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

Electrical Cell Impedance Sensing (ECIS): Feasibility of a Novel In Vitro Approach to Studying Venom Toxicity and Potential Therapeutics

Snakebite envenoming is often discussed in terms of lethality and limb loss, but local tissue injury and coagulotoxic effects of venom are significantly more common acute manifestations of snakebite envenoming (SBE). Local tissue injury and the hemorrhagic and coagulotoxic effects of venom are challenging to study in live animals and can be ethically fraught due to animal welfare concerns such that attention to the 3Rs of animal welfare motivates the development of in vitro techniques in this arena. Herein, we tested the use of a wound-healing study technique known as Electric Cell-Substrate Impedance Sensing (ECIS) to assess populations of cultured cells exposed to venom with or without sPLA2 and/or metalloprotease inhibitors (varespladib and marimastat, respectively). For comparison, the StarMax coagulation analyzer for coagulotoxicity was further used to evaluate the venoms and the neutralizing capabilities of the abovementioned direct toxin inhibitors (DTIs) against the same venoms examined using ECIS. Three viper and three elapid venoms that were examined for their effects on H1975 cells were Agkistrodon contortrix (Eastern Copperhead), Crotalus helleri (Southern Pacific Rattlesnake), and Vipera ammodytes (Horned Viper) and Naja atra (Chinese Cobra), Naja mossambica (Mozambique Spitting Cobra), and Naja nigricollis (Black-necked Spitting Cobra), respectively. The combination of cellular and coagulation techniques appears to usefully discriminate the in vitro capabilities and limitations of specific inhibitors to inhibit specific venom effects. This study suggests that ECIS with or without concomitant coagulation testing is a feasible method to generate reproducible, meaningful preclinical data and could be used with any type of cell line. Importantly, this approach is both quantitative and has the potential of reducing animal use and suffering during the evaluation of potential therapeutics. To further evaluate the potential of this method, rescue studies should be performed.

Rattlesnake Roundup: Point-of-Care Thrombelastographic Methods Define the Molecular Impacts on Coagulation of Crotalus Venom Toxins In Vitro and In Vivo

A malalignment between rattlesnake-envenomed patients' degree of compromised coagulation and the data generated by standard hematological determinations generated with blood samples anticoagulated with calcium (Ca) chelating agents is almost certain. Many rattlesnake venom toxins are Ca-independent toxins that likely continue to damage plasmatic and cellular components of coagulation in blood samples (anticoagulated with Ca chelation) during transportation from the emergency department to the clinical laboratory. The most straightforward approach to abrogate this patient-laboratory malalignment is to reduce "needle to activation time"-the time from blood collection to commencement of laboratory analysis-with utilization of point-of-care (POC) technology such as thrombelastography. The workflow and history of standard and POC approaches to hematological assessment is reviewed. Further, using a preclinical model of envenomation with four different rattlesnake venoms, the remarkably diverse damage to coagulation revealed with POC thrombelastography is presented. It is anticipated that future investigation and potential changes in clinical monitoring practices with POC methods of hematological assessment will improve the management of envenomed patients and assist in precision care.

Poly-Gly Region Regulates the Accessibility of Metal Binding Sites in Snake Venom Peptides

It is supposed that the presence of poly-His regions in close proximity to poly-Gly domains in snake venoms is related to their biological activity; poly-His/poly-Gly (pHpG) peptides inhibit the activity of metalloproteinases during venom storage via the chelation metal ions, necessary for their proper functioning. This work shows that only the histidyl residues from the N-terminal VDHDHDH motif (but not from the poly-His tag) were the primary Zn(II) binding sites and that the poly-Gly domain situated in the proximity of a central proline residue may play a regulatory role in venom gland protection. The proline induces a kink of the peptide, resulting in steric hindrance, which may modulate the accessibility of potential metal binding sites in the poly-His domain and may, in turn, be one of the regulators of Zn(II) accessibility in the venom gland and therefore a modulator of metalloproteinase activity during venom storage.

The proline induces a kink of the peptide, resulting in a steric hindrance, which may modulate the accessibility of potential metal binding sites in the poly-His domain and may, in turn, be one of the regulators of Zn(II) accessibility in the venom gland and therefore a modulator of metalloproteinase activity during venom storage.

A strategy for the enrichment and characterization of disulfide bond-contained proteins from Chinese cobra (Naja atra) venom

A new strategy combined gold-coated magnetic nanocomposites assisted enrichment with mass spectrometry was developed for the characterization of disulfide bond-contained proteins from Chinese cobra (Naja atra) venom. In this work, core-shell nanocomposites were synthesized by the seed-mediated growth method and used for the enrichment of snake venom proteins containing disulfide bonds. A total of 3545 tryptic digested peptides derived from 96 venom proteins in Naja atra venom were identified. The venom proteins comprised 14 toxin families including three-finger toxins, phospholipase A₂ , snake venom metalloproteinase, cobra venom factor, and so forth. Extra 16 venom proteins were detected exclusively in the nanocomposites set, among which 11 venom proteins were from the three-finger toxins family. In the present study, the proposed simple and efficient protocol replaced the tedious and laborious technologies commonly used for pre-separating crude snake venom, suggesting widely implementation in low-abundance or trace disulfide bond-contained proteins or peptides characterization.

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

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

Inhibition of platelet aggregation and blood coagulation by a P-III class metalloproteinase purified from Naja atra venom

Snake venom metalloproteinases (SVMPs) are an important component in viperid and crotalid venoms, and these SVMPs play important and versatile roles in the pathogenesis of snakebite envenoming. The SVMPs from elapid venoms are not well elucidated compared with those from viperid and crotalid venoms. Atrase B is a nonhemorrhagic P-III SVMP purified from the Naja atra venom, which possesses a weak fibrinogenolytic activity. In this paper, the activity and mechanism of atrase B against platelet aggregation and blood coagulation were investigated. The in vitro assay showed that atrase B remarkably inhibited ristocetin- and thrombin-induced platelet aggregation by cleavage of the platelet membrane glycoprotein Ib, and the coagulation of normal human plasma, which may be caused by inhibiting coagulation factor VIII predominantly. When atrase B was intravenously injected into rats at doses of 0.05 and 0.30 mg/kg, the activated partial thromboplastin and the thrombin times were significantly prolonged in a dose-dependent manner. Similarly, the fibrinogen level decreased, but only a high dose of atrase B showed remarkable activity against platelet aggregation. Results suggested that anticoagulation was a more important function of atrase B compared with its activity against platelet aggregation. These results indicated that atrase B may play an important role in the anticoagulant properties of Naja atra venom. In addition, atrase B may be a potent anticoagulant agent because its effectiveness in vivo against platelet aggregation and blood coagulation.

A comparative analysis of the proteomes and biological activities of the venoms from two sea snakes, Hydrophis curtus and Hydrophis cyanocinctus, from Hainan, China

We characterized and compared the venom protein profiles of Hydrophis curtus (synonyms: Lapemis hardwickii, Lapemis curtus and Hydrophis hardwickii) and Hydrophis cyanocinctus, the two representatives of medically important venomous sea snakes in Chinese waters using proteomic approaches. A total of 47 and 38 putative toxins were identified in H. curtus venom (HcuV) and H. cyanocinctus venom (HcyV), respectively, and these toxins could be grouped into 15 functional categories, mainly proteinases, phospholipases, three-finger toxins (3FTxs), lectins, protease inhibitors, ion channel inhibitors, cysteine-rich venom proteins (CRVPs) and snake venom metalloproteases (SVMPs). The constituent ratio of each toxin category varied between HcuV and HcyV with 3FTx (54% in HcuV/69% in HcyV) and PLA2 (38% in HcuV/22% in HcyV) unanimously ranked as the top two most abundant families. Both HcuV and HcyV exhibited relatively high lethality (LD₅₀ values in mice of 0.34 μg/g and 0.24 μg/g, respectively), specific PLA2 activity and hemolytic activity. On the basis of several previous reports of HcuV and HcyV collected from other areas, these findings greatly expand our understanding of geographical variation and interspecies diversity of the two sea snake venoms and can provide a scientific basis for the development of specific sea snake antivenom in the future.

Interspecific and intraspecific venom enzymatic variation among cobras (Naja sp. and Ophiophagus hannah)

The genera Ophiophagus and Naja comprise part of a clade of snakes referred to as cobras, dangerously venomous front-fanged snakes in the family Elapidae responsible for significant human mortality and morbidity throughout Asia and Africa. We evaluated venom enzyme variation for eleven cobra species and three N. kaouthia populations using SDS-PAGE venom fingerprinting and numerous enzyme assays. Acetylcholinesterase and PLA₂ activities were the most variable between species, and PLA₂ activity was significantly different between Malaysian and Thailand N. kaouthia populations. Venom metalloproteinase activity was low and significantly different among most species, but levels were identical for N. kaouthia populations; minor variation in venom L-amino acid oxidase and phosphodiesterase activities were seen between cobra species. Naja siamensis venom lacked the α-fibrinogenolytic activity common to other cobra venoms. In addition, venom from N. siamensis had no detectable metalloproteinase activity and exhibited an SDS-PAGE profile with reduced abundance of higher mass proteins. Venom profiles from spitting cobras (N. siamensis, N. pallida, and N. mossambica) exhibited similar reductions in higher mass proteins, suggesting the evolution of venoms of reduced complexity and decreased enzymatic activity among spitting cobras. Generally, the venom proteomes of cobras show highly abundant three-finger toxin diversity, followed by large quantities of PLA₂s. However, PLA₂ bands and activity were very reduced for N. haje, N. annulifera and N. nivea. Venom compositionalenzy analysis provides insight into the evolution, diversification and distribution of different venom phenotypes that complements venomic data, and this information is critical for the development of effective antivenoms and snakebite treatment.

Biochemical and pharmacological characterization of Trimersurus malabaricus snake venom

Trimeresurus malabaricus is a venomous pit viper species endemic to southwestern part of India. In earlier reports, we have shown that envenomation by T. malabaricus venom leading to strong local tissue damage but the mechanism of action is not clearly revealed. Local tissue damage affected by T. malabaricus venom is of great importance since the poison has serious systemic effects including death in the case of multiple attacks. The present study details the major manifestations of T. malabaricus venom and the induction of local tissue damage, which suggests that most toxins are present in the form of hydrolytic enzymes. Hydrolytic activity of the enzymes was measured and the data indicated that protease and phospholipase A₂ activity was high which is responsible for local tissue damage. Furthermore, the role of hydrolytic enzymes in the induction of pathological events such as hemorrhage, edema, myotoxicity, and blood coagulation examination were assessed through animal models.

Comparison of proteomic profiles of the venoms of two of the 'Big Four' snakes of India, the Indian cobra (Naja naja) and the common krait (Bungarus caeruleus), and analyses of their toxins

Snake venoms are mixtures of biologically-active proteins and peptides, and several studies have described the characteristics of some of these toxins. However, complete proteomic profiling of the venoms of many snake species has not yet been done. The Indian cobra (Naja naja) and common krait (Bungarus caeruleus) are elapid snake species that are among the 'Big Four' responsible for the majority of human snake envenomation cases in India. As understanding the composition and complexity of venoms is necessary for successful treatment of envenomation in humans, we utilized three different proteomic profiling approaches to characterize these venoms: i) one-dimensional SDS-PAGE coupled with in-gel tryptic digestion and electrospray tandem mass spectrometry (ESI-LC-MS/MS) of individual protein bands; ii) in-solution tryptic digestion of crude venoms coupled with ESI-LC-MS/MS; and iii) separation by gel-filtration chromatography coupled with tryptic digestion and ESI-LC-MS/MS of separated fractions. From the generated data, 81 and 46 different proteins were identified from N. naja and B. caeruleus venoms, respectively, belonging to fifteen different protein families. Venoms from both species were found to contain a variety of phospholipases A₂ and three-finger toxins, whereas relatively higher numbers of snake venom metalloproteinases were found in N. naja compared to B. caeruleus venom. The analyses also identified less represented venom proteins including L-amino acid oxidases, cysteine-rich secretory proteins, 5'-nucleotidases and venom nerve growth factors. Further, Kunitz-type serine protease inhibitors, cobra venom factors, phosphodiesterases, vespryns and aminopeptidases were identified in the N. naja venom, while acetylcholinesterases and hyaluronidases were found in the B. caeruleus venom. We further analyzed protein coverage (Lys/Arg rich and poor regions as well as potential glycosylation sites) using in-house software. These studies expand our understanding of the proteomes of the venoms of these two medically-important species.

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

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

BIOLOGICAL SIGNIFICANCE

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

Decreased snake venom metalloproteinase effects via inhibition of enzyme and modification of fibrinogen

Since the introduction of antivenom administration 120 years ago to treat venomous snake bit, it has been the gold standard for saving life and limb. However, this therapeutic approach is not always effective and not without potential life-threatening side effects. We tested a new paradigm to abrogate the plasmatic anticoagulant effects of fibrinogenolytic snake venom metalloproteinases by modification of fibrinogen with iron and carbon monoxide and by inhibiting these Zn(2+) dependent metalloproteinases directly with carbon monoxide exposure. Assessment of the fibrinogenolytic effects of venoms collected from Puff adder, Gaboon viper and Indian cobra snakes on plasmatic coagulation kinetics was performed with thrombelastography. Pretreatment of plasma with iron and carbon monoxide exposure markedly attenuated the effects of all three venoms, and direct pretreatment of each venom with carbon monoxide also significantly decreased the ability to compromise coagulation. These results demonstrated that the introduction of a transition metal (e.g., modulation of the α-chain of fibrinogen with iron), modulation of transition metal in heme (e.g., carbon monoxide modulation of fibrinogen-bound heme iron), and direct inhibition of transition metal containing venom enzymes (e.g., CO binding to Zn(2+) or displacing Zn(2+) from the catalytic site) significantly decreased fibrinogenolytic activity. This biometal modulation strategy to attenuate the anticoagulant effects of snake venom metalloproteinases could potentially diminish hemostatic injury in envenomed patients until antivenom can be administered.

[Fibrinogen/fibrin-specific enzymes from copperhead (Agkistrodon halys halys) and cobra (Naja oxiana eichwald) snake venoms]

Ability of fractions of cobra's (Naja oxiana Eichwald) and copperhead snake's (Agkistrodon halys halys) venoms to hydrolyze fibrinogen/fibrin was studied. In cobra's snake a component with molecular mass of nearly 60 kDa was found to hydrolyze a-chain of fibrinogen but failed to hydrolyze casein/azocasein and fibrin. A fibrinogen-specific metalloproteinase, the enzyme was inhibited by EDTA. Cobra's venom reduced the mass of donor's fresh blood clots. The copperhead snake's venom and the fractions obtained by gel-filtration (HW-50) and ion exchange chromatography (DEAE-650) were found to hydrolyze casein/azocasein, a- and b-chains of fibrinogen/fibrin and donor's blood clots. The results from the study of the venom and proteolytically active fractions are the evidence for a thrombolytic potential in a copperhead snake's venom.

Purification and characterization of tenerplasminin-1, a serine peptidase inhibitor with antiplasmin activity from the coral snake (Micrurus tener tener) venom

A plasmin inhibitor, named tenerplasminin-1 (TP1), was isolated from Micrurus tener tener (Mtt) venom. It showed a molecular mass of 6542Da, similarly to Kunitz-type serine peptidase inhibitors. The amidolytic activity of plasmin (0.5nM) on synthetic substrate S-2251 was inhibited by 91% following the incubation with TP1 (1nM). Aprotinin (2nM) used as the positive control of inhibition, reduced the plasmin amidolytic activity by 71%. Plasmin fibrinolytic activity (0.05nM) was inhibited by 67% following incubation with TP1 (0.1nM). The degradation of fibrinogen chains induced by plasmin, trypsin or elastase was inhibited by TP1 at a 1:2, 1:4 and 1:20 enzyme:inhibitor ratio, respectively. On the other hand, the proteolytic activity of crude Mtt venom on fibrinogen chains, previously attributed to metallopeptidases, was not abolished by TP1. The tPA-clot lysis assay showed that TP1 (0.2nM) acts like aprotinin (0.4nM) inducing a delay in lysis time and lysis rate which may be associated with the inhibition of plasmin generated from the endogenous plasminogen activation. TP1 is the first serine protease plasmin-like inhibitor isolated from Mtt snake venom which has been characterized in relation to its mechanism of action, formation of a plasmin:TP1 complex and therapeutic potential as anti-fibrinolytic agent, a biological characteristic of great interest in the field of biomedical research. They could be used to regulate the fibrinolytic system in pathologies such as metastatic cancer, parasitic infections, hemophilia and other hemorrhagic syndromes, in which an intense fibrinolytic activity is observed.

Biological and Biochemical Potential of Sea Snake Venom and Characterization of Phospholipase A2 and Anticoagulation Activity

This study is designed to isolate and purify a novel anti-clotting protein component from the venom of Enhydrina schistosa, and explore its biochemical and biological activities. The active protein was purified from the venom of E. schistosa by ion-exchange chromatography using DEAE-cellulose. The venom protein was tested by various parameters such as, proteolytic, haemolytic, phospholipase and anti-coagulant activities. 80 % purity was obtained in the final stage of purification and the purity level of venom was revealed as a single protein band of about 44 kDa in SDS-polyacrylamide electrophoresis under reducing conditions. The results showed that the Potent hemolytic activity was observed against cow, goat, chicken and human (A, B and O positive) erythrocytes. Furthermore, the clotting assays showed that the venom of E. schistosa significantly prolonged in activated partial thromboplastin time, thrombin time, and prothrombin time. Venomous enzymes which hydrolyzed casein and gelatin substrate were found in this venom protein. Gelatinolytic activity was optimal at pH 5-9 and (1)H NMR analysis of purified venom was the base line information for the structural determination. These results suggested that the E. schistosa venom holds good promise for the development of novel lead compounds for pharmacological applications in near future.

Neutralization of cobra venom by cocktail antiserum against venom proteins of cobra (Naja naja naja)

Naja naja venom was characterized by its immunochemical properties and electrophoretic pattern which revealed eight protein bands (14 kDa, 24 kDa, 29 kDa, 45 kDa, 48 kDa, 65 kDa, 72 kDa and 99 kDa) by SDS-PAGE in reducing condition after staining with Coomassie Brilliant Blue. The results showed that Naja venom presented high lethal activity. Whole venom antiserum or individual venom protein antiserum (14 kDa, 29 kDa, 65 kDa, 72 kDa and 99 kDa) of venom could recognize N. naja venom by Western blotting and ELISA, and N. naja venom presented antibody titer when assayed by ELISA. The neutralization tests showed that the polyvalent antiserum neutralized lethal activities by both in vivo and in vitro studies using mice and Vero cells. The antiserum could neutralize the lethal activities in in-vivo and antivenom administered after injection of cobra venom through intraperitoneal route in mice. The cocktail antiserum also could neutralize the cytotoxic activities in Vero cell line by MTT and Neutral red assays. The results of the present study suggest that cocktail antiserum neutralizes the lethal activities in both in vitro and in vivo models using the antiserum against cobra venom and its individual venom proteins serum produced in rabbits.

Antivenom activity of triterpenoid (C34H68O2) from Leucas aspera Linn. against Naja naja naja venom induced toxicity: antioxidant and histological study in mice

The isolated and identified triterpenoid, 1-hydroxytetratriacontane-4-one (C34H68O2), obtained from the methanolic leaf extract of Leucas aspera Linn. was explored for the first time for antisnake venom activity. The plant (L. aspera Linn.) extract significantly antagonized the spectacled cobra (Naja naja naja) venom induced lethal activity in a mouse model. It was compared with commercial antiserum obtained from King Institute of Preventive Medicine (Chennai, Tamil Nadu, India). N. naja naja venom induced a significant decrease in antioxidant superoxide dismutase, glutathione (GSH) peroxidase, catalase, reduced GSH and glutathione-S-transferase activities and increased lipid peroxidase (LPO) activity in different organs such as heart, liver, kidney and lungs. The histological changes following the antivenom treatment were also evaluated in all these organs. There were significant alterations in the histology. Triterpenoid from methanol extract of L. aspera Linn. at a dose level of 75 mg per mouse significantly attenuated (neutralized) the venom-induced antioxidant status and also the LPO activity in different organs.

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

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

The buccal gland of Lampetra japonica is a source of diverse bioactive proteins

The parasitic phase lampreys (Lampetra japonica) are bloodsuckers in the marine, and their buccal gland secretion (lamphredin) contains various regulators such as anticoagulants, ion channel blockers, and immune suppressors like those from leeches, insects, ticks, vampire bats, and snakes. This review focuses on the functions and characteristics of the active proteins from the buccal gland of L. japonica for the first time, and provides new insights into the parasitic mechanisms of lampreys and the possibilities of developing drugs such as novel anticoagulants, thrombolytic agents, local anesthetics, and immunosuppressants.

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

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

Anti-coagulant activity of a metalloprotease: further characterization from the Indian cobra (Naja naja) venom

A high molecular mass, non toxic metalloprotease the NN-PF3 with the bound Ca(2+) and Zn(2+) from the Naja naja venom has been studied further for its anticoagulant property. The molecular mass by MALDI-TOF mass spectrometry was 67.81 kDa. The NN-PF3 exhibited fibrin(ogen)olytic activity. In addition to fibrinogen, NN-PF3 hydrolyzed blood and plasma clot with the later hydrolyzed about one fold higher. The alpha polymer of fibrin was preferentially hydrolyzed over the alpha chain but the beta chain and gamma-gamma dimer remained untouched. It was devoid of plasminogen activation property. It prolonged the activated partial thromboplastin time, prothrombin time and the thrombin clotting time of citrated human plasma. It did not affect the thrombin activity. In mice, defibrinogentaion, prolonged bleeding time (P < 0.01) and reduced fibrinogen level were observed following intravenous injection. Human plasma or alpha2-macroglobulin did not, but the polyvalent anti-venom inhibited the NN-PF3 activity. In contrast to most snake venom metalloproteases, it did not degrade extra cellular matrix proteins.

The metalloprotease, NN-PF3 from Naja naja venom inhibits platelet aggregation primarily by affecting α2β1 integrin

NN-PF3 is a non-toxic, anticoagulant, high-molecular-mass (67.81 kDa) metalloprotease from Indian cobra (Naja naja) venom. In the present study, NN-PF3 was investigated for the mechanism of inhibition of collagen-induced aggregation of human platelets. The complete inhibition of collagen-induced aggregation and partial inhibition of ADP- and epinephrine-induced aggregation has the respective IC(50) of 75 ± 5, 185 ± 10, and 232 ± 12 nM, whereas no inhibition of thrombin-, arachidonic acid-, and ristocetin-induced aggregation of platelets was observed in platelet-rich plasma. Further, native NN-PF3 and EDTA-inactivated NN-PF3 inhibited collagen-induced aggregation of washed platelets with respective IC(50) of 75 ± 4 and 180 ± 6 nM. The higher inhibitory effect of native NN-PF3 compared with EDTA-inactivated NN-PF3 suggests the enzymatic and non-enzymatic mechanism of inhibition. NN-PF3 pretreatment affected the collagen binding but not the fibrinogen, and fibronectin binding of washed platelets in adhesion assay suggested that the collagen receptors are affected. Western blot study using anti-integrin α2β1 mAb 6F1 suggested that NN-PF3 binds to integrin α2β1 in a primary structure-dependent manner only and is not cleaved. There was a drastic reduction in the intensity of several intracellular signaling phosphotyrosine protein bands when monoclonal anti-phosphotyrosine antibody was used, suggesting that the major activation pathway of platelets get affected, which occurs through glycoprotein VI. NN-PF3 did not bind to collagen as revealed by Western blot using anti-collagen mAb. Furthermore, neither the proteolytic cleavage of fibrinogen nor its degradation products by NN-PF3 contributed for the collagen-induced platelet aggregation inhibition.

Isolation and biological characterization of Batx-I, a weak hemorrhagic and fibrinogenolytic PI metalloproteinase from Colombian Bothrops atrox venom

A hemorrhagic metalloproteinase, named Batx-I, was isolated from the venom of Bothrops atrox specimens (from Southeastern Colombian region) by a combination of CM-Sephadex C25 ion-exchange and Affi-gel Blue affinity chromatographies. This enzyme accounts for about 45% of venom proteins, and it has an ESI-MS isotope-averaged molecular mass of 23296.2 Da and a blocked N-terminus. Two internal fragments sequenced by mass spectrometric analysis showed similarity to other SVMPs from Bothrops venoms. To investigate the possible participation of Batx-I in the envenomation pathophysiology, proteolytic, fibrinogenolytic, hemorrhagic, and other biological activities were evaluated. The minimal hemorrhagic dose obtained was 17 microg/20 g body weight. The enzyme showed proteolytic activity on azocasein, comparable with activity of BaP1. This activity was inhibited by EDTA and 1, 10 o-phenanthroline but not by aprotinin, pepstatin A or PMSF. Fibrinogenolytic activity was analyzed by SDS-PAGE, revealing a preference for degrading the A alpha- and B beta-chains, although partial degradation of the gamma-chain was also detected. The protein lacks coagulant and defibrinating activity. The CK levels obtained, clearly reflects a myotoxic activity induced by Batx-I. The hemorrhagic and fibrinogenolytic activities exhibited by the isolated PI-SVMP may play a role in the hemorrhagic and blood-clotting disorders observed in patients bitten by B. atrox in Colombia.

Purification and biochemical characterization of a novel hemorrhagic metalloproteinase from horned viper (Cerastes cerastes) venom

Snake venoms contain metalloproteinases that contribute to the local effects observed after envenoming. In this study, a hemorrhagic metalloproteinase (CcH1) was purified from Cerastes cerastes venom by a combination of gel filtration, ion exchange, affinity and RP-HPLC chromatography. The hemorrhagin was homogeneous on SDS-PAGE, with a molecular mass of 25 kDa. Isoelectric focusing revealed a pI of 5.5. CcH1 displayed hemorrhagic and proteolytic activities, but no esterolytic activity. The hemorrhagic and proteolytic activities of CcH1 were inhibited by EDTA and 1,10-phenanthroline, but not by PMSF, suggesting that this protein is a zinc-metalloproteinase. Furthermore, the hemorrhagic and proteolytic activities of CcH1 were stable in solution at up to 40 degrees C, with a loss of activity at > or =70 degrees C. The molecular mass and the inhibition assays suggest that the metalloproteinase CcH1 belongs to class P-I of SVMPs.

A new type of thrombin inhibitor, noncytotoxic phospholipase A2, from the Naja haje cobra venom

Thrombin is a key enzyme in the blood coagulation cascade and is also involved in carcinogenesis; therefore, its inhibitors are of fundamental and clinical importance. Snake venoms are widely used as sources of proteins that affect blood coagulation. We have isolated a new protein, called TI-Nh, from the Naja haje cobra venom. TI-Nh is a mixed-type inhibitor of thrombin (K(i) of 72.8 nM for a synthetic peptide substrate) and effectively inhibits thrombin-induced platelet aggregation with an IC(50) value of 0.2 nM. At concentrations up to approximately 50 nM, at which the thrombin-clotting time is substantially prolonged, TI-Nh exerts no detectable effects on both the intrinsic and extrinsic pathways of the coagulation cascade. It does not hydrolyze either fibrinogen or thrombin. Although TI-Nh bears structural features typical of group IB phospholipases A(2) (PLA(2)s), it possesses relatively weak enzymatic activity and is nontoxic to PC12 cells at concentrations up to 15 microM. Nevertheless, TI-Nh evokes neurite outgrowth in these cells at a concentration of approximately 1 microM, similar to cytotoxic snake PLA(2)s with strong enzymatic activity. TI-Nh is the first thrombin inhibitor found in the venom of the Elapidae snake family, and it is the first phospholipase shown to inhibit thrombin.

Identification of a novel thrombin-like phospholipase A2 from Gloydius ussuriensis snake venom

The coagulant effects of phospholipase A2 with Gln at 49 sites (Gln49-PLA2), purified from Gloydius ussurensis snake venom, were investigated on human citrated plasma and fibrinogen. Gln49-PLA2 clotted human plasma dose-dependently from 180.67 +/- 1.86 s to 19.00 +/- 0.58 s, and reduced the re-calcification time from 7.46 +/- 1.17 to 0.75 +/- 0.33 min and the prothrombin time from 12.4 +/- 0.29 s to 6.95 +/- 0.20 s, but it could not activate factor XIII, and the procoagulant effects were inhibited by heparin. The specific clotting activities of Gln49-PLA2 were equivalent to 1100 NIH thrombin U/mg on human fibrinogen, and the specific arginine esterase activity on the substrate BAEE was 1747 U/mg. Gln49-PLA2 hydrolyzed fibrinopeptide A faster than fibrinopeptide B, and the fibrinongenolytic ability was inhibited by the serine protease inhibitor phenyl-methylsulphonyl fluoride, but not by the metalloprotease inhibitor ethylenediamine tetraacetic acid. This finding demonstrates that Gln49-PLA2 is consistent with thrombin-like properties, and therefore should be a new thrombin-like serine protease.

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.

Characterisation of the fibrinogenolytic properties of the buccal gland secretion from Lampetra japonica

Lampetra japonica is representative of the ancient cyclostomota class of animals, and its buccal gland secretion (called lamphredin) is known to act as an anticoagulant. In this study, it was observed by both native-PAGE and SDS-PAGE that the secretion mainly contained two protein bands, buccal gland secretion protein-1 (BGSP-1, 159,909 Da) and buccal gland secretion protein-2 (BGSP-2, 25,660 Da). The N-terminal amino acids of BGSP-1 (EAESF QNLKT RICGG LNGLG) and BGSP-2 (TSVND WKLLD TKLSA NRKVI) were sequenced. Using a Sephadex G-75 column, we isolated BGSP-1, BGSP-2 and small peptides from the buccal gland secretion, but found only BGSP-1 showed fibrinogenolytic activity. BGSP-1 and lamphredin were found to rapidly degrade the alpha chain of human fibrinogen, slowly degrade the beta chain and hardly degrade the gamma chain. BGSP-1 and lamphredin showed a similar map by SDS-PAGE for the degradation of fibrinogen by cleavage at Ala(10)-Glu(11) and His(368)-Ser(369). BGSP-1 was also found to hydrolyze neuronal protein tau at Glu(12)-Asp(13) and Gln(244)-Thr(245). Further study showed that lamphredin and BGSP-1 were inactivated in the presence of a metal chelating agent EDTA. However, addition of Ca(2+) or Mg(2+) but not Zn(2+) restored the fibrinogenolytic activity. This suggests that BGSP-1 acts in the buccal gland as a metalloproteinase with a broad substrate specificity. Furthermore, the secretion showed cytolytic properties towards human SH-SY5Y and HeLa cells in culture, and lamphredin at a 50-fold dilution induced cell death.

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

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

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

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

Strong myotoxic activity of Trimeresurus malabaricus venom: role of metalloproteases

Trimeresurus malabaricus is an endemic snake found in the Southern region of Western Ghats section of India along with the more widely distributed species like Naja naja and Daboia russelii. T. malabaricus venom is not lethal when injected (i.p.) up to 20 mg/kg body weight in mice, but causes extensive local tissue degeneration. N. naja and D. russelii are highly toxic (i.p.) with minimum local tissue damage in experimental mice. In this study a comparative analysis of local tissue damage of T. malabaricus venom is made with N. naja and D. russelii snake venoms of the Southern regions of Western Ghats. T. malabaricus venom exhibits caseinolytic activity 16 and 24 times more than N. naja and D. russelii venom. Inhibition studies with specific protease inhibitors reveal that the major proteases belong to metalloproteases. T. malabaricus venom hydrolyses gelatin and induces strong hemorrhagic activity in mice. Both N. naja and D. russelii fail to hydrolyze gelatin even at very high concentration and did not induce any hemorrhagic activity. With D. russelii venom small hemorrhagic spot was observed at the site of injection. The hemorrhagic activity of T. malabaricus venom is completely neutralized by metalloprotease inhibitors and not by serine protease inhibitor. The i.m. injection of T. malabaricus venom causes extensive degradation of muscle tissue within 24 h. The light microscopic observation of muscle tissue showed congestion of blood vessels and hemorrhage at the early stage followed by extensive necrosis of muscle fibers. The elevated levels of serum CK and LDH activity further supported the muscle degeneration. Such pathological symptoms were not seen with N. naja and D. russelii snake venom. The hemorrhagic and the muscle necrosis was completely neutralized by metalloprotease inhibitors and not by serine protease inhibitor strongly suggests that the major toxin component in the T. malabaricus venom is metalloprotease and its activity can be easily neutralized using chelating agents and its use in the first aid as chelation therapy is beneficial.

Procoagulant activity of Calotropis gigantea latex associated with fibrin(ogen)olytic activity

The latex of Calotropis gigantea is a rich source of useful components that has medicinal properties and one of the main applications is in controlling bleeding. The crude latex extract contained many proteins, which are highly basic in nature and exhibited strong proteolytic activity. The crude extract hydrolyses casein, human fibrinogen and crude fibrin clot in a dose-dependent manner. The hydrolyzing activity was completely inhibited by IAA indicating they belong to the super family, cysteine proteases. Crude extract hydrolyses Aalpha, Bbeta and gamma subunits of fibrinogen. Among all the subunits the preferential subunit to get hydrolyzed was Aalpha followed by Bbeta and gamma subunit is highly resistant and hydrolyzed at higher protein concentration or over a prolonged incubation time. The crude extract hydrolysis crude fibrin clot strongly compared to trypsin and papain. Pharmacologically the crude extract is hemorrhagic and induces skin hemorrhage at >75 microg and reduces the coagulation time of citrated plasma from 150 to 47 s and promotes blood coagulation. Procoagulation and blood clot hydrolysis are important in wound healing process. This is due to unique cysteine proteases of plant latex and is responsible for the pharmacological actions observed in folk medicine.

Use of Pavo cristatus feather extract for the better management of snakebites: neutralization of inflammatory reactions

In Indian traditional medicine, peacock feather in the form of ash (Bhasma) or water extract are used against snakebite and to treat various problems associated with lungs. This study was aimed to evaluate the water extract of peacock feather (PCF) against the local tissue damage caused due to snakebite. PCF water extract showed inhibition towards phospholipase A2 enzyme activity from snake venom (Naja naja and Vipera russelii), inflammatory fluids (synovial, pleural, ascites) and normal serum in a dose-dependent manner. Hyaluronidase and proteases are other major enzymes in snake venoms responsible for local tissue damage. PCF water extract inhibited hyaluronidase and proteolytic enzyme activities from Vipera russelii, Naja naja and Trimeresurus malabaricus venom. The active principle is a hydrophilic molecule easily extractable in water or polar solvents. PCF water extract gave positive results for the presence of protein and secondary metabolites like carotenoids and steroids. Analysis of metal ions revealed that iron is the major ion (> 20-fold). Other metal ions detected in smaller amount are copper, chromium, zinc and nickel. The least amount of ion detected is gold. Co-injection of PCF water extract with snake venom and inflammatory PLA2 enzymes neutralize the edema inducing activity of all the PLA2 enzymes studied. Since it inhibits hyaluronidase and proteases enzyme activity from snake venom PCF water extract is a powerful neutralizing agent, which has therapeutic application against venom toxicity.

Screening of plants containing Naja naja siamensis cobra venom inhibitory activity using modified ELISA technique

Enzyme-linked immunosorbent assay (ELISA) has been modified for screening plants with antagonistic activity to Naja naja siamensis cobra venom. Aqueous extracts from plants were investigated for their inhibitory effects on the binding of anti-cobra venom antibody to antigen, cobra venom, fixed onto 96-well microtiter plates. Ingredients in extracts were allowed to react with immobilized venom before the subsequent addition of antivenom antibody. Venom components affected by exposure to the extracts, unable to interact with their specific antibody, were predicted to be unable to bind to their native destinations or natural receptors. Curcuma cf. zedoaria, an old Thai medicinal plant, showed clear inhibitory activity in the ELISA test. Neurotoxin and protein degradative enzymes, major components in venom, were identified as targets of this extract in Western immunoblotting analysis. Ingredients in the extract showed high affinity to the toxin in competition assay by immunoprecipitation. The extract attenuated toxin activity by extending contraction time of diaphragm muscle after envenomation and had a potency to protect cellular proteins from venom degradative enzymes. Curcuma parviflora, with less activity in ELISA, exhibited acceptable results in two experiments but negative results in two experiments, whereas Curcuma longa, having low activity in the ELISA test, never showed any favorable results. Screening of 36 samples could classify plants into an inhibition range of 0 to 86%. This modified ELISA is recommended as a preliminary screening method for inhibitors with a large number of samples.