Effects of three novel metalloproteinases from the venom of the West African saw-scaled viper, Echis ocellatus on blood coagulation and platelets

Identification and characterization of the key lethal toxin from jellyfish Cyanea nozakii

Jellyfish Cyanea nozakii venom is a complex mixture of various toxins, most of which are proteinous biological macromolecules and are considered to be responsible for clinical symptoms or even death after a severe sting. Previous transcriptome and proteome analysis identified hundreds of toxins in the venom, including hemolysins, C-type lectin, phospholipase A₂, potassium channel inhibitor, metalloprotease, etc. However, it is not clear which toxin in the venom plays the most important role in lethality. Herein, we isolated the key lethal toxin (Letoxcn) from jellyfish Cyanea nozakii using anion exchange chromatography, size-exclusion chromatography, and cation exchange chromatography. The molecular weight of Letoxcn is ∼50 kDa with the N-terminal sequences of QADAEKVNLPVGVCV. Peptide mass fingerprinting analysis of Letoxcn shows that it may have some motifs of phospholipase, metalloproteinase, thrombin-like enzyme, potassium channel toxin, etc. However, only metalloproteinase activity but no hemolytic, PLA₂, or blood coagulation activity was observed from in vitro toxicity analysis. Overall, this study uncovered and characterized the key lethal toxin in the venom of jellyfish Cyanea nozakii, which will not only help to reveal the molecule mechanism of the lethality, but also develop effective treatment like antivenom for this jellyfish sting in the future.

Intrageneric cross-reactivity of monospecific rabbit antisera against venoms of the medically most important Bitis spp. and Echis spp. African snakes

BACKGROUND

Snakebite envenomation exerts a heavy toll in sub-Saharan Africa. The design and production of effective polyspecific antivenoms for this region demand a better understanding of the immunological characteristics of the different venoms from the most medically important snakes, to select the most appropriate venom combinations for generating antivenoms of wide neutralizing scope. Bitis spp. and Echis spp. represent the most important viperid snake genera in Africa.

METHODOLOGY/PRINCIPAL FINDINGS

Eight rabbit-derived monospecific antisera were raised against the venoms of four species of Bitis spp. and four species of Echis spp. The effects of immunization in the rabbits were assessed, as well as the development of antibody titers, as judged by immunochemical assays and neutralization of lethal, hemorrhagic, and in vitro coagulant effects. At the end of immunizations, local and pulmonary hemorrhage, together with slight increments in the plasma activity of creatine kinase (CK), were observed owing to the action of hemorrhagic and myotoxic venom components. Immunologic analyses revealed a considerable extent of cross-reactivity of monospecific antisera against heterologous venoms within each genus, although some antisera provided a more extensive cross-reactivity than others. The venoms that generated antisera with the broadest coverage were those of Bitis gabonica and B. rhinoceros within Bitis spp. and Echis leucogaster within Echis spp.

CONCLUSIONS/SIGNIFICANCE

The methodology followed in this study provides a rational basis for the selection of the best combination of venoms for generating antivenoms of high cross-reactivity against viperid venoms in sub-Saharan Africa. Results suggest that the venoms of B. gabonica, B. rhinoceros, and E. leucogaster generate antisera with the broadest cross-reactivity within their genera. These experimental results in rabbits need to be translated to large animals used in antivenom production to assess whether these predictions are reproduced in horses or sheep.

Functional Mining of the Crotalus Spp. Venom Protease Repertoire Reveals Potential for Chronic Wound Therapeutics

Chronic wounds are a major health problem that cause millions of dollars in expenses every year. Among all the treatments used, active wound treatments such as enzymatic treatments represent a cheaper and specific option with a fast growth category in the market. In particular, bacterial and plant proteases have been employed due to their homology to human proteases, which drive the normal wound healing process. However, the use of these proteases has demonstrated results with low reproducibility. Therefore, alternative sources of proteases such as snake venom have been proposed. Here, we performed a functional mining of proteases from rattlesnakes (Crotalus ornatus, C. molossus nigrescens, C. scutulatus, and C. atrox) due to their high protease predominance and similarity to native proteases. To characterize Crotalus spp. Proteases, we performed different protease assays to measure and confirm the presence of metalloproteases and serine proteases, such as the universal protease assay and zymography, using several substrates such as gelatin, casein, hemoglobin, L-TAME, fibrinogen, and fibrin. We found that all our venom extracts degraded casein, gelatin, L-TAME, fibrinogen, and fibrin, but not hemoglobin. Crotalus ornatus and C. m. nigrescens extracts were the most proteolytic venoms among the samples. Particularly, C. ornatus predominantly possessed low molecular weight proteases (P-I metalloproteases). Our results demonstrated the presence of metalloproteases capable of degrading gelatin (a collagen derivative) and fibrin clots, whereas serine proteases were capable of degrading fibrinogen-generating fibrin clots, mimicking thrombin activity. Moreover, we demonstrated that Crotalus spp. are a valuable source of proteases that can aid chronic wound-healing treatments.

Snake Venom Metalloproteinases (SVMPs): A structure-function update

Snake venom metalloproteinases (SVMPs) represent a diverse group of multi-domain proteins with several biological activities such as the ability to induce hemorrhage, proteolytic degradation of fibrinogen and fibrin, induction of apoptosis and inhibition of platelet aggregation. Due to these activities, SVMPs are responsible for many of the well-known pathological phenotypes in snake envenomations caused particularly by species from the Viperidae family and the Crotalinae subfamily. These proteins have been classified based on their size and domain structure into P–I, P-II and P-III classes. Comparatively, members of the P–I SVMPs possess the simplest structures, formed by the catalytic metalloproteinase domain only; the P-II SVMPs are moderately more complex, having the canonical disintegrin domain in addition to the metalloproteinase domain; members of the P-III class are more structurally varied, comprising the metalloproteinase, disintegrin-like, and cysteine-rich domains. Proteolytic cleavage, repeated domain loss and presence of other ancillary domains are responsible for structural diversities in the P-III class. However, studies continue to unveil the relationship between the structure and function of these proteins. In this review, we recovered evidences from literature on the structural peculiarities and functional classification of Snake Venom Metalloproteinases. In addition, we reflect on diversities that exist among each class while taking into account specific and up-to-date class-based activities.

Practical context of enzymatic treatment for wound healing: A secreted protease approach (Review)

Skin wounds have been extensively studied as their healing represents a critical step towards achieving homeostasis following a traumatic event. Dependent on the severity of the damage, wounds are categorized as either acute or chronic. To date, chronic wounds have the highest economic impact as long term increases wound care costs. Chronic wounds affect 6.5 million patients in the United States with an annual estimated expense of $25 billion for the health care system. Among wound treatment categories, active wound care represents the fastest-growing category due to its specific actions and lower costs. Within this category, proteases from various sources have been used as successful agents in debridement wound care. The wound healing process is predominantly mediated by matrix metalloproteinases (MMPs) that, when dysregulated, result in defective wound healing. Therapeutic activity has been described for animal secretions including fish epithelial mucus, maggot secretory products and snake venom, which contain secreted proteases (SPs). No further alternatives for use, sources or types of proteases used for wound healing have been found in the literature to date. Through the present review, the context of enzymatic wound care alternatives will be discussed. In addition, substrate homology of SPs and human MMPs will be compared and contrasted. The purpose of these discussions is to identify and propose the stages of wound healing in which SPs may be used as therapeutic agents to improve the wound healing process.

High throughput screening and identification of coagulopathic snake venom proteins and peptides using nanofractionation and proteomics approaches

Snakebite is a neglected tropical disease that results in a variety of systemic and local pathologies in envenomed victims and is responsible for around 138,000 deaths every year. Many snake venoms cause severe coagulopathy that makes victims vulnerable to suffering life-threating haemorrhage. The mechanisms of action of coagulopathic snake venom toxins are diverse and can result in both anticoagulant and procoagulant effects. However, because snake venoms consist of a mixture of numerous protein and peptide components, high throughput characterizations of specific target bioactives is challenging. In this study, we applied a combination of analytical and pharmacological methods to identify snake venom toxins from a wide diversity of snake species that perturb coagulation. To do so, we used a high-throughput screening approach consisting of a miniaturised plasma coagulation assay in combination with a venom nanofractionation approach. Twenty snake venoms were first separated using reversed-phase liquid chromatography, and a post-column split allowed a small fraction to be analyzed with mass spectrometry, while the larger fraction was collected and dispensed onto 384-well plates. After fraction collection, any solvent present in the wells was removed by means of freeze-drying, after which it was possible to perform a plasma coagulation assay in order to detect coagulopathic activity. Our results demonstrate that many snake venoms simultaneously contain both procoagulant and anticoagulant bioactives that contribute to coagulopathy. In-depth identification analysis from seven medically-important venoms, via mass spectrometry and nanoLC-MS/MS, revealed that phospholipase A2 toxins are frequently identified in anticoagulant venom fractions, while serine protease and metalloproteinase toxins are often associated with procoagulant bioactivities. The nanofractionation and proteomics approach applied herein seems likely to be a valuable tool for the rational development of next-generation snakebite treatments by facilitating the rapid identification and fractionation of coagulopathic toxins, thereby enabling specific targeting of these toxins by new therapeutics such as monoclonal antibodies and small molecule inhibitors.

Antivenom Neutralization of Coagulopathic Snake Venom Toxins Assessed by Bioactivity Profiling Using Nanofractionation Analytics

Venomous snakebite is one of the world's most lethal neglected tropical diseases. Animal-derived antivenoms are the only standardized specific therapies currently available for treating snakebite envenoming, but due to venom variation, often this treatment is not effective in counteracting all clinical symptoms caused by the multitude of injected toxins. In this study, the coagulopathic toxicities of venoms from the medically relevant snake species Bothropsasper, Calloselasmarhodostoma, Deinagkistrodonacutus, Daboiarusselii, Echiscarinatus and Echisocellatus were assessed. The venoms were separated by liquid chromatography (LC) followed by nanofractionation and parallel mass spectrometry (MS). A recently developed high-throughput coagulation assay was employed to assess both the pro- and anticoagulant activity of separated venom toxins. The neutralization capacity of antivenoms on separated venom components was assessed and the coagulopathic venom peptides and enzymes that were either neutralized or remained active in the presence of antivenom were identified by correlating bioassay results with the MS data and with off-line generated proteomics data. The results showed that most snake venoms analyzed contained both procoagulants and anticoagulants. Most anticoagulants were identified as phospholipases A2s (PLA2s) and most procoagulants correlated with snake venom metalloproteinases (SVMPs) and serine proteases (SVSPs). This information can be used to better understand antivenom neutralization and can aid in the development of next-generation antivenom treatments.

Successful Management of Two Patients with Intracranial Hemorrhage due to Carpet Viper (Echis ocellatus) Envenomation in a Limited-Resource Environment

The West African carpet viper (Echis ocellatus) causes more deaths than any other snake in sub-Saharan Africa. Carpet viper envenomations are characterized by a venom-induced consumption coagulopathy and systemic bleeding syndrome, in addition to local symptoms of painful progressive swelling and tissue destruction. The highest mortality rate is seen in the final stages of the syndrome, which typically ends with fatal internal bleeding or hemorrhagic shock. We present 2 cases of E ocellatus envenomation with intracranial hemorrhage seen at a rural hospital in Bembèrèkè, Benin, and describe the successful management of these patients in a limited-resource setting. In one case the patient was treated with an ineffective Indian-made antivenom before evaluation by the authors and continued to deteriorate until she was treated with effective antivenom 10 d after the bite. In both cases lumbar puncture was performed for diagnostic or therapeutic purposes with good effect, and both patients made full recoveries without sequelae. These cases demonstrate the remarkable ability of high-quality antivenoms to reverse life-threatening envenomations even in the final stages of the hemorrhagic syndrome and illustrate the dangers posed by low-quality antivenoms that have flooded the market in the developing world.

Purification and characterization of five snake venom metalloproteinases from Egyptian Echis pyramidum pyramidum venom

New five P-III snake venom metalloproteinases (SVMPs): EpyB2 (62 kDa), EpyB3 (62+23 kDa), EpyB4 (60 kDa), EpyB5 (67 kDa) and EpyB6 (66 kDa) of the most dangerous viper, Echis pyramidum pyramidum (Epy), were purified and characterized in a set of biochemical assays. The SVMPs were purified by applying a protocol of two successive chromatographic steps. Three purified SVMPs "EpyB2, EpyB4, and EpyB5" have hemorrhagic activity with MHDs, 7 μg, 7.6 μg and 15 μg, respectively; furthermore, they have high preference towards fibronectin, collagen, gelatin, fibrin and hemoglobin substrates compared with non-hemorrhagic SVMPs (EpyB3 and EpyB6). All the purified SVMPs showed remarkable thermal and pH stability, inhibited by metalloproteinase inhibitors and Zn(2+), Mn(2+), Ni(2+), Co(2+), Cu(2+), and Hg(2+). The purified SVMPs act as α-fibrinogenases, prothrombin activators and procoagulants. In conclusion, Epy venom has multiple SVMPs that are responsible for hemorrhagic events and thus represent a significant health hazard for victims of envenomation, however, they may be useful for treating diseases involving abnormal blood clot formation.

Pharmacological and biochemical studies on the venom of a clinically important viper snake (Echis carinatus) of Pakistan

Echis carinatus (saw-scaled viper) has been the major culprit responsible for serious envenomation casualties throughout the subcontinent. The present study describes the electrophoretic and zymographic characterization of E. carinatus venom and its effect on mammalian smooth muscle. Crude venom showed the presence of disintegrin, PLA2, C-type lectin/lectin-like components, CRISP, Serine protease, l-amino acid oxidase and very high concentrations of SVMPs. E. carinatus venom (1, 10, 30, 50, 100 μg/ml) inhibited the active tension/force of muscle contraction in a time and concentration dependent manner. The observed effects abolished when the venom was heated at 100 °C for 5 min. However, a decrease in bath temperature from 37 °C to 26 °C or an increase in CaCl2 concentration to 5 mM did not prevent the inhibition of contractile activity. The contractile response elicited by exogenous application of 50 mM KCl and 1 μM acetylcholine (ACh) was also significantly inhibited by all venom concentrations. Prior administration of commercially available polyvalent anti-venom partially neutralized and prevented the effect of E. carinatus venom whereas addition of anti-venom at t50 failed to reverse the inhibitory effect. Studies on isolated intestinal muscle indicate involvement of myotoxic and apoptotic components in E. carinatus venom for irreversible damage to muscle tissue.

Mechanism of in vivo anticoagulant and haemolytic activity by a neutral phospholipase A(2) purified from Daboia russelii russelii venom: correlation with clinical manifestations in Russell's Viper envenomed patients

A 13.0 kDa neutral phospholipase A2 (NEUPHOLIPASE) purified from venom of Daboia russelii russelii from eastern India was identified by peptide mass fingerprinting analysis. It exerted dose-dependent PLA2, anticoagulant and indirect haemolytic activities. NEUPHOLIPASE showed preferential binding followed by hydrolysis of phosphatidylserine > phosphatidylcholine >> phosphatidylethanolamine. Circular dichroism analysis of NEUPHOLIPASE showed a high content of alpha helix (54.6%) followed by beta-turn (29.7%) in its secondary structure. Gas-chromatographic analysis of plasma from PLA2-treated mice suggested preferential hydrolysis of pro-coagulant phospholipid PS was the primary mechanism to account for in vivo anticoagulant effect of NEUPHOLIPASE. The NEUPHOLIPASE-treated mice blood showed a significant decrease (p < 0.01) in WBC as well as RBC counts with a corresponding decline in Hb content due to indirect damage to erythrocyte membranes by plasma phospholipids hydrolysis products rather than the direct haemolytic activity of PLA2 under study. NEUPHOLIPASE was non-lethal to BALB/c mice, however; it was detrimental to liver of treated-mice. Pathological symptoms observed in NEUPHOLIPASE-treated mice were correlated with the actual clinical manifestations in Russell's Viper envenomed patients from eastern India indicating some contribution of NEUPHOLIPASE in Russell's Viper venom induced toxicity and pathogenesis.

In vivo evaluation of homeostatic effects of Echis carinatus snake venom in Iran

Background

The venom of the family Viperidae, including the saw-scaled viper, is rich in serine proteinases and metalloproteinases, which affect the nervous system, complementary system, blood coagulation, platelet aggregation and blood pressure. One of the most prominent effects of the snake venom of Echis carinatus (Ec) is its coagulation activity, used for killing prey.

Materials and methods

Subfractions F1A and F1B were isolated from Ec crude venom by a combination of gel chromatography (Sephadex G-75) and ion exchange chromatography on a DEAE-Sepharose (DE-52). These subfractions were then intravenously (IV) injected into NIH male mice. Blood samples were taken before and after the administration of these subfractions. Times for prothrombin, partial thromboplastin and fibrinogen were recorded.

Results and conclusions

Comparison of the prothrombin time before and after F1A and F1B administrations showed that time for blood coagulation after injection is shorter than that of normal blood coagulation and also reduced coagulation time after Ec crude venom injection. This difference in coagulation time shows the intense coagulation activity of these subfractions that significantly increase the coagulation cascade rate and Causes to quick blood coagulation. The LD50 of the Ec crude venom was also determined to be 11.1 μg/mouse. Different crude venom doses were prepared with physiological serum and injected into four mice. Comparison of the prothrombin times after injection of subfractions F1A and F1B showed that the rate of mouse blood coagulation increases considerably. Comparing the partial thromboplastin times after injecting these subfractions with this normal test time showed that the activity rate of intrinsic blood coagulation system rose sharply in mice. Finally, by comparing the fibrinogen time after subfraction injections and normal test time, we can infer intense activation of coagulation cascade and fibrin production.

Revisiting saw-scaled viper (Echis carinatus) bites in the Jaffna Peninsula of Sri Lanka: distribution, epidemiology and clinical manifestations

In Sri Lanka, the saw-scaled viper (Echis carinatus) is distributed in the arid, dry and sandy coastal plains and in a prospective study we describe its bites in the Jaffna peninsula. Of the 304 snake bite admissions to the Jaffna Hospital in 2009, 217 (71.4%) were bitten by either venomous species or envenomed by unidentified snakes. There were 99 (45.6%) reported saw-scaled viper bites, of which 26 were confirmed cases. The length of the offending snakes ranged from 228-310mm and bites mainly occurred in the nearby islands. The median age of the confirmed cases was 34 years (range 1.5-72 years); occupations included housewives (8, 31%), school children (4, 15%) and farmers (2, 8%). In 18 patients (69%), bites occurred in daylight and in 8 (31%) within or near the compounds. The fingers were bitten in 8 (31%) and toes/foot in 11 (42%) cases. There were 2 (8%) dry bites and 19 patients (73%) developed local swelling; one patient developed haemorrhagic blisters. In 24 patients (92%), blood incoagulability manifested between 40 and 1095min after the bite, and three patients (12%) developed spontaneous bleeding. One patient (4%) developed mild acute renal dysfunction. The median time for correction of coagulopathy was 802min (range 180-1669min) with Indian polyvalent antivenom. All recovered. The saw scaled viper is responsible for most venomous bites in the Jaffna peninsula.

Antivenomic assessment of the immunological reactivity of EchiTAb-Plus-ICP, an antivenom for the treatment of snakebite envenoming in sub-Saharan Africa

The immunoreactivity of EchiTAb-Plus-ICP, an antivenom developed for the treatment of snakebite envenoming in sub-Saharan Africa, to venoms of seven Echis and Bitis species, was assessed by "antivenomics." This proteomic approach is based on the ability of an antivenom to immunodeplete homologous or heterologous venom proteins. Our results show an extensive cross-reactivity of this antivenom against all Echis and Bitis venoms studied, as revealed by the complete immunodepletion of the majority of venom components, including metalloproteinases, serine proteinases, C-type lectin-like proteins, some phospholipases A(2) and L-amino acid oxidase. However, some phospholipases A(2), disintegrins and proteinase inhibitors were immunodepleted to only a partial extent. These results support the hypothesis that immunizing horses with a mixture of the venoms of Echis ocellatus, Bitis arietans, and Naja nigricollis generates antibodies capable of recognizing the majority of components of medically-relevant homologous and heterologous viperid venoms of the genera Bitis and Echis from sub-Saharan Africa.

cDNA cloning, expression and fibrin(ogen)olytic activity of two low-molecular weight snake venom metalloproteinases

Two cDNA clones, AplVMP1 and AplVMP2, were isolated from a snake (Agkistrodon piscivorus leucostoma) venom gland cDNA library. The full-length cDNA sequence of AplVMP1 with a calculated molecular mass of 46.61 kDa is 1233 bp in length. AplVMP1 encodes PI class metalloproteinase with an open reading frame of 411 amino acid residues that includes signal peptide, pro-domain and metalloproteinase domains. The full-length cDNA of the AplVMP2 (1371 bp) has a calculated molecular mass of 51.16 kDa and encodes PII class metalloproteinase. The open reading frame of AplVMP2 with a 457 amino acid residues is composed of signal peptide, pro-domain, metalloproteinase and disintegrin domains. AplVMP1 and AplVMP2 showed 85% and 93% amino acid identical to PI class enzyme Agkistrodon contortrix laticinctus ACLPREF and PII class enzyme Agkistrodon piscivorus piscivorus piscivostatin, respectively. When expressed in Escherichia coli, most of recombinant proteins of AplVMP1 and AplVMP2 were in insoluble inclusion bodies, with soluble yields of 0.7 mg/l and 0.4 mg/l bacterial culture, respectively. Both affinity purified recombinant proteins show proteolytic activity on fibrinogen, although having an activity lower than that of crude A. p. leucostoma venom. Proteolytic activities of AplVMP1 and AplVMP2 were completely abolished after incubation with a final concentration of 100 microM of EDTA or 1,10-phenanthroline. Both AplVMP1 and AplVMP2 were active in a fibrin-agarose plate but devoid of hemorrhagic activity when injected (up to 50 microg) subcutaneously into mice, and had no capacity to inhibit platelet aggregation.

Characterization of a novel pro-coagulant metalloprotease (RVBCMP) possessing alpha-fibrinogenase and tissue haemorrhagic activity from venom of Daboia russelli russelli (Russell's viper): evidence of distinct coagulant and haemorrhagic sites in RVBCMP

A novel, basic pro-coagulation metalloprotease (Russell's viper basic coagulant metalloprotease, RVBCMP) with an approximate molecular weight of 15kDa was purified from the venom of Daboia russelli russelli (Russell's viper) from eastern India. RVBCMP exerted dose-dependent coagulation of platelet-poor human plasma; however, RVBCMP possessed less coagulant activity as compared with the coagulant activity of crude Russell's viper venom (RVV). RVBCMP did not show oedema induction, direct haemolysis of washed erythrocytes, hydrolysis of human plasma albumin or globulin, and thrombin-like activity, but exhibited caseinolytic, alpha-fibrinogenolytic, and liver tissue haemorrhagic activities. Inhibition of coagulant and protease activities of RVBCMP by EDTA suggested a metalloprotease nature of this protein. RVBCMP showed antigenicity as was evident from the immunoblotting experiment. None of the tested plant extracts, except Leucus lavandulaefolia, inhibited the coagulant or haemorrhagic activity of RVBCMP. Interestingly, aqueous extracts of the tested plants as well as the commercial polyvalent antivenom raised against crude RVV differentially inhibited the coagulant and tissue haemorrhagic activity of RVBCMP. The current investigation provides a fairly good indication that RVBCMP possesses a distinct, perhaps overlapping, site for coagulant and tissue haemorrhagic activity.

Purification and characterization of patagonfibrase, a metalloproteinase showing α-fibrinogenolytic and hemorrhagic activities, from Philodryas patagoniensis snake venom

Venoms of Colubridae snakes are a rich source of novel compounds, which may have applications in medicine and biochemistry. In the present study, we describe the purification and characterization of a metalloproteinase (patagonfibrase), the first protein to be isolated from Philodryas patagoniensis (Colubridae) snake venom. Patagonfibrase is a single-chain protein, showing a molecular mass of 53,224 Da and an acidic isoelectric point (5.8). It hydrolyzed selectively the Aalpha-chain of fibrinogen and when incubated with fibrinogen or plasma, the thrombin clotting time was prolonged. Prominent hemorrhage developed in mouse skin after intradermal injection of patagonfibrase. When administered into mouse gastrocnemius muscle, it induced local hemorrhage and necrosis, and systemic bleeding in lungs. Patagonfibrase showed proteolytic activity toward azocasein, which was enhanced by Ca(2+) and inhibited by Zn(2+), cysteine, dithiothreitol and Na(2)EDTA. Patagonfibrase impaired platelet aggregation induced by collagen and ADP. Thus, patagonfibrase may play a key role in the pathogenesis of disturbances that occur in P. patagoniensis envenomation, and may be used as a biological tool to explore many facets of hemostasis.

Neutralization of the haemorrhagic activities of viperine snake venoms and venom metalloproteinases using synthetic peptide inhibitors and chelators

Envenoming by the West African saw-scaled viper, Echis ocellatus resembles that of most vipers, in that it results in local blistering, necrosis and sometimes life-threatening systemic haemorrhage. While effective against systemic envenoming, current antivenoms have little or no effect against local tissue damage. The major mediators of local venom pathology are the zinc-dependant snake venom metalloproteinases (SVMPs). The high degree of structural and functional homology between SVMPs and their mammalian relatives the matrix metalloproteinases (MMPs) suggests that substrate/inhibitor interactions between these subfamilies are likely to be analogous. In this study, four recently developed MMP inhibitors (MMPIs) (Marimastat, AG-3340, CGS-270 23A and Bay-12 9566) are evaluated in addition to three metal ion chelators (EDTA, TPEN and BAPTA) for their ability to inhibit the haemorrhagic activities of the medically important E. ocellatus venom and one of its haemorrhagic SVMPs, EoVMP2. As expected, the metal ion chelators significantly inhibited the haemorrhagic activities of both whole E. ocellatus venom and EoVMP2, while the synthetic MMPIs show more variation in their efficacies. These variations suggest that individual MMPIs show specificity towards SVMPs and that their application to the neutralization of local haemorrhage may require a synthetic MMPI mixture, ensuring that a close structural component for each SVMP is represented.

Venom gland EST analysis of the saw-scaled viper, Echis ocellatus, reveals novel α9β1 integrin-binding motifs in venom metalloproteinases and a new group of putative toxins, renin-like aspartic proteases

Echis ocellatus is the most medically important snake in West Africa. However, the composition of its venom and the differential contribution of these venom components to the severe haemorrhagic and coagulopathic pathology of envenoming are poorly understood. To address this situation we assembled a toxin transcriptome based upon 1000 expressed sequence tags (EST) from a cDNA library constructed from pooled venom glands of 10 individual E. ocellatus. We used a variety of bioinformatic tools to construct a fully annotated venom-toxin transcriptome that was interrogated with a combination of BLAST annotation, gene ontology cataloguing and disintegrin-motif searching. The results of these analyses revealed an unusually abundant and diverse expression of snake venom metalloproteinases (SVMP) and a broad toxin-expression profile including several distinct isoforms of bradykinin-potentiating peptides, phospholipase A(2), C-type lectins, serine proteinases and l-amino oxidases. Most significantly, we identified for the first time a conserved alpha(9)beta(1) integrin-binding motif in several SVMPs, and a new group of putative venom toxins, renin-like aspartic proteases.