as a novel and inclusive method for the identification and relative quantification of individual proteins in complex snake venoms. The SoPIL reagent selectively captures and isolates cysteine-containing peptides, and the subsequent tagged peptides are released and analyzed using nanoflow liquid chromatography-tandem mass spectrometry. The SoPIL strategy was used to quantify venom proteins from two pairs of venomous snakes: Crotalus scutulatus scutulatus type A, C. scutulatus scutulatus type B, Crotalus oreganus helleri, and Bothrops colombiensis. The hemorrhagic, hemolytic, clotting ability, and fibrinogenolytic activities of crude venoms were measured and correlated with difference in protein abundance determined by the SoPIL analysis. The SoPIL approach could provide an efficient and widely applicable tool for quantitative proteomics.

The venom gland transcriptome of the Desert Massasauga rattlesnake (Sistrurus catenatus edwardsii): towards an understanding of venom composition among advanced snakes (Superfamily Colubroidea)

Background

Snake venoms are complex mixtures of pharmacologically active proteins and peptides which belong to a small number of superfamilies. Global cataloguing of the venom transcriptome facilitates the identification of new families of toxins as well as helps in understanding the evolution of venom proteomes.

Results

We have constructed a cDNA library of the venom gland of a threatened rattlesnake (a pitviper), Sistrurus catenatus edwardsii (Desert Massasauga), and sequenced 576 ESTs. Our results demonstrate a high abundance of serine proteinase and metalloproteinase transcripts, indicating that the disruption of hemostasis is a principle mechanism of action of the venom. In addition to the transcripts encoding common venom proteins, we detected two varieties of low abundance unique transcripts in the library; these encode for three-finger toxins and a novel toxin possibly generated from the fusion of two genes. We also observed polyadenylated ribosomal RNAs in the venom gland library, an interesting preliminary obsevation of this unusual phenomenon in a reptilian system.

Conclusion

The three-finger toxins are characteristic of most elapid venoms but are rare in viperid venoms. We detected several ESTs encoding this group of toxins in this study. We also observed the presence of a transcript encoding a fused protein of two well-characterized toxins (Kunitz/BPTI and Waprins), and this is the first report of this kind of fusion in a snake toxin transcriptome. We propose that these new venom proteins may have ancillary functions for envenomation. The presence of a fused toxin indicates that in addition to gene duplication and accelerated evolution, exon shuffling or transcriptional splicing may also contribute to generating the diversity of toxins and toxin isoforms observed among snake venoms. The detection of low abundance toxins, as observed in this and other studies, indicates a greater compositional similarity of venoms (though potency will differ) among advanced snakes than has been previously recognized.

Elucidation of trends within venom components from the snake families Elapidae and Viperidae using gel filtration chromatography

Research into snake venom components has intensified over the last number of decades, particularly that work directed towards the discovery of novel agents with potential applications in clinical therapy. In the present study we report, for the first time, defined patterns observed in the G-50 chromatographic elution profiles from 30 snake venoms taken from Elapidae and Viperidae families, as well as previously unreported patterns within subfamilies of these snake species. Development of this chromatographic technique thus offers a rapid method for the general classification of snakes within these families as well as providing insights into hitherto uncharacterised trends within the venoms of snake subfamilies that have opened new avenues for further investigation.

Purification and biological activity of the thrombin-like substance isolated from Bothrops insularis venom

The venom of Bothrops insularis snake, known in Brazil as jararaca ilhoa, contains a variety of proteolytic enzymes such as a thrombin-like substance that is responsible for various pharmacological effects. B. insularis venom chromatography profile showed an elution of seven main fractions. The thrombin-like activity was detected in fractions I and III, the latter being subjected to two other chromatographic procedures, so to say DEAE and Hi Trap Benzamidine. The purity degree of this fraction was confirmed by analytical reverse phase HPLC, which displayed only one main fraction confirmed by SDS-PAGE constituting fraction III. About 5 microg of fraction III protein potentiated the secretion of insulin induced by 2.8 mM of glucose in rats isolated pancreatic beta-cells treated; the increase being around 3-fold higher than its respective control. B. insularis lectin (BiLec; 10 microg/mL) was also studied as to its effect on the renal function of isolated perfused rat kidneys with the use of six Wistar rats. BiLec increased perfusion pressure (PP), renal vascular resistance (RVR), urinary flow (UF) and glomerular filtration rate (GFR). Sodium (%TNa+) and chloride tubular reabsorption (%TCl-) decreased at 120 min, without alteration in potassium transport. In conclusion, the thrombin-like substance isolated from B. insularis venom induced an increase in insulin secretion, in vitro, and transiently altered vascular, glomerular and tubular parameters in the isolated rat kidney.

Anticoagulant proteins from snake venoms: structure, function and mechanism

Over the last several decades, research on snake venom toxins has provided not only new tools to decipher molecular details of various physiological processes, but also inspiration to design and develop a number of therapeutic agents. Blood circulation, particularly thrombosis and haemostasis, is one of the major targets of several snake venom proteins. Among them, anticoagulant proteins have contributed to our understanding of molecular mechanisms of blood coagulation and have provided potential new leads for the development of drugs to treat or to prevent unwanted clot formation. Some of these anticoagulants exhibit various enzymatic activities whereas others do not. They interfere in normal blood coagulation by different mechanisms. Although significant progress has been made in understanding the structure-function relationships and the mechanisms of some of these anticoagulants, there are still a number of questions to be answered as more new anticoagulants are being discovered. Such studies contribute to our fight against unwanted clot formation, which leads to death and debilitation in cardiac arrest and stroke in patients with cardiovascular and cerebrovascular diseases, arteriosclerosis and hypertension. This review describes the details of the structure, mechanism and structure-function relationships of anticoagulant proteins from snake venoms.

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.

Snake venoms and hemostasis

Snake venoms are complex mixtures of biologically active proteins and peptides. Many of them affect hemostasis by activating or inhibiting coagulant factors or platelets, or by disrupting endothelium. Based on sequence, these snake venom components have been classified into various families, such as serine proteases, metalloproteinases, C-type lectins, disintegrins and phospholipases. The various members of a particular family act selectively on different blood coagulation factors, blood cells or tissues. For almost every factor involved in coagulation or fibrinolysis there is a venom protein that can activate or inactivate it. Venom proteins affect platelet function by binding or degrading vWF or platelet receptors, activating protease-activated receptors or modulating ADP release and thromboxane A2 formation. Some venom enzymes cleave key basement membrane components and directly affect capillary blood vessels to cause hemorrhaging. L-Amino acid oxidases activate platelets via H2O2 production.

Molecular cloning of serine proteinases from Bothrops jararaca venom gland

Snake venom is known to contain an abundance of enzyme isoforms, and various disorders associated with envenomation have been ascribed partially to their diversified functions. Crude venom of Bothrops jararaca was subjected to conventional two-dimensional SDS-PAGE, followed by immunoblot analysis using an antiserum raised against KN-BJ 2, a serine proteinase previously isolated from this venom. A number of immunoreactive proteins with comparable molecular masses and different pIs emerged, implying the venom contains yet-unknown serine proteinases. A B. jararaca venom gland cDNA library was subsequently screened with a labeled KN-BJ 2 cDNA as a probe. Among a number of positive cDNA clones, three--HS112, HS114, and HS120--were selected and sequenced. These clones each had an open reading frame of 759-774 bp, and their deduced amino acid sequences illustrated considerable similarities to that of KN-BJ 2 as well as to those of serine proteinases of different origins. However, no apparent match to any of the deposited sequences was found in the current GenBank/EMBL databases, indicating that each of these cDNA clones encodes a serine proteinase distinct from the known enzymes. Analyses of the nucleotide and amino acid sequences of these cDNA clones support the accelerated evolution hypothesis proposed for snake venom enzymes.

Adenosine in the venoms from viperinae snakes of the genus Bitis: Identification and quantitation using LC/MS and CE/MS

Snake venoms are rich sources of toxic proteins and small molecules. This study was directed at molecules of molecular mass below 1 kDa. Thirty different venoms, of either neurotoxic or haemorrhagic type, were fractionated using size-exclusion chromatography. Only venoms of the Puff adder (Bitis arietans), Gaboon viper (Bitis gabonica), and Rhinoceros viper (Bitis nasicornis) exhibited large absorbance peaks at lambda(280 nm) in the total volume range of the chromatographic column indicating the presence of abundant low molecular mass material. Analysis of fractions containing this material using both HPLC and capillary electrophoresis interfaced with electrospray ion-trap mass spectrometry unequivocally established that the bioactive nucleoside, adenosine, was the major component. The concentrations of adenosine found (Puff adder--97.7 x 10(-6) mol L(-1); Gaboon viper--28.0 x 10(-6) mol L(-1); and Rhinoceros viper-56.8 x 10(-6) mol L(-1)) were above those required to activate all known sub-types of adenosine receptors. Adenosine may thus act at the site of envenomation causing local vasodilatation and may play a role in the subsequent systemic hypotension observed.

A novel disintegrin, jerdonatin, inhibits platelet aggregation and sperm-egg binding

A novel disintegrin, jerdonatin, was purified to homogeneity from Trimeresurus jerdonii venom by gel filtration and reversed-phase high-pressure liquid chromatography. We isolated the cDNA encoding jerdonatin from the snake venom gland. Jerdonatin cDNA precursor encoded pre-peptide, metalloprotease and disintegrin domain. Jerdonatin is composed of 72 amino acid residues including 12 cysteines and the tripeptide sequence Arg-Gly-Asp (RGD), a well-known characteristic of the disintegrin family. Molecular mass of jerdonatin was determined to be 8011 Da by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). Jerdonatin inhibited ADP- and collagen-induced human platelet aggregation with IC50 of 123 and 135 nM, respectively. We also investigated the effect of jerdonatin on the binding of B6D2F1 hybrid mice spermatozoa to mice zona-free eggs and their subsequent fusion. Jerdonatin significantly inhibited sperm-egg binding in a concentration-dependent manner, but had no effect on the fusion of sperm-egg. These results indicate that integrins on the egg play a role in mammalian fertilization.

Structure–function relationships and mechanism of anticoagulant phospholipase A2 enzymes from snake venoms

Phospholipase A(2) (PLA(2)) enzymes from snake venom are toxic and induce a wide spectrum of pharmacological effects, despite similarity in primary, secondary and tertiary structures and common catalytic properties. Thus, the structure-function relationships and the mechanism of this group of small proteins are subtle, complex and intriguing challenges. This review, taking the PLA(2) enzymes from spitting cobra (Naja nigricollis) venom as examples, describes the mechanism of anticoagulant effects. The strongly anticoagulant CM-IV inhibits both the extrinsic tenase and prothrombinase complexes, whereas the weakly anticoagulant PLA(2) enzymes (CM-I and CM-II) inhibit only the extrinsic tenase complex. CM-IV binds to factor Xa and interferes in its interaction with factor Va and the formation of prothrombinase complex. In contrast, CM-I and CM-II do not affect the formation of prothrombinase complex. In addition, CM-IV inhibits the extrinsic tenase complex by a combination of enzymatic and nonenzymatic mechanisms, while CM-I and CM-II inhibit by only enzymatic mechanism. These functional differences explain the disparity in the anticoagulant potency of N. nigricollis PLA(2) enzymes. Similarly, human secretory enzyme binds to factor Xa and inhibits the prothrombinase complex. We predicted the anticoagulant region of PLA(2) enzymes using a systematic and direct comparison of amino acid sequences. This region between 54 and 77 residues is basic in the strongly anticoagulant PLA(2) enzymes and neutral or negatively charged in weakly and non-anticoagulant enzymes. The prediction is validated independently by us and others using both site directed mutagenesis and synthetic peptides. Thus, strongly anticoagulant CM-IV binds to factor Xa (its target protein) through the specific anticoagulant site on its surface. In contrast, weakly anticoagulant enzymes, which lack the anticoagulant region fail to bind specifically to the target protein, factor Xa in the coagulation cascade. Thus, these studies strongly support the target model which suggests that protein-protein interaction rather than protein-phospholipid interaction determines the pharmacological specificity of PLA(2) enzymes.

Snake Venom: Any Clue for Antibiotics and CAM?

Lately several naturally occurring peptides presenting antimicrobial activity have been described in the literature. However, snake venoms, which are an enormous source of peptides, have not been fully explored for searching such molecules. The aim of this work is to review the basis of antimicrobial mechanisms revealing snake venom as a feasible source for searching an antibiotic prototype. Therefore, it includes (i) a description of the constituents of the snake venoms involved in their main biological effects during the envenomation process; (ii) examples of snake venom molecules of commercial use; (iii) mechanisms of action of known antibiotics; and (iv) how the microorganisms can be resistant to antibiotics. This review also shows that snake venoms are not totally unexplored sources for antibiotics and complementary and alternative medicine (CAM).

Biochemical properties of a bushmaster snake venom serine proteinase (LV-Ka), and its kinin releasing activity evaluated in rat mesenteric arterial rings

A serine proteinase with kallikrein-like activity (LV-Ka) has been purified to homogeneity from bushmaster snake (Lachesis muta muta) venom. Physicochemical studies indicated that LV-Ka is a single chain glycoprotein with a molecular mass (Mr) of 33 kDa under reducing conditions which was reduced to 28 kDa after treatment with N-Glycosidase F (PNGase F). LV-Ka can be bounded and neutralized by serum alpha2-macroglobulin (alpha2-M), a prevalent mammalian protease inhibitor that is capable of forming a macromolecular complex with LV-Ka (Mr >180 kDa). Cleavage of alpha2-M by the enzyme resulted in the formation of 90-kDa fragments. The proteolytic activity of LV-Ka against dimethylcasein could be inhibited by alpha2-M, and the binding ratio of the inhibitor:enzyme complex was found to be 1:1. The Michaelis constant, Km, and catalytic rate constant, kcat, of LV-Ka on four selective chromogenic substrates were obtained from Lineweaver-Burk plots. LV-Ka exhibits substrate specificities not only for the glandular kallikrein H-D-Val-Leu-Arg-pNA (S-2266) but also for the plasmin substrates S-2251 and Tos-Gly-Pro-Lys-pNA. Bovine kininogen incubated with LV-Ka generated a polypeptide that dose dependently contracted mesenteric arterial rings from spontaneously hypertensive rats (SHR) in a similar way as bradykinin (BK) does. As it happens with BK, LV-Ka generated polypeptide was inhibited by HOE-140, a bradykinin B2-receptor antagonist and by indomethacin, a cyclo-oxygenase inhibitor. These results strongly suggest that the polypeptide generated by LV-Ka by cleavage of bovine kininogen is bradykinin. In addition, our studies may help to understand the mechanism of action involved in hypotension produced by envenomation of bushmaster snake.

Kallikrein-like proteinase from bushmaster snake venom

A kallikrein-like proteinase of Lachesis muta muta (bushmaster) venom, designated LV-Ka, was purified by gel filtration and anion exchange chromatographies. Physicochemical studies indicated that the purified enzyme is a 33 kDa monomeric glycoprotein, the Mr of which fell to 28 kDa after deglycosylation with PNGase F. Approximately 77% of the protein sequence was determined by sequencing the various fragments derived from digestions with endoproteases. The partial sequence obtained suggests that LV-Ka is of a similar size to other serine proteinases (i.e., approximately 234 amino acid residues). Sequence studies on the NH2-terminal region of the protein indicate that LV-Ka shares a high degree of sequence homology with the kallikrein-like enzymes EI and EII from Crotalus atrox, with crotalase from Crotalus adamanteus and significant homology with other serine proteinases from snake venoms and vertebrate serum enzymes. LV-Ka showed kallikrein-like activity, releasing bradikinin from kininogen as evidenced by guinea pig bioassay. In addition, intravenous injection of the proteinase (0.8 microg/g) was shown to lower blood pressure in experimental rats. In vitro, the isolated proteinase was shown to have neither fibrin(ogeno)lytic activity nor coagulant effect. LV-Ka was active upon the kallikrein substrates S-2266 and S-2302 (specific activity=13.0 and 31.5 U/mg, respectively; crude venom=0.25 and 6.0 U/mg) but had no proteolytic effect on dimethylcasein and insulin B chain. Its enzymatic activity was inhibited by NPGB and PMSF, indicating that the enzyme is a serine proteinase. Interestingly, one of the other reactions catalyzed by plasma kallikrein, the activation of plasminogen was one of the activities exhibited by LV-Ka.

Intestinal ischemia after bushmaster (Lachesis muta) snakebite--a case report

After a snakebite by the Costa Rican bushmaster Lachesis stenophrys, a 64-year-old patient developed cardiovascular shock and coagulopathy. After intensive care and antivenom treatment, he was discharged after 4 days but had to be hospitalised again 3 days later because of abdominal pain and bowel obstruction. An emergency laparotomy revealed a necrotic ileum and caecum, and an obstruction of the superior mesenteric artery. Until now, this type of intestinal ischemic complication after a snakebite has not been reported in the literature. The effects of bushmaster venom are discussed.

An internet database of crotaline venom found in the United States

Many snake venoms have been shown to be complex mixtures of pharmacologically important molecules, some of which have potential therapeutic value in the treatment of clot-induced ischemia, cancer and other human disorders. The literature contains many references on how venom and/or venom components are being used in medicine. Within the United States, there are 44 subspecies of poisonous snakes. Despite this rather vast diversity, 90% of the venom-related biomedical research conducted on native snakes found in the United States has been done on a limited number of the more common species. Since the venoms from most of the native species are not available or characterized, their composition and potential usefulness in medicine and applied biomedical research has not been explored. The Natural Toxins Research Center (NTRC) at Texas A&M University-Kingsville has developed a serpentarium that presently houses a population of over 250 snakes composed of 11 species and 20 subspecies. These snakes are cataloged on the Internet database along with their geographical location data, proteolytic activities, high performance liquid chromatography (HPLC) and electrophoretic titration (ET) profiles. Many of these snake venoms have never been characterized and few locale-specific differences within a species have been examined. These venoms can be queried through an on-line search routine. The database will be a useful starting point for anyone interested in isolating fibrinolytic enzymes, specific toxins, hemorrhagins, or other pharmacologically active proteins from snake venoms.

Characterization of a thrombin-like enzyme from the venom of Trimeresurus jerdonii

From the venom of Trimeresurus jerdonii, a distinct thrombin-like enzyme, called jerdonobin, was purified by DEAE A-25 ion-exchange chromatography, Sephadex G-75 gel filtration, and fast protein liquid chromatography (FPLC). SDS-PAGE analysis of this enzyme shows that it consists of a single polypeptide chain with a molecular weight of 38,000. The NH(2)-terminal amino acid sequence of jerdonobin has great homology with venom thrombin-like enzymes documented. Jerdonobin is able to hydrolyze several chromogenic substrates. The enzyme directly clots fibrinogen with an activity of 217 NIH units/mg. The fibrinopeptides released, identified by HPLC, consisted of fibrinopeptide A and a small amount of fibrinopepide B. The activities of the enzyme were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB). However, metal chelator (EDTA) had no effect on it, indicating it is venom serine protease.

Purification and characterization of brevinase, a heterogeneous two-chain fibrinolytic enzyme from the venom of Korean snake, Agkistrodon blomhoffii brevicaudus

A fibrinolytic enzyme, designated as brevinase, was purified from the venom of Korean snake, Agkistrodon blomhoffii brevicaudus. Brevinase cleaved both the Aalpha- and Bbeta-chains of fibrinogen but did not affect the gamma-chain. It showed beta-fibrinogenase activity devoid of fibrinogen clotting and caseinolytic activity. The fibrinolytic activity was completely inhibited by PMSF, DFP, Pefabloc, and DTT, indicating brevinase is a serine protease requiring disulfide bridge(s) for its activity. It kept 80% of the initial activity after heating at 100 degrees C for 3 min, showed an equal maximum activity in the pH range from 5.5 to 8.5, and was inactivated by Zn(2+). Brevinase consists of two polypeptide chains of 16.5 and 17 kDa linked by disulfide bridge(s). The N-terminal amino acid sequences of 16.5 and 17 kDa chains showed homology to the N-terminal and the internal (central region) amino acid sequences of single-chain fibrinolytic enzymes in snake venom, respectively.

Snake venoms and the hemostatic system

Snake venoms are complex mixtures containing many different biologically active proteins and peptides. A number of these proteins interact with components of the human hemostatic system. This review is focused on those venom constituents which affect the blood coagulation pathway, endothelial cells, and platelets. Only highly purified and well characterized snake venom proteins will be discussed in this review. Hemostatically active components are distributed widely in the venom of many different snake species, particularly from pit viper, viper and elapid venoms. The venom components can be grouped into a number of different categories depending on their hemostatic action. The following groups are discussed in this review: (i) enzymes that clot fibrinogen; (ii) enzymes that degrade fibrin(ogen); (iii) plasminogen activators; (iv) prothrombin activators; (v) factor V activators; (vi) factor X activators; (vii) anticoagulant activities including inhibitors of prothrombinase complex formation, inhibitors of thrombin, phospholipases, and protein C activators; (viii) enzymes with hemorrhagic activity; (ix) enzymes that degrade plasma serine proteinase inhibitors; (x) platelet aggregation inducers including direct acting enzymes, direct acting non-enzymatic components, and agents that require a cofactor; (xi) platelet aggregation inhibitors including: alpha-fibrinogenases, 5'-nucleotidases, phospholipases, and disintegrins. Although many snake venoms contain a number of hemostatically active components, it is safe to say that no single venom contains all the hemostatically active components described here. Several venom enzymes have been used clinically as anticoagulants and other venom components are being used in pre-clinical research to examine their possible therapeutic potential. The disintegrins are an interesting group of peptides that contain a cell adhesion recognition motif, Arg-Gly-Asp (RGD), in the carboxy-terminal half of their amino acid sequence. These agents act as fibrinogen receptor (integrin GPIIb/IIIa) antagonists. Since this integrin is believed to serve as the final common pathway leading to the formation of platelet-platelet bridges and platelet aggregation, blockage of this integrin leads to inhibition of platelet aggregation regardless of the stimulating agent. Clinical trials suggest that platelet GPIIb/IIIa blockade is an effective therapy for the thrombotic events and restenosis frequently accompanying cardiovascular and cerebrovascular disease. Therefore, because of their clinical poten tial, a large number of disintegrins have been isolated and characterized.

Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejnegeri) venom

From the venom of Chinese green tree viper (Trimeresurus stejnegeri), three distinct fibrinogenolytic enzymes: stejnefibrase-1, stejnefibrase-2 and stejnefibrase-3, were purified by gel filtration, ion-exchange chromatography and reverse-phase high-performance chromatography (HPLC). SDS-PAGE analysis of those three enzymes showed that they consisted of a single polypeptide chain with mol. wt of 50000, 31000 and 32000, respectively. Like TSV-PA (a specific plasminogen activator) and stejnobin (a fibrinogen-clotting enzyme) purified from the same venom, stejnefibrase-1, -2 and -3 were able to hydrolyze several chromogenic substrate. On the other hand, different from TSV-PA and stejnobin, stejnefibrase-1, -2 and -3 did not activate plasminogen and did not possess fibrinogen-clotting activity. The three purified enzymes directly degraded fibrinogen to small fragments and rendered it unclottable by thrombin. Stejnefibrase-2 degraded preferentially Bbeta-chain while stejnefibrase-1 and -3 cleaved concomitantly Aalpha and Bbeta-chains of fibrinogen. None of these proteases degraded the gamma-chain of fibrinogen. When correlated with the loss of clottability of fibrinogen, the most active enzyme was stejnefibrase-1. The activities of the three enzymes were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB), indicating that like TSV-PA and stejnobin, they are venom serine proteases.

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases

Trimeresurus stejnegeri venom which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin.

Effects of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation and characterization of a prothrombin activator

The action of Pallas' viper (Agkistrodon halys pallas) venom on blood coagulation was examined in vitro and a strong anticoagulant effect was observed. This action was abolished after treatment with a specific inhibitor of phospholipase A2 activity (p-bromophenacyl bromide), revealing a procoagulant action in low concentrations of treated venom (around 1 microgram/ml). The effect of the venom on haemostasis was further characterized by measuring its ability to activate purified blood coagulation factors. It is concluded that A. halys pallas venom contains prothrombin activation activity. A prothrombin activator (aharin) was purified from the venom by Sephadex G-75 gel filtration and ion-exchange chromatography on a Mono-Q column. It consisted of a single polypeptide chain, with a mol. wt of 63,000. Purified aharin possessed no amidolytic activity on chromogenic substrates. It did not act on other blood coagulation factors, such as factor X and plasminogen, nor did it cleave or clot purified fibrinogen. The prothrombin activation activity of aharin was readily inhibited by ethylenediamine tetracetic acid (a metal chelator), but specific serine protease inhibitors such as diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride had no effect on it. These observations suggest that, like those prothrombin activators from Echis carinatus and Bothrops atrox venoms, the prothrombin activator from A. halys pallas venom is a metalloproteinase.

Pharmacological profile of rat pleurisy induced by Bothrops jararaca venom

Bothrops jararaca venom (30 micrograms/site) triggered a marked inflammatory reaction in the pleural cavity that was long-lasting and reproducible. In the first 1 h after pleurisy induction, a significant decrease of total and differential cell count was observed in comparison with control values, despite the gradual enhancement of fluid leakage. A significant increase of cell migration was observed after 3 h of pleurisy induction, due to mononuclear and neutrophil cells that peaked 8 h later and this was followed by a gradual decrease, remaining elevated up to 24 h. In parallel with cell influx, a significant increase of fluid leakage that peaked between 1 and 8 h was observed, being completely abolished after 12 h following pleurisy induction. This inflammatory response was not associated in parallel with significant changes in circulating leucocyte cells and it was significantly inhibited by compound 48/80, cyproheptadine, pyrilamine, dexamethasone, indomethacin and phenidone. Preheating of the venom (100 degrees C) caused a significant decrease of both leakage of fluid and cell migration in the pleural cavity 8 h after pleurisy induction. Previous exposure to the venom (30 micrograms/site, 5 days before) produced a significant decrease of both cell migration and fluid leakage 4 h after triggering pleurisy with the same dose of the venom. Otherwise, prior daily treatment with the venom (10 micrograms/site, 4 days) resulted only in marked fluid leakage reduction 1 h after treating the animals with BJV (30 micrograms/site). These results show that the venom elicits pro-inflammatory effects in the rat pleural cavity which involve the participation of several mediators, including histamine, 5-hydroxytryptamine and products of arachidonic pathways.

Molecular cloning and expression of catrocollastatin, a snake-venom protein from Crotalus atrox (western diamondback rattlesnake) which inhibits platelet adhesion to collagen

A 50 kDa protein that inhibits platelet adhesion to collagen has been isolated from snake venom of Crotalus atrox (western diamondback rattlesnake) and has been named 'catrocollastatin'. The cDNA cloning of catrocollastatin has been accomplished. A full-length cDNA of 2310 bp with an open reading frame between nucleotides 51 and 1880 was obtained. The deduced amino acid sequence consists of 609 amino acids. The cDNA-predicted amino acid sequence is highly similar to that of haemorrhagic metalloproteinase jararhagin from Bothrops jararaca venom, HR1B from Trimeresurus flavoviridis, Ht-e from C. atrox and trigramin from T. gramineus. Like jararhagin and HR1B, catrocollastatin is a multidomain molecule composed of an N-terminal domain, a metalloproteinase domain, a disintegrin-like domain and a cysteine-rich C-terminal domain. In the disintegrin-like domain, the frequently seen RGD (Arg-Gly-Asp) sequence is replaced by SECD (Ser-Glu-Cys-Asp). This cDNA was expressed in Spodoptera frugiperda (fall armyworm) (Sf9) insect cells using a baculovirus expression system. Like native catrocollastatin, the expressed protein is capable of selectively blocking collagen-induced platelet aggregation. This is the first full-length clone of a high-molecular-mass haemorrhagin to be expressed.