Isolation and characterization of a metalloproteinase with weak hemorrhagic activity from the venom of the snake Bothrops asper (terciopelo)

Role of collagens and perlecan in microvascular stability: exploring the mechanism of capillary vessel damage by snake venom metalloproteinases

Hemorrhage is a clinically important manifestation of viperid snakebite envenomings, and is induced by snake venom metalloproteinases (SVMPs). Hemorrhagic and non-hemorrhagic SVMPs hydrolyze some basement membrane (BM) and associated extracellular matrix (ECM) proteins. Nevertheless, only hemorrhagic SVMPs are able to disrupt microvessels; the mechanisms behind this functional difference remain largely unknown. We compared the proteolytic activity of the hemorrhagic P-I SVMP BaP1, from the venom of Bothrops asper, and the non-hemorrhagic P-I SVMP leucurolysin-a (leuc-a), from the venom of Bothrops leucurus, on several substrates in vitro and in vivo, focusing on BM proteins. When incubated with Matrigel, a soluble extract of BM, both enzymes hydrolyzed laminin, nidogen and perlecan, albeit BaP1 did it at a faster rate. Type IV collagen was readily digested by BaP1 while leuc-a only induced a slight hydrolysis. Degradation of BM proteins in vivo was studied in mouse gastrocnemius muscle. Western blot analysis of muscle tissue homogenates showed a similar degradation of laminin chains by both enzymes, whereas nidogen was cleaved to a higher extent by BaP1, and perlecan and type IV collagen were readily digested by BaP1 but not by leuc-a. Immunohistochemistry of muscle tissue samples showed a decrease in the immunostaining of type IV collagen after injection of BaP1, but not by leuc-a. Proteomic analysis by LC/MS/MS of exudates collected from injected muscle revealed higher amounts of perlecan, and types VI and XV collagens, in exudates from BaP1-injected tissue. The differences in the hemorrhagic activity of these SVMPs could be explained by their variable ability to degrade key BM and associated ECM substrates in vivo, particularly perlecan and several non-fibrillar collagens, which play a mechanical stabilizing role in microvessel structure. These results underscore the key role played by these ECM components in the mechanical stability of microvessels.

Neutralizing Effects of Nectandra angustifolia Extracts against Bothrops neuwiedi Snake Venom

Leaves extracts and essential oil of Nectandra angustifolia were explored for the first time for neutralization of Bothrops neuwiedi diporus snake venom. The ethanol extract was the most active and inhibited both venom activities (hemolytic and coagulant), while the oil was only active on the coagulant activity. These observations confirmed that certain medicinal plants from Corrientes and Chaco Provinces possess significant snake venom neutralizing capacity and need further examination for their active constituents. Analysis by GC and GC-MS of the essential oil and the enantiomeric excess found for α-pinene, β-pinene and limonene allowed a better characterization of this species.

Poor regenerative outcome after skeletal muscle necrosis induced by Bothrops asper venom: alterations in microvasculature and nerves

Background

Viperid snakebite envenoming is characterized by prominent local tissue damage, including muscle necrosis. A frequent outcome of such local pathology is deficient skeletal muscle regeneration, which causes muscle dysfunction, muscle loss and fibrosis, thus provoking permanent sequelae that greatly affect the quality of life of patients. The causes of such poor regenerative outcome of skeletal muscle after viperid snakebites are not fully understood.

Methodology/Principal Findings

A murine model of muscle necrosis and regeneration was adapted to study the effects of the venom and isolated toxins of Bothrops asper, the medically most important snake in Central America. Gastrocnemius muscle was injected with either B. asper venom, a myotoxic phospholipase A₂ (Mtx), a hemorrhagic metalloproteinase (SVMP), or saline solution. At various time intervals, during one month, tissue samples were collected and analyzed by histology, and by immunocytochemical and immunohistochemical techniques aimed at detecting muscle fibers, collagen, endothelial cells, myoblasts, myotubes, macrophages, TUNEL-positive nuclei, and axons. A successful regenerative response was observed in muscle injected with Mtx, which induces myonecrosis but does not affect the microvasculature. In contrast, poor regeneration, with fibrosis and atrophic fibers, occurred when muscle was injected with venom or SVMP, both of which provoke necrosis, microvascular damage leading to hemorrhage, and poor axonal regeneration.

Conclusions/Significance

The deficient skeletal muscle regeneration after injection of B. asper venom is likely to depend on the widespread damage to the microvasculature, which affects the removal of necrotic debris by phagocytes, and the provision of nutrients and oxygen required for regeneration. In addition, deficient axonal regeneration is likely to contribute to the poor regenerative outcome in this model.

Snake venom metalloproteinases: structure, function and relevance to the mammalian ADAM/ADAMTS family proteins

Metalloproteinases are among the most abundant toxins in many Viperidae venoms. Snake venom metalloproteinases (SVMPs) are the primary factors responsible for hemorrhage and may also interfere with the hemostatic system, thus facilitating loss of blood from the vasculature of the prey. SVMPs are phylogenetically most closely related to mammalian ADAM (a disintegrin and metalloproteinase) and ADAMTS (ADAM with thrombospondin type-1 motif) family of proteins and, together with them, constitute the M12B clan of metalloendopeptidases. Large SVMPs, referred to as the P-III class of SVMPs, have a modular architecture with multiple non-catalytic domains. The P-III SVMPs are characterized by higher hemorrhagic and more diverse biological activities than the P-I class of SVMPs, which only have a catalytic domain. Recent crystallographic studies of P-III SVMPs and their mammalian counterparts shed new light on structure-function properties of this class of enzymes. The present review will highlight these structures, particularly the non-catalytic ancillary domains of P-III SVMPs and ADAMs that may target the enzymes to specific substrates. This article is part of a Special Issue entitled: Proteolysis 50years after the discovery of lysosome.

Purification and characterization of a metalloproteinase, Porthidin-1, from the venom of Lansberg's hog-nosed pitvipers (Porthidium lansbergii hutmanni)

Porthidium lansbergii hutmanni is a small pit viper found on Margarita Island, Venezuela. Local tissue damage is one of the most obvious characteristics of P. l. hutmanni envenomation, which can lead to diverse pathological effects, such as hemorrhage, edema, blistering, necrosis, lymphatic vessel damage and degradation of extracellular matrix. Metalloproteinases are one of the major components in venoms responsible for these effects. To date, very little is known or has been reported on P. l. hutmanni venom. Crude P. l. hutmanni venom had a LD(50) of 2.5 mg/kg and was considered very hemorrhagic (minimal hemorrhagic dose [MHD]: 0.98 μg) when compared to other hemorrhagic (Bothrops) venoms in Venezuela. Crude P. l. hutmanni venom also inhibited ADP-induced platelet aggregation. A metalloproteinase, Porthidin-1, from this venom was isolated by three chromatography steps (Sephadex G100, Superose 12 HR10/30 and Bioscale Q2). Porthidin-1 falls in the SVMP P-I class having a molecular weight of 23 kDa, verified by both SDS-PAGE and mass spectrometry. High-resolution mass spectrometry and a database search identified a peptide from Porthidin-1 (YNGDLDK) belonging to the SVMP family of proteins. Porthidin-1 contained hemorrhagic, fibrino(geno)lytic, caseinolytic and gelatinolytic activities, and these activities were capable of being neutralized by metalloproteinase inhibitors but not serine proteinase inhibitors. The peptide YNGDLDK shared similarities with five venom proteins with a BLAST e-value of <1. This work details the biochemical and pathophysiological effects that can result from envenomations, and highlights the importance and significance for characterizing unknown or poorly documented venoms from different geographical regions.

Identification of novel proteins from the venom of a cryptic snake Drysdalia coronoides by a combined transcriptomics and proteomics approach

We have investigated the transcriptome and proteome of the venom of a cryptic Australian elapid snake Drysdalia coronoides. To probe into the transcriptome, we constructed a partial cDNA library from the venom gland of D. coronoides. The proteome of the venom of D. coronoides was explored by tryptic digestion of the crude venom followed by HPLC separation of the resulting peptides and MALDI-TOF/TOF mass spectrometric analysis. Importantly, the tandem MS data of the tryptic peptides of the venom not only confirmed the predicted protein sequences deduced from the transcriptome, but also added to our knowledge about the venom composition through identification of two more toxin families. Using both the approaches, we were able to identify proteins belonging to eight different snake venom protein superfamilies, namely, three-finger toxins, serine protease inhibitors, cysteine rich secretory proteins, phospholipases A(2), venom nerve growth factors, snake venom metalloproteases, vespryns, and a new family phospholipase B. We also identified three novel proteins belonging to the three-finger toxin superfamily.

Purification and characterization of a new weak hemorrhagic metalloproteinase BmHF-1 from Bothrops marajoensis snake venom

BmHF-1, from the venom of Bothrops marajoensis, was purified by Sephadex G-75 and HPLC-RP on micro-Bondapak C-18 column chromatography. It presented a molecular mass of 27162.36 Da determined by MALDI-TOF MS. BmHF-1 had a sequence of 238 residues of amino acids. The multiple alignment of its amino acid sequence and those of other snake venom metalloproteinases showed high structural similarity, mainly among P-I class. The enzyme initially cleaves the Aalpha-chain of fibrinogen, followed by the Bbeta-chain, and shows no effects on the gamma-chain. BmHF-1 had, caseinolytic and weakly hemorrhagic activities, which were inhibited by EDTA. In contrast, PMSF did not affect these activities. The caseinolytic activity of BmHF-1 had a pH optimum of 8.0 and was stable in solution up to 40 degrees C; activity was completely lost at > or = 70 degrees C. The proteolytic activity was also inhibited by sDa (opossum sera) and Da2-1, Da2-II, antihemorrhagic factors isolated from the opossum sera of Didelphis albiventris. BmHF-1 presents weak hemorrhagic activity, with a MHD of 41.14 microg and it induces dose-dependent edema. We could concluded that, despite its weak hemorrhagic activity, BmHF-1 contributes to local tissue damage by inducing edema, releasing pharmacologically active mediators from protein precursors due to its enzymatic action.

High resolution analysis of snake venom metalloproteinase (SVMP) peptide bond cleavage specificity using proteome based peptide libraries and mass spectrometry

Both serine and metalloproteinases have been shown to play the role of toxins in the venoms of many snakes. Determination of the natural protein substrates of these toxins is an important feature in the toxinological characterization of these proteinases. Furthermore, characterization of their peptide bond specificity is of value for understanding active site preference of the proteinase associated with effective proteolysis as well as of use in the design of peptide substrates and inhibitor lead compounds. Typically the determination of peptide bond cleavage specificity of snake venom serine proteinases (SVSPs) and snake venom metalloproteinases (SVMPs) has been performed using limited sets of peptides or small oligopeptides as experimental substrates. Although this approach has yielded valuable data it is generally limited in scope due to the relatively small sets of substrates used to generate the consensus specificity sequences for these proteinases. In this study we use a large, plasma based, proteome-derived peptide library as substrates along with mass spectrometry to explore the peptide bond specificity of three PI SVMPs and one PIII SVMP to determine their individual peptide cleavage consensus sequences. All of the proteinases assayed displayed a clear preference for a leucine residue in the P1' site. Careful analysis of the specificity profiles of the SVMPs examined showed interesting differences in the preferences at the other P and P' sites suggesting functional differences between these proteinases. The PI SVMPs, leucurolysin-a, atrolysin C, and BaP1, showed preferences across the full P4 to P4' range whereas the PIII SVMP bothropasin showed a narrower range of preferences across the sites. In silico docking experiments with the experimentally derived consensus sequences as well as with comparison of the results to those in the literature regarding peptide bond specificity based on both peptide and protein substrates give rise to a fresh understanding of the specificity of these SVMPS and may serve as a foundation for future experiments to better elucidate their mechanism of action in the complex pathophysiology of snakebite envenomation.

Immunochemical and biological characterization of monoclonal antibodies against BaP1, a metalloproteinase from Bothrops asper snake venom

BaP1 is a P-I class of Snake Venom Metalloproteinase (SVMP) relevant in the local tissue damage associated with envenomations by Bothrops asper, a medically-important species in Central America and parts of South America. Six monoclonal antibodies (MoAb) against BaP1 (MABaP1) were produced and characterized regarding their isotype, dissociation constant (K(d)), specificity and ability to neutralize BaP1-induced hemorrhagic and proteolytic activity. Two MABaP1 are IgM, three are IgG1 and one is IgG2b. The K(d)s of IgG MoAbs were in the nM range. All IgG MoAbs recognized conformational epitopes of BaP1 and B. asper venom components but failed to recognize venoms from 27 species of Viperidae, Colubridae and Elapidae families. Clone 7 cross-reacted with three P-I SVMPs tested (moojeni protease, insularinase and neuwiedase). BaP1-induced hemorrhage was totally neutralized by clones 3, 6 and 8 but not by clone 7. Inhibition of BaP1 enzymatic activity on a synthetic substrate by MABaP1 was totally achieved by clones 3 and 6, and partially by clone 8, but not by clone 7. In conclusion, these neutralizing MoAbs against BaP1 may become important tools to understand structure-function relationships of BaP1 and the role of P-I class SVMP in snakebite envenomation.

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.

Cell death induced by Bothrops asper snake venom metalloproteinase on endothelial and other cell lines

Two adherent cell lines, BAEC and HeLa, and non-adherent Jurkat, were treated with snake venom metalloproteinase BaP1 to determine whether cytotoxicity, previously reported for this toxin, could be mediated by the process of anoikis. It was observed that there was no correlation between the ability of this toxin to induce loss of adherence, and the cytotoxic effect, since concentrations that do not induce loss of adherence (3-6 microg/mL), were able to trigger 50% of cytotoxicity in BAEC. In the case of HeLa, where toxicity was very low (less than 20% at maximun concentrations and times of exposure), significant detachment and no toxicity was observed at concentrations of 1.5 microg/mL, showing also no correlation between both events. We also observed differences between BAEC toxicity measured by XTT reduction and DNA fragmentation determined by flow cytometry (as an indicator of apoptosis), since concentrations that induce 100% of cytotoxicity barely showed any DNA fragmentation (12% at 24h), suggesting that if apoptosis was involved, DNA damage is still not present, although chromatin condensation, another indicator of apoptosis, is observed in 40% of the cells. Inhibition of BAEC cytotoxicity by caspase inhibitors indicate that apoptosis is playing a role in this process, but other mechanisms of cell death could be participating also. Another way to determine whether the mechanism of cell death was related to anoikis was using a non-adherent cell line, which should show substrate independence. We determined by TUNEL that at 50 microg/ml BaP1 triggered 50% of apoptosis at 96 h, an effect that was seen earlier, suggesting also that if this toxin was inducing apoptosis in a non-adherent cell line, the mechanism could not be related to loss of attachment. Cell cycle arrest in S phase was also observed in Jurkat cells, an effect that could be leading to apoptosis. In conclusion, since there was no correlation between cell detachment and cytotoxicity (and apoptosis) in adherent cell lines and due to the ability of BaP1 to induce apoptosis in a non-adherent cell line, we suggest that this enzyme is toxic by a mechanism not related to anoikis, and that in the case of Jurkat cells, it is likely to be related to its ability to induce cell cycle arrest. Processes other than apoptosis could be also involved in the cell death mechanism mediated by BaP1 on BAEC.

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.

Neutralization of venom-induced hemorrhage by equine antibodies raised by immunization with a plasmid encoding a novel P-II metalloproteinase from the lancehead pitviper Bothrops asper

In this work, the cDNA encoding a novel P-II type metalloproteinase from Bothrops asper venom glands was cloned, sequenced and used for DNA immunization of animals with accelerated DNA-coated tungsten microparticles and the helius Gene Gun system. Specific antibodies against B. asper venom antigens were induced in mice co-immunized with the plasmid encoding the P-II metalloproteinase together with an expression plasmid encoding the murine IL-2. Similarly, specific antibodies against B. asper venom antigens were also induced in a horse co-immunized with the plasmid encoding the P-II metalloproteinase, together with a plasmid encoding the equine IL-6. The equine antibodies induced by immunization with the P-II metalloproteinase encoding plasmid cross react with several proteins of B. asper, Crotalus durissus durissus, and Lachesis stenophrys venoms in western blot, demonstrating antigenic similarity between the cloned metalloproteinase and other metalloproteinases present in these venoms. Furthermore, the equine antibodies induced by immunization with the P-II metalloproteinase encoding plasmid completely neutralized the hemorrhagic activity of the whole B. asper venom and partially the hemorrhagic activity of C. durissus durissus venom. The neutralizing ability of the produced antibodies raises, for the first time, the possibility of developing therapeutic antivenoms in horses by DNA immunization using tungsten microparticles.

Effects of Bothrops asper snake venom on lymphatic vessels: insights into a hidden aspect of envenomation

BACKGROUND

Envenomations by the snake Bothrops asper represent a serious medical problem in Central America and parts of South America. These envenomations concur with drastic local tissue pathology, including a prominent edema. Since lymph flow plays a role in the maintenance of tissue fluid balance, the effect of B. asper venom on collecting lymphatic vessels was studied.

METHODOLOGY/PRINCIPAL FINDINGS

B. asper venom was applied to mouse mesentery, and the effects were studied using an intravital microscopy methodology coupled with an image analysis program. B. asper venom induced a dose-dependent contraction of collecting lymphatic vessels, resulting in a reduction of their lumen and in a halting of lymph flow. The effect was reproduced by a myotoxic phospholipase A(2) (PLA(2)) homologue isolated from this venom, but not by a hemorrhagic metalloproteinase or a coagulant thrombin-like serine proteinase. In agreement with this, treatment of the venom with fucoidan, a myotoxin inhibitor, abrogated the effect, whereas no inhibition was observed after incubation with the peptidomimetic metalloproteinase inhibitor Batimastat. Moreover, fucoidan significantly reduced venom-induced footpad edema. The myotoxic PLA(2) homologue, known to induce skeletal muscle necrosis, was able to induce cytotoxicity in smooth muscle cells in culture and to promote an increment in the permeability to propidium iodide in these cells.

CONCLUSIONS/SIGNIFICANCE

Our observations indicate that B. asper venom affects collecting lymphatic vessels through the action of myotoxic PLA(2)s on the smooth muscle of these vessels, inducing cell contraction and irreversible cell damage. This activity may play an important role in the pathogenesis of the pronounced local edema characteristic of viperid snakebite envenomation, as well as in the systemic biodistribution of the venom, thus representing a potential therapeutical target in these envenomations.

Assessment of metalloproteinase inhibitors clodronate and doxycycline in the neutralization of hemorrhage and coagulopathy induced by Bothrops asper snake venom

Snake venom metalloproteinases (SVMPs) play a prominent role in the local and systemic manifestations of viperid snakebite envenomations. Thus, the possibility of using metalloproteinase inhibitors in the treatment of these envenomations is a promising therapeutic alternative. This study assessed the ability of two metalloproteinase inhibitors, the biphosphonate clodronate and the tetracycline doxycycline, to inhibit proteolytic, hemorrhagic, coagulant and defibrinogenating effects of Bothrops asper venom. Both compounds were able to inhibit these activities, at concentrations in the mM range, when incubated with venom prior to testing. However, when inhibition of hemorrhage was assessed in assays involving independent injection of venom and drug, inhibition was poor, even when these compounds were injected immediately after envenomation. These findings support the concept that the effectiveness of compounds, such as clodronate and doxycycline, whose inhibitory action on SVMPs is based on zinc chelation alone, is limited, and stress the view that more specific molecules are required for an effective inhibition of SVMPs in vivo.

Skin pathology induced by snake venom metalloproteinase: acute damage, revascularization, and re-epithelization in a mouse ear model

Viperid snakebite envenomation induces blistering and dermonecrosis. The pathological alterations induced by a snake venom metalloproteinase in the skin were investigated in a mouse ear model. Metalloproteinase BaP1, from Bothrops asper, induced rapid edema, hemorrhage, and blistering; the latter two effects were abrogated by preincubation with the metalloproteinase inhibitor batimastat. Neutrophils did not play a role in the pathology, as depletion of these cells resulted in a similar histological picture. Blisters are likely to result from the direct proteolytic activity of BaP1 of proteins at the dermal-epidermal junction, probably at the lamina lucida, as revealed by immunostaining for type IV collagen and laminin. Widespread apoptosis of keratinocytes was detected by the TUNEL assay, whereas no apoptosis of capillary endothelial cells was observed. BaP1 induced a drastic reduction in the microvessel density, revealed by immunostaining for the endothelial marker vascular endothelial growth factor receptor-2. This was followed by a rapid angiogenic response, leading to a partial revascularization. Skin damage was followed by inflammation and granulation tissue formation. Then, a successful re-epithelization process occurred, and the skin of the ear regained its normal structure by 2 weeks. Venom metalloproteinase-induced skin damage reproduces the pathological changes described in snakebitten patients.

Unusual accelerated rate of deletions and insertions in toxin genes in the venom glands of the pygmy copperhead (Austrelaps labialis) from Kangaroo island

Background

Toxin profiling helps in cataloguing the toxin present in the venom as well as in searching for novel toxins. The former helps in understanding potential pharmacological profile of the venom and evolution of toxins, while the latter contributes to understanding of novel mechanisms of toxicity and provide new research tools or prototypes of therapeutic agents.

Results

The pygmy copperhead (Austrelaps labialis) is one of the less studied species. In this present study, an attempt has been made to describe the toxin profile of A. labialis from Kangaroo Island using the cDNA library of its venom glands. We sequenced 658 clones which represent the common families of toxin genes present in snake venom. They include (a) putative long-chain and short-chain neurotoxins, (b) phospholipase A₂, (c) Kunitz-type protease inhibitor, (d) CRISPs, (e) C-type lectins and (f) Metalloproteases. In addition, we have also identified a novel protein with two Kunitz-type domains in tandem similar to bikunin.

Conclusion

Interestingly, the cDNA library reveals that most of the toxin families (17 out of 43 toxin genes; ~40%) have truncated transcripts due to insertion or deletion of nucleotides. These truncated products might not be functionally active proteins. However, cellular trancripts from the same venom glands are not affected. This unusual higher rate of deletion and insertion of nucleotide in toxin genes may be responsible for the lower toxicity of A. labialis venom of Kangroo Island and have significant effect on evolution of toxin genes.

Isolation and structural characterization of a new fibrin(ogen)olytic metalloproteinase from Bothrops moojeni snake venom

A proteinase, named BmooMPalpha-I, from the venom of Bothrops moojeni, was purified by DEAE-Sephacel, Sephadex G-75 and heparin-agarose column chromatography. The enzyme was purified to homogeneity as judged by its migration profile in SDS-PAGE stained with coomassie blue, and showed a molecular mass of about 24.5 kDa. Its complete cDNA was obtained by RT-PCR and the 615 bp codified for a mature protein of 205 amino acid residues. The multiple alignment of its deduced amino acid sequence and those of other snake venom metalloproteinases showed a high structural similarly, mainly among class P-IB proteases. The enzyme cleaves the Aalpha-chain of fibrinogen first, followed by the Bbeta-chain, and shows no effects on the gamma-chain. On fibrin, the enzyme hydrolyzed only the beta-chain, leaving the gamma-dimer apparently untouched. It was devoid of phospholipase A(2), hemorrhagic and thrombin-like activities. Like many venom enzymes, it is stable at pH values between 4 and 10 and stable at 70 degrees C for 15 min. The inhibitory effects of EDTA on the fibrinogenolytic activity suggest that BmooMPalpha-I is a metalloproteinase and inhibition by beta-mercaptoethanol revealed the important role of the disulfide bonds in the stabilization of the native structure. Aprotinin and benzamidine, specific serine proteinase inhibitors, had no effect on BmooMPalpha-I activity. Since the BmooMPalpha-I enzyme was found to cause defibrinogenation when administered i.p. on mice, it is expected that it may be of medical interest as a therapeutic agent in the treatment and prevention of arterial thrombosis.

Individual venom variability in the South American rattlesnake Crotalus durissus cumanensis

Crotalus durissus cumanensis snake venoms from different Venezuelan regions, showed biochemical and hemostatic variations. Fibrino(geno)lytic, hemorrhagic and procoagulant activities and gel-filtration chromatography and SDS-PAGE profiles were analyzed. Differences were observed in fibrinolytic activity: kallikrein-like amidolytic activity was highest in venoms of Santa Teresa, and Margarita. Lagunetica and Carrizales venoms showed the maximum fibrin lysis. The highest hemorrhagic activity was seen in Lagunetica venom. Margarita had the lowest LD(50) of 0.18. Lagunetica, Carrizales and Anzoátegui induced a rapid degradation of fibrinogen alpha chains and slower degradation on beta chains, which could possibly due to a higher content of alpha fibrinogenases in these venoms. This fibrinogenolytic activity is decreased by metalloprotease inhibitors. All venoms, except Carrizales, presented thrombin-like activity. Anzoátegui, Carrizales and Lagunetica, in which fibrinolytic activity was present, showed the largest concentration of high molecular mass components. These results represent a new finding, not previously described, of fibrinolytic activity in South American C. durissus venoms. Santa Teresa and Margarita had fibrinolytic activity, and lack of hemorrhagic activity, representing an important finding in Venezuelan venoms since the description of a fibrinolytic molecule without hemorrhagic activity can have valuable potential in thrombolytic therapy.

Cytotoxic, thrombolytic and edematogenic activities of leucurolysin-a, a metalloproteinase from Bothrops leucurus snake venom

Leucurolysin-a (leuc-a), a 23 kDa non-hemorrhagic metalloproteinase, is found in venom of the viper Bothrops leucurus. Here, we examine the biological consequences of leuc-a, including thrombolytic activity, direct effects on endothelial cells in culture and edematogenic activity in vivo. We demonstrate fibrinolytic activity of leuc-a, in which the protease specifically degrades alpha, beta, and gamma-gamma chains. While not causing hemorrhaging, leuc-a does cause thrombolytic activities in whole blood clots. Endothelial cells are highly resistant to leuc-a in culture. Cell viability suffered only when cells were exposed to large quantities of the protease. Nevertheless, leuc-a induces changes in cell morphology. The impact of leuc-a on cell adhesion was confirmed by an adhesion assay, in which cell adhesion to fibronectin decreased due to leuc-a. This mild cellular impact is unlike that of crude venom, where lower concentrations triggered cell death and a greater reduction in cell adhesion. Also, leuc-a increased microvessel permeability with marked edema in mice peritoneum and foot pads. These effects are similar to those of other P-I class SVPMs. These in vivo effects were weaker when crude venom was tested. In conclusion, albeit not showing significant hemorrhagic activity, leuc-a can induce a prominent edema which appears to be significant in the local effects observed after B. leucurus venom accidents.

The snake venom metalloproteinase BaP1 induces joint hypernociception through TNF-alpha and PGE2-dependent mechanisms

BACKGROUND AND PURPOSE

Matrix metalloproteinases (MMPs) have been implicated in joint tissue destruction in arthritis. However, MMPs have not been assigned a role in joint pain. We investigated the ability of BaP1, a metalloproteinase from Bothrops asper snake venom, with structural homology to MMPs, to induce joint hypernociception.

EXPERIMENTAL APPROACH

Animals received intra-articular (i.art.) BaP1. Hypernociception was assessed using the rat-knee joint articular incapacitation test. Cell influx, prostaglandin E(2) (PGE(2)), and TNF-alpha levels were assessed in joint exudates following BaP1 injection.

KEY RESULTS

BaP1 (5 microg per joint) provoked hypernociception between 1 and 6 h after i.art. injection. Cell influx, mostly neutrophils, was maximal 3 h after BaP1 i.art. injection. BaP1 also led to increase in PGE(2) and TNF-alpha levels in the joint exudates. Pretreatment with either indomethacin (4 mg.kg(-1) i.p.) or with an anti-TNF-alpha antiserum (i.art.) significantly inhibited both BaP1-induced joint hypernociception and cell influx. In isolated rat peritoneal macrophages, BaP1 increased cyclooxygenase (COX)-2 expression, while not altering that of COX-1.

CONCLUSIONS AND IMPLICATIONS

This is the first demonstration that a metalloproteinase promotes joint hypernociception. This effect involves local release of PGE(2) and TNF-alpha. BaP1-induced increase in PGE(2) is associated to increased COX-2 expression in macrophages. Blocking PGE(2) or TNF-alpha inhibits BaP1-induced hypernociception. In addition to unravelling a hitherto unknown mechanism whereby TNF blockade provides analgesia in arthritis, the data show, for the first time that MMPs are involved in inflammatory joint hypernociception and induce COX-2 expression.

Local and systemic pathophysiological alterations induced by a serine proteinase from the venom of the snake Bothrops jararacussu

The local and systemic pathophysiological alterations induced by BjussuSP-I, a thrombin-like serine proteinase from the venom of the snake Bothrops jararacussu, were assessed in mice. BjussuSP-I induced a mild edema but no local myonecrosis or hemorrhage. It did not induce any microvascular alteration in the cremaster muscle. Intramuscular injection of BjussuSP-I promoted an increase in the expression of proMMP-9, but it did not induce the activation of proMMP-2 or proMMP-9 synthesized in muscle tissue injected with a myotoxic phospholipase A(2) homolog. BjussuSP-I induced defibrin(ogen)ation upon intravenous and intramuscular injections, with reduction in plasma fibrinogen concentration and increments in the levels of fibrin degradation products and D-dimer. When compared with animals having normal coagulation, mice defibrin(ogen)ated by BjussuSP-I developed a slightly larger hemorrhagic lesion in the skin when injected with metalloproteinase BaP1. Intravenous injection of sublethal doses of BjussuSP-I promoted a series of behavioral and motor changes similar to those previously described for 'gyroxin', i.e. opisthotonus and a circular body movement along the longitudinal axis.

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.

Novel insights into capillary vessel basement membrane damage by snake venom hemorrhagic metalloproteinases: a biochemical and immunohistochemical study

The hemorrhagic activity characteristic of viperid snake envenomations is due to the action of venom metalloproteinases (SVMPs) on the capillary vessel basement membrane (BM). This study compared the action of two SVMPs on BM in vitro (degradation of Matrigel) and in vivo (immunohistochemical assessment of BM markers in mouse gastrocnemius muscle). SVMPs BaP1 (belonging to the P-I class) and jararhagin (of the P-III class) had a similar proteolytic activity on azocasein and degraded Matrigel with a slightly different cleavage pattern, since BaP1 exerted a limited proteolysis of both laminin and nidogen, whereas jararhagin predominantly degraded nidogen. In contrast with this pattern of limited proteolysis of BM proteins observed in vitro, immunohistochemical analysis of laminin, nidogen and type IV collagen, as well as of the endothelial cell marker VEGFR-2, in the hemorrhagic areas in the muscle, revealed a pronounced reduction in the immunostaining of these three BM components, associated with a loss of the endothelial cell marker. BM of muscle fibers was affected to a lesser extent. In conclusion, in vitro results demonstrated that SVMPs induce a pattern of limited proteolysis on BM components. The drastic loss of these antigens in affected capillaries in vivo is likely to depend on the combination of limited proteolysis of BM and the action of hemodynamic biophysical forces, previously shown to play a role in SVMP-induced capillary damage, which may cause a mechanical disruption of BM structure.

Inflammatory effects of BaP1 a metalloproteinase isolated from Bothrops asper snake venom: leukocyte recruitment and release of cytokines

The inflammatory events induced by BaP1, a 22.7 kDa metalloproteinase isolated from Bothrops asper snake venom, were studied. BaP1 i.p. injection in mice induced a marked inflammatory cell infiltrate into peritoneal cavity of animals with predominance of neutrophils in the early phase followed by mononuclear cells in the late period. Inhibition of enzymatic activity of BaP1 by chelation with EDTA resulted in a drastic reduction of this effect. In addition, BaP1 induced a significant increase of blood neutrophil numbers before its accumulation in peritoneal cavity, thus suggesting a stimulatory action of BaP1 on mechanisms of cell mobilization from bone marrow reserve compartments. A reduction in the number of neutrophils was observed in the exudate when antibodies against LECAM-1, CD18 and LFA-1 were used, suggesting the involvement of these adhesion molecules in the effects of BaP1. In contrast, there was no effect with antibodies against ICAM-1 and PECAM-1. Moreover, a conspicuous increment in the levels of IL-1 and TNF-alpha, but not of LTB4, was observed in peritoneal washes collected from mice injected with BaP1. It is concluded that BaP1 induces in vivo a marked leukocyte influx, which parallels an increased number of these cells in the blood, and is associated to the expression of specific leukocyte adhesion molecules and release of chemotactic inflammatory cytokines. Since BaP1 is a P-I class metalloproteinase, these results indicate that the proteolytic domain of metalloproteinases per se can trigger specific inflammatory events.

Blood flow is required for rapid endothelial cell damage induced by a snake venom hemorrhagic metalloproteinase

The effects of blood flow interruption on the ultrastructural alterations induced by a snake venom hemorrhagic metalloproteinase on skeletal muscle capillary endothelial cells were studied. Saline solution or the metalloproteinase BaP1, from the venom of Bothrops asper, was injected into the gastrocnemius muscles of mice with normal blood flow perfusion or with blood supply abrogated by two different protocols. Tissue was collected 5 min after injection, and both histological and ultrastructural analyses of the muscle capillary vessels were performed. Muscle with normal perfusion injected with saline solution had the typical morphology of normal capillaries, whereas injection of metalloproteinase to muscle with normal blood flow induced prominent degenerative changes in endothelial cells, such as reduction in cell thickness, decrease in the amount of pinocytotic vesicles, prominent distention and rupture leading to extravasation. In contrast, endothelial cells of capillaries from tissue devoid of blood flow and injected with the metalloproteinase did not show degenerative changes. The only alterations observed were a reduction in the capillary lumen and the presence of cytoplasmic projections, or 'pseudopods', both of which were also present in capillaries from tissue devoid of blood flow and injected with saline solution, thus suggesting that such changes are due to the drop in transmural pressure as a consequence of blood flow interruption. Our observations support the hypothesis that biophysical forces operating in the microvasculature, i.e., transmural pressure-dependent wall tension and shear stress, play a significant role in the pathogenesis of endothelial cell damage and hemorrhage induced by snake venom metalloproteinases.

Crystal structure of a non-hemorrhagic fibrin(ogen)olytic metalloproteinase complexed with a novel natural tri-peptide inhibitor from venom of Agkistrodon acutus

Thrombotic occlusive diseases pose a great threat to human health. Thrombolytic agents are in widespread use for the dissolution of arterial and venous pathologic thrombi in these kinds of diseases. Snake venom metalloproteinases (SVMPs) can act directly on fibrin/fibrinogen and are therefore potential candidates for therapeutic use against thrombotic occlusive diseases. In this study, we have determined the crystal structure of FII, a novel non-hemorrhagic SVMP isolated from Anhui Agkistrodon acutus snake venom by molecular replacement. The structure reveals that FII is a member of the P-I class SVMPs. The Zn2+ ion essential for hydrolytic activity is found in the active site and is tetrahedrally co-ordinated by three histidine residues and water molecule. Unambiguous electron density for a tri-peptide with sequence KNL is also found located near the active site. Biochemical evidences show that the tri-peptide KNL can inhibit the enzymatic activity of FII.

Jararhagin and its multiple effects on hemostasis

Jararhagin is a 52 kDa hemorrhagic P-III metalloproteinase isolated from the venom of the medically important Brazilian pit-viper Bothrops jararaca. It is a member of the reprolysin family of zinc metalloproteinases containing a catalytic metalloproteinase domain followed by a disintegrin-like and a cysteine-rich domain. The impact of jararhagin on hemostasis has been extensively studied using in vitro and in vivo model systems as well as in clinical studies. Jararhagin-induced hemorrhage is the result of the degradation of sub-endothelial matrix proteins leading to the disruption of the blood vessel endothelium, with accompanying disturbances in platelet function. The versatility of jararhagin is further demonstrated by its direct action on von Willebrand factor, the degradation of fibrinogen, by its inhibition of platelet adhesion to collagen and by its inability to be affected by the plasma inhibitor alpha(2)-macroglobulin. Collagen-induced platelet aggregation is inhibited by jararhagin though the binding of the molecule to the alpha(2) subunit I domain of the platelet surface alpha(2)beta(1) integrin (collagen receptor). Jararhagin also cleaves the beta(1) subunit of the same integrin, inhibiting platelet interaction and ultimately causing impairment of signal transduction. The effect of jararhagin on cell systems other than platelets is evaluated; in fibroblasts, jararhagin functions as a collagen-mimetic substrate and, in endothelial cells, it causes apoptosis and indirectly inhibits cell proliferation by release of angiostatin-like compounds. Jararhagin induces a strong pro-inflammatory response characterized by intense leukocyte accumulation at the site of the injection. Although hemorrhage and edema are a response to the direct effect of jararhagin, jararhagin-induced inflammation and necrosis are dependent on macrophages and key pro-inflammatory cytokines or their receptors. Some data also indicate that the toxin possesses anti-tumorgenic properties. Methods for inhibiting jararhagin are reviewed; this encompasses the use of synthetic peptides to the isolation of naturally occurring mammalian peptides and the development of toxin-specific antibodies through DNA immunisation and monoclonal antibody technologies. The availability of jararhagin makes it an important tool for research into the mechanisms of action of similar toxins, for insights into cellular interactions and for clinical investigations into the treatment of envenomings from B. jararaca.

Inflammatory effects of snake venom metalloproteinases

Metalloproteinases are abundant enzymes in crotaline and viperine snake venoms. They are relevant in the pathophysiology of envenomation, being responsible for local and systemic hemorrhage frequently observed in the victims. Snake venom metalloproteinases (SVMP) are zinc-dependent enzymes of varying molecular weights having multidomain organization. Some SVMP comprise only the proteinase domain, whereas others also contain a disintegrin-like domain, cysteine-rich, and lectin domains. They have strong structural similarities with both mammalian matrix metalloproteinases (MMP) and members of ADAMs (a disintegrin and metalloproteinase) group. Besides hemorrhage, snake venom metalloproteinase induce local myonecrosis, skin damage, and inflammatory reaction in experimental models. Local inflammation is an important characteristic of snakebite envenomations inflicted by viperine and crotaline snake species. Thus, in the recent years there is a growing effort to understand the mechanisms responsible for SVMP-induced inflammatory reaction and the structural determinants of this effect. This short review focuses the inflammatory effects evoked by SVMP.

Structural considerations of the snake venom metalloproteinases, key members of the M12 reprolysin family of metalloproteinases

The importance of proteinases in the pathologies associated with Viperid envenoming has long been appreciated. Over the past 40 years substantial research has clearly implicated metalloproteinases in the venom (snake venom metalloproteinases; SVMPs) as playing key roles in the development of such symptoms as hemorrhage, edema, hypotension, hypovolemia, inflammation and necrosis. In spite of this wealth of information there are still many unresolved questions pertaining to the structural basis for the various SVMPS giving rise to the diversity of activities. In this short review we will not attempt to provide an exhaustive collation of structural studies on the SVMPs; however, we will give a brief outline of the structural classification of the SVMPs; as well as relate them to the other members of the reprolysin family of metalloproteinases, the ADAMs. The information put forth in the text does not allow specific conclusions to be drawn on the structural basis for SVMP functional diversity, but it is our goal that it will allow for the development of testable hypotheses that can be experimentally pursued. What the reader will observe is that there are very interesting structural features displayed by the various SVMP classes and subclasses that provide insight into their functional characteristics.

Inhibitory effects of Piper umbellatum and Piper peltatum extracts towards myotoxic phospholipases A2 from Bothrops snake venoms: isolation of 4-nerolidylcatechol as active principle

Phospholipases A(2) (PLA(2)) are important constituents of snake venoms, being responsible for several of their toxic actions. Extracts from plants used in folk medicine were screened for inhibition of the enzymatic activity of myotoxin I, a PLA(2) from Bothrops asper. Piper umbellatum and Piper peltatum extracts tested positive, and their fractionation resulted in the isolation of 4-nerolidylcatechol. Its inhibitory effects towards toxic activities of two Bothrops myotoxins, representing catalytically active (Asp49) and catalytically inactive (Lys49) types of group II PLA(2)s, respectively, were characterized. The enzyme activity of B. asper myotoxin I was completely inhibited by 4-nerolidylcatechol at an inhibitor:toxin ratio of 10:1 (wt/wt) with an IC50 of approximately 1mM. In addition, 4-nerolidylcatechol inhibited representatives of groups I and III of PLA(2)s. Its preincubation with Bothrops myotoxins significantly reduced their myotoxic and edema-inducing activities in animal experiments. However, when 4-nerolidylcatechol was administered in situ, immediately after toxin injection, its inhibitory ability was substantially lower or negligible. This might be explained by the rapid action of these toxins in vivo, together with the slow inactivation of PLA(2) activity observed in vitro. Electrophoretic and chromatographic analyses of myotoxins ruled out major changes in protein charge, hydrophobicity, or gross molecular mass being involved in the inhibition mechanism. Mass spectrometry determinations are consistent with the covalent modification of myotoxin by one molecule of 4-nerolidylcatechol. Finally, a novel compound was isolated from both Piper species, sharing the nerolidyl skeleton, but nevertheless not being inhibitory towards the PLA(2)s studied.

Crystallization and preliminary X-ray studies of a non-haemorrhagic fibrin(ogen)olytic metalloproteinase from the venom of Agkistrodon acutus

A non-haemorrhagic fibrin(ogen)olytic metalloproteinase from the venom of Agkistrodon acutus has been crystallized by the hanging-drop method. The crystals belong to space group P3(1)21, with unit-cell parameters a = b = 80.57, c = 66.77 A and one molecule in the asymmetric unit. X-ray diffraction data were collected to 1.86 A resolution.

Purification and characterization of a hemorrhagic metalloproteinase from Bothrops lanceolatus (Fer-de-lance) snake venom

Bothrops snake venoms contain metalloproteinases that contribute to the local effects seen after envenoming. In this work, a hemorrhagic metalloproteinase (BlaH1) was purified from the venom of the snake Bothrops lanceolatus by a combination of gel filtration, affinity (metal chelating) and hydrophobic interaction chromatographies. The hemorrhagin was homogeneous by SDS-PAGE and had a molecular mass of 28 kDa that was unaltered by treatment with beta-mercaptoethanol. BlaH1 gave a single band in immunoelectrophoresis and immunoblotting using commercial bothropic antivenom. BlaH1 had hemorrhagic, caseinolytic, fibrinogenolytic, collagenolytic and elastinolytic activities, but no phospholipase A(2) activity. The hemorrhagic and caseinolytic activities were inhibited by EDTA, indicating that they were metal ion-dependent. In contrast, aprotinin, benzamidine and PMSF did not affect these activities. The caseinolytic activity of BlaH1 had a pH optimum of 8.0 and was stable in solution at up to 40 degrees C; activity was completely lost at > or =70 degrees C. The hemorrhagic activity was neutralized by commercial bothropic antivenom. These properties suggest that this new hemorrhagin belongs to class P-I snake venom metalloproteinases.

Role of TNF-α, IL-1β and IL-6 in the local tissue damage induced by Bothrops asper snake venom: an experimental assessment in mice

The role of the cytokines TNF-alpha, IL-1beta and IL-6 in the acute local pathological effects induced by Bothrops asper snake venom was assessed in mice. Intramuscular injection of this venom induced increments in IL-1beta and IL-6 in muscle, but no elevations of TNF-alpha were detected. Pentoxifylline (PTX), a methylxanthine derivative that inhibits the synthesis of TNF-alpha, and antibodies against these three cytokines were used to assess the role of these cytokines in venom-induced effects. As a control, PTX pretreatment was effective at abrogating lethality and serum TNF-alpha increments in mice subjected to endotoxemia induced by injection of Escherichia coli lipopolysaccharide, although it did not affect the increment in IL-1beta and IL-6 in such endotoxic model. PTX failed to reduce lethality, hemorrhage, myonecrosis, dermonecrosis and edema induced by B. asper venom. Moreover, pretreatment with anti-cytokine antibodies was also ineffective at reducing venom-induced myonecrosis and hemorrhage. It is concluded that TNF-alpha, IL-1beta and IL-6 do not have a significant role in the pathogenesis of the acute local pathological effects induced by B. asper venom in mice, although this does not exclude the possibility that these cytokines play a role in other aspects of venom-induced local pathology, as well as in the reparative and regenerative responses that take place after the onset of tissue damage.