Characterization of snake venom components acting on blood coagulation and platelet function

Snake Venoms in Drug Discovery: Valuable Therapeutic Tools for Life Saving

Animal venoms are used as defense mechanisms or to immobilize and digest prey. In fact, venoms are complex mixtures of enzymatic and non-enzymatic components with specific pathophysiological functions. Peptide toxins isolated from animal venoms target mainly ion channels, membrane receptors and components of the hemostatic system with high selectivity and affinity. The present review shows an up-to-date survey on the pharmacology of snake-venom bioactive components and evaluates their therapeutic perspectives against a wide range of pathophysiological conditions. Snake venoms have also been used as medical tools for thousands of years especially in tradition Chinese medicine. Consequently, snake venoms can be considered as mini-drug libraries in which each drug is pharmacologically active. However, less than 0.01% of these toxins have been identified and characterized. For instance, Captopril^® (Enalapril), Integrilin^® (Eptifibatide) and Aggrastat^® (Tirofiban) are drugs based on snake venoms, which have been approved by the FDA. In addition to these approved drugs, many other snake venom components are now involved in preclinical or clinical trials for a variety of therapeutic applications. These examples show that snake venoms can be a valuable source of new principle components in drug discovery.

Biochemistry of the Thrombin-Like TLBpic and Its Purification fromBothrops pictus“Jergon de la Costa” (Reptilia: Viperidae)

The venom of snakes is composed of a heterogeneous mixture of simple and complex substances, with inflammation and hyperalgesia being the first symptom caused by the action ofBothropsvenom, generating processes such as leukocyte infiltration, hemorrhage, and the intravascular formation of thrombi. Within the simple substances, we have free amino acids, peptides, nucleotides, carbohydrates, lipids, and biogenic amines (organic molecules) as well as cations and anions (inorganic constituents). Of the ions, we can highlight calcium, which is an important cofactor of some proteolytic enzymes as well as phospholipases A2. And magnesium and zinc are important cofactors of venom metalloproteases. Complex substances are related to proteins and enzymes. Studies related to the total venom of snake present in several organic substances act as pain mediators and are called biogenic amines, such as bradykinin, histamine, 4-hydroxytryptamine,N-methyl-5-hydroxytryptamine,N′-N′-dimethyl-5-hydroxytryptamine, and serotonin. In the present study, a fraction with serinoprotease and coagulant activity has been purified on fibrinogen, called TLBpic, using a cationic ion exchange chromatographic system coupled to an HPLC system. The main characteristic of our protocol is the speed, and the high recovery of the fraction with optimal terms gave result of evidence in the SDS-PAGE gel. The ESI (electrospray ionisation), corresponding to the electrophoresis of proteins in polyacrylamide gels and to their denaturing solubilization in the presence of the SDS ionic detergent, uniting the proteins, breaking hydrophobic interactions, showing a molecular mass of ∼30 kDa, demonstrating high molecular homogeneity that exists in this family of proteins, is a soft ionization method, in which the samples were ionized by the addition or removal of a proton, with very little extra energy to cause fragmentation of the produced ions. Samples with molecular masses greater than 1200 Da originate multicharged ions (M + nH)n+ in the positive ionization mode; this methodology guarantees that the purified material has a high degree of purity.

Can Surgery in Patient with Protobothrops Mucrosquamatus Envenomation be Predicted in Emergency Department?

Objective

Protobothrops mucrosquamatus, a Crotalinae snake with haemorrhagic venom, is responsible for the most common poisoning snakebites in Taiwan. Although a specific antivenin has been developed to treat this snakebite, surgical intervention is still needed in some patients because of the progression of tissue injury. Early risk stratification is important to identify the early signs of need for surgery. The purpose of this study was to investigate the early predictors for surgery in patients with P. mucrosquamatus envenomation.

Methods

The medical records of inpatients with P. mucrosquamatus envenomation between 2008 and 2013 were retrospectively reviewed. Clinical information was collected and analysed between surgical and nonsurgical patients.

Results

A total of 60 patients with P. mucrosquamatus envenomation, including 8 surgical patients (13.3%) and 52 non-surgical patients (86.7%), presented to the emergency department during the study period. Compartment syndrome (62.5%) and tissue necrosis (37.5%) were the main reasons for surgery. Comparison between surgical and non-surgical patients showed significantly higher white blood cell count (17.1 × 103/μL vs. 8.5 × 103/μL; p=0.002) and peak D-dimer level (1924.8 ng/mL vs. 730.0 ng/mL; p=0.006) in the surgical group. Ecchymosis (p=0.009), haemorrhagic bulla formation (p=0.002), leukocytosis (p=0.002), elevated peak D-dimer level (>1000 ng/mL) (p=0.005), and rhabdomyolysis (creatine kinase level >1000 IU/L) (p=0.007) were the significant signs relevant to surgery. On multivariate analysis, leukocytosis and ecchymosis were the most significant predictors of surgery in patients with P. mucrosquamatus envenomation.

Conclusions

Patients with P. mucrosquamatus envenomation presenting with leukocytosis and wound ecchymosis will have a high probability of requiring surgical therapy. (Hong Kong j.emerg.med. 2016;23:210-219)

Peptide Mimetic Drugs for Modulating Thrombosis and Hemostasis

Preclinical Research Hemostasis is the complex physiological process that stems bleeding at an injury site while simultaneously maintaining unobstructed circulation in other areas of the body. This system is kept in balance with finely tuned regulation by pro- and antithrombotic agents. When this balance is thrown out of equilibrium, uncontrolled bleeding, or thrombotic complications can occur. Because of the high number of hemostatic disorders, researchers are continually searching for improved technologies for controlling coagulation. Recently, peptide mimetic strategies have been employed to target and regulate various stages of the coagulation cascade. In this review, we present an overview of the coagulation cascade and provide a summary of various peptide-mimetic approaches for its modulation. Drug Dev Res 78 : 236-244, 2017. © 2017 Wiley Periodicals, Inc.

Evaluation of Risk Factors and Follow-Up Criteria for Severity of Snakebite in Children

Background

Snakebites are an emergency medical condition and require rapid treatment procedures in children.

Objectives

This study aimed to present an overview of the demographic characteristics, clinical presentations, laboratory findings, severity, and complications that developed in pediatric patients due to snakebites.

Patients and Methods

A total of 151 children with snakebite were enrolled in the study. All patients had a history of snakebite obtained between June 2006 and August 2015 retrospectively.

Results

Duration of hospitalization (P < 0.001), rural occurrence (P < 0.001), white blood cell (WBC) count (P = 0.002), aspartate aminotransferase to alanine aminotransferase (AST/ALT) ratio (P = 0.010), hypoproteinemia (P = 0.001), hypoalbuminemia (P < 0.001), and hypocalcemia (P = 0.005) were significantly high in the severe snakebite group. WBC (P = 0.006) and AST/ALT ratio (P = 0.018) were significantly higher on the first day of the snakebite than on subsequent days.

Conclusions

Children admitted to the hospital due to snakebite should be monitored for at least 24 - 48 hours even if no signs of clinical envenomation could be observed. According to the severity of the disease, antivenom should be administered to the patients. Duration of hospitalization, rural occurrence, WBC count, AST/ALT ratio, CK, hypoproteinemia, hypoalbuminemia, and hypocalcemia can be associated with the severity of snakebite. WBC AST/ALT ratio can be used as follow-up criteria in children with snakebite

A RNA-seq approach to identify putative toxins from acrorhagi in aggressive and non-aggressive Anthopleura elegantissima polyps

BACKGROUND

The use of venom in intraspecific aggression is uncommon and venom-transmitting structures specifically used for intraspecific competition are found in few lineages of venomous taxa. Next-generation transcriptome sequencing allows robust characterization of venom diversity and exploration of functionally unique tissues. Using a tissue-specific RNA-seq approach, we investigate the venom composition and gene ontology diversity of acrorhagi, specialized structures used in intraspecific competition, in aggressive and non-aggressive polyps of the aggregating sea anemone Anthopleura elegantissima (Cnidaria: Anthozoa: Hexacorallia: Actiniaria: Actiniidae).

RESULTS

Collectively, we generated approximately 450,000 transcripts from acrorhagi of aggressive and non-aggressive polyps. For both transcriptomes we identified 65 candidate sea anemone toxin genes, representing phospholipase A2s, cytolysins, neurotoxins, and acrorhagins. When compared to previously characterized sea anemone toxin assemblages, each transcriptome revealed greater within-species sequence divergence across all toxin types. The transcriptome of the aggressive polyp had a higher abundance of type II voltage gated potassium channel toxins/Kunitz-type protease inhibitors and type II acrorhagins. Using toxin-like proteins from other venomous taxa, we also identified 612 candidate toxin-like transcripts with signaling regions, potentially unidentified secretory toxin-like proteins. Among these, metallopeptidases and cysteine rich (CRISP) candidate transcripts were in high abundance. Furthermore, our gene ontology analyses identified a high prevalence of genes associated with "blood coagulation" and "positive regulation of apoptosis", as well as "nucleoside: sodium symporter activity" and "ion channel binding". The resulting assemblage of expressed genes may represent synergistic proteins associated with toxins or proteins related to the morphology and behavior exhibited by the aggressive polyp.

CONCLUSION

We implement a multifaceted approach to investigate the assemblage of expressed genes specifically within acrorhagi, specialized structures used only for intraspecific competition. By combining differential expression, phylogenetic, and gene ontology analyses, we identify several candidate toxins and other potentially important proteins in acrorhagi of A. elegantissima. Although not all of the toxins identified are used in intraspecific competition, our analysis highlights some candidates that may play a vital role in intraspecific competition. Our findings provide a framework for further investigation into components of venom used exclusively for intraspecific competition in acrorhagi-bearing sea anemones and potentially other venomous animals.

Isolation and biochemical characterization of a new thrombin-like serine protease from Bothrops pirajai snake venom

This paper presents a novel serine protease (SP) isolated from Bothrops pirajai, a venomous snake found solely in Brazil that belongs to the Viperidae family. The identified SP, named BpirSP-39, was isolated by three chromatographic steps (size exclusion, bioaffinity, and reverse phase chromatographies). The molecular mass of BpirSP-39 was estimated by SDS-PAGE and confirmed by mass spectrometry (39,408.32 Da). The protein was able to form fibrin networks, which was not observed in the presence of serine protease inhibitors, such as phenylmethylsulfonyl fluoride (PMSF). Furthermore, BpirSP-39 presented considerable thermal stability and was apparently able to activate factor XIII of the blood coagulation cascade, unlike most serine proteases. BpirSP-39 was capable of hydrolyzing different chromogenic substrates tested (S-2222, S-2302, and S-2238) while Cu(2+) significantly diminished BspirSP-39 activity on the three tested substrates. The enzyme promoted platelet aggregation and also exhibited fibrinogenolytic, fibrinolytic, gelatinolytic, and amidolytic activities. The multiple alignment showed high sequence similarity to other thrombin-like enzymes from snake venoms. These results allow us to conclude that a new SP was isolated from Bothrops pirajai snake venom.

Biochemical and biological characterization of two serine proteinases from Colombian Crotalus durissus cumanensis snake venom

Two clotting serine proteinases, named Cdc SI and Cdc SII, were isolated and characterized for the first time from Colombian Crotalus durissus cumanensis snake venom. The enzymes were purified using two chromatographic steps: molecular exclusion on Sephacryl S-200 and RP-HPLC on C8 Column. The molecular masses of the proteins, determined by MALDI-TOF mass spectrometry, were 28,561.4 and 28,799.2 Da for Cdc SI and Cdc SII, respectively. The aim of the present study was to evaluate enzymatic, coagulant and toxic properties of the two enzymes. The serine proteinases hydrolyzed specific chromogenic substrate (BaPNA) and exhibited a Michaelis-Menten behavior. Cdc SI had V(max) of 0.038 ± 0.003 nmol/min and K(M) of 0.034 ± 0.017 mM, while Cdc SII displayed values of V(max) of 0.267 ± 0.011 nmol/min and K(M) of 0.145 ± 0.023 mM. N-terminal sequences were VIGGDEXNIN and VIGGDICNINEHNFLVALYE for Cdc SI and Cdc SII, respectively. Molecular masses, N-terminal sequences, inhibition assays, and enzymatic profile suggest that Cdc SI and Cdc SII belong to the family of snake venom thrombin-like enzymes. These serine proteinases differed in their clotting activity on human plasma, showing a minimum coagulant dose of 25 μg and 0.571 μg for Cdc SI and Cdc SII, respectively. Enzymes also showed coagulant activity on bovine fibrinogen and degraded chain α of this protein. Toxins lack hemorrhagic and myotoxic activities, but are capable to induce defibrin(ogen)ation, moderate edema, and an increase in vascular permeability. These serine proteinases may contribute indirectly to the local hemorrhage induced by metalloproteinases, by causing blood clotting disturbances, and might also contribute to cardiovascular alterations characteristic of patients envenomed by C. d. cumanensis in Colombia.

Snake venom metalloproteinases

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

Biochemistry of envenomation

Venoms and toxins are of significant interest due to their ability to cause a wide range of pathophysiological conditions that can potentially result in death. Despite their wide distribution among plants and animals, the biochemical pathways associated with these pathogenic agents remain largely unexplored. Impoverished and underdeveloped regions appear especially susceptible to increased incidence and severity due to poor socioeconomic conditions and lack of appropriate medical treatment infrastructure. To facilitate better management and treatment of envenomation victims, it is essential that the biochemical mechanisms of their action be elucidated. This review aims to characterize downstream envenomation mechanisms by addressing the major neuro-, cardio-, and hemotoxins as well as ion-channel toxins. Because of their use in folk and traditional medicine, the biochemistry behind venom therapy and possible implications on conventional medicine will also be addressed.

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.

Antihaemorrhagic potentials of Fagonia cretica against Naja naja karachiensis (black Pakistan cobra) venom

Plants have been extensively used as a remedy for the treatment of snake bites. The aim of this study was to determine the antivenom potentials of methanolic extract from the aerial parts (leaves and twigs) of Fagonia cretica L. on a haemorrhage induced by venom from Naja naja karachiensis. The haemorrhagic response of venom was dose dependent from 0.1 to 4.0 µg per 1.5 µL phosphate buffer saline (PBS) on vitelline veins of fertilised hens' eggs in their shells. The extract effectively eliminated and neutralised, in a dose-dependent manner, the haemorrhagic activity of snake venom. The minimum effective neutralising dose of F. cretica extract was found to be 15 µg per 1.5 µL PBS. The extract possesses potentials as haemorrhagic inhibitor against snake venom compared to the standard antiserum and various plants reported in the literature. This study also provides a scientific base for the use of F. cretica in traditional medicine for the treatment of snake bite.

Molecular cloning and biochemical characterization of a myotoxin inhibitor from Bothrops alternatus snake plasma

Phospholipases A(2) (PLA(2)s) are important components of Bothrops snake venoms, that can induce several effects on envenomations such as myotoxicity, inhibition or induction of platelet aggregation and edema. It is known that venomous and non-venomous snakes present PLA(2) inhibitory proteins (PLIs) in their blood plasma. An inhibitory protein that neutralizes the enzymatic and toxic activities of several PLA(2)s from Bothrops venoms was isolated from Bothrops alternatus snake plasma by affinity chromatography using the immobilized myotoxin BthTX-I on CNBr-activated Sepharose. Biochemical characterization of this inhibitory protein, denominated αBaltMIP, showed it to be a glycoprotein with Mr of ~24,000 for the monomeric subunit. CD spectra of the PLA(2)/inhibitor complexes are considerably different from those corresponding to the individual proteins and data deconvolution suggests that the complexes had a relative gain of helical structure elements in comparison to the individual protomers, which may indicate a more compact structure upon complexation. Theoretical and experimental structural studies performed in order to obtain insights into the structural features of αBaltMIP indicated that this molecule may potentially trimerize in solution, thus strengthening the hypothesis previously raised by other authors about snake PLIs oligomerization.

Structure and function of snake venom proteins affecting platelet plug formation

Many snake venom proteins have been isolated that affect platelet plug formation by interacting either with platelet integrins, membrane glycoprotein Ib (GPIb), or plasma von Willebrand factor (VWF). Among them, disintegrins purified from various snake venoms are strong inhibitors of platelet aggregation. Botrocetin and bitiscetin derived from Bothrops jararaca and Bitis arietans venom, respectively, induce VWF-dependent platelet agglutination in vitro. Several GPIb-binding proteins have also been isolated from snake venoms. In this review, we focus on the structure and function of those snake venom proteins that influence platelet plug formation. These proteins are potentially useful as reagents for the sub-diagnosis of platelet disorder or von Willebrand disease, as well as for clinical and basic research of thrombosis and hemostasis.

Platelet-active substances in the venom of Bothrops moojeni snake-a novel evaluation method using whole blood aggregometry

The objective of the present study was an investigation of the crude Bothrops moojeni venom, aiming at the identification of new compounds with platelet-activating or -inhibiting activity. The venom was separated by gel filtration chromatography into 18 fractions, which were tested by means of whole blood aggregometry for their activities affecting the aggregation of blood platelets. In order to eliminate interferences caused by prothrombin activators or thrombin like-enzymes, which are frequently present in snake venoms, a test method for screening protein mixtures was developed. To avoid clotting of the blood samples, the thrombin inhibitor hirudin and the synthetic inhibitor of fibrin polymerization Pefabloc FG were applied. In the present study, a platelet aggregation activator with an activity resembling thrombocytin from B. atrox was identified in one of the examined venom fractions. In addition, a platelet antagonist-most likely a disintegrin-with broad inhibitory activity against aggregation triggered by collagen, adenosine diphosphate and thrombin receptor activating peptide, was identified.

A novel anti-platelet aggregation tripeptide from Agkistrodon acutus venom: isolation and characterization

AAP, a tripeptide that inhibited rabbit platelet aggregation, was isolated from Agkistrodon acutus venom by ion-exchange, gel filtration and reverse-phase chromatography. Amino acid sequences which determined mainly by amino acid analyses and NMR spectroscopy indicated it was a tripeptide including pyroglutamic acid, asparagine and tryptophane residues. The ESMS experiment assigned a molecular weight of 429 Da. AAP inhibited rabbit platelet aggregation induced by ADP, PAF-acether, collagen and thrombin, the IC(50)s were 178 microM, 332 microM, 179 microM and 203 microM, respectively. AAP also inhibited thrombus formation in vivo thrombosis model and prevented the combination between fibrinogen and GP IIb/IIIa. Besides, AAP was not toxic after intravenous injection into mice at a higher dose. Those studies might be helpful to delineate unknown mechanisms involved in platelet aggregation and serve as a model for developing antithrombotic agents.

Functional and structural analysis of two fibrinogen-activating enzymes isolated from the venoms of Crotalus durissus terrificus and Crotalus durissus collilineatus

Fibrinogen-activating enzymes, widely distributed in Crotalidae and Viperidae venoms, are single-chain glycosylated serine proteases that display high macromolecular selectivity and are often referred to as thrombin-like enzymes (TLEs). TLEs serve as structural models to extend our understanding of the structure-function relationships of blood coagulation factors, have been clinically used for the treatment of thrombotic diseases, and are used as tools in clinical assays. The combination of gel filtration and ion-exchange chromatography proved to be successful in obtaining milligram quantities of pure samples of TLEs from the venoms of Crotalus durissus terrificus (white venom) and Crotalus durissus collilineatus (yellow venom). Functional characterization indicates that both enzymes preferentially degrade the Bb chain of bovine fibrinogen and possess edema-inducing and coagulant activities. However, the TLE from C. d. collilineatus venom shows twofold higher coagulant activity with a minimum coagulant dose (MCD) of 0.6 microg/microl, whereas the enzyme isolated from C. d. terrificus indicated an MCD of 1.5 microg/microl. Molecular modeling of gyroxin and structural comparisons with other highly conserved snake venom serine proteases, underlines the key role played by the surface charge distribution and the double insertion in the 174-surface loop in macromolecular substrate recognition by TLEs.

A novel serine protease from the snake venom of Agkistrodon blomhoffii ussurensis

A novel serine protease, ABUSV-SPase, was isolated to homogeneity for the first time from Chinese Agkistrodon blomhoffii ussurensis snake venom, and its enzymatic and structural properties were characterized by multiple techniques. ABUSV-SPase is a stable monomeric protein with a molecular mass of 26,752.6a.m.u. It reacts optimally with its substrate Nalpha-tosyl-l-arginine methyl ester (TAME) at pH 7.0 and 41 degrees C. ESI-MS/MS analysis indicates that ABUSV-SPase is a new serine protease, sharing peptide homologies with various snake venom serine proteases, especially the snake venom thrombin-like enzymes of this group, and serine protease precursors. It is a zinc-containing protein, and although zinc is not essential for activity, its replacement by various divalent metal ions, including Mg2+, Mn2+, and Ca2+, increases the TAME hydrolysis activity of the enzyme. The intrinsic fluorescences of Tyr and Trp residues of ABUSV-SPase have emission wavelengths red-shifted by 12.8nm and 3.6nm from those of free Tyr and Trp, respectively. The zinc ion increases the hydrophobicity of the environment of the Trp residues, increases the thermostability of the protein, and affects the protein secondary structure to stabilize the enzyme, but appears to have no direct role in its esterase hydrolysis activity.

The action of Lonomin V (Lonomia achelous) on fibronectin functional properties

Lonomia achelous caterpillar, Lepidoptera distributed along some South American countries, induces a hemorrhagic syndrome in people who come into contact with its bristles. A clinical characteristic in these patients is that fresh healed wounds are re-opened and bleed. In order to explain this symptomatology, we evaluated the effect of Lonomin V (a protein isolated from L. achelous hemolymph), on some functional properties of fibronectin, which in turn plays an important role in the hemostasis. The effect of Lonomin V on fibronectin was studied by SDS-PAGE in reduced condition, binding to gelatin and heparin, crosslinking to fibrin and platelet adhesion. Formation of degradation products of 120, 66, 50, 40 and 29 kDa, some of which retain affinity to heparin and gelatin were observed; however, the fibronectin degradation fragments presented a significant decrease of crosslinking capacity to fibrin and platelet adhesion, suggesting that the proteolysis of fibronectin by Lonomin V induces changes in its crosslinking sites and on platelet receptors. These findings might partially explain the wound dehiscence observed in the patients. Due to its effect on adhesive proteins with concomitant impairment of some functional properties, Lonomin V might be useful for cellular adhesion studies involved in hemostasis such as platelet adhesion.

Molecular characterization and phylogenetic analysis of BjussuMP-I: A RGD-P-III class hemorrhagic metalloprotease from Bothrops jararacussu snake venom

Snake venom metalloproteases (SVMPs) embody zinc-dependent multidomain enzymes responsible for a relevant pathophysiology in envenomation, including local and systemic hemorrhage. The molecular features responsible for hemorrhagic potency of SVMPs have been associated with their multidomains structures which can target these proteins them to several receptors of different tissues and cellular types. BjussuMP-I, a SVMP isolated from the Bothrops jararacussu venom, has been characterized as a P-III hemorrhagic metalloprotease. The complete cDNA sequence of BjussuMP-I with 1641bp encodes open reading frames of 547 amino acid residues, which conserve the common domains of P-III high molecular weight hemorrhagic metalloproteases: (i) pre-pro-peptide, (ii) metalloprotease, (iii) disintegrin-like and (iv) rich cysteine domain. BjussuMP-I induced lyses in fibrin clots and inhibited collagen- and ADP-induced platelet aggregation. We are reporting, for the first time, the primary structure of an RGD-P-III class snake venom metalloprotease. A phylogenetic analysis of the BjussuMP-I metalloprotease/catalytic domain was performed to get new insights into the molecular evolution of the metalloproteases. A theoretical molecular model of this domain was built through folding recognition (threading) techniques and refined by molecular dynamics simulation. Then, the final BjussuMP-I catalytic domain model was compared to other SVMPs and Reprolysin family proteins in order to identify eventual structural differences, which could help to understand the biochemical activities of these enzymes. The presence of large hydrophobic areas and some conserved surface charge-positive residues were identified as important features of the SVMPs and other metalloproteases.

Purification and partial characterization of two phospholipases A2 from Bothrops leucurus (white-tailed-jararaca) snake venom

Two proteins with phospholipase A(2) (PLA(2)) activity were purified to homogeneity from Bothrops leucurus (white-tailed-jararaca) snake venom through three chromatographic steps: Conventional gel filtration on Sephacryl S-200, ion-exchange on Q-Sepharose and reverse phase on Vydac C4 HPLC column. The molecular mass for both enzymes was estimated to be approximately 14 kDa by SDS-PAGE. The N-terminal sequences (48 residues) show that one enzyme presents lysine at position 48 and the other an aspartic acid in this position, and therefore they were designated blK-PLA(2) and blD-PLA(2) respectively. blK-PLA(2) presented negligible levels of PLA(2) activity as compared to that of blD-PLA(2). The PLA(2) activity of both enzymes is Ca(2+)-dependent. blD-PLA(2) did not have any effect upon platelet aggregation induced by arachidonic acid, ADP or collagen, but strongly inhibits coagulation and is able to stimulate Ehrlich tumor growth but not angiogenesis.

A novel plasminogen activator from Agkistrodon blomhoffii Ussurensis venom (ABUSV-PA): Purification and characterization

A plasminogen activator with arginine ester hydrolysis activity (ABUSV-PA) has been identified and purified to homogeneity from Chinese Agkistrodon blomhoffii Ussurensis snake venom. ABUSV-PA, a monomeric protein with molecular mass of 27815.2 Da, was purified 180-fold with 0.02% recovery for protein and 3.6% recovery for esterase activity. ABUSV-PA reacts optimally with its substrate N(alpha)-tosyl-l-arginine-methyl ester (TAME) at approximately pH 7.5 and at 51 degrees C. Measurement from inductively coupled plasma-atomic emission spectroscopy (ICP-AES) reveals that ABUSV-PA is a Zn(2+)-containing protein with a stoichiometry of 1:1 [Zn(2+)]:[ABUSV-PA]. Analyses of esterase hydrolysis and UV absorption and CD spectra indicate that Zn(2+) plays an important role in maintaining the structural integrity rather than the esterase activity of ABUSV-PA. Divalent metal ions, including Ca(2+), Mg(2+), Cu(2+), Ni(2+), Mn(2+), and Co(2+), increase the TAME hydrolysis activity of ABUSV-PA. A red-shift of the emission wavelengths of the synchronous fluorescence of ABUSV-PA, compared to those of free Tyr and Trp, indicates a conformation where the Tyr and Trp residues are in exposed hydrophilic environments. The presence of zinc increases the hydrophobicity of the conformational environments surrounding the Trp residues of ABUSV-PA and affects the secondary structure of ABUSV-PA, as proved by UV absorption and CD spectroscopy.

Vipera lebetina venom contains all types of snake venom metalloproteases

Snake venoms contain four classes of metalloproteases that all have a typical zinc-chelating sequence (HEXXHGXXH). N-terminal sequences and internal sequences of different purified metalloproteases were determined using Edman sequencing and LC MS/MS technique. Oligonucleotides were designed and used as primers for cDNA cloning from Vipera lebetina venom gland cDNA library. We found that isoforms of fibrinolytic enzyme lebetase Le-4 and Le-3 are synthesized in different way: Le-4 is synthesized as P-I type metalloprotease, Le-3 is synthesized with disintegrin-like domain as P-II type protease and processed post-translationally. An endothelial cell apoptosis-inducing heterodimeric glycosylated metalloprotease, V. lebetina apoptosis-inducing protease (VLAIP), belongs to P-III type containing metalloprotease, disintegrin-like and cysteine-rich domains. All these enzymes hydrolyze the Aalpha-chain and more slowly the Bbeta-chain of fibrinogen. Treatment of HUVEC cells with VLAIP induces changes in the attachment of cells to the substrate and causes apoptosis. V. lebetina venom contains also P-IV type-specific coagulant factor X activator (VLFXA) that cleaves the Arg52-Ile53 bond in the heavy chain of human factor X. VLFXA is a glycoprotein composed of a heavy chain and two C-type lectin-like light chains linked by disulfide bonds. The heavy and light chains of VLFXA are synthesized from different genes.

Insights into the substrate specificity of a novel snake venom serine peptidase by molecular modeling

The cDNA encoding BthaTL, a serine peptidase from the venom of the snake Bothrops alternatus, was cloned and sequenced. The deduced primary structure shows over 62% of identity with snake venom thrombin-like enzymes (SVTLEs), molecules with high substrate specificity toward different natural substrates. Indeed, a phylogenetic reconstruction by two different methods clustered this enzyme close to other SVTLEs. These enzymes generally affect the hemostatic system in several ways, and therefore are used as tools in pharmacology and clinical diagnosis. A three-dimensional model of BthaTL was built by homology modeling using TSV-PA (Trimeresurus stejnegeri venom plasminogen activator) crystal structure as template. BthaTL model showed that the typical catalytic triad conformation of serine peptidases was preserved. The calcium coordination ligands were absent or adopt an unfavorable conformation, preventing interactions with metals. On the other hand, the Asp97-Arg174 saline bridge of TSV-PA was not found and its specificity determinant Phe193 is replaced by a Gly in BthaTL. The substitution of essential residues in the neighborhoods of the catalytic site cleft of BthaTL indicates that these two proteins do not share the same enzymatic specificity, what means that BthaTL will probably not activate plasminogen. Such observations may be helpful in the understanding of the molecular mechanism for substrate specificity of these enzymes.

Releasing or expression modulating mediator involved in hemostasis by Berythractivase and Jararhagin (SVMPs)

PIII snake venom metalloproteases (SVMPs) are structurally related to ADAMs (a disintegrin and metalloprotease human family of proteins). Berythractivase and Jararhagin are PIII SVMPs with 69% homology with different hemostatic properties. In order to clarify these differences and further characterize the biological effects of these proteins, we compared the effect of both proteases on human umbilical vein endothelial cell (HUVEC) for evaluating the release and modulation of coagulation and fibrinolysis mechanisms as well as the expression of their correlated genes. We found that both proteins increase the von Willebrand factor liberation, but did not modulate gene expression. Berythractivase, differently from Jararhagin increased the expression of tissue factor. Our results showed that both SVMPs (Berythractivase and Jararhagin) activate HUVEC releasing or modulating mediators involved in hemostasis. Meanwhile, we can suggest through the up-regulation of TF gene that the studied SVMP acts in a specific manner, suggesting that Jararhagin has preferentially a local action, while Berythractivase can be assumed as a systemic pro-coagulant protein with activity on the surface of HUVECs.

Characterization of a New Platelet Aggregating Factor from Crotoxin Crotalus durissus cascavella Venom

In this article we investigated the platelet aggregating activity of whole crotoxin and its subunits isolated from Crotalus durissus cascavella venom. During the purification protocols of the venom, using HPLC molecular exclusion, we detected the presence of two different serine protease activities in the gyroxin fraction, and another in the crotoxin fraction, which induced strong and irreversible platelet aggregation, in addition to blood coagulation. From crotoxin, we isolated PLA2, crotapotin (both fractions corresponding approximately 85% of whole crotoxin) and another minor fraction (F20) that exhibited serine protease activity. After a new fractionation on reverse phase HPLC chromatography, we obtained three other fractions named as F201, F202 and F203. F202 was obtained with high degree of molecular homogeneity with molecular mass of approximately 28 kDa and a high content of acidic amino residues, such as aspartic acid and glutamic acid. Other important amino acids were histidine, cysteine and lysine. This protein exhibited a high specificity for BApNA, a Michaelis-Menten behavior with Vmax estimated in 5.64 microM/min and a Km value of 0.58 mM for this substrate. In this work, we investigated the ability of F202 to degrade fibrinogen and observed alpha and beta chain cleavage. Enzymatic as well as the platelet aggregation activities were strongly inhibited when incubated with TLCK and PMSF, specific inhibitors of serine protease. Also, F202 induced platelet aggregation in washed and platelet-rich plasma, and in both cases, TLCK inhibited its activity. The N-terminal amino acid sequence of F202 presented a high amino acid sequence homology with other thrombin-like proteins, but it was significantly different from gyroxin. These results showed that crotoxin is a highly heterogeneous protein composed of PLA2, thrombin-like and other fractions that might explain the diversity of physiological and pharmacological activities of this protein.

Secretory phospholipase A2 of group IIA: Is it an offensive or a defensive player during atherosclerosis and other inflammatory diseases?

Since its discovery in the serum of patients with severe inflammation and in rheumatoid arthritic fluids, the secretory phospholipase A2 of group IIA (sPLA2-IIA) has been chiefly considered as a proinflammatory enzyme, the result of which has been very intense interest in selective inhibitors of sPLA2-IIA in the hope of developing new and efficient therapies for inflammatory diseases. The recent discovery of the antibacterial properties of sPLA2-IIA, however, has raised the question of whether the upregulation of sPLA2-IIA during inflammation is to be considered uniformly negative and the hindrance of sPLA2-IIA in every instance beneficial. The aim of this review is for this reason, along with the results of various investigations which argue for the proinflammatory and proatherogenic effects of an upregulation of sPLA2-IIA, also to array data alongside which point to a protective function of sPLA2-IIA during inflammation. Thus, it could be shown that sPLA2-IIA, apart from the bactericidal effects, possesses also antithrombotic properties and indeed plays a possible role in the resolution of inflammation and the accelerated clearance of oxidatively modified lipoproteins during inflammation via the liver and adrenals. Based on these multipotent properties the knowledge of the function of sPLA2-IIA during inflammation is a fundamental prerequisite for the development and establishment of new therapeutic strategies to prevent and treat severe inflammatory diseases up to and including sepsis.

Effects of arginine-glycine-aspartic acid (RGD) containing snake venom peptides on parthenogenetic development and in vitro fertilization of bovine oocytes

The ability of synthetic arginine-glycine-aspartic acid (RGD)-containing peptides to induce intracellular calcium transients similar to those observed at fertilization by spermatozoa in the bovine has been reported (Campbell et al., 2000: Biol Reprod 62:1702-1709; Sessions et al., 2006. Mol Reprod Dev). These results also indicated the ability of synthetic RGD-containing peptides to induce activation and subsequent parthenogenetic development to the blastocyst stage, although, at numbers lower than observed with control in vitro fertilization (IVF). Evidence has been provided indicating the important effect of surrounding regions on the biological activity of the RGD sequence (Zhu and Evans, 2002; Sessions et al., 2006). The current experiments were designed to use natural RGD-containing sequences (disintegrins) to understand their effects. A total of three RGD-containing snake venom peptides (Kistrin (K), Elegantin (Ele), and Echistatin (Ech)) and one nonRGD-containing venom (Erabutoxin B (EB; control) were used at three concentrations (0.1, 1, and 10 micro g /ml) to induce parthenogenetic development to the blastocyst stage and in conjunction (1.0, 5.0, and 10 micro g/ml) with spermatozoa to evaluate competitive inhibition of fertilization and subsequent development. A (P < 0.01) higher number of bovine oocytes developed to the blastocyst stage after incubation with K, Ele and Ech at 1.0 micro g/ml, and was not different (P > 0.01) from IVF control. Fertilization was significantly reduced (P < 0.01) at all concentrations of K, Ele and Ech as compared to IVF control. No reduction (P > 0.05) was observed in EB (nonRGD) treated oocytes. These results support the involvement of a disintegrin-integrin interaction at fertilization in the bovine resulting in activation and subsequent development.

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.

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.

Practical applications of snake venom toxins in haemostasis

Snake venom toxins affecting haemostasis have facilitated extensively the routine assays of haemostatic parameters in the coagulation laboratory. Snake venom thrombin-like enzymes (SVTLE) are used for fibrinogen/fibrinogen breakdown product assay and for the detection of fibrinogen dysfunction. SVTLE are not inhibited by heparin and can thus can be used for assaying antithrombin III and other haemostatic variables in heparin-containing samples. Snake venoms are a rich source of prothrombin activators and these are utilised in prothrombin assays, for studying dysprothrombinaemias and for preparing meizothrombin and non-enzymic forms of prothrombin. Russell's viper (Daboia russelli) venom (RVV) contains toxins which have been used to assay blood clotting factors V, VII, X, platelet factor 3 and, importantly, lupus anticoagulants (LA). Other prothrombin activators (from the taipan, Australian brown snake and saw-scaled viper) have now been used to assay LA. Protein C and activated protein C resistance can be measured by means of RVV and Protac, a fast acting inhibitor from Southern copperhead snake venom and von Willebrand factor can be studied with botrocetin from Bothrops jararaca venom. The disintegrins, a large family of Arg-Gly-Asp (RGD)-containing snake venom proteins, show potential for studying platelet glycoprotein receptors, notably, GPIIb/IIIa and Ib. Snake venom toxins affecting haemostasis are also used in the therapeutic setting: Ancrod (from the Malayan pit viper, Calloselasma rhodostoma), in particular, has been used as an anticoagulant to achieve 'therapeutic defibrination'. Other snake venom proteins show promise in the treatment of a range of haemostatic disorders.

The snake venom metalloproteases berythractivase and jararhagin activate endothelial cells

PIII snake venom metalloproteases (SVMPs) are metalloproteases structurally related to ADAMs (a disintegrin and metalloprotease human family of proteins). Berythractivase and jararhagin are PIII SVMPs with 69% homology that have different hemostatic properties. In order to clarify these differences and further characterize the biological effects of these proteins, we have analyzed the effect of both proteases on human umbilical-vein endothelial cell functions. We found that both proteins enhanced nitric oxide generation, prostacyclin production and interleukin-8 release. Berythractivase but not jararhagin increased the expression of decay accelerating factor. Jararhagin decreased cell viability in a concentration-dependent manner and induced cellular apoptosis, while berythractivase did not modulate cell survival. Our results show for the first time that, besides the known anti-aggregating or procoagulant effects of PIII SVMPs, these proteins trigger endothelial cell effector responses. Although structurally related, berythractivase and jararhagin induce a dissimilar generation and release of endothelial molecules that may account for their different hemorrhagic activity.

Duvernoy's gland secretion of Philodryas patagoniensis from the northeast of Argentina: its effects on blood coagulation

Duvernoy's gland secretion of Philodryas patagoniensis exhibits high hemorrhagic activity, containing enzymes that are able to degrade the vascular wall. In this work we aim to determine if the secretion can also affect the hemostatic system by causing changes in blood coagulation. Procoagulant and coagulant activities were evaluated on plasma and fibrinogen, respectively. The delay in the thrombin clotting time of fibrinogen previously incubated with the secretion was also determined. Specific hydrolysis of fibrinogen and fibrin incubated with the secretion at different time intervals was shown by electrophoresis on polyacrylamide gel. To determine the structural characteristics of the enzymes degrading fibrinogen and fibrin, secretion were incubated in the presence of 45 mM Na(2)EDTA, 40 mM Benzamidine, and/or 2 mM PMSF before the incubation with fibrinogen or fibrin, respectively. The effect in vivo was investigated in adult male rats injected with different dose of secretion, aliquots of blood were withdrawn at different time intervals, and the fibrinogen concentration was determined. Duvernoy's gland secretion of P. patagoniensis did not clot plasma or fibrinogen. It exhibited a potent fibrinogenolytic activity degrading the Aalpha-chain faster than the Bbeta-chain, whereas gamma-chain was resistant. This latter corresponded with a strong delay in the thrombin clotting time of fibrinogen (4 mg/ml) pre-incubated with the secretion, being 9.53 microg the amount of protein from Duvernoy's gland secretion that increased the thrombin clotting time from 20 to 60 s. In vivo, the loss of rat plasma fibrinogen was proportional to the amount of secretion injected. The secretion also hydrolyzed fibrin degrading the alpha-monomer. Inhibition studies with Na(2)EDTA, Benzamidine, and/or PMSF showed that metalloproteinases and serinoproteinases are the main enzymes responsible for the hydrolyzing activity on fibrinogen and fibrin. All these results demonstrate that Duvernoy's gland secretion of P. patagoniensis possesses enzymes able to hydrolyze plasma components playing a relevant role in the blood coagulation. These hydrolyzing activities and those acting on the wall of blood vessels let the secretion exhibit a high hemorrhagic activity, which may result in permanent sequelae or even cause the death of the victims bitten by this colubrid snake.

Factor X activator from Vipera lebetina venom is synthesized from different genes

Vipera lebetina venom contains specific coagulant Factor X activator (VLFXA) that cleaves the Arg52-Ile53 bond in the heavy chain of human factor X. VLFXA is a glycoprotein that is composed of a heavy chain (HC) and two light chains (LC) linked by disulfide bonds. The complete amino acid sequences of the three chains of the factor X activator from V. lebetina snake venom are deduced from the nucleotide sequences of cDNAs encoding these chains. The full-length cDNA (2347 bp) sequence of the HC encodes an open reading frame (ORF) of 612 amino acids that includes signal peptide, propeptide and mature metalloproteinase with disintegrin-like and cysteine-rich domains. The light chain LC1 contains 123 and LC2 135 amino acid residues. Both light chains belong to the class of C-type lectin-like proteins. The N-termini of VLFXA chains and inner sequences of peptide fragments detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC MS/MS) from protein sequence are 100% identical to the sequences deduced from the cDNA. The molecular masses of tryptic fragments of VLFXA chains analyzed by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) also confirm the protein sequences deduced from the cDNAs. These are the first cloned factor X activator heavy and light chains. We demonstrate that the heavy and light chains are synthesized from different genes.

Most cited papers in Toxicon

Citation of a published work is one of the parameters considered in the analysis of relevance and importance of scientific contributions. In 2002, for the first time the Impact Factor of Toxicon has risen above 2.0, placing it at the 17th position among 76 journals in the 'toxicology' field. The aim of this article was to identify the most cited articles in Toxicon, that have contributed to the steady increase of its Impact Factor. The number of citations, complete reference and type of all documents appearing in Toxicon in the period 1963-2003 were retrieved from the ISI Web-of-Science homepage. The documents retrieved were sorted by the number of citations received. A 'citation index', defined as the number of citations divided by the number of years since publication, was calculated for each document. It was clearly seen that reviews in Toxicon received 4.4-fold more citations than articles. Unexpectedly, it was found that recent papers were proportionally more cited than old ones. A decrease in the proportion of papers dealing on 'snake*' through out the period and the broadened range of subjects of the most cited papers recently published in Toxicon reflects an increased 'visibility' in other fields of toxinology. Research on plant toxins gained its own space in Toxicon with newer publications showing high citation indexes. It can be postulated that these facts helped to increase Toxicon's Impact Factor from 1.248 in 1999 to 2.003 in 2002. With the increased number of issues in Toxicon as well as publications of subject-dedicated volumes containing mostly reviews, the Impact Factor of Toxicon is expected to keep rising in the near future.

A prothrombin activator from Bothrops erythromelas (jararaca-da-seca) snake venom: characterization and molecular cloning

A novel prothrombin activator enzyme, which we have named 'berythractivase', was isolated from Bothrops erythromelas (jararaca-da-seca) snake venom. Berythractivase was purified by a single cation-exchange-chromatography step on a Resource S (Amersham Biosciences) column. The overall purification (31-fold) indicates that berythractivase comprises about 5% of the crude venom. It is a single-chain protein with a molecular mass of 78 kDa. SDS/PAGE of prothrombin after activation by berythractivase showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin, independent of the prothrombinase complex. Chelating agents, such as EDTA and o -phenanthroline, rapidly inhibited the enzymic activity of berythractivase, like a typical metalloproteinase. Human fibrinogen A alpha-chain was slowly digested only after longer incubation with berythractivase, and no effect on the beta- or gamma-chains was observed. Berythractivase was also capable of triggering endothelial proinflammatory and procoagulant cell responses. von Willebrand factor was released, and the surface expression of both intracellular adhesion molecule-1 and E-selectin was up-regulated by berythractivase in cultured human umbilical-vein endothelial cells. The complete berythractivase cDNA was cloned from a B. erythromelas venom-gland cDNA library. The cDNA sequence possesses 2330 bp and encodes a preproprotein with significant sequence similarity to many other mature metalloproteinases reported from snake venoms. Berythractivase contains metalloproteinase, desintegrin-like and cysteine-rich domains. However, berythractivase did not elicit any haemorrhagic response. These results show that, although the primary structure of berythractivase is related to that of snake-venom haemorrhagic metalloproteinases and functionally similar to group A prothrombin activators, it is a prothrombin activator devoid of haemorrhagic activity. This is a feature not observed for most of the snake venom metalloproteinases, including the group A prothrombin activators.

Platelet sodium-proton exchanger and phospholipid-dependent procoagulant activity in patients with type 2 diabetes

Platelet Na(+)/H(+) exchanger (NHE) activity, phospholipid-dependent thrombin generation, and platelet factor 3 (PF3) availability were measured in 83 type 2 diabetics and in 40 age- and sex-matched healthy subjects. Na(+)/H(+) exchanger activity was significantly increased in diabetic patients in comparison to the controls (kappa = 4.29 +/- 0.71 x 10(-3) x s(-1) v 3.21 +/- 0.64 x 10(-3) x s(-1), P <.00001). However, there was no significant difference between subjects with (kappa = 4.28 +/- 0.75 x 10(-3) x s(-1)) and without (kappa = 4.26 +/- 0.32 x10(-3) x s(-1)) arterial hypertension, as well as between patients with normo- and microalbuminuria or overt proteinuria (kappa = 4.26 +/- 0.58 x 10(-3) x s(-1), kappa = 4.47 +/- 0.93 x 10(-3) x s(-1) and kappa = 4.07 +/- 0.38 x10(-3) x s(-1), respectively). Comparatively high NHE activity was observed in the group of patients with hemoglobin A(1c) (HbA(1c)) less than 7.5%. Multiple regression analysis revealed that the factors independently related to platelet Na(+)/H(+) exchanger activity were: total PF3 activity (beta = 0.77, P =.011) and triglyceride (TG) concentration (beta = 0.44, P =.039). Phospholipid-dependent thrombin generation and PF3 availability were also enhanced in all plasma fractions of diabetic patients, especially in platelet-poor plasma (PPP) and platelet-free plasma (PFP) (P <.0001 and P <.00001, respectively). There was a positive correlation between NHE activity and thrombin generation, as well as with PF3 availability in all plasma fractions. Our results suggest that enhanced platelet Na(+)/H(+) exchanger activity associated with raised phospholipid-dependent procoagulant activity may increase the risk of vascular damage in type 2 diabetic patients.

Application of Recombinant Rhodostomin in Studying Cell Adhesion

Rhodostomin from venom of Agkistrodon rhodostoma (also called Calloselasma rhodostoma) contains 68 amino acid residues including 6 pairs of disulfide bonds and an arginine-glycine-aspartic acid (RGD) sequence at positions 49-51. It has been known as one of the strongest antagonists to platelet aggregation among the family termed disintegrin. In this review paper, in addition to introducing the characteristics of disintegrin and its related molecules, the advantages of using recombinant DNA technology to produce rhodostomin are described. The recombinant rhodostomin has been demonstrated to facilitate cell adhesion via interaction between the RGD motif of rhodostomin and integrins on the cell surface. This property allowed us to use the recombinant rhodostomin as an extracellular matrix to study cell adhesion and to distinguish attachment efficiency between two melanoma cell lines B16-F1 and B16-F10, the former is a low metastasis cell while the latter is a high metastasis cell. Furthermore, by using the recombinant rhodostomin as a substrate, osteoprogenitor-like cells are able to be selected and enriched within 3 days from rat bone marrow which contains a heterogeneous cell population. Finally, we show that the recombinant rhodostomin can be immobilized on beads and which serve as an affinity column to dissect cell-surface protein(s) binding to the RGD motif of rhodostomin.

Purification, characterization and crystallization of Jararacussin-I, a fibrinogen-clotting enzyme isolated from the venom of Bothrops jararacussu

A fibrinogen-clotting enzyme, Jararacussin-I, was purified from the venom of Bothrops jararacussu by a combination of ion exchange chromatography using Resource 15S resin and affinity chromatography using Benzamidine Sepharose 6B resin. Jararacussin-I displays a molecular mass of 28 kDa as estimated by sodium dodecyl sulphate-PAGE and possesses an isoelectric point of 5.0. The coagulant specific activity of the enzyme was determined to be 45.8 NIHU/mg using bovine fibrinogen as the substrate and the esterase specific activity was determined to be 258.7 U/mg. The protease inhibitors, benzamidine and DTT inhibited the esterase specific activity by 72.4 and 69.7%, respectively. The optimal temperature and pH for the degradation of both chains of fibrinogen and esterase specific activity were determined to be 37 degrees C and 7.4-8.0, respectively. The enzyme was inactivated at both 4 and 75 degrees C. Single crystals of Jararacussin-I were obtained and complete three-dimensional X-ray diffraction data was collected at the Brazilian National Synchrotron Source (LNLS) to a resolution of 2.4A.

Actions of two serine proteases from Trimeresurus jerdonii venom on chromogenic substrates and fibrinogen

Jerdonobin and jerdofibrase are two serine proteases purified from the venom of Trimeresurus jerdonii. The Michaelis constant K(m) and the catalytic rate constant K(cat) of jerdonobin or jerdofibrase on three chromogenic substrates, H-D-Pro-Phe-Arg-pNA (S2302), H-D-Phe-pipecolyl-Arg-pNA (S2238), and H-D-Val-Leu-Lys-pNA (S2251) were obtained from lineweaver-Burk plots. Jerdofibrase could hydrolyze all three substrates, but jerdonobin had no detectable activity on S2251, suggesting a relatively broader substrate specificity for jerdofibrase than jerdonobin. By SDS-PAGE, jerdofibrase preferentially degraded Bbeta-chain of fibrinogen. It also degraded Aalpha-chain of fibrinogen with relatively slow activity, but did not act on the gamma-chain. In contrast, jerdonobin did not degrade fibrinogen within 12 h. Fibrinopeptides liberation test, identified by HPLC, showed jerdonobin released fibrinopeptide A and a small amount of fibrinopeptide B. Unlike jerdonobin, jerdofibrase mainly released fibrinopeptide B. These results indicate that the two enzymes differ in their ability to hydrolyze chromogenic substrates and in their actions on fibrinogen.

A non-toxic anticoagulant metalloprotease: purification and characterization from Indian cobra (Naja naja naja) venom

A non-toxic potent anticoagulant metalloprotease NN-PF(3) has been purified to homogeneity from the Indian cobra (Naja naja naja) venom through a combination of column chromatography and electrophoresis. NN-PF(3) is a single chain protein with a molecular weight of 68 kDa by SDS-PAGE. It hydrolysed casein, gelatin, haemoglobin and bovine fibrinogen, but did not hydrolyse bovine serum albumin or synthetic substrates such as TAME, BAEE and BAPNA. EDTA, EGTA and cyanide inhibited the enzymatic activity while 1,10-phenanthroline, PMSF, leupetin and pepstatin did not show any effect. NN-PF(3) is a metalloprotease containing Ca(2+) and Zn(2+) at a molar ratio of 1:1.2 and 1:0.4, respectively, as revealed by atomic absorption spectroscopy. NN-PF(3) was non-lethal up to an i.p. dose of 15 mg/kg body weight of mice and is devoid of myotoxicity, cytotoxicity and haemorrhagic activity. It is weakly oedematic, but strongly anticoagulant in property and the effect observed was both dose and time dependent.

Neutralization of a snake venom hemorrhagic metalloproteinase prevents coagulopathy after subcutaneous injection of Bothrops jararaca venom in rats

Coagulopathy is one of the major complications following envenomations by crotalid and viperid snakes. The present study was undertaken to examine the effect of a hemorrhagic metalloproteinase in Bothrops jararaca venom, jararafibrase I (JF I), on the development of coagulopathy using rat snakebite model. Coagulation parameters were monitored after subcutaneous injection of B. jararaca crude venom, JF I-neutralized venom and purified JF I in rats. Crude venom induced unclottable blood and fibrinogen consumption, while JF I-neutralized venom and purified JF I did not induce coagulopathy. Plasma venom antigen level of rats given JF I-neutralized venom was lower than that of rats given crude venom. We conclude that venom hemorrhagic metalloproteinases play an important role in the development of coagulopathy through rapid spreading of venom coagulation components from the injected area into systemic circulation.