Structural and functional analysis of BmjMIP, a phospholipase A2 myotoxin inhibitor protein from Bothrops moojeni snake plasma

Neutralization of "Chaco eagle" (Buteogallus coronatus) serum on some activities of Bothrops spp. venoms

Several species of reptiles and mammals have components in their sera that can neutralize toxic components present in snake venoms. In this manuscript, we studied the neutralizing capacity of Chaco eagle's (Buteogallus coronatus) serum. This South American bird of prey eats snakes as a regular part of its diet and has anatomical features that protect from snakes' bites. The neutralizing potency of the Chaco eagle's serum was tested on lethal, hemorrhagic, procoagulant, and phospholipase activities of the venom of "yarará grande" (Bothrops alternatus) and on phospholipase activity of "yarará ñata" (Bothrops ammodytoides) venom; both snakes are known to be the prey of Chaco eagle. Sera of crested caracara (Caracara plancus-a scavenger, omnivorous pan-American bird of prey), secretary bird (Saggitarius serpentarius-an omnivorous bird of prey from Africa that can include venomous snakes in its diet), common hen (Gallus gallus), rat (Rattus norvegicus), mouse (Mus musculus), horse (Equus caballus), and dog (Canis lupus familiaris) were also tested to compare the inhibitory capacity of neutralization. To test isologous and xenologous neutralization, sera from Bothrops alternatus and white-eared opossum (Didelphis albiventris), respectively, were used due to their known inhibitory activity on Bothrops venoms. As a control for the neutralization activity, antibothropic antivenom was used. Chaco eagle's serum neutralized hemorrhagic and phospholipasic activity and slightly neutralized the coagulation and the lethal activity of Bothrops spp. venom. The neutralizing capacity was present in the non-immunoglobulin fraction of the serum, which showed components of acidic characteristics and lower molecular weight than IgY, in correspondence with the characteristics of PLA₂s and SVMPs inhibitors described in sera from some snakes and mammals. These studies showed that Chaco eagle's serum neutralizes all toxic activities tested at a higher level than sera from animal species in which inhibitors of snake venoms have not been described (p < 0.05), while it is lower or similar in neutralizing capacity to white-eared opossum and B. alternatus sera.

Convergent evolution of toxin resistance in animals

Convergence is the phenomenon whereby similar phenotypes evolve independently in different lineages. One example is resistance to toxins in animals. Toxins have evolved many times throughout the tree of life. They disrupt molecular and physiological pathways in target species, thereby incapacitating prey or deterring a predator. In response, molecular resistance has evolved in many species exposed to toxins to counteract their harmful effects. Here, we review current knowledge on the convergence of toxin resistance using examples from a wide range of toxin families. We explore the evolutionary processes and molecular adaptations driving toxin resistance. However, resistance adaptations may carry a fitness cost if they disrupt the normal physiology of the resistant animal. Therefore, there is a trade‐off between maintaining a functional molecular target and reducing toxin susceptibility. There are relatively few solutions that satisfy this trade‐off. As a result, we see a small set of molecular adaptations appearing repeatedly in diverse animal lineages, a phenomenon that is consistent with models of deterministic evolution. Convergence may also explain what has been called ‘autoresistance’. This is often thought to have evolved for self‐protection, but we argue instead that it may be a consequence of poisonous animals feeding on toxic prey. Toxin resistance provides a unique and compelling model system for studying the interplay between trophic interactions, selection pressures and the molecular mechanisms underlying evolutionary novelties.

A comparative study of endogenous phospholipase A2 inhibitors in the serum of Brazilian pit vipers

This work compared the presence of phospholipase A₂ inhibitors (PLIs) in the serum of 19 snake species maintained at Instituto Butantan to better understand the mechanisms of venom resistance in snakes and improve the treatment of snakebite. PLI was isolated from blood of 19 snake species by one-step chromatography and identified in all samples, besides its identity was confirmed through the interaction with both phospholipase A₂ and anti-γPLI. These findings highlight the diversity of snake serum PLIs and emphasize the importance of structure-function studies.

Antimyotoxic Activity of Synthetic Peptides Derived from Bothrops atrox Snake Gamma Phospholipase A2 Inhibitor Selected by Virtual Screening

Background:

Several studies have aimed to identify molecules that inhibit the toxic actions of snake venom phospholipases A2 (PLA2s). Studies carried out with PLA2 inhibitors (PLIs) have been shown to be efficient in this assignment.

Objective:

This work aimed to analyze the interaction of peptides derived from Bothrops atrox PLIγ (atPLIγ) with a PLA2 and to evaluate the ability of these peptides to reduce phospholipase and myotoxic activities.

Methods:

Peptides were subjected to molecular docking with a homologous Lys49 PLA2 from B. atrox venom modeled by homology. Phospholipase activity neutralization assay was performed with BthTX-II and different ratios of the peptides. A catalytically active and an inactive PLA2 were purified from the B. atrox venom and used together in the in vitro myotoxic activity neutralization experiments with the peptides.

Results:

The peptides interacted with amino acids near the PLA2 hydrophobic channel and the loop that would be bound to calcium in Asp49 PLA2. They were able to reduce phospholipase activity and peptides DFCHNV and ATHEE reached the highest reduction levels, being these two peptides the best that also interacted in the in silico experiments. The peptides reduced the myotubes cell damage with a highlight for the DFCHNV peptide, which reduced by about 65%. It has been suggested that myotoxic activity reduction is related to the sites occupied in the PLA2 structure, which could corroborate the results observed in molecular docking.

Conclusion:

This study should contribute to the investigation of the potential of PLIs to inhibit the toxic effects of PLA2s.

Comparative compositional and functional analyses of Bothrops moojeni specimens reveal several individual variations

Snake venoms are complex protein mixtures with different biological activities that can act in both their preys and human victims. Many of these proteins play a role in prey capture and in the digestive process of these animals. It is known that some snakes are resistant to the toxicity of their own venom by mechanisms not yet fully elucidated. However, it was observed in the Laboratory of Herpetology of Instituto Butantan that some Bothrops moojeni individuals injured by the same snake species showed mortalities caused by envenoming effects. This study analyzed the biochemical composition of 13 venom and plasma samples from Bothrops moojeni specimens to assess differences in their protein composition. Application of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed distinct venom protein profiles, but very homogeneous plasma profiles. Western Blotting (WB) was performed with plasma samples, which were submitted to incubation with the respective venom. Some individuals showed an immunorecognized band zone around 25 kDa, indicating interaction between the same individual plasma and venom proteins. Crossed-WB assay using non-self-plasma and venom showed that this variability is due to venom protein composition instead of plasma composition. These venoms presented higher caseinolytic, collagenolytic and coagulant activities than the venoms without these regions recognized by WB. Mass spectrometry analyses performed on two individuals revealed that these individuals present, in addition to higher protein concentrations, other exclusive proteins in their composition. When these same two samples were tested in vivo, the results also showed higher lethality in these venoms, but lower hemorrhagic activity than in the venoms without these regions recognized by WB. In conclusion, some Bothrops moojeni specimens differ in venom composition, which may have implications in envenomation. Moreover, the high individual venom variability found in this species demonstrates the importance to work with individual analyses in studies involving intraspecific venom variability and venom evolution.

In-Depth Venome of the Brazilian Rattlesnake Crotalus durissus terrificus: An Integrative Approach Combining Its Venom Gland Transcriptome and Venom Proteome

Snake venoms are complex mixtures mainly composed of proteins and small peptides. Crotoxin is one of the most studied components from Crotalus venoms, but many other components are less known due to their low abundance. The venome of Crotalus durissus terrificus, the most lethal Brazilian snake, was investigated by combining its venom gland transcriptome and proteome to create a holistic database of venom compounds unraveling novel toxins. We constructed a cDNA library from C. d. terrificus venom gland using the Illumina platform and investigated its venom proteome through high resolution liquid chromotography-tandem mass spectrometry. After integrating data from both data sets, more than 30 venom components classes were identified by the transcriptomic analysis and 15 of them were detected in the venom proteome. However, few of them (PLA₂, SVMP, SVSP, and VEGF) were relatively abundant. Furthermore, only seven expressed transcripts contributed to ∼82% and ∼73% of the abundance in the transcriptome and proteome, respectively. Additionally, novel venom proteins are reported, and we highlight the importance of using different databases to perform the data integration and discuss the structure of the venom components-related transcripts identified. Concluding, this research paves the way for novel investigations and discovery of future pharmacological agents or targets in the antivenom therapy.

Proteopeptidomic, Functional and Immunoreactivity Characterization of Bothrops moojeni Snake Venom: Influence of Snake Gender on Venom Composition

Venom composition varies across snakes from all taxonomic levels and is influenced by the snakes’ age, habitat, diet, and sexual dimorphism. The present study reports the first in-depth investigation of venom composition in male and female Bothrops moojeni (B. moojeni) snakes (BmooM and BmooF, respectively) through three proteomics approaches associated with functional, cytotoxic, and immunoreactivity characterization. Compared with BmooM venom, BmooF venom exhibited weaker hyaluronidase, metalloproteinase, and phospholipase activity; stronger recognition by anti-bothropic serum; 1.4-fold stronger cytotoxicity; and greater number of peptides. The increased L-amino acid oxidase expression probably accounted for the stronger immunoreactivity and cytotoxicity of BmooF venom. BmooF and BmooM venom shared only 19% peptides. Some venom components were gender-specific, such as phospholipases B, phospholipase inhibitor, and hyaluronidases in BmooM, and cysteine-rich secretory proteins in BmooF. In conclusion, we describe herein the first proteomics study of B. moojeni snake venom and an in-depth characterization of gender-specific differences in venom composition. Altogether, our findings not only stress the importance of considering the snake’s gender during antivenom production, but also help to identify new potential drugs and biotechnological tools.

Anticancer and antibacterial effects of Iranian viper (Vipera latifii) venom; an in-vitro study

Viper venom contains antibacterial and cytotoxic components. The aim of this study was to identify and evaluate the antimicrobial and cytotoxic properties of the crude venom of Vipera latifii (V. latifii). Lyophilized venom of V. latifii was quantified by Bradford method and its antibacterial activity (6.25-400 μg/ml) was assessed using the MTT, MIC, Disc diffusion, and Well diffusion assays. Also, its cytotoxic activity was investigated using MTT reduction, Neutral uptake, and Comet assay on human liver cancer (HepG2) cell line. Crude venom showed antibacterial effects against Bacillus subtilis and Staphylococcus aureus, but was not effective on Escherichia coli. Also, the crude venom showed apoptotic and necrotic effects on human liver cancer cells. The venom of V. latifii can inhibit the growth of bacteria and cancer cells. These findings suggest that this may be a potential source of molecules with antibacterial and anticancer characteristics.

Purification and characterization of the first γ-phospholipase inhibitor (γPLI) from Bothrops jararaca snake serum

Phospholipases A₂ (PLA₂) are enzymes acting on the cell membrane phospholipids resulting in fatty acids and lysophospholipids and deconstructing the cell membrane. This protein is commonly found in snake venoms, causing tissue inflammation in the affected area. Evidence indicates that snakes have natural resistance to their own venom due to protective properties in plasma, that inhibit the action of proteins present in their venom. Given that, this study aimed to purify and characterize a γPLI from Bothrops jararaca serum, named γBjPLI. PLA₂ inhibitor was isolated using two chromatographic steps: an ion exchange column (DEAE), followed by an affinity column (crotoxin coupled to a CNBr-activated Sepharose resin). The purity and biochemical characterization of the isolated protein were analyzed by RP-HPLC, SEC, SDS-PAGE, circular dichroism and mass spectrometry. The ability to inhibit PLA₂ was determined by enzymatic activity, neutralization of paw edema and myonecrosis. The protein purity was confirmed by RP-HPLC and SEC, whilst an apparent molecular mass of 25 kDa and 20 kDa was obtained by SDS-PAGE, under reducing and non-reducing conditions, respectively. According to mass spectrometry analysis, this protein showed 72% and 68% of coverage when aligned to amino acid sequences of two proteins already described as PLIs. Thus, the inhibitory activity of enzymatic, edema and myonecrotic activities by γBjPLI suggests a role of this inhibitor for protection of these snakes against self-envenomation.

Isolation, purification and characterization of 5'-phosphodiesterase from Aspergillus fumigatus

5'-Phosphodiesterase (5'-PDE) catalyzes the hydrolysis of ribonucleic acid to obtain a mixture of ribonucleotides, such as 5'-guanosine monophosphate and 5'-adenosine monophosphate. In this study, a 5'-PDE was newly isolated and purified from Aspergillus fumigatus. Following purification, this enzyme exhibited a specific activity of 1036.76 U/mg protein, a molecular weight of 9.5 kDa, and an optimal temperature and pH for enzyme activity of 60°C and 5.0, respectively. However, its activity was partially inhibited by Fe3+, Cu2+, and Zn2+, but slightly improved by the presence of K+ and Na+. Additionally, chemical-modification experiments were also applied to investigate the structural information of 5'-PDE, in which the residues containing carboxyl and imidazole groups were essential for enzyme activity based on their localization in the 5'-PDE active site. Furthermore, purified 5'-PDE could specifically catalyze the synthesis of ribonucleotides with a Vmax 0.71 mmol/mg·min and a KM of 13.60 mg/mL.

Alpha-type phospholipase A2 inhibitors from snake blood

It is of popular and scientific knowledge that toxins from snake venom (among them the PLA2 and myotoxins) are neutralized by various compounds, such as antibodies and proteins purified from animal blood. Venomous and nonvenomous snakes have PLA2 inhibitory proteins, called PLIs, in their blood serum. One hypothesis that could explain the presence of these PLIs in the serum of venomous snakes would be self-protection against the enzymes of their own venom, which eventually could reach the circulatory system. However, the presence of PLIs in non-venomous snakes suggests that their physiological role might not be restricted to protection against PLA2 toxins, but could be extended to other functions, as in the innate immune system and local regulation of PLA2s. The present study aimed to review the currently available literature on PLA2 and myotoxin alpha inhibitors present in snake plasma, thus helping to improve the research on these molecules. Furthermore, this review includes current information regarding the mechanism of action of these inhibitors in an attempt to better understand their application, and proposes the use of these molecules as new models in snakebite therapy. These molecules may help in the neutralization of different types of phospholipases A2 and myotoxins, complementing the conventional serum therapy.

Endogenous phospholipase A2 inhibitors in snakes: a brief overview

The blood plasma of numerous snake species naturally comprises endogenous phospholipase A₂ inhibitors, which primarily neutralize toxic phospholipases A₂ that may eventually reach their circulation. This inhibitor type is generally known as snake blood phospholipase A₂ inhibitors (sbPLIs). Most, if not all sbPLIs are oligomeric glycosylated proteins, although the carbohydrate moiety may not be essential for PLA₂ inhibition in every case. The presently known sbPLIs belong to one of three structural classes – namely sbαPLI, sbβPLI or sbγPLI – depending on the presence of characteristic C-type lectin-like domains, leucine-rich repeats or three-finger motifs, respectively. Currently, the most numerous inhibitors described in the literature are sbαPLIs and sbγPLIs, whereas sbβPLIs are rare. When the target PLA₂ is a Lys49 homolog or an Asp49 myotoxin, the sbPLI is denominated a myotoxin inhibitor protein (MIP). In this brief overview, the most relevant data on sbPLIs will be presented. Representative examples of sbαPLIs and sbγPLIs from two Old World – Gloydius brevicaudus and Malayopython reticulatus – and two New World – Bothrops alternatus and Crotalus durissus terrificus – snake species will be emphasized.

rBaltMIP, a recombinant alpha-type myotoxin inhibitor from Bothrops alternatus (Rhinocerophis alternatus) snake, as a potential candidate to complement the antivenom therapy

Phospholipase A₂ inhibitors (PLIs) are important targets in the search and development of new drugs. This study aimed at evaluating the potential of an alpha-type phospholipase A₂ inhibitor from Bothrops alternatus (Rhinocerophis alternatus) snake in its recombinant form (rBaltMIP) to complement the conventional antivenom therapy. Biochemical experiments showed that rBaltMIP presented pI 5.8 and molecular masses of ∼21 kDa by SDS-PAGE and 19.57 kDa by MALDI/TOF MS. After tryptic peptides sequencing, the results were compared with other PLIs available in databases, showing 100% identity between rBaltMIP and its native inhibitor BaltMIP and from 92% to 96% identity with other inhibitors. Myotoxic activities of BthTX-I and BthTX-II toxins were measured via plasma CK levels, showing myotoxic effective concentrations (EC50) of 0.1256 μg/μL and 0.6183 μg/μL, respectively. rBaltMIP neutralized the myotoxicity caused by these two toxins up to 65%, without promoting primary antibody response against itself. Nevertheless, this recombinant PLI was immunogenic when standard immunization protocol with Freud's adjuvant was used. In paw edema assays, EC50 of 0.02581 μg/μL and 0.02810 μg/μL, respectively, were observed with edema reductions of up to 40% by rBaltMIP, suggesting its use as an additional antivenom. In addition, myotoxicity neutralization experiments with the myotoxin BthTX-I showed that rBaltMIP was more effective in inhibiting muscle damage than the conventional antivenom. Thus, considering the severity of envenomations due to Bothrops alternatus (Rhinocerophis alternatus) and the low neutralization of their local effects (such as myotoxicity) by the current antivenoms, rBaltMIP is a promising molecule for the development of novel therapeutic strategies for clinical applications.

Novel phospholipase A2 inhibitors from python serum are potent peptide antibiotics

Antimicrobial peptides (AMPs) play a vital role in defense against resistant bacteria. In this study, eight different AMPs synthesized from Python reticulatus serum protein were tested for bactericidal activity against various Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Burkholderia pseudomallei (KHW and TES strains), and Proteus vulgaris) using a disc-diffusion method (20 μg/disc). Among the tested peptides, phospholipase A2 inhibitory peptide (PIP)-18[59-76], β-Asp65-PIP[59-67], D-Ala66-PNT.II, and D60,65E-PIP[59-67] displayed the most potent bactericidal activity against all tested pathogens in a dose-dependent manner (100-6.8 μg/ml), with a remarkable activity noted against S. aureus at 6.8 μg/ml dose within 6 h of incubation. Determination of minimum inhibitory concentrations (MICs) by a micro-broth dilution method at 100-3.125 μg/ml revealed that PIP-18[59-76], β-Asp65-PIP[59-67] and D-Ala66-PNT.II peptides exerted a potent inhibitory effect against S. aureus and B. pseudomallei (KHW) (MICs 3.125 μg/ml), while a much less inhibitory potency (MICs 12.5 μg/ml) was noted for β-Asp65-PIP[59-67] and D-Ala66-PNT.II peptides against B. pseudomallei (TES). Higher doses of peptides had no effect on the other two strains (i.e., Klebsiella pneumoniae and Streptococcus pneumoniae). Overall, PIP-18[59-76] possessed higher antimicrobial activity than that of chloramphenicol (CHL), ceftazidime (CF) and streptomycin (ST) (30 μg/disc). When the two most active peptides, PIP-18[59-76] and β-Asp65-PIP[59-67], were applied topically at a 150 mg/kg dose for testing wound healing activity in a mouse model of S. aureus infection, the former accelerates faster wound healing than the latter peptide at 14 days post-treatment. The western blot data suggest that the topical application of peptides (PIP-18[59-67] and β-Asp65-PIP[59-67]) modulates NF-kB mediated wound repair in mice with relatively little haemolytic (100-1.56 μg/ml) and cytotoxic (1000-3.125 μg/ml) effects evident on human cells in vitro.

Heterologous expression and biochemical and functional characterization of a recombinant alpha-type myotoxin inhibitor from Bothrops alternatus snake

Venomous and non-venomous snakes possess phospholipase A2 (PLA2) inhibitory proteins (PLIs) in their blood serum. This study shows the expression and biochemical and functional characterization of a recombinant alpha inhibitor from Bothrops alternatus snake, named rBaltMIP. Its expression was performed in Pichia pastoris heterologous system, resulting in an active recombinant protein. The expressed inhibitor was tested regarding its ability to inhibit the phospholipase activity of different PLA2s, showing slight inhibitions especially at the molar ratios of 1:1 and 1:3 (PLA2:PLI). rBaltMIP was also effective in decreasing the myotoxic activity of the tested toxins at molar ratios greater than 1:0.4 (myotoxin:PLI). The inhibition of the myotoxic activity of different Asp49 (BthTX-II and PrTX-III) and Lys49 (BthTX-I and PrTX-I) myotoxins was also performed without the prior incubation of myotoxins/inhibitor in order to analyze the real possibility of using snake plasma inhibitors or recombinant inhibitors as therapeutic agents for treating envenomations. As a result, rBaltMIP was able to significantly inhibit the myotoxicity of Lys49 myotoxins. Histopathological analysis of the gastrocnemius muscles of mice showed that the myotoxins are able to induce severe damage to the muscle fibers of experimental animals by recruiting a large number of leukocyte infiltrates, besides forming an intense accumulation of intercellular fluid, leading to local edema. When those myotoxins were incubated with rBaltMIP, a reduction of the damage site could be observed. Furthermore, the cytotoxic activity of Asp49 PLA2s and Lys49 PLA2-like enzymes on C2C12 cell lines was decreased, as shown by the higher cell viabilities after preincubation with rBaltMIP. Heterologous expression would enable large-scale obtainment of rBaltMIP, thus allowing further investigations for the elucidation of possible mechanisms of inhibition of snake PLA2s, which have not yet been fully clarified.

Rapid purification of a new P-I class metalloproteinase from Bothrops moojeni venom with antiplatelet activity

The present study aimed to evaluate the proteolytic and biological activities of a new metalloproteinase from B. moojeni venom. The purification of BmooMPα-II was carried out through two chromatographic steps (ion-exchange and affinity). BmooMPα-II is a monomeric protein with an apparent molecular mass of 22.5 kDa on SDS-PAGE 14% under nonreducing conditions. The N-terminal sequence (FSPRYIELVVVADHGMFTKYKSNLN) revealed homology with other snake venom metalloproteinases, mainly among P-I class. BmooMPα-II cleaves Aα-chain of fibrinogen followed by Bβ-chain, and does not show any effect on the γ-chain. Its optimum temperature and pH for the fibrinogenolytic activity were 30–50°C and pH 8, respectively. The inhibitory effects of EDTA and 1,10-phenantroline on the fibrinogenolytic activity suggest that BmooMPα-II is a metalloproteinase. This proteinase was devoid of haemorrhagic, coagulant, or anticoagulant activities. BmooMPα-II caused morphological alterations in liver, lung, kidney, and muscle of Swiss mice. The enzymatically active protein yet inhibited collagen, ADP, and ristocetin-induced platelet aggregation in a concentration-dependent manner. Our results suggest that BmooMPα-II contributes to the toxic effect of the envenomation and that more investigations to elucidate the mechanisms of inhibition of platelet aggregation may contribute to the studies of snake venom on thrombotic disorders.

Interaction of characteristic structural elements of persimmon tannin with Chinese cobra PLA2

To more fully understand the mechanism by which persimmon tannin (PT) inhibited phospholipase A2 (PLA2) and the structural requirements of PT for the inhibition, the interactions between PLA2 and seven characteristic structural elements of PT including epigallocatechin-3-gallate (EGCG), myricetin, epicatechin-3-gallate (ECG), epicatechin-3-gallate-(4β → 8, 2β → O → 7)-epicatechin-3-gallate (A-type ECG dimer), epigallocatechin-3-gallate-(4β → 8, 2β → O → 7)-epigallocatechin-3-gallate (A-type EGCG dimer), epicatechin-(4β → 8, 2β → O → 7)-epicatechin (A-type EC dimer) and epicatechin-(4β → 8)-epicatechin (B-type EC dimer) were studied by enzymatic and spectroscopic methods. Molecular docking was also used to explore the possible residues involved in the interactions. The results revealed that A-type EGCG dimer and A-type ECG dimer showed higher inhibitory effects on the catalytic activity of PLA2 than monomers and B-type dimer. They induced greater conformational changes in PLA2 than other structural elements. In addition, molecular docking studies revealed that expect for lysine residues, other residues such as Trp18, Try27, Gly29, His47 and Tyr63 were involved in the interactions. We propose that A-type EGCG and ECG dimer units may be structural requirements for the interaction between PT and PLA2. Our data provide an additional structural basis for anti-PLA2 activity of persimmon tannin.

Proteomic Analysis of the Ontogenetic Variability in Plasma Composition of Juvenile and Adult Bothrops jararaca Snakes

The ontogenetic variability in venom composition of some snake genera, including Bothrops, as well as the biological implications of such variability and the search of new molecules that can neutralize the toxic components of these venoms have been the subject of many studies. Thus, considering the resistance of Bothrops jararaca to the toxic action of its own venom and the ontogenetic variability in venom composition described in this species, a comparative study of the plasma composition of juvenile and adult B. jararaca snakes was performed through a proteomic approach based on 2D electrophoresis and mass spectrometry, which allowed the identification of proteins that might be present at different levels during ontogenetic development. Among the proteins identified by mass spectrometry, antihemorrhagic factor Bj46a was found only in adult plasma. Moreover, two spots identified as phospholipase A₂ inhibitors were significantly increased in juvenile plasma, which can be related to the higher catalytic PLA₂ activity shown by juvenile venom in comparison to that of adult snakes. This work shows the ontogenetic variability of B. jararaca plasma, and that these changes can be related to the ontogenetic variability described in its venom.

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

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

Inhibitory activities of the heterotrimers formed from two α-type phospholipase A2 inhibitory proteins with different enzyme affinities and importance of the intersubunit electrostatic interaction in trimer formation

α-type phospholipase A2 inhibitory protein (PLIα) isolated from the serum of the venomous snake Glyoidius brevicaudus, GbPLIα, is a homotrimer of subunits having a C-type lectin-like domain. The serum protein from nonvenomous snake Elaphe quadrivirgata, EqPLIα-LP, is homologous to GbPLIα, but it does not show any inhibitory activity against PLA2s. When a mixture of denaturant-treated monomeric forms of GbPLIα and EqPLIα-LP was used to reconstitute their trimers, no significant amounts of heterotrimers composed of GbPLIα and EqPLIα-LP subunits could be formed. On the other hand, when a mixture of denaturant-treated monomeric forms of GbPLIα and the recombinant chimeric EqPLIα-LP, Eq13Gb37Eq, in which the residues 13-36 were replaced by those of GbPLIα, was used to reconstitute their trimers, significant amounts of their heterotrimers were observed. Furthermore, when a mixture of denaturant-treated monomeric forms of EqPLIα-LP and the recombinant chimeric GbPLIα, Gb13Eq37Gb, in which the residues 13-36 were replaced by those of EqPLIα-LP, was used, significant amounts of their heterotrimers were observed. By comparison of the respective inhibitory activities of the heterotrimeric subspecies, it was suggested that the inhibitory activity of the trimer was governed by one subunit with the highest activity, and not affected by the number of these subunits. The intermolecular electrostatic interactions between Glu23 and Lys28 of GbPLIα were also suggested to be important in stabilizing the trimeric structure. The importance of the electrostatic interaction was supported by the less stability of the homotrimeric structure of a mutant GbPLIα with a single amino acid substitution, GbPLIα(K28E).

Inhibition of hemorragic snake venom components: old and new approaches

Snake venoms are complex toxin mixtures. Viperidae and Crotalidae venoms, which are hemotoxic, are responsible for most of the envenomations around the world. Administration of antivenins aimed at the neutralization of toxins in humans is prone to potential risks. Neutralization of snake venom toxins has been achieved through different approaches: plant extracts have been utilized in etnomedicine. Direct electric current from low voltage showed neutralizing properties against venom phospholipase A2 and metalloproteases. This mini-review summarizes new achievements in venom key component inhibition. A deeper knowledge of alternative ways to inhibit venom toxins may provide supplemental treatments to serum therapy.

Hypothesis of snake and insect venoms against Human Immunodeficiency Virus: a review

Background

Snake and insect venoms have been demonstrated to have beneficial effects in the treatment of certain diseases including drug resistant human immunodeficiency virus (HIV) infection. We evaluated and hypothesized the probable mechanisms of venoms against HIV.

Methods

Previous literatures published over a period of 30 years (1979-2009) were searched using the key words snake venom, insect venom, mechanisms and HIV. Mechanisms were identified and discussed.

Results & Conclusion

With reference to mechanisms of action, properties and components of snake venom such as sequence homology and enzymes (protease or L- amino acid oxidase) may have an effect on membrane protein and/or act against HIV at multiple levels or cells carrying HIV virus resulting in enhanced effect of anti-retroviral therapy (ART). This may cause a decrease in viral load and improvement in clinical as well as immunological status. Insect venom and human Phospholipase A₂ (PLA₂) have potential anti-viral activity through inhibition of virion entry into the cells. However, all these require further evaluation in order to establish its role against HIV as an independent one or as a supplement.

Identification and characterization of phospholipase A2 inhibitors from the serum of the Japanese rat snake, Elaphe climacophora

Two distinct phospholipase A2 (PLA2) inhibitory proteins (PLIs) were purified from the serum of the Japanese rat snake, Elaphe climacophora. The 150-kDa inhibitor, a trimer of a 50-kDa subunit, specifically inhibited the basic PLA2 purified from the venom of Gloydius brevicaudus, whereas the 120-kDa one composed of two distinct 25-kDa subunits. A and B, inhibited both the acidic and basic PLA2s of G. brevicaudus. On the basis of their amino acid sequences, these inhibitors were assigned as PLI beta and PLI gamma, respectively. A PLI alpha homolog (PLI alpha-like protein; PLI alpha-LP) having an apparent molecular weight of 50-kDa and composed of 15-kDa subunits was also purified from the E. climacophora serum. This homolog was immunoreactive with antibody raised against the G. brevicaudus PLI alpha, but lacked in the inhibitory activity toward the acidic and basic PLA2s. The cDNAs encoding PLI alpha-LP, PLI beta, PLI gamma-A, and PLI gamma-B were cloned from liver RNA, and their nucleotide sequences were compared with those of other venomous and non-venomous snakes.

Fast method for monitoring phospholipase A2 activity by liquid chromatography-electrospray ionization mass spectrometry

A new liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method for the fast determination of phospholipase A(2) (PLA(2)) activity has been developed. For the first time, the method allows the parallel detection of glycerophosphatidylcholine (GroPCho) as PLA(2) substrate as well as of its products fatty acid (FA) and lyso-GroPCho. ESI-MS was carried out in negative ion mode, detecting the FA as [M-H](-) ions and the lyso-GroPCho and GroPCho as acetate adducts [M+Ac](-). Utilizing a fast gradient on a short C(5)-modified silica gel column with 3 microm particles, five GroPChos, five FAs and six lyso-GroPChos could be separated according to their chain length in less than 3 min. A very high average chromatographic efficiency of 41,200 theoretical plates (plate height 0.5 microm) was achieved for the separation of the GroPChos. The method was applied for monitoring the release of arachidonic acid (20:4 FA) and 1-stearoyl-lyso-sn-GroPCho (18:0 GroPCho) from unilamellar vesicles of 1-stearoyl-2-arachidonoyl-sn-GroPCho (18:0/20:4 GroPCho). With a limit of detection of 0.5 pmol (total amount injected on column) for the FAs and lyso-GroPChos and 1.5 pmol for the GroPChos as well as a linear range of 1.5 decades, the method has proven to be suitable for the monitoring of different secretory PLA(2) (sPLA(2)) conversions. Furthermore, it was applied to screen a small library of PLA(2) inhibitors for their activity towards sPLA(2) type V and snake venom of Bothrops moojeni. In both cases, active samples could be directly identified. With its short analysis time, its high chromatographic efficiency and the parallel detection of substrate and all products, the developed LC-ESI-MS method is well suited for the analysis of PLA(2) activity.

Prospection, structural analysis and phylogenetic relationships of endogenous gamma-phospholipase A(2) inhibitors in Brazilian Bothrops snakes (Viperidae, Crotalinae)

During the last 20 years, there have been an increasing number of reports on endogenous phospholipase A(2) inhibitors (PLIs) in the sera of snakes. These studies have demonstrated the existence of three different structural classes of PLIs (alpha, beta and gamma). The gamma class members are potent inhibitors of phospholipases A(2) (PLA(2)) from the venom of Viperidae snakes. These enzymes, together with the mammalian pro-inflammatory PLA(2), belong to the IIA class of the PLA(2)-superfamily. Although coming from distinct sources, these phospholipases A(2) share main structural features. For this reason, gammaPLIs have been considered as potential models for the development of selective inhibitors of pro-inflammatory PLA(2) in humans. In spite of the rich diversity of the ophidian fauna in Brazil, only two gammaPLI representatives, from Crotalus durissus terrificus and Lachesis muta, have been described in Brazilian snakes so far. Here we investigated the presence of transcripts of novel gammaPLIs in six Bothrops species (Viperidae, Crotalinae) commonly found in our country: Bothrops alternatus, Bothrops erythromelas, Bothrops jararaca, Bothrops jararacussu, Bothrops moojeni and Bothrops neuwiedi. gammaPLI transcripts were present in every species analysed. The deduced mature proteins possessed 181 amino acid residues following a 19-residue signal peptide, similar to the gammaPLIs from C. d. terrificus taken as our model, with the exception of the deduced proteins from B. erythromelas and B. neuwiedi snakes. In these particular cases, an insertion of 4-amino acid residues was consistently present. A Bayesian tree was obtained for the Brazilian Bothrops gammaPLIs, showing four clusters: (1) L. muta and B. jararacussu, (2) B. alternatus, (3) B. erythromelas and B. neuwiedi, (4) B. jararaca and B. moojeni. Detailed structural analysis and further comparisons of these novel Bothrops inhibitors with gammaPLIs from New and Old World snakes are provided.

An alpha-type phospholipase A(2) inhibitor from Bothrops jararacussu snake plasma: structural and functional characterization

An inhibitory protein that neutralizes the enzymatic, toxic and pharmacological activities of several phospholipases A(2) from Bothrops venoms was isolated from B. jararacussu snake plasma by affinity chromatography using the immobilized myotoxin BthTX-I on Sepharose gel. Biochemical characterization of this inhibitory protein, denominated alphaBjussuMIP, showed it to be an oligomeric glycoprotein with M(r) of 24,000 for the monomeric subunit. Secondary structural analysis by circular dichroism revealed 44% alpha-helix, 18% beta-sheet, 10% beta-turn and 28% random coil structures. Circular dichroism spectroscopy indicated that no significant alterations in the secondary structure of either alphaBjussuMIP or the target protein occur following their interaction. The product from the reaction with reverse transcriptase produced a cDNA fragment of 432 bp that codifies for a mature protein of 144 amino acid residues. The first 21 amino acid residues from the N-terminal and five tryptic peptides were characterized by mass spectrometry of the mature protein and confirmed by the nucleotide sequence. Alignment of alphaBjussuMIP with other snake inhibitors showed a sequence similarity of 73-92% with these alphaPLIs. alphaBjussuMIP was relatively stable within the pH range of 6-12 and temperatures from 0 degrees C to 80 degrees C, even after deglycosylation. The results showed effects against Bothrops phospholipase A(2) activities (enzymatic, edema inducing, myotoxic, cytotoxic and bactericidal), suggesting that alphaBjussuMIP may prove useful in the treatment of snakebite envenomations.

Subunit structure and inhibition specificity of alpha-type phospholipase A2 inhibitor from Protobothrops flavoviridis

The alpha-type phospholipase A2 inhibitor (PLIalpha) in the plasma of the Habu snake, Protobothrop flavoviridis, was shown to be a trimer of two homologous subunits, PLIalpha-A and PLIalpha-B, each of which contains one C-type lectin-like domain (CTLD). Since one molecule of trimeric PLIalpha binds stoichiometrically to one molecule of P. flavoviridis acidic phospholipase A2 (PLA2), the trimeric structure is critical for its inhibitory activity. Hydrophobic chromatography separated the purified P. flavoviridis PLIalpha into four different trimeric subspecies, A3-PLIalpha, A2B-PLIalpha, AB2-PLIalpha, and B3-PLIalpha, with different combinations of the two subunits. The trimeric PLIalpha could be reconstituted from the purified subunits, and the four different trimeric subspecies were formed through random association of the two subunits. The inhibitory activity of the PLIalpha-A homotrimer (A3-PLIalpha) was more specific than that of the PLIalpha-B homotrimer (B3-PLIalpha). This difference in inhibitory properties between the two homotrimers was probably caused by the amino acid differences at residues 10-37.

Purification and characterization of antitoxic proteins from the serum of Agkistrodon halys Pallas

In this study, the authors report the purification and characterization of antitoxic proteins from the serum of Agkistrodon halys Pallas. Two antitoxic proteins have been successfully isolated by the methods of (NH4)(2)SO(4) fractional precipitation, chromatography and preparative discontinuous polyacrylamide gel electrophoresis (PAGE). We have measured their molecular weights by Sephadex G-150 chromatography and 0.1% SDS-Tris-HCl discontinue PAGE respectively. Antitoxin I was about 138,000+/-40 Da and antitoxin II was about 76,000+/-40 Da, they are all single-chain peptides. We have measured their capacity to neutralize the toxicity of agkistrodotoxin (ATX), and their capacity to inhibit the PLA(2) activity of ATX. The results showed that antitoxin I could increase LD(50) of ATX from 0.25+/-0.05 to 0.445+/-0.13 mg/kg, decrease its PLA(2) activity from 2.36 to 1.72 microm/mg min, and antitoxin II could increase LD(50) of ATX from 0.25+/-0.05 to 0.56+/-0.12 mg/kg, decrease Phospholipase A(2) (PLA(2)) activity from 2.36 to 1.2 microm/mg min. When the natural antitoxins were mixed with different amounts of ATX and inoculated intraperitonially into eight mice, it was found that 0.5 mg antitoxin I could neutralize the toxicity of 0.4 mg ATX and 0.5 mg antitoxin II could neutralize the toxicity of 0.5 mg ATX completely. These antitoxic proteins could neutralize the toxicity of ATX completely and inhibit ATX's PLA(2) activity partially.

Isolation, characterization and molecular cloning of AnMIP, a new alpha-type phospholipase A2 myotoxin inhibitor from the plasma of the snake Atropoides nummifer (Viperidae: Crotalinae)

A new phospholipase A(2) (PLA(2))-inhibitory protein was isolated from the plasma of Atropoides nummifer, a crotaline snake from Central America. This inhibitor was named AnMIP, given its ability to neutralize the activity of basic PLA(2) myotoxins of its own and related venoms. The cDNA of AnMIP was cloned and sequenced, showing that it belongs to the alpha group of phospholipase A(2) inhibitors (PLIs). AnMIP appears as a homotrimer in the native state, held together by non-covalent forces, with a subunit molecular mass of 22,247-22,301 and an isoelectric point of 4.1-4.7. This trimeric structure is the first observed in a PLIalpha from American crotaline snakes, previously reported only in Asian species. Sequencing, mass spectrometry, and analytical isoelectrofocusing indicated the existence of isoforms, as reported for other PLIalphas isolated from snake plasma. The inhibitory profile of AnMIP showed specificity towards group II PLA(2)s, either belonging to the catalytically-active (D49) or -inactive (K49) subtypes, exemplified in this study by Bothrops asper myotoxin I and A. nummifer myotoxin II, respectively. By phylogenetic analysis it was shown that AnMIP is closely related to CgMIP-II, previously isolated from the plasma of Cerrophidion godmani, showing 93% amino acid sequence identity.

Expression of recombinant human antibody fragments capable of inhibiting the phospholipase and myotoxic activities of Bothrops jararacussu venom

Phospholipases A(2) are components of Bothrops venoms responsible for disruption of cell membrane integrity via hydrolysis of its phospholipids. This study used a large nonimmune human scFv library named Griffin.1 (MRC, Cambridge, UK) for selection of recombinant antibodies against antigens present in Bothrops jararacussu venom and identification of specific antibodies able to inhibit phospholipase activity. Four clones were identified as capable of inhibiting this activity in vitro. These clones were able to reduce in vivo the myotoxic activity of BthTX-I and BthTX-II PLA(2), but had no effect on the in vitro anticoagulant activity of BthTX-II. This work shows the potential of using recombinant scFv libraries in the search for antibodies that neutralize relevant venom components.

Bothrops moojeni myotoxin-II, a Lys49-phospholipase A2 homologue: an example of function versatility of snake venom proteins

MjTX-II, a myotoxic phospholipase A(2) (PLA(2)) homologue from Bothrops moojeni venom, was functionally and structurally characterized. The MjTX-II characterization included: (i) functional characterization (antitumoral, antimicrobial and antiparasitic effects); (ii) effects of structural modifications by 4-bromophenacyl bromide (BPB), cyanogen bromide (CNBr), acetic anhydride and 2-nitrobenzenesulphonyl fluoride (NBSF); (iii) enzymatic characterization: inhibition by low molecular weight heparin and EDTA; and (iv) molecular characterization: cDNA sequence and molecular structure prediction. The results demonstrated that MjTX-II displayed antimicrobial activity by growth inhibition against Escherichia coli and Candida albicans, antitumoral activity against Erlich ascitic tumor (EAT), human breast adenocarcinoma (SK-BR-3) and human T leukemia cells (JURKAT) and antiparasitic effects against Schistosoma mansoni and Leishmania spp., which makes MjTX-II a promising molecular model for future therapeutic applications, as well as other multifunctional homologous Lys49-PLA(2)s or even derived peptides. This work provides useful insights into the structural determinants of the action of Lys49-PLA(2) homologues and, together with additional strategies, supports the concept of the presence of others "bioactive sites" distinct from the catalytic site in snake venom myotoxic PLA(2)s.

Biological and Structural Characterization of a New PLA2 from the Crotalus durissus collilineatus Venom

In the present article we report on the biological characterization and amino acid sequence of a new basic Phospholipases A2 (PLA2) isolated from the Crotalus durissus collilineatus venom (Cdcolli F6), which showed the presence of 122 amino acid residues with a pI value of 8.3, molecular mass of 14 kDa and revealed an amino acid sequence identity of 80% with crotalic PLA2s such as Mojave B, Cdt F15, and CROATOX. This homology, however, dropped to 50% if compared to other sources of PLA2s such as from the Bothrops snake venom. Also, this PLA2 induced myonecrosis, although this effect was lower than that of BthTx-I or whole crotoxin and it was able to induce a strong blockage effect on the chick biventer neuromuscular preparation, independently of the presence of the acid subunid (crotapotin). The neurotoxic effect was strongly reduced by pre-incubation with heparin or with anhydrous acetic acid and p-BPB showed a similar reduction. The p-BPB did not reduce significantly the myotoxic activity induced by the PLA2, but the anhydrous acetic acid treatment and the pre-incubation of PLA2 with heparin reduced significantly its effects. This protein showed a strong antimicrobial activity against Xanthomonas axonopodis passiforae (Gram-negative), which was drastically reduced by incubation of this PLA2 with p-BPB, but this effect was marginally reduced after treatment with anhydrous acetic acid. Our findings here allow to speculate that basic amino acid residues on the C-terminal and molecular regions near catalytic site regions such as Calcium binding loop or beta-wing region may be involved in the binding of this PLA2 to the molecular receptor to induce the neurotoxic effect. The bactericidal effect, however, was completely dependent on the enzymatic activity of this protein.

Bactericidal and neurotoxic activities of two myotoxic phospholipases A2 from Bothrops neuwiedi pauloensis snake venom

Two basic myotoxic PLA(2)s, namely BnpTX-I and II, were isolated from Bothrops neuwiedi pauloensis snake venom through three chromatographic steps: ion-exchange chromatography on CM-Sepharose, gel filtration on Sephadex G-50 and reverse phase HPLC on a C18 column. Both PLA(2)s showed a M(r) around 14,000 for the monomer and 28,000 for the dimer (as estimated by SDS-PAGE), pI approximately 7.8 and approximately 121 amino acid residues cross-linked by seven disulfide bonds. The N-terminal sequences revealed significant homology with Asp49 basic myotoxic PLA(2)s from other snake venoms. The catalytic and anticoagulant activities of BnpTX-I were higher than those of BnpTX-II. Both were able to induce cytotoxicity in vitro, as well as, myotoxicity, edema and lethality in mice. BnpTX-I also induced neurotoxic effect on mouse neuromuscular preparations and bactericidal activity on Eschericia coli and Staphylococcus aureus. After chemical modification of BnpTX-I with BPB or incubation with EDTA or Mn(2+) ions, the catalytic activity was completely abolished, while the toxic and pharmacological activities were partially reduced. Interaction with heparin inhibited the cytotoxic and bactericidal effects. Anti-BthTX-I, anti-BthTX-II and anti-115-129-C terminal antibodies strongly recognize both BnpTX-I and II. It is shown that the neurotoxic effect induced by B. neuwiedi pauloensis venom is due to the presence of myotoxic PLA(2)s. The data also corroborate the hypothesis of a partial dissociation between toxic and enzymatic domains. In addition, BnpTX-I displays a heparin binding C-terminal region, which is probably responsible for the cytotoxic and bactericidal effects.

Effect of crotapotin on the biological activity of Asp49 and Lys49 phospholipases A(2) from Bothrops snake venoms

Myonecrosis, in addition to edema and other biological manifestations, are conspicuous effects of Bothrops snake venoms, some of them caused by phospholipases A(2) (PLA(2)s). Asp49-PLA(2)s are catalytically active, whereas Lys49-PLA(2)s, although highly toxic, have little or no enzymatic activity upon artificial substrates, due to a substitution of lysine for aspartic acid at position 49. Crotapotin (CA), the acidic counterpart of crotoxin PLA(2) (CB), is a PLA(2)-like protein from Crotalus durissus terrificus snake venom, and is considered a chaperone protein for CB, able to increase its lethality about ten fold, but to inhibit the formation of the rat paw edema induced by carrageenin and by snake venoms. In this study, we demonstrate that CA significantly inhibits the edema induced by BthTX-I (23% inhibition), BthTX-II (27%), PrTX-I (25%), PrTX-III (35%) and MjTX-II (10%) on the mouse paw. CK levels evoked by isolated Asp49 or Lys49-PLA(2)s were reduced by 40% to 54% in the presence of CA and, in all cases, the membrane damaging activity of the toxins was also reduced. Circular dichroism spectra of the PLA(2)s in the presence and absence of CA showed that there was not any detectable secondary structural modification due to association between CA and the myotoxins. However, Fourier Transformed Infrared (FT-IR) analysis indicated that ionic and hydrophobic contacts contributed to stabilize this interaction.

Toxins in anti-nociception and anti-inflammation

The use of toxins as novel molecular probes to study the structure-function relationship of ion-channels and receptors as well as potential therapeutics in the treatment of wide variety of diseases is well documented. The high specificity and selectivity of these toxins have attracted a great deal of interest as candidates for drug development. This review highlights the involvement of the proteins and peptide toxins as well as non-proteinaceous compounds derived from both venomous and non-venomous animals, in anti-nociception and anti-inflammation. The possible mechanisms of these potential therapeutic agents and possible clinical applications in the treatment of pain and inflammation are also summarized.

Chemical modifications of phospholipases A2 from snake venoms: effects on catalytic and pharmacological properties

Phospholipases A2 (PLA2s) constitute major components of snake venoms and have been extensively investigated not only because they are very abundant in these venoms but mainly because they display a wide range of biological effects, including neurotoxic, myotoxic, cytotoxic, edema-inducing, artificial membrane disrupting, anti-coagulant, platelet aggregation inhibiting, hypotensive, bactericidal, anti-HIV, anti-tumoral, anti-malarial and anti-parasitic. Due to this functional diversity, these structurally similar proteins aroused the interest of many researchers as molecular models for study of structure-function relationships. One of the main experimental strategies used for the study of myotoxic PLA2s is the traditional chemical modification of specific amino acid residues (His, Met, Lys, Tyr, Trp and others) and examination of the consequent effects upon the enzymatic, toxic and pharmacological activities. This line of research has provided useful insights into the structural determinants of the action of these enzymes and, together with additional strategies, supports the concept of the presence of 'pharmacological sites' distinct from the catalytic site in snake venom myotoxic PLA2s.

Natural phospholipase A(2) myotoxin inhibitor proteins from snakes, mammals and plants

A renewed interest in the phenomenon of inter- and intra-species resistance towards the toxicity of snake venoms, coupled with the search for new strategies for treatment of snake envenomations, has prompted the discovery of proteins which neutralize the major toxic components of these venoms. Among these emerging groups of proteins are inhibitors of toxic phospholipases A2 (PLA2s), many of which exhibit a wide range of toxic effects including muscle-tissue damage, neurotoxicity, and inflammation. These proteins have been isolated from both venomous and non-venomous snakes, mammals, and most recently from medicinal plant extracts. The snake blood-derived inhibitors have been grouped into three major classes, alpha, beta, and gamma, based on common structural motifs found in other proteins with diverse physiological properties. In mammals, DM64, an anti-myotoxic protein isolated from opossum serum, belongs to the immunoglobulin super gene family and is homologous to human alpha1B-glycoprotein and DM43, a metalloproteinase inhibitor from the same organism. In plants, a short note is made of WSG, a newly described anti-toxic-PLA2 glycoprotein isolated from Withania somnifera (Ashwaganda), a medicinal plant whose aqueous extracts neutralize the PLA2 activity of the Naja naja venom. The implications of these new groups of PLA2 toxin inhibitors in the context of our current understanding of snake biology as well as in the development of novel therapeutic reagents in the treatment of snake envenomations worldwide are discussed.