Three snake venoms from Bothrops genus induced apoptosis and cell cycle arrest in K562 human leukemic cell line

Cancer is indisputably one of the leading causes of death worldwide. Snake venoms are a potential source of bioactive compounds, complex mixtures constituted mainly of proteins and peptides with several pharmacological possibilities, including the potential to inhibit tumoral cell growth. In the present study, it was evaluated the antitumor effect of crude venom of Bothrops erythromelas (BeV), Bothrops jararaca (from Southern and Southeastern- BjsV and BjsdV, respectively) and Bothrops alternatus (BaV) in in vitro Chronic myeloid leukemia (CML) cancer cell line model. After 24 h of cell exposure to 10 and 50 μg/mL, BjsV, BjsdV, and BaV exerted a decrease in cell viability in both concentrations. BeV was not cytotoxic and, therefore wasn't chosen for further mechanism of action investigation. Furthermore, morphological alterations show modification typical of apoptosis. Also, was observes a significant cell cycle arrest in the S phase by BjsdV and BaV treatment. Flow cytometry evidenced the involvement of changes in the cell membrane permeability and the mitochondrial function by BjsV and BjsdV, corroborating with the triggering of the apoptotic pathway by the venom administration. BjsV, BjsdV, and BaV also led to extensive DNA damage and were shown to modulate the gene expression of transcripts related to the cell cycle progression and suppress the expression of the BCR-ABL1 oncogene. Altogether, these findings suggest that the venoms trigger the apoptosis pathway due to mitochondrial damage and cell cycle arrest, with modulation of intracellular pathways important for CML progression. Thus, indicating the pharmacological potential of these venoms in the development of new antitumoral compounds.

A rational in silico approach to identify inhibitors of Batroxrhagin from Bothrops atrox

Bothrops atrox venom comprises several types of bioactive molecules, enzymatic and non-enzymatic, among those, Batroxrhagin is the most predominant SVMP P-III enzyme, which are responsible for induction of local and systemic hemorrhage and muscle fibers damage, impairing regeneration. Due to great difficulties in establishing an antibothropic drug, new strategies must be addressed to achieve a more effective and efficient treatment. There are no studies of specific catalytic inhibitors of Batroxrhagin. However, there are in vitro studies that have described similar metalloprotease inhibitors. The inhibitor batimastat was used as a leading compound for the search and selection of similar candidates. This molecule is widely cited as a metalloprotease inhibitor and as an antimetastatic. In addition to batimastat-like molecules, four other reported metalloprotease inhibitors were included to compose the study's positive control group. Hence, 580 molecules were tested. The three-dimensional structure of B. atrox Batroxrhagin was predicted based on homologous structures using Modeller 9.20. Molecular docking calculation was performed using Autodock 4.2 and molecular surfaces and interactions were analyzed using Biovia/Discovery Studio 2017. Among 576 molecules, 42 similar to batismast resulted in a better energy of interaction than all positive controls, including batimastat itself. The batimastat-like molecules with lowest energy and positive controls were subjected to molecular dynamics for 30 ns in Gromacs 2019.4. This batimastat-like molecule produced better stability among all the Batroxrhagin-ligand complexes analyzed. Overall, the proposed compounds present justifiable evidence for future in vitro tests aiming to inhibit Batroxrhagin. Communicated by Ramaswamy H. Sarma.

Isolation of the Anticoagulant and Procoagulant Fractions of the Venom of Iranian Endemic Echis carinatus

Background

The venom of Echis carinatus contains both procoagulant and anticoagulant components that can either promote or block the blood coagulation cascade, and some of these components affect platelet function in different ways.

Objectives

The present study focuses on setting up a procedure for the purification of crude venom and designing appropriate clotting tests in order to characterize the procoagulant and anticoagulant fractions of E. carinatus venom.

Methods

Chromatographic methods, including gel filtration, ion-exchange chromatography, and reverse-phase high-performance liquid chromatography (HPLC), were applied for purifying these fractions. Coagulant activity testing, prothrombin time (PT), and activated partial thromboplastin time (APTT) were used to determine procoagulant and anticoagulant properties. For measuring molecular weight, 15% SDS-PAGE electrophoresis with a molecular weight standard ranging from 6.5 to 200 kDa was used.

Results

We obtained five fractions named F₁, F₂, F₃, F₄, and F₅. The F₁ and F₂ fractions showed procoagulant activity, and the F₅ fraction had anticoagulant activity. The molecular weight of F_2.4.2 from fraction F₂ and F_5.1 from fraction F₅ were analyzed by SDS-PAGE electrophoresis under the reducing condition. These factors were identified as a single protein band at the end of purification. The molecular weights of these purified fractions were estimated to be 7.5 kDa and 38 kDa for F_5.1(b) and F_2.4.2(b), respectively.

Conclusions

Our findings suggest an efficient and suitable procedure for the identification and purification of the procoagulant and anticoagulant factors of the venom of Iranian E. carinatus using the PT and APTT assays.

Pharmacological re-assessment of traditional medicinal plants-derived inhibitors as antidotes against snakebite envenoming: A critical review

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional healers have used medicinal plants to treat snakebite envenomation worldwide; however, mostly without scientific validation. There have been many studies on the therapeutic potential of the natural products against snake envenomation.

AIM OF THE STUDY

This review has highlighted snake venom inhibitory activity of bioactive compounds and peptides from plants that have found a traditional use in treating snakebite envenomation. We have systematically reviewed the scenario of different phases of natural snake venom inhibitors characterization covering a period from 1994 until the present and critically analysed the lacuna of the studies if any, and further scope for their translation from bench to bedside.

MATERIALS AND METHODS

The medicinal plant-derived compounds used against snakebite therapy were reviewed from the available literature in public databases (Scopus, MEDLINE) from 1994 till 2020. The search words used were 'natural inhibitors against snakebite,' 'natural products as therapeutics against snakebite,' 'natural products as antidote against snake envenomation,' ' snake venom toxin natural inhibitors,' 'snake venom herbal inhibitors'. However, the scope of this review does not include computational (in silico) predictions without any wet laboratory validation and snake venom inhibitory activity of the crude plant extracts. In addition, we have also predicted the ADMET properties of the identified snake venom inhibitors to highlight their valuable pharmacokinetics for future clinical studies.

RESULTS

The therapeutic application of plant-derived natural inhibitors to treat snakebite envenomation as an auxiliary to antivenom therapy has been gaining significant momentum. Pharmacological reassessment of the natural compounds derived from traditional medicinal plants has demonstrated inhibition of the principal toxic enzymes of snake venoms at various extents to curb the lethal and/or deleterious effects of venomous snakebite. Nevertheless, such molecules are yet to be commercialized for clinical application in the treatment of snakebite. There are many obstacles in the marketability of the plant-derived natural products as snake envenomation antidote and strategies must be explored for the translation of these compounds from drug candidates to their clinical application.

CONCLUSION

In order to minimize the adverse implications of snake envenomation, strategies must be developed for the smooth transition of these plant-derived small molecule inhibitors from bench to bedside. In this article we have presented an inclusive review and have critically analysed natural products for their therapeutic potential against snake envenomation, and have proposed a road map for use of natural products as antidote against snakebite.

Harnessing the Natural Toxic Metabolites in COVID-19

SARS-CoV-2 is a novel coronavirus and the cause of the recent pandemic; it is an enveloped β-coronavirus. SARS-CoV-2 appear in the Wuhan City of China for the first time and outspread worldwide quickly. Due to its person-to-person fast transmission, COVID-19 is becoming a global problem. SARS-CoV-2 enter into cells by using ACE2 receptors that are numerous in the lungs and finally can cause acute respiratory distress syndrome (ARDS). Dry cough, sore throat, fever, body pain, headache, GIT discomfort, diarrhoea, and fatigue are some of the COVID-19 symptoms. There is no definite and certain treatment for disease caused by SARS-CoV-2 till now. Some pharmacological effects of toxins, toxoids, and venoms have been proven, and their effects on some diseases have been evaluated. This study aimed to investigate the role of toxins, toxoids, and venom in the pathophysiology of COVID-19 disease.

BthTX-II from Bothrops jararacussu venom has variants with different oligomeric assemblies: An example of snake venom phospholipases A2 versatility

Phospholipases A₂ (PLA₂s) are found in almost every venomous snake family. In snakebites, some PLA₂s can quickly cause local myonecrosis, which may lead to permanent sequelae if antivenom is administered belatedly. They hydrolyse phospholipids in membranes through a catalytic calcium ions-dependent mechanism. BthTX-II is a basic PLA₂ and the second major component in the venom of Bothrops jararacussu. Herein, using the software SEQUENCE SLIDER, which integrates crystallographic, mass spectrometry and genetic data, we characterized the primary, tertiary and quaternary structure of two BthTX-II variants (called a and b), which diverge in 7 residues. Crystallographic structure BthTX-IIa is in a Tense-state with its distorted calcium binding loop buried in the dimer interface, contrarily, the novel BthTX-IIb structure is a monomer in a Relax-state with a fatty acid in the hydrophobic channel. Structural data in solution reveals that both variants are monomeric in neutral physiological conditions and mostly dimeric in an acidic environment, being catalytic active in both situations. Therefore, we propose two myotoxic mechanisms for BthTX-II, a catalytic one associated with the monomeric assembly, whereas the other has a calcium independent activity related to its C-terminal region, adopting a dimeric conformation similar to PLA₂-like proteins.

L-amino acid oxidase from snake venom: Biotransformation and induction of apoptosis in human colon cancer cells

This study evaluated the potential of antitumor activity of snake venom from Vipera ammodytes and L-amino acid oxidase from Crotalus adamanteus on different colorectal cancer cell lines through determination of cytotoxic activity by MTT assay, pro-apoptotic activity by acridine orange/ethidium bromide staining, and concentrations of redox status parameters (superoxide, reduced glutathione, lipid peroxidation) by colorimetric methods. The expression of genes involved in the biotransformation process and metabolite efflux was determined by qPCR method, while protein expression of glutathione synthetase and P-glycoprotein were analysed by immunocytochemistry. The analysis of cell death shows that snake venom dominantly leads cells to necrosis. Induction of apoptosis by L-amino acid oxidase was in correlation with oxidative disbalance in cancer cells. Gene expression profile of membrane transporters and CYP genes were different in each cell line and in correlation with their sensitivity of treatment. Our results show that L-amino acid oxidase from snake venom is a potent cytotoxic substance with pronounced pro-apoptotic activity. The inhibition of P-glycoprotein suggests that L-amino acid oxidase is a good substance for furter research of antitumor effect, with unexpressed potential for occurrence of drug resistance in vitro.

P-I metalloproteinases and L-amino acid oxidases from Bothrops species inhibit angiogenesis

BACKGROUND

Snake venoms are composed of pharmacologically active proteins that are evolutionarily diverse, stable and specific to targets. Hence, venoms have been explored as a source of bioactive molecules in treating numerous diseases. Recent evidences suggest that snake venom proteins may affect the formation of new blood vessels. Excessive angiogenesis has been implicated in several pathologies including tumours, diabetic retinopathy, arthritis, inter alia. In the present study, we have examined the effects of P-I metalloproteinases isolated from Bothrops moojeni (BmMP-1) and Bothrops atrox (BaMP-1) and L-amino acid oxidases (LAAO) isolated from B. moojeni (BmLAAO) and B. atrox (BaLAAO) on biochemical and functional aspects of angiogenesis.

METHODS

P-I metalloproteinases and LAAO were purified from venom by molecular size exclusion and ion-exchange chromatography and subsequently confirmed using mass spectrometry. The P-I metalloproteinases were characterized by azocaseinolytic, fibrinogenolytic and gelatinase activity and LAAO activity was assessed by enzyme activity on L-amino acids. Influence of these proteins on apoptosis and cell cycle in endothelial cells was analysed by flow cytometry. The angiogenic activity was determined by in vitro 3D spheroid assay, Matrigel tube forming assay, and in vivo agarose plug transformation in mice.

RESULTS

P-I metalloproteinases exhibited azocaseinolytic activity, cleaved α and partially β chain of fibrinogen, and displayed catalytic activity on gelatin. LAAO showed differential activity on L-amino acids. Flow cytometry analysis indicated that both P-I metalloproteinases and LAAO arrested the cells in G0/G1 phase and further induced both necrosis and apoptosis in endothelial cells. In vitro, P-I metalloproteinases and LAAO exhibited significant anti-angiogenic properties in 3D spheroid and Matrigel models by reducing sprout outgrowth and tube formation. Using agarose plug transplants in mice harbouring P-I metalloproteinases and LAAO we demonstrated a marked disruption of vasculature at the periphery.

CONCLUSION

Our research suggests that P-I metalloproteinases and LAAO exhibit anti-angiogenic properties in vitro and in vivo.

Synergism of in vitro plasmodicidal activity of phospholipase A2 isoforms isolated from panamanian Bothrops asper venom

Bothrops asper is one of the most important snake species in Central America, mainly because of its medical importance in countries like Ecuador, Panama and Costa Rica, where this species causes a high number of snakebite accidents. Several basic phospholipases A₂ (PLA₂s) have been previously characterized from B. asper venom, but few studies have been carried out with its acidic isoforms. In addition, since snake venom is a rich source of bioactive substances, it is necessary to investigate the biotechnological potential of its components. In this context, this study aimed to carry out the biochemical characterization of PLA₂ isoforms isolated from B. asper venom and to evaluate the antiparasitic potential of these toxins. The venom and key fractions were subjected to different chromatographic steps, obtaining nine PLA₂s, four acidic ones (BaspAc-I, BaspAc-II, BaspAc-III and BaspAc-IV) and five basic ones (BaspB-I, BaspB-II, BaspB-III, BaspB-IV and BaspB-V). The isoelectric points of the acidic PLA₂s were also determined, which presented values ranging between 4.5 and 5. The findings indicated the isolation of five unpublished isoforms, four Asp49-PLA, corresponding to the group of acidic isoforms, and one Lys49-PLA₂-like. Acidic PLA₂s catalyzed the degradation of all substrates evaluated; however, for the basic PLA₂s, there was a preference for phosphatidylglycerol and phosphatidic acid. The antiparasitic potential of the toxins was evaluated, and the acidic PLA₂s demonstrated action against the epimastigote forms of T. cruzi and promastigote forms of L. infantum, while the basic PLA₂s BaspB-II and BaspB-IV showed activity against P. falciparum. The results indicated an increase of up to 10 times in antiplasmodial activity, when the Asp49-PLA₂ and Lys49-PLA₂ were associated with one another, denoting synergistic action between these PLA₂ isoforms. These findings correspond to the first report of synergistic antiplasmodial action for svPLA₂s, demonstrating that these molecules may be important targets in the search for new antiparasitic agents.

Mechanistic insights of snake venom disintegrins in cancer treatment

Snake venoms are a potential source of various enzymatic and non-enzymatic compounds with a defensive role for the host. Various peptides with significant medicinal properties have been isolated and characterized from these venoms. Few of these are FDA approved. They inhibit tumor cells adhesion, migration, angiogenesis and metastasis by inhibiting integrins on transmembrane cellular surfaces. This plays important role in delaying tumor growth, neovascularization and development. Tumor targeting and smaller size make them ideal candidates as novel therapeutic agents for cancer treatment. This review is based on sources of these disintegrins, their targeting modality, classification and underlying anti-cancer potential.

Envenomation by opisthoglyphous snake Thamnodynastes hypoconia (Cope, 1860) (Dipsadinae: Tachymenini) in southern Brazil

We report here a case of human envenoming by Thamnodynastes hypoconia, a common and abundant non-front-fanged snake belonging to the subfamily Dipsadinae. The case was registered in the municipality of Tapes, Rio Grande do Sul state, Brazil, in a 27-year-old female. The snakebite was on the wrist of the left arm while handling the snake in a field outing. No pain sensation was noted during the bite, and after 20 minutes edema developed along the hand and forearm with a slight sensation of numbness and mild pain when moving the fingers. After 15 hours, the victim began to develop erythema, paraesthesia, and a sensation of warmth at the bite site. After 30 hours, ecchymosis occurred on the fingers and forearms, and the edema began to decrease. After 70 hours from the time of the bite, ecchymosis along with pruritus and mild pain were still evident. The patient was treated with prescribed medications, and after 7 days no further symptoms were observed. This is the first reported case of envenoming by T. hypoconia.

Snake venom-derived bradykinin-potentiating peptides: A promising therapy for COVID-19?

The severe acute respiratory syndrome coronavirus‐2 (SARS‐COV‐2), a novel coronavirus responsible for the recent infectious pandemic, is known to downregulate angiotensin‐converting enzyme‐2 (ACE2). Most current investigations focused on SARS‐COV‐2‐related effects on the renin–angiotensin system and especially the resultant increase in angiotensin II, neglecting its effects on the kinin–kallikrein system. SARS‐COV‐2‐induced ACE2 inhibition leads to the augmentation of bradykinin 1‐receptor effects, as ACE2 inactivates des‐Arg9‐bradykinin, a bradykinin metabolite. SARS‐COV‐2 also decreases bradykinin 2‐receptor effects as it affects bradykinin synthesis by inhibiting cathepsin L, a kininogenase present at the site of infection and involved in bradykinin production. The physiologies of both the renin–angiotensin and kinin–kallikrein system are functionally related suggesting that any intervention aiming to treat SARS‐COV‐2‐infected patients by triggering one system but ignoring the other may not be adequately effective. Interestingly, the snake‐derived bradykinin‐potentiating peptide (BPP‐10c) acts on both systems. BPP‐10c strongly decreases angiotensin II by inhibiting ACE, increasing bradykinin‐related effects on the bradykinin 2‐receptor and increasing nitric oxide‐mediated effects. Based on a narrative review of the literature, we suggest that BPP‐10c could be an optimally effective option to consider when aiming at developing an anti‐SARS‐COV‐2 drug.

Venoms and Isolated Toxins from Snakes of Medical Impact in the Northeast Argentina: State of the Art. Potential Pharmacological Applications

Among the ophidians that inhabit the Northeast of Argentina, the genus Bothrops such as B. alternatus and B. diporus species (also known as yararás) and Crotalus durisus terrificus (named cascabel), represent the most studied snake venom for more than thirty years. These two genera of venomous snakes account for the majority of poisonous snake envenomations and therefore, constitute a medical emergency in this region. This review presents a broad description of the compiled knowledge about venomous snakebite: its pathophysiological action, protein composition, isolated toxins, toxin synergism, toxin-antitoxin cross-reaction assays. Properties of some isolated toxins support a potential pharmacological application.

Potential of Matrix Metalloproteinase Inhibitors for the Treatment of Local Tissue Damage Induced by a Type P-I Snake Venom Metalloproteinase

Snake bite envenoming is a public health problem that was recently included in the list of neglected tropical diseases of the World Health Organization. In the search of new therapies for the treatment of local tissue damage induced by snake venom metalloproteinases (SVMPs), we tested the inhibitory activity of peptidomimetic compounds designed as inhibitors of matrix metalloproteinases on the activities of the SVMP Batx-I, from Bothrops atrox venom. The evaluated compounds show great potential for the inhibition of Batx-I proteolytic, hemorrhagic and edema-forming activities, especially the compound CP471474, a peptidomimetic including a hydroxamate zinc binding group. Molecular dynamics simulations suggest that binding of this compound to the enzyme is mediated by the electrostatic interaction between the hydroxamate group and the zinc cofactor, as well as contacts, mainly hydrophobic, between the side chain of the compound and amino acids located in the substrate binding subsites S1 and S1′. These results show that CP471474 constitutes a promising compound for the development of co-adjuvants to neutralize local tissue damage induced by snake venom metalloproteinases.

Isolation, Biochemical Characterization and Antiparasitic Activity of BmatTX-IV, A Basic Lys49-Phospholipase A2 from the Venom of Bothrops mattogrossensis from Paraguay

Background:

Functional and structural diversity of proteins of snake venoms is coupled with a wide repertoire of pharmacological effects. Snake venoms are targets of studies linked to searching molecules with biotechnological potential.

Methods:

A homologue phospholipase A2 (BmatTX-IV) was obtained using two chromatographic techniques. Mass spectrometry and two-dimensional gel electrophoresis were used to determine the molecular mass and isoelectric point, respectively. By means of Edman degradation chemistry, it was possible to obtain the partial sequence of amino acids that comprise the isolated toxin. Trypanocidal, leishmanicidal and cytoxic activity against Trypanosoma cruzi, Leishmania infantum and murine fibrobasts was determinated.

Results:

Combination of both chromatographic steps used in this study demonstrated efficacy to obtain the PLA2-Lys49. BmatTX-IV showed molecular mass and isoelectric point of 13.55 kDa and 9.3, respectively. Amino acid sequence of N-terminal region (51 residues) shows the presence of Lys49 residue at position 49, a distinctive trait of enzymatically inactive PLA2. Bothrops mattogrossensis snake venom showed IC50 values of 11.9 μg/mL against Leishmania infantum promastigotes and of 13.8 μg/mL against Trypanosoma cruzi epimastigotes, respectively. On the other hand, the venom showed a high cytotoxic activity (IC50 value of 16.7 μg/mL) against murine fibroblasts, whereas the BmatTX-IV showed IC50 value of 81.2 μg/mL.

Conclusion:

Physicochemical and biological characterization of snake venoms components is critically important, since these complex mixtures provide a source of molecules with antiparasitic potential, making further studies necessary to identify and characterize components with higher efficacy and selectivity.

A perspective view of top-down proteomics in snake venom research

The venom produced by snakes contains complex mixtures of pharmacologically active proteins and peptides which play a crucial role in the pathophysiology of snakebite diseases. The deep understanding of venom proteomes can help to improve the treatment of this "neglected tropical disease" (as expressed by the World Health Organization [WHO]) and to develop new drugs. The most widely used technique for venom analysis is liquid chromatography/tandem mass spectrometry (LC/MS/MS)-based bottom-up (BU) proteomics. Considering the fact that multiple multi-locus gene families encode snake venom proteins, the major challenge for the BU proteomics is the limited sequence coverage and also the "protein inference problem" which result in a loss of information for the identification and characterization of toxin proteoforms (genetic variation, alternative mRNA splicing, single nucleotide polymorphism [SNP] and post-translational modifications [PTMs]). In contrast, intact protein measurements with top-down (TD) MS strategies cover almost complete protein sequences, and prove the ability to identify venom proteoforms and to localize their modifications and sequence variations.

Snake Venom Peptides: Tools of Biodiscovery

Nature endowed snakes with a lethal secretion known as venom, which has been fine-tuned over millions of years of evolution. Snakes utilize venom to subdue their prey and to survive in their natural habitat. Venom is known to be a very poisonous mixture, consisting of a variety of molecules, such as carbohydrates, nucleosides, amino acids, lipids, proteins and peptides. Proteins and peptides are the major constituents of the dry weight of snake venoms and are of main interest for scientific investigations as well as for various pharmacological applications. Snake venoms contain enzymatic and non-enzymatic proteins and peptides, which are grouped into different families based on their structure and function. Members of a single family display significant similarities in their primary, secondary and tertiary structures, but in many cases have distinct pharmacological functions and different bioactivities. The functional specificity of peptides belonging to the same family can be attributed to subtle variations in their amino acid sequences. Currently, complementary tools and techniques are utilized to isolate and characterize the peptides, and study their potential applications as molecular probes, and possible templates for drug discovery and design investigations.

Comprehensive Snake Venomics of the Okinawa Habu Pit Viper, Protobothrops flavoviridis, by Complementary Mass Spectrometry-Guided Approaches

The Asian world is home to a multitude of venomous and dangerous snakes, which are used to induce various medical effects in the preparation of traditional snake tinctures and alcoholics, like the Japanese snake wine, named Habushu. The aim of this work was to perform the first quantitative proteomic analysis of the Protobothrops flavoviridis pit viper venom. Accordingly, the venom was analyzed by complimentary bottom-up and top-down mass spectrometry techniques. The mass spectrometry-based snake venomics approach revealed that more than half of the venom is composed of different phospholipases A2 (PLA₂). The combination of this approach and an intact mass profiling led to the identification of the three main Habu PLA₂s. Furthermore, nearly one-third of the total venom consists of snake venom metalloproteinases and disintegrins, and several minor represented toxin families were detected: C-type lectin-like proteins (CTL), cysteine-rich secretory proteins (CRISP), snake venom serine proteases (svSP), l-amino acid oxidases (LAAO), phosphodiesterase (PDE) and 5'-nucleotidase. Finally, the venom of P. flavoviridis contains certain bradykinin-potentiating peptides and related peptides, like the svMP inhibitors, pEKW, pEQW, pEEW and pENW. In preliminary MTT cytotoxicity assays, the highest cancerous-cytotoxicity of crude venom was measured against human neuroblastoma SH-SY5Y cells and shows disintegrin-like effects in some fractions.

Comparative Venomics of the Vipera ammodytes transcaucasiana and Vipera ammodytes montandoni from Turkey Provides Insights into Kinship

The Nose-horned Viper (Vipera ammodytes) is one of the most widespread and venomous snakes in Europe, which causes high frequent snakebite accidents. The first comprehensive venom characterization of the regional endemic Transcaucasian Nose-horned Viper (Vipera ammodytes transcaucasiana) and the Transdanubian Sand Viper (Vipera ammodytes montandoni) is reported employing a combination of intact mass profiling and bottom-up proteomics. The bottom-up analysis of both subspecies identified the major snake protein families of viper venoms. Furthermore, intact mass profiling revealed the presence of two tripeptidic metalloprotease inhibitors and their precursors. While previous reports applied multivariate analysis techniques to clarify the taxonomic status of the subspecies, an accurate classification of Vipera ammodytestranscaucasiana is still part of the ongoing research. The comparative analysis of the viper venoms on the proteome level reveals a close relationship between the Vipera ammodytes subspecies, which could be considered to clarify the classification of the Transcaucasian Nose-horned Viper. However, the slightly different ratio of some venom components could be indicating interspecific variations of the two studied subspecies or intraspecies alternations based on small sample size. Additionally, we performed a bioactivity screening with the crude venoms against several human cancerous and non-cancerous cell lines, which showed interesting results against a human breast adenocarcinoma epithelial cell line. Several fractions of Vipera a. transcaucasiana demonstrated a strong cytotoxic effect on triple negative MDA MB 231 breast cancer cells.

Computational Studies of Snake Venom Toxins

Most snake venom toxins are proteins, and participate to envenomation through a diverse array of bioactivities, such as bleeding, inflammation, and pain, cytotoxic, cardiotoxic or neurotoxic effects. The venom of a single snake species contains hundreds of toxins, and the venoms of the 725 species of venomous snakes represent a large pool of potentially bioactive proteins. Despite considerable discovery efforts, most of the snake venom toxins are still uncharacterized. Modern bioinformatics tools have been recently developed to mine snake venoms, helping focus experimental research on the most potentially interesting toxins. Some computational techniques predict toxin molecular targets, and the binding mode to these targets. This review gives an overview of current knowledge on the ~2200 sequences, and more than 400 three-dimensional structures of snake toxins deposited in public repositories, as well as of molecular modeling studies of the interaction between these toxins and their molecular targets. We also describe how modern bioinformatics have been used to study the snake venom protein phospholipase A2, the small basic myotoxin Crotamine, and the three-finger peptide Mambalgin.

Snake Venom PLA2, a Promising Target for Broad-Spectrum Antivenom Drug Development

Snakebite envenomation is a neglected global health problem, causing substantial mortality, disability, and psychological morbidity, especially in rural tropical and subtropical zones. Antivenin is currently the only specific medicine for envenomation. However, it is restricted by cold storage, snakebite diagnosis, and high price. Snake venom phospholipase A₂s (svPLA₂s) are found in all kinds of venomous snake families (e.g., Viperidae, Elapidae, and Colubridae). Along with their catalytic activity, svPLA₂s elicit a wide variety of pharmacological effects that play a pivotal role in envenomation damage. Hence, neutralization of the svPLA₂s could weaken or inhibit toxic damage. Here we overviewed the latest knowledge on the distribution, pathophysiological effects, and inhibitors of svPLA₂s to elucidate the potential for a novel, wide spectrum antivenom drug targeting svPLA₂s.

It is time for top-down venomics

The protein composition of animal venoms is usually determined by peptide-centric proteomics approaches (bottom-up proteomics). However, this technique cannot, in most cases, distinguish among toxin proteoforms, herein called toxiforms, because of the protein inference problem. Top-down proteomics (TDP) analyzes intact proteins without digestion and provides high quality data to identify and characterize toxiforms. Denaturing top-down proteomics is the most disseminated subarea of TDP, which performs qualitative and quantitative analyzes of proteoforms up to ~30 kDa in high-throughput and automated fashion. On the other hand, native top-down proteomics provides access to information on large proteins (> 50 kDA) and protein interactions preserving non-covalent bonds and physiological complex stoichiometry. The use of native and denaturing top-down venomics introduced novel and useful techniques to toxinology, allowing an unprecedented characterization of venom proteins and protein complexes at the toxiform level. The collected data contribute to a deep understanding of venom natural history, open new possibilities to study the toxin evolution, and help in the development of better biotherapeutics.

Isolation and biochemical characterization of bradykinin-potentiating peptides from Bitis gabonica rhinoceros

Background

Venoms represent a still underexplored reservoir of bioactive components that might mitigate or cure diseases in conditions in which conventional therapy is ineffective. The bradykinin-potentiating peptides (BPPs) comprise a class of angiotensin-I converting enzyme (ACE) inhibitors. The BPPs usually consist of oligopeptides with 5 to 13 residues with a high number of proline residues and the tripeptide Ile-Pro-Pro (IPP-tripeptide) in the C-terminus region and have a conserved N-terminal pyroglutamate residue. As a whole, the action of the BPPs on prey and snakebite victims results in the decrease of the blood pressure. The aim of this work was to isolate and characterize novel BPPs from the venom of Bitis gabonica rhinoceros.

Methods

The crude venom of B. g. rhinoceros was fractionated by size exclusion chromatography and the peptide fraction (<7 kDa) was separated by reverse phase chromatography (RP-HPLC) and analyzed by ESI-IT-TOF-MS/MS. One new BPP was identified, synthetized and assayed for ACE inhibition and, in vivo, for edema potentiation.

Results

Typical BPP signatures were identified in three RP-HPLC fractions. CID fragmentation presented the usual y-ion of the terminal P-P fragment as a predominant signal at m/z 213.1. De novo peptide sequencing identified one Bothrops-like BPP and one new BPP sequence. The new BPP was synthesized and showed poor inhibition over ACE, but displayed significant bradykinin-induced edema potentiation.

Conclusions

So far, few BPPs are described in Viperinae, and based on the sequenced peptides, two non-canonical sequences were detected. The possible clinical role of this new peptides remains unclear.

Strategies in 'snake venomics' aiming at an integrative view of compositional, functional, and immunological characteristics of venoms

This work offers a general overview on the evolving strategies for the proteomic analysis of snake venoms, and discusses how these may be combined through diverse experimental approaches with the goal of achieving a more comprehensive knowledge on the compositional, toxic, and immunological characteristics of venoms. Some recent developments in this field are summarized, highlighting how strategies have evolved from the mere cataloguing of venom components (proteomics/venomics), to a broader exploration of their immunological (antivenomics) and functional (toxicovenomics) characteristics. Altogether, the combination of these complementary strategies is helping to build a wider, more integrative view of the life-threatening protein cocktails produced by venomous snakes, responsible for thousands of deaths every year.

From Marine Venoms to Drugs: Efficiently Supported by a Combination of Transcriptomics and Proteomics

The potential of marine natural products to become new drugs is vast; however, research is still in its infancy. The chemical and biological diversity of marine toxins is immeasurable and as such an extraordinary resource for the discovery of new drugs. With the rapid development of next-generation sequencing (NGS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), it has been much easier and faster to identify more toxins and predict their functions with bioinformatics pipelines, which pave the way for novel drug developments. Here we provide an overview of related bioinformatics pipelines that have been supported by a combination of transcriptomics and proteomics for identification and function prediction of novel marine toxins.

Snake venom toxins: toxicity and medicinal applications

Snake venoms are complex mixtures of small molecules and peptides/proteins, and most of them display certain kinds of bioactivities. They include neurotoxic, cytotoxic, cardiotoxic, myotoxic, and many different enzymatic activities. Snake envenomation is a significant health issue as millions of snakebites are reported annually. A large number of people are injured and die due to snake venom poisoning. However, several fatal snake venom toxins have found potential uses as diagnostic tools, therapeutic agent, or drug leads. In this review, different non-enzymatically active snake venom toxins which have potential therapeutic properties such as antitumor, antimicrobial, anticoagulating, and analgesic activities will be discussed.

Mapping Proteoforms and Protein Complexes From King Cobra Venom Using Both Denaturing and Native Top-down Proteomics

Characterizing whole proteins by top-down proteomics avoids a step of inference encountered in the dominant bottom-up methodology when peptides are assembled computationally into proteins for identification. The direct interrogation of whole proteins and protein complexes from the venom of Ophiophagus hannah (king cobra) provides a sharply clarified view of toxin sequence variation, transit peptide cleavage sites and post-translational modifications (PTMs) likely critical for venom lethality. A tube-gel format for electrophoresis (called GELFrEE) and solution isoelectric focusing were used for protein fractionation prior to LC-MS/MS analysis resulting in 131 protein identifications (18 more than bottom-up) and a total of 184 proteoforms characterized from 14 protein toxin families. Operating both GELFrEE and mass spectrometry to preserve non-covalent interactions generated detailed information about two of the largest venom glycoprotein complexes: the homodimeric l-amino acid oxidase (∼130 kDa) and the multichain toxin cobra venom factor (∼147 kDa). The l-amino acid oxidase complex exhibited two clusters of multiproteoform complexes corresponding to the presence of 5 or 6 N-glycans moieties, each consistent with a distribution of N-acetyl hexosamines. Employing top-down proteomics in both native and denaturing modes provides unprecedented characterization of venom proteoforms and their complexes. A precise molecular inventory of venom proteins will propel the study of snake toxin variation and the targeted development of new antivenoms or other biotherapeutics.

Isolation and characterization of Bradykinin potentiating peptides from Agkistrodon bilineatus venom

Background

Snake venom is a source of many pharmacologically important molecules. Agkistrodon bilineatus commonly known as Cantil, is spread over Central America particularly in Mexico and Costa Rica. From the venom of Agkistrodon bilineatus we have isolated and characterised six hypotensive peptides, and two bradykinin inhibitor peptides. The IC-50 value of four synthesized peptides was studied, towards angiotensin converting enzyme, in order to study the structure-function relationship of these peptides.

Results

The purification of the peptides was carried out by size exclusion chromatography, followed by reverse phase chromatography. Sequences of all peptides were determined applying MALDI-TOF/TOF mass spectrometry. These hypotensive peptides bear homology to bradykinin potentiating peptides and venom vasodilator peptide. The peptide with m/z 1355.53 (M + H)⁺¹, and the corresponding sequence ZQWAQGRAPHPP, we identified for the first time. A precursor protein containing a fragment of this peptide was reported at genome level, (Uniprot ID P68515), in Bothrops insularis venom gland. These proline rich hypotensive peptides or bradykinin potentiating peptides are usually present in the venom of Crotalinae, and exhibit specificity in binding to the C domain of somatic angiotensin converting enzyme. Four of these hypotensive peptides, were selected and synthesized to obtain the required quantity to study their IC50 values in complex with the angiotensin converting enzyme. The peptide with the sequence ZLWPRPQIPP displayed the lowest IC50 value of 0.64 μM. The IC50 value of the peptide ZQWAQGRAPHPP was 3.63 μM.

Conclusion

The canonical snake venom BPPs classically display the IPP motif at the C-terminus. Our data suggest that the replacement of the highly conserved hydrophobic isoleucine by histidine does not affect the inhibitory activity, indicating that isoleucine is not mandatory to inhibit the angiotensin converting enzyme. The evaluation of IC 50 values show that the peptide with basic pI value exhibits a lower IC 50 value.

Bothropoides pauloensis venom effects on isolated perfused kidney and cultured renal tubular epithelial cells

Snake envenomation (Bothrops genus) is common in tropical countries and acute kidney injury is one of the complications observed in Bothrops snakebite with relevant morbidity and mortality. Here, we showed that Bothropoides pauloensis venom (BpV) decreased cell viability (IC50 of 7.5 μg/mL). Flow cytometry with annexin V and propidium iodide showed that cell death occurred predominantly by apoptosis and late apoptosis, through caspases 3 and 7 activation, mitochondrial membrane potential collapse and ROS overproduction. BpV reduced perfusion pressure, renal vascular resistance, urinary flow, glomerular filtration rate, percentage of sodium, chloride or potassium tubular transportation. These findings demonstrated that BpV cytotoxicity on renal epithelial cells might be responsible for the nephrotoxicity observed in isolated kidney.

A novel fibrinogenase from Agkistrodon acutus venom protects against LPS-induced endotoxemia via regulating NF-κB pathway

CONTEXT

Endotoxins including lipopolysaccharide (LPS) could cause endotoxemia which often results in excessive inflammation, organ dysfunction, sepsis, disseminated intravascular coagulation (DIC) or even death. Previously, a novel fibrinogenase (FII) showed protective effects on LPS-induced DIC via activating protein C and suppressing inflammatory cytokines.

OBJECTIVE

To evaluate whether FII has protective effect on LPS-induced endotoxemia in mice and learn about the role of NF-κB pathway in TNF-α producing process.

METHODS

BALB/C mice were intraperitoneally injected (i.p.) with (a) 30 mg/kg LPS, (b) LPS + 0.3 mg/kg FII, (c) LPS + 1.0 mg/kg FII, (d) LPS + 3.0 mg/kg FII or (e) saline. Both survival rate and organ function were tested, including alanine aminotransferase (ALT), blood urine nitrogen (BUN) and tissue section, and TNF-α was examined by ELISA. RAW 264.7 macrophage was administered with (a) LPS, (b) LPS + FII, (c) FII alone or (d) saline, and TNF-α and phosphorylation (P)-NF-κB (P65) were determined by Western blot.

RESULTS

The administration of LPS led to 65% mortality rate, a rise of serum TNF-α, BUN and ALT levels, and both liver and renal tissue damage were observed. While FII treatment significantly increased the survival rate of LPS-induced endotoxemia mice model, histopathology and protein analysis results also revealed that FII remarkably protected liver and renal from LPS damage as well as decreasing TNF-α level. In vitro, FII significantly decreased LPS-induced TNF-α production and the expression of P-NF-κB (P65).

CONCLUSIONS

Our findings suggested that FII had protective effect on LPS-induced endotoxemia and organ injuries by suppressing the activation of NF-κB which decreased TNF-α level.

Bioinformatics-Aided Venomics

Venomics is a modern approach that combines transcriptomics and proteomics to explore the toxin content of venoms. This review will give an overview of computational approaches that have been created to classify and consolidate venomics data, as well as algorithms that have helped discovery and analysis of toxin nucleic acid and protein sequences, toxin three-dimensional structures and toxin functions. Bioinformatics is used to tackle specific challenges associated with the identification and annotations of toxins. Recognizing toxin transcript sequences among second generation sequencing data cannot rely only on basic sequence similarity because toxins are highly divergent. Mass spectrometry sequencing of mature toxins is challenging because toxins can display a large number of post-translational modifications. Identifying the mature toxin region in toxin precursor sequences requires the prediction of the cleavage sites of proprotein convertases, most of which are unknown or not well characterized. Tracing the evolutionary relationships between toxins should consider specific mechanisms of rapid evolution as well as interactions between predatory animals and prey. Rapidly determining the activity of toxins is the main bottleneck in venomics discovery, but some recent bioinformatics and molecular modeling approaches give hope that accurate predictions of toxin specificity could be made in the near future.

Venomics of the beaked sea snake, Hydrophis schistosus: A minimalist toxin arsenal and its cross-neutralization by heterologous antivenoms

The venom proteome of Hydrophis schistosus (syn: Enhydrina schistosa) captured in Malaysian waters was investigated using reverse-phase HPLC, SDS-PAGE and high-resolution liquid chromatography-tandem mass spectrometry. The findings revealed a minimalist profile with only 18 venom proteins. These proteins belong to 5 toxin families: three-finger toxin (3FTx), phospholipase A2 (PLA2), cysteine-rich secretory protein (CRISP), snake venom metalloprotease (SVMP) and L-amino acid oxidase (LAAO). The 3FTxs (3 short neurotoxins and 4 long neurotoxins) constitute 70.5% of total venom protein, 55.8% being short neurotoxins and 14.7% long neurotoxins. The PLA2 family consists of four basic (21.4%) and three acidic (6.1%) isoforms. The minor proteins include one CRISP (1.3%), two SVMPs (0.5%) and one LAAO (0.2%). This is the first report of the presence of long neurotoxins, CRISP and LAAO in H. schistosus venom. The neurotoxins and the basic PLA2 are highly lethal in mice with an intravenous median lethal dose of <0.2 μg/g. Cross-neutralization by heterologous elapid antivenoms (Naja kaouthia monovalent antivenom and Neuro polyvalent antivenom) was moderate against the long neurotoxin and basic PLA2, but weak against the short neurotoxin, indicating that the latter is the limiting factor to be overcome for improving the antivenom cross-neutralization efficacy.

Omics meets biology: application to the design and preclinical assessment of antivenoms

Snakebite envenoming represents a neglected tropical disease that has a heavy public health impact worldwide, mostly affecting poor people involved in agricultural activities in Africa, Asia, Latin America and Oceania. A key issue that complicates the treatment of snakebite envenomings is the poor availability of the only validated treatment for this disease, antivenoms. Antivenoms can be an efficacious treatment for snakebite envenoming, provided they are safe, effective, affordable, accessible and administered appropriately. The shortage of antivenoms in various regions, particularly in Sub-Saharan Africa and some parts of Asia, can be significantly alleviated by optimizing the use of current antivenoms and by the generation of novel polyspecific antivenoms having a wide spectrum of efficacy. Complementing preclinical testing of antivenom efficacy using in vivo and in vitro functional neutralization assays, developments in venomics and antivenomics are likely to revolutionize the design and preclinical assessment of antivenoms by being able to test new antivenom preparations and to predict their paraspecific neutralization to the level of species-specific toxins.

Cytotoxic and apoptotic activities of the plancitoxin I from the venom of crown-of-thorns starfish (Acanthaster planci) on A375.S2 cells

This study reports on a cytotoxic toxin derived from the venom of the crown-of-thorns starfish Acanthaster planci (CAV). The protein toxin was isolated through both ion-exchange and gel-filtration chromatography, and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrum analyzes. The CAV was identified as plancitoxin I protein. The mechanistic role of the CAV toxin was explored in human malignant melanoma A375.S2 cell death. The results indicated that after incubation with CAV toxin, cells significantly decreased in A375.S2 cell viability and increased in the lactate dehydrogenase (LDH) level in a dose-dependent manner. The assays indicated that CAV toxin promoted reactive oxygen species (ROS) production, induced nitric oxide (NO) formation, lost mitochondrial membrane potential (ΔΨm) and induced inter-nucleosomal DNA fragmentation in A375.S2 cells. The molecular cytotoxicity of the CAV toxin was tested through evaluation of the apoptosis/necrosis ratio by double staining with annexin V-FITC and a propidium iodide (PI) assay. The results suggested that CAV toxin induced a cytotoxic effect in A375.S2 cells via the apoptotic procedure, and may be associated with the regulation of the p38 pathways.

Two color morphs of the pelagic yellow-bellied sea snake, Pelamis platura, from different locations of Costa Rica: snake venomics, toxicity, and neutralization by antivenom

The yellow-bellied sea snake, Pelamis platura, is the most broadly distributed snake species. Despite being endowed with a highly lethal venom, a proteomic analysis of its toxin composition was unavailable. The venoms of specimens collected in Golfo de Papagayo and Golfo Dulce (Costa Rica), where two distinctive color morphs occur, were chromatographically compared. The latter inhabits a fjord-like gulf where the transit of oceanic sea snakes into and from the basin is restricted, thus possibly affecting gene flow. RP-HPLC evidenced a conserved venom protein profile in both populations, despite their divergent color phenotypes. Following a trend observed in other sea snakes, P. platura venom is relatively simple, being composed of proteins of the three-finger toxin (3FTx), phospholipase A2 (PLA2), cysteine-rich secretory protein (CRISP), 5'-nucleotidase, and metalloproteinase families. The first three groups represent 49.9%, 32.9%, and 9.1% of total venom protein, respectively. The most abundant component (~26%) is pelamitoxin (P62388), a short-chain 3FTx, followed by a major basic PLA2 (~20%) and a group of three isoforms of CRISPs (~9%). Whereas isolated pelamitoxin was highly lethal to mice, neither the PLA2 nor the CRISP fraction caused death. However, the PLA2 rapidly increased plasma creatine kinase activity after intramuscular injection, indicating its myotoxic action. Differing from myotoxic PLA2s of viperids, this PLA2 was not cytolytic to murine myogenic cells in vitro, suggesting possible differences in its mechanism of action. The median lethal dose (LD50) estimates for P. platura crude venom in mice and in three species of fishes did not differ significantly. The sea snake antivenom manufactured by CSL Ltd. (Australia), which uses Enhydrina schistosa as immunogen, cross-recognized the three major components of P. platura venom and, accordingly, neutralized the lethal activity of crude venom and pelamitoxin, therefore being of potential usefulness in the treatment of envenomations by this species.

BIOLOGICAL SIGNIFICANCE

Integrative analyses of animal venoms that combine the power of proteomics (venomics) with the characterization of their functional and immunological properties are significantly expanding knowledge on these remarkable bioweapons, both from a basic and a medical perspective. Costa Rica harbors a unique population of the yellow-bellied sea snake, Pelamis platura, that is restricted to a fjord-like gulf (Golfo Dulce). This population differs markedly from oceanic populations found elsewhere along the Pacific coast of this country, by presenting a patternless bright yellow coloration, instead of the typical bicolored or tricolored pattern of this species. It has been suggested that the dominance of this yellow-morph in Golfo Dulce might reflect gene flow restrictions, caused by the oceanographic conditions at this location. The present study demonstrates that the remarkable phenotypic variation between the two color morphs inhabiting Golfo Dulce and Golfo de Papagayo, respectively, is not associated with differences in the expression of venom components, as shown by their conserved RP-HPLC profiles. Proteomic analysis revealed the relatively simple toxin composition of P. platura venom, which contains three predominant types of proteins: three-finger toxins (protein abundance: 49.9%), phospholipases A2 (32.9%), and cysteine-rich secretory proteins (9.1%), together with few minor components. Further, the involvement of these most abundant proteins in the toxic effects of the venom, and their cross-recognition and neutralization by a sea snake antivenom produced against the venom of Enhydrina schistosa, were analyzed.

Next-generation snake venomics: protein-locus resolution through venom proteome decomplexation

Venom research has been continuously enhanced by technological advances. High-throughput technologies are changing the classical paradigm of hypothesis-driven research to technology-driven approaches. However, the thesis advocated in this paper is that full proteome coverage at locus-specific resolution requires integrating the best of both worlds into a protocol that includes decomplexation of the venom proteome prior to liquid chromatography-tandem mass spectrometry matching against a species-specific transcriptome. This approach offers the possibility of proof-checking the species-specific contig database using proteomics data. Immunoaffinity chromatography constitutes the basis of an antivenomics workflow designed to quantify the extent of cross-reactivity of antivenoms against homologous and heterologous venom toxins. In the author's view, snake venomics and antivenomics form part of a biology-driven conceptual framework to unveil the genesis and natural history of venoms, and their within- and between-species toxicological and immunological divergences and similarities. Understanding evolutionary trends across venoms represents the Rosetta Stone for generating broad-ranging polyspecific antivenoms.

Venomous snakes of Costa Rica: biological and medical implications of their venom proteomic profiles analyzed through the strategy of snake venomics

In spite of its small territory of ~50,000km(2), Costa Rica harbors a remarkably rich biodiversity. Its herpetofauna includes 138 species of snakes, of which sixteen pit vipers (family Viperidae, subfamily Crotalinae), five coral snakes (family Elapidae, subfamily Elapinae), and one sea snake (Family Elapidae, subfamily Hydrophiinae) pose potential hazards to human and animal health. In recent years, knowledge on the composition of snake venoms has expanded dramatically thanks to the development of increasingly fast and sensitive analytical techniques in mass spectrometry and separation science applied to protein characterization. Among several analytical strategies to determine the overall protein/peptide composition of snake venoms, the methodology known as 'snake venomics' has proven particularly well suited and informative, by providing not only a catalog of protein types/families present in a venom, but also a semi-quantitative estimation of their relative abundances. Through a collaborative research initiative between Instituto de Biomedicina de Valencia (IBV) and Instituto Clodomiro Picado (ICP), this strategy has been applied to the study of venoms of Costa Rican snakes, aiming to obtain a deeper knowledge on their composition, geographic and ontogenic variations, relationships to taxonomy, correlation with toxic activities, and discovery of novel components. The proteomic profiles of venoms from sixteen out of the 22 species within the Viperidae and Elapidae families found in Costa Rica have been reported so far, and an integrative view of these studies is hereby presented. In line with other venomic projects by research groups focusing on a wide variety of snakes around the world, these studies contribute to a deeper understanding of the biochemical basis for the diverse toxic profiles evolved by venomous snakes. In addition, these studies provide opportunities to identify novel molecules of potential pharmacological interest. Furthermore, the establishment of venom proteomic profiles offers a fundamental platform to assess the detailed immunorecognition of individual proteins/peptides by therapeutic or experimental antivenoms, an evolving methodology for which the term 'antivenomics' was coined (as described in an accompanying paper in this special issue).

BIOLOGICAL SIGNIFICANCE

Venoms represent an adaptive trait and an example of both divergent and convergent evolution. A deep understanding of the composition of venoms and of the principles governing the evolution of venomous systems is of applied importance for exploring the enormous potential of venoms as sources of chemical and pharmacological novelty but also to fight the consequences of snakebite envenomings. Key to this is the identification of evolutionary and ecological trends at different taxonomical levels. However, the evolution of venomous species and their venoms do not always follow the same course, and the identification of structural and functional convergences and divergences among venoms is often unpredictable by a phylogenetic hypothesis. Snake venomics is a proteomic-centered strategy to deconstruct the complex molecular phenotypes the venom proteomes. The proteomic profiles of venoms from sixteen out of the 22 venomous species within the Viperidae and Elapidae families found in Costa Rica have been completed so far. An integrative view of their venom composition, including the identification of geographic and ontogenic variations, is hereby presented. Venom proteomic profiles offer a fundamental platform to assess the detailed immunorecognition of individual venom components by therapeutic or experimental antivenoms. This aspect is reviewed in the companion paper. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

Intraspecific venom variation in the medically significant Southern Pacific Rattlesnake (Crotalus oreganus helleri): biodiscovery, clinical and evolutionary implications

Due to the extreme variation of venom, which consequently results in drastically variable degrees of neutralization by CroFab antivenom, the management and treatment of envenoming by Crotalus oreganus helleri (the Southern Pacific Rattlesnake), one of the most medically significant snake species in all of North America, has been a clinician's nightmare. This snake has also been the subject of sensational news stories regarding supposed rapid (within the last few decades) evolution of its venom. This research demonstrates for the first time that variable evolutionary selection pressures sculpt the intraspecific molecular diversity of venom components in C. o. helleri. We show that myotoxic β-defensin peptides (aka: crotamines/small basic myotoxic peptides) are secreted in large amounts by all populations. However, the mature toxin-encoding nucleotide regions evolve under the constraints of negative selection, likely as a result of their non-specific mode of action which doesn't enforce them to follow the regime of the classic predator-prey chemical arms race. The hemorrhagic and tissue destroying snake venom metalloproteinases (SVMPs) were secreted in larger amounts by the Catalina Island and Phelan rattlesnake populations, in moderate amounts in the Loma Linda population and in only trace levels by the Idyllwild population. Only the Idyllwild population in the San Jacinto Mountains contained potent presynaptic neurotoxic phospholipase A2 complex characteristic of Mohave Rattlesnake (Crotalus scutulatus) and Neotropical Rattlesnake (Crotalus durissus terrificus). The derived heterodimeric lectin toxins characteristic of viper venoms, which exhibit a diversity of biological activities, including anticoagulation, agonism/antagonism of platelet activation, or procoagulation, appear to have evolved under extremely variable selection pressures. While most lectin α- and β-chains evolved rapidly under the influence of positive Darwinian selection, the β-chain lectin of the Catalina Island population appears to have evolved under the constraint of negative selection. Both lectin chains were conspicuously absent in both the proteomics and transcriptomics of the Idyllwild population. Thus, we not only highlight the tremendous biochemical diversity in C. o. helleri's venom-arsenal, but we also show that they experience remarkably variable strengths of evolutionary selection pressures, within each toxin class among populations and among toxin classes within each population. The mapping of geographical venom variation not only provides additional information regarding venom evolution, but also has direct medical implications by allowing prediction of the clinical effects of rattlesnake bites from different regions. Such information, however, also points to these highly variable venoms as being a rich source of novel toxins which may ultimately prove to be useful in drug design and development.

BIOLOGICAL SIGNIFICANCE

These results have direct implications for the treatment of envenomed patients. The variable venom profile of Crotalus oreganus helleri underscores the biodiscovery potential of novel snake venoms.