In vitro antibacterial and hemolytic activities of crotamine, a small basic myotoxin from rattlesnake Crotalus durissus

Crotamine derived from Crotalus durissus terrificus venom combined with drugs increases in vitro antibacterial and antifungal activities

This study investigated crotamine (CTA), a peptide derived from the venom of the South American rattlesnake Crotalus durissus terrificus, known for its exceptional cell penetration potential. The objective was to explore the antibacterial and antifungal activity of CTA, its ability to inhibit efflux pumps and evaluate the effectiveness of its pharmacological combination with antibiotics and antifungals. In microbiological assays, CTA in combination with antibiotics was tested against strains of S. aureus and the inhibition of NorA, Tet(K) and MepA efflux pumps was also evaluated. CTA alone did not present clinically relevant direct antibacterial action, presenting MIC > 209.7 µM against strains S. aureus 1199B, IS-58, K2068. The standard efflux pump inhibitor CCCP showed significant effects in all negative relationships to assay reproducibility. Against the S. aureus 1199B strain, CTA (20.5 µM) associated with norfloxacin diluted 10 × (320.67 µM) showed a potentiating effect, in relation to the control. Against the S. aureus IS-58 strain, the CTA associated with tetracycline did not show a significant combinatorial effect, either with 2304 or 230.4 µM tetracycline. CTA at a concentration of 2.05 µM associated with ciprofloxacin at a concentration of 309.4 µM showed a significant potentiating effect. In association with EtBr, CTA at concentrations of 2.05 and 20.5 µM potentiated the effect in all strains tested, reducing the prevention of NorA, Tet(K) and MepA efflux pumps. In the C. albicans strain, a potentiating effect of fluconazole (334.3 µM) was observed when combined with CTA (2.05 µM). Against the C. tropicalis strain, a significant effect was also observed in the association of fluconazole 334.3 µM, where CTA 2.05 µM considerably reduced fungal growth and decreased the potentiation of fluconazole. Against the C. krusei strain, no significant potentiating effect of fluconazole was obtained by CTA. Our results indicate that CTA in pharmacological combination potentiates the effects of antibiotics and antifungal. This represents a new and promising antimicrobial strategy for treating a wide variety of infections.

Short Antimicrobial Peptide Derived from the Venom Gland Transcriptome of Pamphobeteus verdolaga Increases Gentamicin Susceptibility of Multidrug-Resistant Klebsiella pneumoniae

Infectious diseases account for nine percent of annual human deaths, and the widespread emergence of antimicrobial resistances threatens to significantly increase this number in the coming decades. The prospect of antimicrobial peptides (AMPs) derived from venomous animals presents an interesting alternative for developing novel active pharmaceutical ingredients (APIs). Small, cationic and amphiphilic peptides were predicted from the venom gland transcriptome of Pamphobeteus verdolaga using a custom database of the arthropod's AMPs. Ninety-four candidates were chemically synthesized and screened against ATCC® strains of Escherichia coli and Staphylococcus aureus. Among them, one AMP, named PvAMP66, showed broad-spectrum antimicrobial properties with selectivity towards Gram-negative bacteria. It also exhibited activity against Pseudomonas aeruginosa, as well as both an ATCC® and a clinically isolated multidrug-resistant (MDR) strain of K. pneumoniae. The scanning electron microscopy analysis revealed that PvAMP66 induced morphological changes of the MDR K. pneumoniae strain suggesting a potential "carpet model" mechanism of action. The isobologram analysis showed an additive interaction between PvAMP66 and gentamicin in inhibiting the growth of MDR K. pneumoniae, leading to a ten-fold reduction in gentamicin's effective concentration. A cytotoxicity against erythrocytes or peripheral blood mononuclear cells was observed at concentrations three to thirteen-fold higher than those exhibited against the evaluated bacterial strains. This evidence suggests that PvAMP66 can serve as a template for the development of AMPs with enhanced activity and deserves further pre-clinical studies as an API in combination therapy.

Past, Present, and Future of Naturally Occurring Antimicrobials Related to Snake Venoms

This review focuses on proteins and peptides with antimicrobial activity because these biopolymers can be useful in the fight against infectious diseases and to overcome the critical problem of microbial resistance to antibiotics. In fact, snakes show the highest diversification among reptiles, surviving in various environments; their innate immunity is similar to mammals and the response of their plasma to bacteria and fungi has been explored mainly in ecological studies. Snake venoms are a rich source of components that have a variety of biological functions. Among them are proteins like lectins, metalloproteinases, serine proteinases, L-amino acid oxidases, phospholipases type A₂, cysteine-rich secretory proteins, as well as many oligopeptides, such as waprins, cardiotoxins, cathelicidins, and β-defensins. In vitro, these biomolecules were shown to be active against bacteria, fungi, parasites, and viruses that are pathogenic to humans. Not only cathelicidins, but all other proteins and oligopeptides from snake venom have been proteolyzed to provide short antimicrobial peptides, or for use as templates for developing a variety of short unnatural sequences based on their structures. In addition to organizing and discussing an expressive amount of information, this review also describes new β-defensin sequences of Sistrurus miliarius that can lead to novel peptide-based antimicrobial agents, using a multidisciplinary approach that includes sequence phylogeny.

Biological and Medical Aspects Related to South American Rattlesnake Crotalus durissus (Linnaeus, 1758): A View from Colombia

In Colombia, South America, there is a subspecies of the South American rattlesnake Crotalus durissus, C. d. cumanensis, a snake of the Viperidae family, whose presence has been reduced due to the destruction of its habitat. It is an enigmatic snake from the group of pit vipers, venomous, with large articulated front fangs, special designs on its body, and a characteristic rattle on its tail. Unlike in Brazil, the occurrence of human envenomation by C. durisus in Colombia is very rare and contributes to less than 1% of envenomation caused by snakes. Its venom is a complex cocktail of proteins with different biological effects, which evolved with the purpose of paralyzing the prey, killing it, and starting its digestive process, as well as having defense functions. When its venom is injected into humans as the result of a bite, the victim presents with both local tissue damage and with systemic involvement, including a diverse degree of neurotoxic, myotoxic, nephrotoxic, and coagulopathic effects, among others. Its biological effects are being studied for use in human health, including the possible development of analgesic, muscle relaxant, anti-inflammatory, immunosuppressive, anti-infection, and antineoplastic drugs. Several groups of researchers in Brazil are very active in their contributions in this regard. In this work, a review is made of the most relevant biological and medical aspects related to the South American rattlesnake and of what may be of importance for a better understanding of the snake C. d. cumanensis, present in Colombia and Venezuela.

Myotoxin-3 from the Pacific Rattlesnake Crotalus oreganus oreganus Venom Is a New Microtubule-Targeting Agent

Microtubule targeting agents (MTA) are anti-cancer molecules that bind tubulin and interfere with the microtubule functions, eventually leading to cell death. In the present study, we used an in vitro microtubule polymerization assay to screen several venom families for the presence of anti-microtubule activity. We isolated myotoxin-3, a peptide of the crotamine family, and three isoforms from the venom of the Northern Pacific rattlesnake Crotalus oreganus oreganus, which was able to increase tubulin polymerization. Myotoxin-3 turned out to be a cell-penetrating peptide that slightly diminished the viability of U87 glioblastoma and MCF7 breast carcinoma cells. Myotoxin 3 also induced remodeling of the U87 microtubule network and decreased MCF-7 microtubule dynamic instability. These effects are likely due to direct interaction with tubulin. Indeed, we showed that myotoxin-3 binds to tubulin heterodimer with a Kd of 5.3 µM and stoichiometry of two molecules of peptide per tubulin dimer. Our results demonstrate that exogenous peptides are good candidates for developing new MTA and highlight the richness of venoms as a source of pharmacologically active molecules.

An Emergent Role for Mitochondrial Bioenergetics in the Action of Snake Venom Toxins on Cancer Cells

Beyond the role of mitochondria in apoptosis initiation/execution, some mitochondrial adaptations support the metastasis and chemoresistance of cancer cells. This highlights mitochondria as a promising target for new anticancer strategies. Emergent evidence suggests that some snake venom toxins, both proteins with enzymatic and non-enzymatic activities, act on the mitochondrial metabolism of cancer cells, exhibiting unique and novel mechanisms that are not yet fully understood. Currently, six toxin classes (L-amino acid oxidases, thrombin-like enzymes, secreted phospholipases A2, three-finger toxins, cysteine-rich secreted proteins, and snake C-type lectin) that alter the mitochondrial bioenergetics have been described. These toxins act through Complex IV activity inhibition, OXPHOS uncoupling, ROS-mediated permeabilization of inner mitochondrial membrane (IMM), IMM reorganization by cardiolipin interaction, and mitochondrial fragmentation with selective migrastatic and cytotoxic effects on cancer cells. Notably, selective internalization and direct action of snake venom toxins on tumor mitochondria can be mediated by cell surface proteins overexpressed in cancer cells (e.g. nucleolin and heparan sulfate proteoglycans) or facilitated by the elevated Δψm of cancer cells compared to that non-tumor cells. In this latter case, selective mitochondrial accumulation, in a Δψm-dependent manner, of compounds linked to cationic snake peptides may be explored as a new anti-cancer drug delivery system. This review analyzes the effect of snake venom toxins on mitochondrial bioenergetics of cancer cells, whose mechanisms of action may offer the opportunity to develop new anticancer drugs based on toxin scaffolds.

Origins, genomic structure and copy number variation of snake venom myotoxins

Crotamine, myotoxin a and homologs are short peptides that often comprise major fractions of rattlesnake venoms and have been extensively studied for their bioactive properties. These toxins are thought to be important for rapidly immobilizing mammalian prey and are implicated in serious, and sometimes fatal, responses to envenomation in humans. While high quality reference genomes for multiple venomous snakes are available, the loci that encode myotoxins have not been successfully assembled in any existing genome assembly. Here, we integrate new and existing genomic and transcriptomic data from the Prairie Rattlesnake (Crotalus viridis viridis) to reconstruct, characterize, and infer the chromosomal locations of myotoxin-encoding loci. We integrate long-read transcriptomics (Pacific Bioscience's Iso-Seq) and short-read RNA-seq to infer gene sequence diversity and characterize patterns of myotoxin and paralogous β-defensin expression across multiple tissues. We also identify two long non-coding RNA sequences which both encode functional myotoxins, demonstrating a newly discovered source of venom coding sequence diversity. We also integrate long-range mate-pair chromatin contact data and linked-read sequencing to infer the structure and chromosomal locations of the three myotoxin-like loci. Further, we conclude that the venom-associated myotoxin is located on chromosome 1 and is adjacent to non-venom paralogs. Consistent with this locus contributing to venom composition, we find evidence that the promoter of this gene is selectively open in venom gland tissue and contains transcription factor binding sites implicated in broad trans-regulatory pathways that regulate snake venoms. This study provides the best genomic reconstruction of myotoxin loci to date and raises questions about the physiological roles and interplay between myotoxin and related genes, as well as the genomic origins of snake venom variation.

Cytocompatible Amphipathic Carbon Quantum Dots as Potent Membrane-Active Antibacterial Agents with Low Drug Resistance and Effective Inhibition of Biofilm Formation

It is very challenging to design nanomaterials with both excellent antibacterial activity and cytocompatibility when facing bacterial infection. Here, inspired by antimicrobial peptides (AMPs), we fabricate carbon quantum dots (CQDs) derived from hydrophobic tryptophan and hydrophilic lysine or arginine (Lys/Trp-CQDs and Arg/Trp-CQDs), which possess amphipathic properties. These CQDs could effectively destroy bacterial membranes without developing resistance, inhibit biofilms formed by Staphylococcus aureus, and exhibit good in vitro biocompatibility. The antibacterial activities are caused by not only surface cationic structures and excess intracellular reactive oxygen species (ROS) generated by the CQDs but also the effects of the surface hydrophobic groups. These combined mechanisms of actions lead to bacterial membrane disruption, which raises the hope for combating bacterial infection without concern about drug resistance. What's more, the effect of amphiphilicity on balancing sterilization with biocompatibility expands the research ideas for developing available antibacterial nanomaterials.

Antimicrobial Activity of Snake β-Defensins and Derived Peptides

β-defensins are antimicrobial peptides presenting in vertebrate animals. They participate in innate immunity, but little is known about them in reptiles, including snakes. Although several β-defensin genes were described in Brazilian snakes, their function is still unknown. The peptide sequence from these genes was deduced, and synthetic peptides (with approximately 40 amino acids and derived peptides) were tested against pathogenic bacteria and fungi using microbroth dilution assays. The linear peptides, derived from β-defensins, were designed applying the bioisosterism strategy. The linear β-defensins were more active against Escherichia coli, Micrococcus luteus, Citrobacter freundii, and Staphylococcus aureus. The derived peptides (7–14 mer) showed antibacterial activity against those bacteria and on Klebsiella pneumoniae. Nonetheless, they did not present activity against Candida albicans, Cryptococcus neoformans, Trychophyton rubrum, and Aspergillus fumigatus showing that the cysteine substitution to serine is deleterious to antifungal properties. Tryptophan residue showed to be necessary to improve antibacterial activity. Even though the studied snake β-defensins do not have high antimicrobial activity, they proved to be attractive as template molecules for the development of antibiotics.

Revisiting the potential of South American rattlesnake Crotalus durissus terrificus toxins as therapeutic, theranostic and/or biotechnological agents

The potential biotechnological and biomedical applications of the animal venom components are widely recognized. Indeed, many components have been used either as drugs or as templates/prototypes for the development of innovative pharmaceutical drugs, among which many are still used for the treatment of human diseases. A specific South American rattlesnake, named Crotalus durissus terrificus, shows a venom composition relatively simpler compared to any viper or other snake species belonging to the Crotalus genus, although presenting a set of toxins with high potential for the treatment of several still unmet human therapeutic needs, as reviewed in this work. In addition to the main toxin named crotoxin, which is under clinical trials studies for antitumoral therapy and which has also anti-inflammatory and immunosuppressive activities, other toxins from the C. d. terrificus venom are also being studied, aiming for a wide variety of therapeutic applications, including as antinociceptive, anti-inflammatory, antimicrobial, antifungal, antitumoral or antiparasitic agent, or as modulator of animal metabolism, fibrin sealant (fibrin glue), gene carrier or theranostic agent. Among these rattlesnake toxins, the most relevant, considering the potential clinical applications, are crotamine, crotalphine and gyroxin. In this narrative revision, we propose to organize and present briefly the updates in the accumulated knowledge on potential therapeutic applications of toxins collectively found exclusively in the venom of this specific South American rattlesnake, with the objective of contributing to increase the chances of success in the discovery of drugs based on toxins.

Acute toxicity, antinociceptive, and anti-inflammatory activities of the orally administered crotamine in mice

Crotamine is a polypeptide toxin isolated from rattlesnake venom. Although several studies have been developed identifying many biological effects of isolated crotamine, none of them evaluated its acute toxicity, antinociceptive, and anti-inflammatory activities through oral administration. All in vivo experiments from this study were performed in mice. The up-and-down procedure and hippocratic screening were carried out to evaluate possible pharmacological and toxic effects. Antinociceptive and anti-inflammatory activities of this toxin were evaluated using acetic acid-induced abdominal writhing, formalin-induced pain assays, croton oil-induced ear edema, and carrageenan-induced pleurisy. Crotamine did not cause lethality or signs of intoxication up to the maximum dose tested (10.88 mg/kg). The number of contortions was reduced significantly by 34, 57, and 74% at the oral doses of 0.08, 0.16, and 0.32 mg/kg, respectively. At the dose of 0.16 mg/kg, crotamine decreases pain time-reactivity at neurogenic phase by 45% and at inflammatory phase by 60%. Also, crotamine elicited antiedematogenic activity through the attenuation of the croton oil-induced ear edema by 77%. In the carrageenan-induced pleurisy, the leukocyte, neutrophil, and mononuclear cell migration to the lesion site were reduced by 52%, 46%, and 59%, respectively. Altogether, crotamine demonstrated in vivo antinociceptive and anti-inflammatory effect through acute oral administration, generating an anti-migratory mechanism of action at non-toxic doses.

Effect of Isolated Proteins from Crotalus Durissus Terrificus Venom on Leishmania (Leishmania) Amazonensis-Infected Macrophages

BACKGROUND

Cutaneous and mucocutaneous leishmaniasis are parasitic diseases characterized by skin manifestations. In Brazil, Leishmania (Leishmania) amazonensis is one of the etiological agents of cutaneous leishmaniasis. The therapeutic arsenal routinely employed to treat infected patients is unsatisfactory, especially for pentavalent antimonials, as they are often highly toxic, poorly tolerated and of variable effectiveness. This study aimed to evaluate in vitro the leishmanicidal activity of toxins isolated from Crotalus durissus terrificus venom as a new approach for the treatment of leishmaniasis.

METHODS

The comparative effects of crotamine, crotoxin, gyrotoxin, convulxin and PLA2 on bone marrow-derived macrophages infected with L. (L.) amazonensis as well as the release of TGF-β from the treated macrophages were studied.

RESULTS AND DISCUSSION

Crotamine had the strongest inhibitory effect on parasite growth rate (IC50: 25.65±0.52 μg/mL), while convulxin showed the weakest inhibitory effect (IC50: 52.7±2.21 μg/mL). In addition, TGF-β was significantly reduced after the treatment with all toxins evaluated.

CONCLUSION

The Crotalus durissus terrificus toxins used in this study displayed significant activity against L. (L.) amazonensis, indicating that all of them could be a potential alternative for the treatment of cutaneous leishmaniasis.

Venom peptides in association with standard drugs: a novel strategy for combating antibiotic resistance - an overview

Development of antibiotic resistance that leads to resurgence of bacterial infections poses a threat to disease-free existence for humankind and is a challenge for the welfare of the society at large. Despite research efforts directed towards treatment of pathogens, antibiotics within new improved classes have not emerged for years, a fact largely attributable to the pharmacological necessities compelling drug development. Recent reversion to the use of natural products alone or in combination with standard drugs has opened up new vistas for alternative therapeutics. The success of this strategy is evident in the sudden interest in plant extracts as additives/synergists for treatment of maladies caused by drug-resistant bacterial strains. Animal venoms have long fascinated scientists as sources of pharmacologically active components that can be exploited for the treatment of specific ailments and should be promoted further to clinical trials. In the present review, we outline the scope and possible methods for the applications of animal venoms in combination with commercial antibiotics to offer a better treatment approach against antibiotic-resistant infections.

Antimicrobials from Venomous Animals: An Overview

The inappropriate or excessive use of antimicrobial agents caused an emerging public health problem due to the resulting resistance developed by microbes. Therefore, there is an urgent need to develop effective antimicrobial strategies relying on natural agents with different mechanisms of action. Nature has been known to offer many bioactive compounds, in the form of animal venoms, algae, and plant extracts that were used for decades in traditional medicine. Animal venoms and secretions have been deeply studied for their wealth in pharmaceutically promising molecules. As such, they were reported to exhibit many biological activities of interest, such as antibacterial, antiviral, anticancer, and anti-inflammatory activities. In this review, we summarize recent findings on the antimicrobial activities of crude animal venoms/secretions, and describe the peptides that are responsible of these activities.

Hitchhiking with Nature: Snake Venom Peptides to Fight Cancer and Superbugs

Abstract

For decades, natural products in general and snake venoms (SV) in particular have been a rich source of bioactive compounds for drug discovery, and they remain a promising substrate for therapeutic development. Currently, a handful of SV-based drugs for diagnosis and treatment of various cardiovascular disorders and blood abnormalities are on the market. Likewise, far more SV compounds and their mimetics are under investigation today for diverse therapeutic applications, including antibiotic-resistant bacteria and cancer. In this review, we analyze the state of the art regarding SV-derived compounds with therapeutic potential, focusing on the development of antimicrobial and anticancer drugs. Specifically, information about SV peptides experimentally validated or predicted to act as antimicrobial and anticancer peptides (AMPs and ACPs, respectively) has been collected and analyzed. Their principal activities both in vitro and in vivo, structures, mechanisms of action, and attempts at sequence optimization are discussed in order to highlight their potential as drug leads.

Key Contribution

This review describes the state of the art in snake venom-derived peptides and their therapeutic applications. This work reinforces the potential of snake venom components as therapeutic agents, particularly in the quest for new antimicrobial and anticancer drugs.

Crotamine and crotalicidin, membrane active peptides from Crotalus durissus terrificus rattlesnake venom, and their structurally-minimized fragments for applications in medicine and biotechnology

A global public health crisis has emerged with the extensive dissemination of multidrug-resistant microorganisms. Antimicrobial peptides (AMPs) from plants and animals have represented promising tools to counteract those resistant pathogens due to their multiple pharmacological properties such as antimicrobial, anticancer, immunomodulatory and cell-penetrating activities. In this review, we will focus on crotamine and crotalicidin, which are two interesting examples of membrane active peptides derived from the South America rattlesnake Crotalus durrisus terrificus venom. Their full-sequences and structurally-minimized fragments have potential applications, as anti-infective and anti-proliferative agents and diagnostics in medicine and in pharmaceutical biotechnology.

Antibacterial and Hemolytic Activity of Crotalus Triseriatus and Crotalus Ravus Venom

Rattlesnakes have venoms with a complex toxin mixture comprised of polypeptides and proteins. Previous studies have shown that some of these polypeptides are of high value for the development of new medical treatments. The aim of the present study is to evaluate, in vitro, the antibacterial and hemolytic activity of Crotalus triseriatus and Crotalus ravus venoms. A direct field search was conducted to obtain Crotalus triseriatus and Crotalus ravus venom samples. These were evaluated to determine their antibacterial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa through the techniques of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). Hemolytic activity was also determined. Antibacterial activity was determined for treatments (Crotalus triseriatus 2) CT2 and (Crotalus ravus 3) CR3, obtaining a Minimum Inhibitory Concentration of 50 µg/mL and a Minimum Bactericidal Concentration of 100 µg/mL against Pseudomonas aeruginosa. CT1 (Crotalus triseriatus 1), CT2, and CR3 presented hemolytic activity; on the other hand, Crotalus ravus 4 (CR4) did not show hemolytic activity. The results of the present study indicate for the first time that Crotalus triseriatus and Crotalus ravus venoms contain some bioactive compounds with bactericidal activity against Pseudomonas aeruginosa which could be used as alternative treatment in diseases caused by this pathogenic bacterium.

Amplification of Snake Venom Toxicity by Endogenous Signaling Pathways

The active components of snake venoms encompass a complex and variable mixture of proteins that produce a diverse, but largely stereotypical, range of pharmacologic effects and toxicities. Venom protein diversity and host susceptibilities determine the relative contributions of five main pathologies: neuromuscular dysfunction, inflammation, coagulopathy, cell/organ injury, and disruption of homeostatic mechanisms of normal physiology. In this review, we describe how snakebite is not only a condition mediated directly by venom, but by the amplification of signals dysregulating inflammation, coagulation, neurotransmission, and cell survival. Although venom proteins are diverse, the majority of important pathologic events following envenoming follow from a small group of enzyme-like activities and the actions of small toxic peptides. This review focuses on two of the most important enzymatic activities: snake venom phospholipases (svPLA2) and snake venom metalloproteases (svMP). These two enzyme classes are adept at enabling venom to recruit homologous endogenous signaling systems with sufficient magnitude and duration to produce and amplify cell injury beyond what would be expected from the direct impact of a whole venom dose. This magnification produces many of the most acutely important consequences of envenoming as well as chronic sequelae. Snake venom PLA2s and MPs enzymes recruit prey analogs of similar activity. The transduction mechanisms that recruit endogenous responses include arachidonic acid, intracellular calcium, cytokines, bioactive peptides, and possibly dimerization of venom and prey protein homologs. Despite years of investigation, the precise mechanism of svPLA2-induced neuromuscular paralysis remains incomplete. Based on recent studies, paralysis results from a self-amplifying cycle of endogenous PLA2 activation, arachidonic acid, increases in intracellular Ca2+ and nicotinic receptor deactivation. When prolonged, synaptic suppression supports the degeneration of the synapse. Interaction between endothelium-damaging MPs, sPLA2s and hyaluronidases enhance venom spread, accentuating venom-induced neurotoxicity, inflammation, coagulopathy and tissue injury. Improving snakebite treatment requires new tools to understand direct and indirect effects of envenoming. Homologous PLA2 and MP activities in both venoms and prey/snakebite victim provide molecular targets for non-antibody, small molecule agents for dissecting mechanisms of venom toxicity. Importantly, these tools enable the separation of venom-specific and prey-specific pathological responses to venom.

Antibacterial properties of snake venom components

An increasing problem in the field of health protection is the emergence of drug-resistant and multi-drug-resistant bacterial strains. They cause a number of infections, including hospital infections, which currently available antibiotics are unable to fight. Therefore, many studies are devoted to the search for new therapeutic agents with bactericidal and bacteriostatic properties. One of the latest concepts is to search for this type of substances among toxins produced by venomous animals. In this approach, however, special attention is paid to snake venom because it contains molecules with antibacterial properties. Thorough investigations have shown that the phospholipases A2 (PLA2) and l-amino acids oxidases (LAAO), as well as fragments of these enzymes, are mainly responsible for the bactericidal properties of snake venoms. Some preliminary research studies also suggest that fragments of three-finger toxins (3FTx) are bactericidal. It has also been proven that some snakes produce antibacterial peptides (AMP) homologous to human defensins and cathelicidins. The presence of these proteins and peptides means that snake venoms continue to be an interesting material for researchers and can be perceived as a promising source of antibacterial agents.

Intradermal Application of Crotamine Induces Inflammatory and Immunological Changes In Vivo

Crotamine is a single-chain polypeptide with cell-penetrating properties, which is considered a promising molecule for clinical use. Nevertheless, its biosafety data are still scarce. Herein, we assessed the in vivo proinflammatory properties of crotamine, including its local effect and systemic serum parameters. Sixty male Wistar rats were intradermically injected with 200, 400 and 800 µg crotamine and analyzed after 1, 3 and 7 days. Local effect of crotamine was assessed by determination of MPO and NAG activities, NO levels and angiogenesis. Systemic inflammatory response was assessed by determination of IL-10, TNF-α, CRP, NO, TBARS and SH groups. Crotamine induced macrophages and neutrophils chemotaxis as evidenced by the upregulation of both NAG (0.5–0.6 OD/mg) and MPO (0.1–0.2 OD/mg) activities, on the first and third day of analysis, respectively. High levels of NO were observed for all concentrations and time-points. Moreover, 800 μg crotamine resulted in serum NO (64.7 μM) and local tissue NO (58.5 μM) levels higher or equivalent to those recorded for their respective histamine controls (55.7 μM and 59.0 μM). Crotamine also induced a significant angiogenic response compared to histamine. Systemically, crotamine induced a progressive increase in serum CRP levels up to the third day of analysis (22.4–45.8 mg/mL), which was significantly greater than control values. Crotamine (400 μg) also caused an increase in serum TNF-α, in the first day of analysis (1095.4 pg/mL), however a significant increase in IL-10 (122.2 pg/mL) was also recorded for the same time-point, suggesting the induction of an anti-inflammatory effect. Finally, crotamine changed the systemic redox state by inducing gradual increase in serum levels of TBARS (1.0–1.8 μM/mL) and decrease in SH levels (124.7–19.5 μM/mL) throughout the experimental period of analysis. In summary, rats intradermally injected with crotamine presented local and systemic acute inflammatory responses similarly to histamine, which limits crotamine therapeutic use on its original form.

Mechanistic Landscape of Membrane-Permeabilizing Peptides

Membrane permeabilizing peptides (MPPs) are as ubiquitous as the lipid bilayer membranes they act upon. Produced by all forms of life, most membrane permeabilizing peptides are used offensively or defensively against the membranes of other organisms. Just as nature has found many uses for them, translational scientists have worked for decades to design or optimize membrane permeabilizing peptides for applications in the laboratory and in the clinic ranging from antibacterial and antiviral therapy and prophylaxis to anticancer therapeutics and drug delivery. Here, we review the field of membrane permeabilizing peptides. We discuss the diversity of their sources and structures, the systems and methods used to measure their activities, and the behaviors that are observed. We discuss the fact that "mechanism" is not a discrete or a static entity for an MPP but rather the result of a heterogeneous and dynamic ensemble of structural states that vary in response to many different experimental conditions. This has led to an almost complete lack of discrete three-dimensional active structures among the thousands of known MPPs and a lack of useful or predictive sequence-structure-function relationship rules. Ultimately, we discuss how it may be more useful to think of membrane permeabilizing peptides mechanisms as broad regions of a mechanistic landscape rather than discrete molecular processes.

EVALUATION OF THE ANTIBACTERIAL ACTIVITY OF Crotalus durissus terrificus CRUDE VENOM

Abstract Snake venoms are recognized as a promising source of pharmacologically active substances and are potentially useful for the development of new antimicrobial drugs. This study aimed to investigate the antimicrobial activity of the venom from the rattlesnake Crotalus durissus terrificus against several bacteria. Antibacterial activity was determined by using the plate microdilution method and the activity on the bacterial envelope structure was screened by using the crystal violet assay. The proteins in crude venom were separated by electrophoresis and characterized regarding their proteolytic activity. C. d. terrificus venom exhibited antimicrobial action against gram-positive and gram-negative bacteria. MIC values were defined for Pseudomonas aeruginosa ATCC 27853 (62.5 µg/mL), Staphylococcus aureus ATCC 25923 (125 µg/mL), and Micrococcus luteus ATCC 9341 (≤500 µg/mL). For Salmonella enterica serovar typhimurium ATCC 14028 and Corynebacterium glutamicum ATCC 13032, the decrease in bacterial growth was not detected visually, but was statistically significant. The crystal violet assay demonstrated that the crude venom increased bacterial cell permeability and the secreted protein profile agreed with previous reports. The results suggest that the proteins with lytic activity against bacteria in C. d. terrificus venom deserve further characterization as they may offer reinforcements to the weak therapeutic arsenal used to fight microbial multidrug resistance.

Vipers of the Middle East: A Rich Source of Bioactive Molecules

Snake venom serves as a tool of defense against threat and helps in prey digestion. It consists of a mixture of enzymes, such as phospholipase A2, metalloproteases, and l-amino acid oxidase, and toxins, including neurotoxins and cytotoxins. Beside their toxicity, venom components possess many pharmacological effects and have been used to design drugs and as biomarkers of diseases. Viperidae is one family of venomous snakes that is found nearly worldwide. However, three main vipers exist in the Middle Eastern region: Montivipera bornmuelleri, Macrovipera lebetina, and Vipera (Daboia) palaestinae. The venoms of these vipers have been the subject of many studies and are considered as a promising source of bioactive molecules. In this review, we present an overview of these three vipers, with a special focus on their venom composition as well as their biological activities, and we discuss further frameworks for the exploration of each venom.

Developing Small Molecule Therapeutics for the Initial and Adjunctive Treatment of Snakebite

The World Health Organization (WHO) recently added snakebite envenoming to the priority list of Neglected Tropical Diseases (NTD). It is thought that ~75% of mortality following snakebite occurs outside the hospital setting, making the temporal gap between a bite and antivenom administration a major therapeutic challenge. Small molecule therapeutics (SMTs) have been proposed as potential prereferral treatments for snakebite to help address this gap. Herein, we discuss the characteristics, potential uses, and development of SMTs as potential treatments for snakebite envenomation. We focus on SMTs that are secretory phospholipase A2 (sPLA2) inhibitors with brief exploration of other potential drug targets on venom molecules.

Mechanistic insights into functional characteristics of native crotamine

The chemical composition of snake venoms is a complex mixture of proteins and peptides that can be pharmacologically active. Crotamine, a cell-penetrating peptide, has been described to have antimicrobial properties and it exerts its effects by interacting selectively with different structures, inducing changes in the ion flow pattern and cellular responses. However, its real therapeutic potential is not yet fully known. Bearing in mind that crotamine is a promising molecule in therapeutics, this study investigated the action of purified molecule in three aspects: I) antibacterial action on different species of clinical interest, II) the effect of two different concentrations of the molecule on platelet aggregation, and III) its effects on isolated mitochondria. Crotamine was purified to homogeneity in a single step procedure using Heparin Sepharose. The molecular mass of the purified enzyme was 4881.4 Da, as determined by mass spectrometry. To assess antibacterial action, changes in the parameters of bacterial oxidative stress were determined. The peptide showed antibacterial activity on Escherichia coli (MIC: 2.0 μg/μL), Staphylococcus aureus (MIC: 8-16 μg/μL) and methicillin-resistant Staphylococcus aureus (MIC: 4.0-8.0 μg/μL), inducing bacterial death by lipid peroxidation and oxidation of target proteins, determined by thiobarbituric acid reactive substances and sulfhydryl groups, respectively. Crotamine induced increased platelet aggregation (IPA) at the two concentrations analyzed (0.1 and 1.4 μg/μL) compared to ADP-induced aggregation of PRP. Mitochondrial respiratory parameters and organelle structure assays were used to elucidate the action of the compound in this organelle. The exposure of mitochondria to crotamine caused a decrease in oxidative phosphorylation and changes in mitochondrial permeability, without causing damage in the mitochondrial redox state. Together, these results support the hypothesis that, besides the antimicrobial potential, crotamine acts on different molecular targets, inducing platelet aggregation and mitochondrial dysfunction.

Anti-Salmonella Activity Modulation of Mastoparan V1-A Wasp Venom Toxin-Using Protease Inhibitors, and Its Efficient Production via an Escherichia coli Secretion System

A previous study highlighted that mastoparan V1 (MP-V1), a mastoparan from the venom of the social wasp Vespula vulgaris, is a potent antimicrobial peptide against Salmonella infection, which causes enteric diseases. However, there exist some limits for its practical application due to the loss of its activity in an increased bacterial density and the difficulty of its efficient production. In this study, we first modulated successfully the antimicrobial activity of synthetic MP-V1 against an increased Salmonella population using protease inhibitors, and developed an Escherichia coli secretion system efficiently producing active MP-V1. The protease inhibitors used, except pepstatin A, significantly increased the antimicrobial activity of the synthetic MP-V1 at minimum inhibitory concentrations (determined against 10⁶ cfu/mL of population) against an increased population (10⁸ cfu/mL) of three different Salmonella serotypes, Gallinarum, Typhimurium and Enteritidis. Meanwhile, the E. coli strain harboring OmpA SS::MP-V1 was identified to successfully secrete active MP-V1 into cell-free supernatant, whose antimicrobial activity disappeared in the increased population (10⁸ cfu/mL) of Salmonella Typhimurium recovered by adding a protease inhibitor cocktail. Therefore, it has been concluded that our challenge using the E. coli secretion system with the protease inhibitors is an attractive strategy for practical application of peptide toxins, such as MP-V1.

Evaluation in zebrafish model of the toxicity of rhodamine B-conjugated crotamine, a peptide potentially useful for diagnostics and therapeutics

Crotamine is defensin-like cationic peptide from rattlesnake venom that possesses anticancer, antimicrobial, and antifungal properties. Despite these promising biological activities, toxicity is a major concern associated with the development of venom-derived peptides as therapeutic agents. In the present study, we used zebrafish as a system model to evaluate the toxicity of rhodamine B-conjugated (RhoB) crotamine derivative. The lethal toxic concentration of RhoB-crotamine was as low as 4 μM, which effectively kill zebrafish larvae in less than 10 min. With non-lethal concentrations (<1 μM), crotamine caused malformation in zebrafish embryos, delayed or completely halted hatching, adversely affected embryonic developmental programming, decreased the cardiac functions, and attenuated the swimming distance of zebrafish. The RhoB-crotamine translocated across vitelline membrane and accumulated in zebrafish yolk sac. These results demonstrate the sensitive responsivity of zebrafish to trial crotamine analogues for the development of novel therapeutic peptides with improved safety, bioavailability, and efficacy profiles.

Therapeutic potential of krait venom

Kraits belong to Elapideae and are widely distributed in East and South-East Asian countries. Krait venom possesses neurotoxins, membrane toxins, cardiotoxins, three finger toxins, metalloproteinases, cholinesterases, L-amino acid oxidases and serine proteases. The therapeutic potential of krait venom in pathophysiological conditions such as microbial and parasitic infections, cancer, arthritis, inflammation and blood coagulation disorder is discussed in this review. More intensive new research ventures are required to establish the therapeutic potential of krait venom in complex and emerging diseases.

Antivenomics as a tool to improve the neutralizing capacity of the crotalic antivenom: a study with crotamine

Background

Snakebite treatment requires administration of an appropriate antivenom that should contain antibodies capable of neutralizing the venom. To achieve this goal, antivenom production must start from a suitable immunization protocol and proper venom mixtures. In Brazil, antivenom against South American rattlesnake (Crotalus durissus terrificus) bites is produced by public institutions based on the guidelines defined by the regulatory agency of the Brazilian Ministry of Health, ANVISA. However, each institution uses its own mixture of rattlesnake venom antigens. Previous works have shown that crotamine, a toxin found in Crolatus durissus venom, shows marked individual and populational variation. In addition, serum produced from crotamine-negative venoms fails to recognize this molecule.

Methods

In this work, we used an antivenomics approach to assess the cross-reactivity of crotalic antivenom manufactured by IVB towards crotamine-negative venom and a mixture of crotamine-negative/crotamine-positive venoms.

Results

We show that the venom mixture containing 20% crotamine and 57% crotoxin produced a strong immunogenic response in horses. Antivenom raised against this venom mixture reacted with most venom components including crotamine and crotoxin, in contrast to the antivenom raised against crotamine-negative venom.

Conclusions

These results indicate that venomic databases and antivenomics analysis provide a useful approach for choosing the better venom mixture for antibody production and for the subsequent screening of antivenom cross-reactivity with relevant snake venom components.

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.

A brief update on potential molecular mechanisms underlying antimicrobial and wound-healing potency of snake venom molecules

Infectious diseases remain a significant cause of morbidity and mortality worldwide. A wide range of diverse, novel classes of natural antibiotics have been isolated from different snake species in the recent past. Snake venoms contain diverse groups of proteins with potent antibacterial activity against a wide range of human pathogens. Some snake venom molecules are pharmacologically attractive, as they possess promising broad-spectrum antibacterial activities. Furthermore, snake venom proteins (SVPs)/peptides also bind to integrins with high affinity, thereby inhibiting cell adhesion and accelerating wound healing in animal models. Thus, SVPs are a potential alternative to chemical antibiotics. The mode of action for many antibacterial peptides involves pore formation and disruption of the plasma membrane. This activity often includes modulation of nuclear factor kappa B (NF-κB) activation during skin wound healing. The NF-κB pathway negatively regulates the transforming growth factor (TGF)-β1/Smad pathway by inducing the expression of Smad7 and eventually reducing in vivo collagen production at the wound sites. In this context, SVPs that regulate the NF-κB signaling pathway may serve as potential targets for drug development.

Viperatoxin-II: A novel viper venom protein as an effective bactericidal agent

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Two novel viperatoxins (VipTx-I and VipTx-II) from Indian Russell’s viper snake venom were purified and characterized.

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VipTx-II but not VipTx-I showed strong antimicrobial effects against S. aureus and Burkholderia pseudomallei (strains KHW/TES), Proteus vulgaris and P. mirabilis.

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In broth dilution assays, VipTx-II had a potent bactericidal effect at the lowest dilutions against B. pseudomallei (strains KHW/TES), S. aureus and P. mirabilis.

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Protein-induced bactericidal potency was closely associated with pore formation and membrane damage.

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These proteins showed a low level of cytotoxic effects on human cells.

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have become a rising threat to public health. There is an urgent need for development of promising new therapeutic agents against drug resistant bacteria like S. aureus. This report discusses purification and characterization of proteins from Indian Russell’s viper snake venom. Novel 15-kDa proteins called “Viperatoxin” (VipTx-I and VipTx-II) were extracted from the whole venom and evaluated using in vitro antimicrobial experiments. The N-terminal amino acid sequence of “Viperatoxin” showed high sequence homology to daboiatoxin isolated from the same venom and also matched phospholipase A₂ (PLA₂) enzymes isolated from other snake venoms. In an in vitro plate assay, VipTx-II but not VipTx-I showed strong antimicrobial effects against S. aureus and Burkholderia pseudomallei (KHW & TES), Proteus vulgaris and P. mirabilis. The VipTx-II was further tested by a broth-dilution assay at 100–3.1 μg/ml concentrations. The most potent bactericidal effect was found at the lowest dilutions (MICs of 6.25 μg/ml) against B. pseudomallei, S. aureus and P. vulgaris (MICs of 12.25 μg/ml). Electron microscopic investigation revealed that the protein-induced bactericidal potency was closely associated with pore formation and membrane damage, even at the lowest concentrations (<20 μg/ml). The toxin caused a low level of cytotoxic effects as observed in human (THP-1) cells at higher concentrations. Molecular weight determinations of VipTx-II by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one major, along with a few minor bands. The results indicate that VipTx-II plays a significant role in bactericidal and membrane damaging effects in vitro. Non-cytotoxic properties on human cells highlight it as a promising candidate for further evaluation of antimicrobial potential in vivo.

Structural characterization of a novel peptide with antimicrobial activity from the venom gland of the scorpion Tityus stigmurus: Stigmurin

A new antimicrobial peptide, herein named Stigmurin, was selected based on a transcriptomic analysis of the Brazilian yellow scorpion Tityus stigmurus venom gland, an underexplored source for toxic peptides with possible biotechnological applications. Stigmurin was investigated in silico, by circular dichroism (CD) spectroscopy, and in vitro. The CD spectra suggested that this peptide interacts with membranes, changing its conformation in the presence of an amphipathic environment, with predominance of random coil and beta-sheet structures. Stigmurin exhibited antibacterial and antifungal activity, with minimal inhibitory concentrations ranging from 8.7 to 69.5μM. It was also showed that Stigmurin is toxic against SiHa and Vero E6 cell lines. The results suggest that Stigmurin can be considered a potential anti-infective drug.

Soluble prokaryotic expression and purification of crotamine using an N-terminal maltose-binding protein tag

Crotamine is a peptide toxin found in the venom of the rattlesnake Crotalus durissus terrificus. Interestingly, crotamine demonstrates promising anticancer, antimicrobial, and antifungal activities. The crotamine peptide can also deliver plasmids into rapidly dividing cells, such as cancer and stem cells, and demonstrates potent analgesic effects. Efficiently producing crotamine in mammalian cells is difficult because it is both cell-permeable and cytotoxic. Prokaryotic expression of this peptide is also difficult to maintain because it does not fold properly in the cytoplasm, resulting in aggregation and in the formation of inclusion bodies. In our current study, we show for the first time that N-terminal fusion with three protein tags-N-utilization substance protein A (NusA), protein disulfide isomerase b'a' domain (PDIb'a'), and maltose-binding protein (MBP)-enables the soluble overexpression of crotamine in the cytoplasm of Escherichia coli. MBP-tagged crotamine was purified using Ni affinity, anion exchange, and MBP chromatography. The tag was cleaved using TEV protease, and the final product was pure on a silver-stained gels. In total, 0.9 mg pure crotamine was obtained from each liter of bacterial culture with endotoxin level approximately 0.15 EU/μg, which is low enough to use in biomedical applications. The identity and intramolecular disulfide bonds were confirmed using MALDI-TOF MS analysis. Purified crotamine inhibited the hKv1.3 channel (but not hKv1.5) in a dose-dependent manner with IC50 value of 67.2 ± 44.7 nM (n = 10), indicating the correct protein folding. The crotamine product fused with MBP at its N-terminus also inhibited the hKv1.3 channel, suggesting that the N-terminus is not involved in the channel binding of the toxin.

Are ticks venomous animals?

INTRODUCTION

As an ecological adaptation venoms have evolved independently in several species of Metazoa. As haematophagous arthropods ticks are mainly considered as ectoparasites due to directly feeding on the skin of animal hosts. Ticks are of major importance since they serve as vectors for several diseases affecting humans and livestock animals. Ticks are rarely considered as venomous animals despite that tick saliva contains several protein families present in venomous taxa and that many Ixodida genera can induce paralysis and other types of toxicoses. Tick saliva was previously proposed as a special kind of venom since tick venom is used for blood feeding that counteracts host defense mechanisms. As a result, the present study provides evidence to reconsider the venomous properties of tick saliva.

RESULTS

Based on our extensive literature mining and in silico research, we demonstrate that ticks share several similarities with other venomous taxa. Many tick salivary protein families and their previously described functions are homologous to proteins found in scorpion, spider, snake, platypus and bee venoms. This infers that there is a structural and functional convergence between several molecular components in tick saliva and the venoms from other recognized venomous taxa. We also highlight the fact that the immune response against tick saliva and venoms (from recognized venomous taxa) are both dominated by an allergic immunity background. Furthermore, by comparing the major molecular components of human saliva, as an example of a non-venomous animal, with that of ticks we find evidence that ticks resemble more venomous than non-venomous animals. Finally, we introduce our considerations regarding the evolution of venoms in Arachnida.

CONCLUSIONS

Taking into account the composition of tick saliva, the venomous functions that ticks have while interacting with their hosts, and the distinguishable differences between human (non-venomous) and tick salivary proteins, we consider that ticks should be referred to as venomous ectoparasites.

Use of medicinal fauna in Mexican traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Mexico has great biodiversity of fauna. The use of fauna with medicinal properties is a common practice since pre-Hispanic times. In the last decade, there has been an interest in ethnozoological studies in Mexico. Therefore, more studies are needed in order to gather information regarding the use of fauna with medicinal properties in México. Ethnozoological studies are necessary in order to discover new medications for human health. This review presents current information in terms of ethnozoological, conservation status, trade, toxicological and pharmacological effects of fauna used for medicinal purposes in Mexican traditional medicine (MTM), based on scientific literature. Future prospects for research with medicinal fauna are discussed.

MATERIALS AND METHODS

Bibliographic investigation was carried out by analyzing recognized books and peer-reviewed papers, consulting worldwide accepted scientific databases from the last five decades. Reports included in this review complied with the three criteria cited as follows: (i) used in Mexican traditional medicine for medicinal and/or magical-religious purposes, (ii) with experimental studies regarding the toxicological or medicinal effects and/or with studies exploring mechanisms of medicinal effects, and (iii) with information obtained from a clear source.

RESULTS

A total of 163 animal species, belonging to 79 families and 4 taxonomic categories, used for medicinal purposes are reported in this review. Medicinal fauna used in MTM come from birds (48), fishes (3), insects (22), mammals (49) and reptiles (41). The most versatile species which had the greatest number of medicinal properties were Mephitis macroura (21 uses), Crotalus atrox (17 uses), Dasypus novemcinctus (13 uses) and Didelphis virginiana (13 uses). However, 14 of the 161 species listed in this review are classified as endangered. Animal species are mainly used for the treatment of inflammatory, respiratory and gastrointestinal diseases. Furthermore, insects and reptiles are the animal groups with more pharmacological studies. Approximately, 11% and 5% of medicinal fauna have been tested in terms of their pharmacological and toxicological effects, respectively.

CONCLUSION

Despite the use of medicinal fauna in MTM, during centuries, there are a very limited number of scientific studies published on this topic. This review highlights the need to perform pharmacological, toxicological and chemical studies with medicinal fauna used in MTM.

Wound healing activity and mechanisms of action of an antibacterial protein from the venom of the eastern diamondback rattlesnake (Crotalus adamanteus)

Basic phospholipase A₂ was identified from the venom of the eastern diamondback rattlesnake. The Crotalus adamanteus toxin-II (CaTx-II) induced bactericidal effects (7.8 µg/ml) on Staphylococcus aureus, while on Burkholderia pseudomallei (KHW), and Enterobacter aerogenes were killed at 15.6 µg/ml. CaTx-II caused pore formation and membrane damaging effects on the bacterial cell wall. CaTx-II was not cytotoxic on lung (MRC-5), skin fibroblast (HEPK) cells and in mice. CaTx-II-treated mice showed significant wound closure and complete healing by 16 days as compared to untreated controls (**P<0.01). Histological examination revealed enhanced collagen synthesis and neovascularization after treatment with CaTx-II versus 2% Fusidic Acid ointment (FAO) treated controls. Measurement of tissue cytokines revealed that interleukin-1 beta (IL-1β) expression in CaTx-II treated mice was significantly suppressed versus untreated controls. In contrast, cytokines involved in wound healing and cell migration i.e., monocyte chemotactic protein-1 (MCP-1), fibroblast growth factor-basic (FGF-b), chemokine (KC), granulocyte-macrophage colony-stimulating factor (GM-CSF) were significantly enhanced in CaTx-II treated mice, but not in the controls. CaTx-II also modulated nuclear factor-kappa B (NF-κB) activation during skin wound healing. The CaTx-II protein highlights distinct snake proteins as a potential source of novel antimicrobial agents with significant therapeutic application for bacterial skin infections.

Snake venoms: attractive antimicrobial proteinaceous compounds for therapeutic purposes

Gram-positive and -negative bacteria are dangerous pathogens that may cause human infection diseases, especially due to the increasingly high prevalence of antibiotic resistance, which is becoming one of the most alarming clinical problems. In the search for novel antimicrobial compounds, snake venoms represent a rich source for such compounds, which are produced by specialized glands in the snake's jawbone. Several venom compounds have been used for antimicrobial effects. Among them are phospholipases A2, which hydrolyze phospholipids and could act on bacterial cell surfaces. Moreover, metalloproteinases and L-amino acid oxidases, which represent important enzyme classes with antimicrobial properties, are investigated in this study. Finally, antimicrobial peptides from multiple classes are also found in snake venoms and will be mentioned. All these molecules have demonstrated an interesting alternative for controlling microorganisms that are resistant to conventional antibiotics, contributing in medicine due to their differential mechanisms of action and versatility. In this review, snake venom antimicrobial compounds will be focused on, including their enormous biotechnological applications for drug development.

Quantitative high-throughput profiling of snake venom gland transcriptomes and proteomes (Ovophis okinavensis and Protobothrops flavoviridis)

Background

Advances in DNA sequencing and proteomics have facilitated quantitative comparisons of snake venom composition. Most studies have employed one approach or the other. Here, both Illumina cDNA sequencing and LC/MS were used to compare the transcriptomes and proteomes of two pit vipers, Protobothrops flavoviridis and Ovophis okinavensis, which differ greatly in their biology.

Results

Sequencing of venom gland cDNA produced 104,830 transcripts. The Protobothrops transcriptome contained transcripts for 103 venom-related proteins, while the Ovophis transcriptome contained 95. In both, transcript abundances spanned six orders of magnitude. Mass spectrometry identified peptides from 100% of transcripts that occurred at higher than contaminant (e.g. human keratin) levels, including a number of proteins never before sequenced from snakes. These transcriptomes reveal fundamentally different envenomation strategies. Adult Protobothrops venom promotes hemorrhage, hypotension, incoagulable blood, and prey digestion, consistent with mammalian predation. Ovophis venom composition is less readily interpreted, owing to insufficient pharmacological data for venom serine and metalloproteases, which comprise more than 97.3% of Ovophis transcripts, but only 38.0% of Protobothrops transcripts. Ovophis venom apparently represents a hybrid strategy optimized for frogs and small mammals.

Conclusions

This study illustrates the power of cDNA sequencing combined with MS profiling. The former quantifies transcript composition, allowing detection of novel proteins, but cannot indicate which proteins are actually secreted, as does MS. We show, for the first time, that transcript and peptide abundances are correlated. This means that MS can be used for quantitative, non-invasive venom profiling, which will be beneficial for studies of endangered species.

Structure of the polypeptide crotamine from the Brazilian rattlesnake Crotalus durissus terrificus

The crystal structure of the myotoxic, cell-penetrating, basic polypeptide crotamine isolated from the venom of Crotalus durissus terrificus has been determined by single-wavelength anomalous dispersion techniques and refined at 1.7 Å resolution. The structure reveals distinct cationic and hydrophobic surface regions that are located on opposite sides of the molecule. This surface-charge distribution indicates its possible mode of interaction with negatively charged phospholipids and other molecular targets to account for its diverse pharmacological activities. Although the sequence identity between crotamine and human β-defensins is low, the three-dimensional structures of these functionally related peptides are similar. Since crotamine is a leading member of a large family of myotoxic peptides, its structure will provide a basis for the design of novel cell-penetrating molecules.