Snake venomics: Comparative analysis of the venom proteomes of the Tunisian snakesCerastes cerastes, Cerastes vipera andMacrovipera lebetina

Emerging anticancer potential and mechanisms of snake venom toxins: A review

Animal-derived venom, like snake venom, has been proven to be valuable natural resources for the drug development. Previously, snake venom was mainly investigated in its pharmacological activities in regulating coagulation, vasodilation, and cardiovascular function, and several marketed cardiovascular drugs were successfully developed from snake venom. In recent years, snake venom fractions have been demonstrated with anticancer properties of inducing apoptotic and autophagic cell death, restraining proliferation, suppressing angiogenesis, inhibiting cell adhesion and migration, improving immunity, and so on. A number of active anticancer enzymes and peptides have been identified from snake venom toxins, such as L-amino acid oxidases (LAAOs), phospholipase A2 (PLA2), metalloproteinases (MPs), three-finger toxins (3FTxs), serine proteinases (SPs), disintegrins, C-type lectin-like proteins (CTLPs), cell-penetrating peptides, cysteine-rich secretory proteins (CRISPs). In this review, we focus on summarizing these snake venom-derived anticancer components on their anticancer activities and underlying mechanisms. We will also discuss their potential to be developed as anticancer drugs in the future.

Composition characterization of various viperidae snake venoms using MS-based proteomics N-glycoproteomics and N-glycomics

Viperidae snake species is widely abundant and responsible for most envenomation cases in Turkey. The structural and compositional profiles of snake venom have been investigated to study the venom component variation across different species and to profile the venom biological activity variation against prey. In this context, we used proteomics, glycoproteomics and glycomics strategies to characterize the protein, glycoproteins and glycan structural and compositional profiles of various snake venoms in the Viperidae family. Moreover, we compared these profiles using the downstream bioinformatics and machine learning classification modules. The overall mass spectrometry profiles identified 144 different proteins, 36 glycoproteins and 78 distinct N-glycan structures varying in composition across the five venoms. A high amount of the characterized proteins belongs to the glycosylated protein family Trypsin-like serine protease (Tryp_SPc), Disintegrin (DISIN), and ADAM Cysteine-Rich (ACR). Most identified N-glycans have a complex chain carrying galactosylated N-glycans abundantly. The glycan composition data obtained from glycoproteomics aligns consistently with the findings from glycomics. The clustering and principal component analyses (PCA) illustrated the composition-based similarities and differences between each snake venom species' proteome, glycoproteome and glycan profiles. Specifically, the N-glycan profiles of M. xanthina (Mx) and V. a. ammodytes (Vaa) venoms were identical and difficult to differentiate; in contrast, their proteome profiles were distinct. Interestingly, the variety of the proteins across the species highlighted the impact of glycosylation on the diversity of the glycosylated protein families. This proposed high throughput approach provides accurate and comprehensive profiles of the composition and function of various Viperidae snake venoms.

Functional Characterization and Anti-Tumor Effect of a Novel Group II Secreted Phospholipase A2 from Snake Venom of Saudi Cerastes cerates gasperetti

Secreted phospholipases A2 are snake-venom proteins with many biological activities, notably anti-tumor activity. Phospholipases from the same snake type but different geographical locations have shown similar biochemical and biological activities with minor differences in protein sequences. Thus, the discovery of a new phospholipase A2 with unique characteristics identified in a previously studied venom could suggest the origins of these differences. Here, a new Group II secreted phospholipase A2 (Cc-PLA2-II) from the snake venom of Saudi Cerastes cerastes gasperetti was isolated and characterized. The purified enzyme had a molecular weight of 13.945 kDa and showed high specific activity on emulsified phosphatidylcholine of 1560 U/mg at pH 9.5 and 50 °C with strict calcium dependence. Interestingly, stability in extreme pH and high temperatures was observed after enzyme incubation at several pH levels and temperatures. Moreover, a significant dose-dependent cytotoxic anti-tumor effect against six human cancer cell lines was observed with concentrations of Cc-PLA2 ranging from 2.5 to 8 µM. No cytotoxic effect on normal human umbilical-vein endothelial cells was noted. These results suggest that Cc-PLA2-II potentially has angiogenic activity of besides cytotoxicity as part of its anti-tumor mechanism. This study justifies the inclusion of this enzyme in many applications for anticancer drug development.

Venomics of the milos viper (Macrovipera schweizeri) unveils patterns of venom composition and exochemistry across blunt-nosed viper venoms

Introduction: Snakebite is a neglected tropical disease and a globally important driver of death and morbidity. Vipers of the genus Macrovipera (Viperidae: Viperinae) are among the snakes of higher medical importance in the Old World. Despite the medical relevance of Macrovipera venoms, the knowledge regarding them is heterogeneously distributed with virtually all works conducted so far focusing on subspecies of Macrovipera lebetinus, while other species within the genus are largely overlooked. Here we present the first proteomic evaluation of the venom from the Greek endemic Milos viper (Macrovipera schweizeri). In line with clinical symptoms typically elicited by Macrovipera envenomations, Milos viper venom primarily comprises coagulotoxic and cytotoxic protein families, such as metalloproteinases (svMP) and serine proteases (svSP). Methods: We conducted comparative bioactivity assays on venoms from M. schweizeri and the M. lebetinus subspecies M. lebetinus cernovi, M. lebetinus obtusa, and M. lebetinus turanica, and showed that they all exhibit similarities in levels of cytotoxicity proteolytic activity, and inhibition of prokaryotic growth. Lastly, we compared Macrovipera venom profiles by 1D-SDS-PAGE and RP-HPLC, as well as our proteomic data with previously published Macrovipera venom proteomes. Results and discussion: The analyzes performed to reveal that a general venom profile seems to be conserved across blunt-nosed vipers, and that, M. schweizeri envenomations, similarly to those caused by other blunt-nosed vipers, are able to cause significant tissue damage. The present work represents an important starting point for the development of comparative studies across the full taxonomic range of the genus Macrovipera and can potentially help optimize the treatment of envenomations caused by M. schweizeri.

Insight into the Toxicological and Pathophysiological Effects of Moroccan Vipers' Venom: Assessing the Efficacy of Commercial Antivenom for Neutralization

Morocco is one of the richest countries in biodiversity in the Mediterranean region, especially in its ophidian fauna. In total, there are eight species of venomous snakes, with seven belonging to the Viperidae family, responsible for 67.2% of severe envenomation cases in the country. Cerastes cerastes, Daboia mauritanica and Bitis arietans are considered among the most venomous vipers whose bites cause high levels of morbidity, disability or mortality. Despite their wide distribution in the kingdom, the incidence of these snakebites remains poorly understood and largely underestimated. Moreover, intraspecific variations in the venom composition significantly affect the effectiveness of antivenoms. Due to the unavailability of locally produced antivenoms, we evaluated the efficacy of Inoserp-MENA, the only available antivenom in Morocco, against C. cerastes, D. mauritanica and B. arietans. First, we conducted a comprehensive characterization of these venoms, including an LD₅₀ test to examine their toxicity and SDS-PAGE as a technique to analyze the enzymes responsible for biological activities, such as hemorrhagic and edematous activities and myotoxicity, which generate physiopathological effects in the skin, paws and muscles of envenomed mice. Then, we assessed the ability of Inoserp-MENA antivenom to neutralize the toxic activities of Moroccan vipers. Our results indicate that the venom of C. cerastes, D. mauritanica and B. arietans are toxic, causing severe alterations such as edema, myotoxicity, myonecrosis and significant hemorrhages with the formation of hemorrhagic foci. C. cerastes venom is more dangerous in terms of lethality and hemorrhages, while B. arietans venom is more edematous. The effects of C. cerastes venom were effectively neutralized, but Inoserp-MENA antivenom failed to protect mice against the toxic effects induced by B. arietans and D. mauritanica venom. The study reveals alarming shortcomings in the effectiveness of the current commercially available antivenom's dosage and neutralization capabilities, highlighting the urgent need to develop a region-specific viper envenomation therapy.

Venomous Bites, Stings and Poisoning by European Vertebrates as an Overlooked and Emerging Medical Problem: Recognition, Clinical Aspects and Therapeutic Management

Europe presents a high number of venomous and poisonous animals able to elicit medically relevant symptoms in humans. However, since most of the accidents involving venomous or poisonous animals in Europe are unreported, their incidence and morbidity are severely overlooked. Here we provide an overview of the European vertebrate species of greatest toxicological interest, the clinical manifestations their toxins can cause, and their treatment. We report the clinical symptoms induced by envenomations and poisoning caused by reptiles, fishes, amphibians and mammals in Europe, ranging from mild, local symptoms (e.g., erythema, edema) to systemic and potentially deadly. The present work constitutes a tool for physicians to recognize envenomation/poisoning symptoms caused by the most medically relevant European vertebrates and to decide which approach is the most appropriate to treat them.

Medically important snakes and snakebite envenoming in Iran

Snakebite is a common health condition in Iran with a diverse snake fauna, especially in tropical southern and mountainous western areas of the country with plethora of snake species. The list of medically important snakes, circumstances and effects of their bite, and necessary medical care require critical appraisal and should be updated regularly. This study aims to review and map the distributions of medically important snake species of Iran, re-evaluate their taxonomy, review their venomics, describe the clinical effects of envenoming, and discuss medical management and treatment, including the use of antivenom. Nearly 350 published articles and 26 textbooks with information on venomous and mildly venomous snake species and snakebites of Iran, were reviewed, many in Persian (Farsi) language, making them relatively inaccessible to an international readership. This has resulted in a revised updated list of Iran's medically important snake species, with taxonomic revisions of some, compilation of their morphological features, remapping of their geographical distributions, and description of species-specific clinical effects of envenoming. Moreover, the antivenom manufactured in Iran is discussed, together with treatment protocols that have been developed for the hospital management of envenomed patients.

Impact of Envenomation With Snake Venoms on Rabbit Carcass Decomposition and Differential Adult Dipteran Succession Patterns

The current study investigates the postmortem successional patterns of necrophagous dipteran insects and the rabbit carcass decomposition rate upon envenomation with snake venom. In total, 15 rabbits, Oryctolagus cuniculus domesticus L. (Lagomorpha, Leporidae), were divided into 3 groups (5 rabbits each; n = 5); the first and second groups were injected with lethal doses of venoms from the Egyptian cobra, Naja haje L. (Squamata, Elapidae), and the horned viper, Cerastes cerastes L. (Squamata, viperidae), respectively. The third group (control) was injected with 0.85% physiological saline and euthanized with CO2. The carcass decomposition stages: fresh, bloating, decay, and dry were recorded and monitored. Data revealed that envenomation shortened the decomposition process by 3 d, 20% shorter than the control. The overall succession pattern of fly species revealed a lower abundance during the fresh stage, which peaked during the decay stage, and declined to the minimum number in the dry stage at the end of the 15-d experimental duration. A total of 2,488 individual flies, belonging to 21 species of 10 families, were collected from all experimental carcasses. The Calliphoridae, Muscidae, and Sarcophagidae were the most abundant and diverse families, whereas the other seven families were rare and least abundant. Although C. cerastes venom was significantly less lethal than N. haje, it showed a faster carcass decomposition process and a higher impact on fly abundance. These data showed that envenomation impacts insect succession and carcass decomposition, which should be taken into account when using insects in forensic investigations since envenomation with snake venoms is one of the leading causes of death worldwide.

The First Snake Venom KTS/Disintegrins-Integrin Interactions Using Bioinformatics Approaches

Snake venom contains a number of active molecules that have been shown to possess high anti-tumor activities; disintegrins are an excellent example among these. Their ability to interact and bind with integrins suggests that they could be very valuable molecules for the development of new cancer therapeutic approaches. However, in the absence of a clear Lysine-Threonine-Serine (KTS) Disintegrins Integrin interaction model, the exact compound features behind it are still unknown. In this study, we investigated the structural characteristics of three KTS-disintegrins and the interaction mechanisms with the α1β1 integrin receptor using in silico bioinformatics approaches. Normal mode analysis showed that the flexibility of the KTSR motif and the C-terminal region play a key role and influence the KTS-Disintegrin-integrin interaction. Protein-protein docking also suggested that the interaction involving the KTSR motif is highly dependent on the residue following K21, S23 and R24. These findings contribute to a better understanding of the KTS-Disintegrin-Integrin structural differences and their interactions with α1β1 receptors, which could improve the selection process of the best active molecules for antitumor therapies.

High-throughput proteomics and in vitro functional characterization of the 26 medically most important elapids and vipers from sub-Saharan Africa

Venomous snakes are important parts of the ecosystem, and their behavior and evolution have been shaped by their surrounding environments over the eons. This is reflected in their venoms, which are typically highly adapted for their biological niche, including their diet and defense mechanisms for deterring predators. Sub-Saharan Africa is rich in venomous snake species, of which many are dangerous to humans due to the high toxicity of their venoms and their ability to effectively deliver large amounts of venom into their victims via their bite. In this study, the venoms of 26 of sub-Saharan Africa's medically most relevant elapid and viper species were subjected to parallelized toxicovenomics analysis. The analysis included venom proteomics and in vitro functional characterization of whole venom toxicities, enabling a robust comparison of venom profiles between species. The data presented here corroborate previous studies and provide biochemical details for the clinical manifestations observed in envenomings by the 26 snake species. Moreover, two new venom proteomes (Naja anchietae and Echis leucogaster) are presented here for the first time. Combined, the presented data can help shine light on snake venom evolutionary trends and possibly be used to further improve or develop novel antivenoms.

The Contribution of Phospholipase A2 and Metalloproteinases to the Synergistic Action of Viper Venom on the Bioenergetic Profile of Vero Cells

Increasing concern about the use of animal models has stimulated the development of in vitro cell culture models for analysis of the biological effects of snake venoms. However, the complexity of animal venoms and the extreme synergy of the venom components during envenomation calls for critical review and analysis. The epithelium is a primary target for injected viper venom's toxic substances, and therefore, is a focus in modern toxinology. We used the Vero epithelial cell line as a model to compare the actions of a crude Macrovipera lebetina obtusa (Levantine viper) venom with the actions of the same venom with two key enzymatic components inhibited (specifically, phospholipase A2 (PLA2) and metalloproteinases) in the bioenergetic cellular response, i.e., oxygen uptake and reactive oxygen species generation. In addition to the rate of free-radical oxidation and lipid peroxidation, we measured real-time mitochondrial respiration (based on the oxygen consumption rate) and glycolysis (based on the extracellular acidification rate) using a Seahorse analyzer. Our data show that viper venom drives an increase in both glycolysis and respiration in Vero cells, while the blockage of PLA2 or/and metalloproteinases affects only the rates of the oxidative phosphorylation. PLA2-blocking in venom also increases cytotoxic activity and the overproduction of reactive oxygen species. These data show that certain components of the venom may have a different effect within the venom cocktail other than the purified enzymes due to the synergy of the venom components.

A Review of the Proteomic Profiling of African Viperidae and Elapidae Snake Venoms and Their Antivenom Neutralisation

Snakebite envenoming is a neglected tropical disease (NTD) that results from the injection of snake venom of a venomous snake into animals and humans. In Africa (mainly in sub-Saharan Africa), over 100,000 envenomings and over 10,000 deaths per annum from snakebite have been reported. Difficulties in snakebite prevention and antivenom treatment are believed to result from a lack of epidemiological data and underestimated figures on snakebite envenoming-related morbidity and mortality. There are species- and genus-specific variations associated with snake venoms in Africa and across the globe. These variations contribute massively to diverse differences in venom toxicity and pathogenicity that can undermine the efficacy of adopted antivenom therapies used in the treatment of snakebite envenoming. There is a need to profile all snake venom proteins of medically important venomous snakes endemic to Africa. This is anticipated to help in the development of safer and more effective antivenoms for the treatment of snakebite envenoming within the continent. In this review, the proteomes of 34 snake venoms from the most medically important snakes in Africa, namely the Viperidae and Elipdae, were extracted from the literature. The toxin families were grouped into dominant, secondary, minor, and others based on the abundance of the protein families in the venom proteomes. The Viperidae venom proteome was dominated by snake venom metalloproteinases (SVMPs-41%), snake venom serine proteases (SVSPs-16%), and phospholipase A₂ (PLA₂-17%) protein families, while three-finger toxins (3FTxs-66%) and PLA₂s (16%) dominated those of the Elapidae. We further review the neutralisation of these snake venoms by selected antivenoms widely used within the African continent. The profiling of African snake venom proteomes will aid in the development of effective antivenom against snakebite envenoming and, additionally, could possibly reveal therapeutic applications of snake venom proteins.

Comparative Venom Proteomics of Iranian, Macrovipera lebetina cernovi, and Cypriot, Macrovipera lebetina lebetina, Giant Vipers

Envenoming by Macrovipera lebetina subspecies causes severe life-threatening difficulties for people living in North Africa and the Middle East. To better understand the pathophysiology of envenoming and improve patient management, knowledge about the venom components of the subspecies is essential. Here, the venom proteomes of Macrovipera lebetina lebetina from Cyprus and Macrovipera lebetina cernovi from Iran were characterized using RP-HPLC separation of the crude venom proteins, SDS-PAGE of fractionated proteins, and LC-MS/MS of peptides obtained from in-gel tryptic digestion of protein bands. Moreover, we also used high-resolution shot-gun proteomics to gain more reliable identification, where the whole venom proteomes were subjected directly to in-solution digestion before LC-HR-MS/MS. The data revealed that both venoms consisted of at least 18 protein families, of which snake venom Zn2+-dependent metalloprotease (SVMP), serine protease, disintegrin, phospholipase A2, C-type lectin-like, and L-amino acid oxidase, together accounted for more than 80% of the venoms’ protein contents. Although the two viper venoms shared mostly similar protein classes, the relative occurrences of these toxins were different in each snake subspecies. For instance, P-I class of SVMP toxins were found to be more abundant than P-III class in the venoms of M. l. cernovi compared to M. l. lebetina, which gives hints at a more potent myonecrotic effect and minor systemic hemorrhage following envenoming by M. l. cernovi than M. l. lebetina. Moreover, single-shot proteomics also revealed many proteins with low abundance (<1%) within the venoms, such as aminopeptidase, hyaluronidase, glutaminyl-peptide cyclotransferase, cystatin, phospholipase B, and vascular endothelial growth factor. Our study extends the in-depth understanding of the venom complexity of M. lebetina subspecies, particularly regarding toxin families associated with envenoming pathogenesis and those hard-detected protein classes expressed in trace amounts.

From Snake Venoms to Therapeutics: A Focus on Natriuretic Peptides

Snake venom is a cocktail of multifunctional biomolecules that has evolved with the purpose of capturing prey and for defense. These biomolecules are classified into different classes based on their functions. They include three-finger toxins, natriuretic peptides, phospholipases and metalloproteinases. The focus for this review is on the natriuretic peptide (NP), which is an active component that can be isolated from the venoms of vipers and mambas. In these venoms, NPs contribute to the lowering of blood pressure, causing a rapid loss of consciousness in the prey such that its mobility is reduced, paralyzing the prey, and often death follows. Over the past 30 years since the discovery of the first NP in the venom of the green mamba, venom NPs have shown potential in the development of drug therapy for heart failure. Venom NPs have long half-lives, different pharmacological profiles, and may also possess different functions in comparison to the mammalian NPs. Understanding their mechanisms of action provides the strategies needed to develop new NPs for treatment of heart failure. This review summarizes the venom NPs that have been identified over the years and how they can be useful in drug development.

Terrestrial venomous animals, the envenomings they cause, and treatment perspectives in the Middle East and North Africa

The Middle East and Northern Africa, collectively known as the MENA region, are inhabited by a plethora of venomous animals that cause up to 420,000 bites and stings each year. To understand the resultant health burden and the key variables affecting it, this review describes the epidemiology of snake, scorpion, and spider envenomings primarily based on heterogenous hospital data in the MENA region and the pathologies associated with their venoms. In addition, we discuss the venom composition and the key medically relevant toxins of these venomous animals, and, finally, the antivenoms that are currently in use to counteract them. Unlike Asia and sub-Saharan Africa, scorpion stings are significantly more common (approximately 350,000 cases/year) than snakebites (approximately 70,000 cases/year) and present the most significant contributor to the overall health burden of envenomings, with spider bites being negligible. However, this review also indicates that there is a substantial lack of high-quality envenoming data available for the MENA region, rendering many of these estimates speculative. Our understanding of the venoms and the toxins they contain is also incomplete, but already presents clear trends. For instance, the majority of snake venoms contain snake venom metalloproteinases, while sodium channel-binding toxins and potassium channel-binding toxins are the scorpion toxins that cause most health-related challenges. There also currently exist a plethora of antivenoms, yet only few are clinically validated, and their high cost and limited availability present a substantial health challenge. Yet, some of the insights presented in this review might help direct future research and policy efforts toward the appropriate prioritization of efforts and aid the development of future therapeutic solutions, such as next-generation antivenoms.

Old World Vipers-A Review about Snake Venom Proteomics of Viperinae and Their Variations

Fine-tuned by millions of years of evolution, snake venoms have frightened but also fascinated humanity and nowadays they constitute potential resources for drug development, therapeutics and antivenoms. The continuous progress of mass spectrometry techniques and latest advances in proteomics workflows enabled toxinologists to decipher venoms by modern omics technologies, so-called ‘venomics’. A tremendous upsurge reporting on snake venom proteomes could be observed. Within this review we focus on the highly venomous and widely distributed subfamily of Viperinae (Serpentes: Viperidae). A detailed public literature database search was performed (2003–2020) and we extensively reviewed all compositional venom studies of the so-called Old-World Vipers. In total, 54 studies resulted in 89 venom proteomes. The Viperinae venoms are dominated by four major, four secondary, six minor and several rare toxin families and peptides, respectively. The multitude of different venomics approaches complicates the comparison of venom composition datasets and therefore we differentiated between non-quantitative and three groups of quantitative workflows. The resulting direct comparisons within these groups show remarkable differences on the intra- and interspecies level across genera with a focus on regional differences. In summary, the present compilation is the first comprehensive up-to-date database on Viperinae venom proteomes and differentiating between analytical methods and workflows.

Examination of the Efficacy and Cross-Reactivity of a Novel Polyclonal Antibody Targeting the Disintegrin Domain in SVMPs to Neutralize Snake Venom

Snake envenomation can result in hemorrhage, local necrosis, swelling, and if not treated properly can lead to adverse systemic effects such as coagulopathy, nephrotoxicity, neurotoxicity, and cardiotoxicity, which can result in death. As such, snake venom metalloproteinases (SVMPs) and disintegrins are two toxic components that contribute to hemorrhage and interfere with the hemostatic system. Administration of a commercial antivenom is the common antidote to treat snake envenomation, but the high-cost, lack of efficacy, side effects, and limited availability, necessitates the development of new strategies and approaches for therapeutic treatments. Herein, we describe the neutralization ability of anti-disintegrin polyclonal antibody on the activities of isolated disintegrins, P-II/P-III SVMPs, and crude venoms. Our results show disintegrin activity on platelet aggregation in whole blood and the migration of the SK-Mel-28 cells that can be neutralized with anti-disintegrin polyclonal antibody. We characterized a SVMP and found that anti-disintegrin was also able to inhibit its activity in an in vitro proteolytic assay. Moreover, we found that anti-disintegrin could neutralize the proteolytic and hemorrhagic activities from crude Crotalus atrox venom. Our results suggest that anti-disintegrin polyclonal antibodies have the potential for a targeted approach to neutralize SVMPs in the treatment of snakebite envenomations.

Venom natriuretic peptides guide the design of heart failure therapeutics

Heart failure (HF) affects over 26 million people world-wide. It is a syndrome triggered by loss of normal cardiac function due to many acute (eg myocardial infarction) and/or chronic (eg hypertension) causes and characterized by mixed beneficial and deleterious activation of a complex of multifaceted neurohormonal systems the net effect of which frequently is further adverse disruption of pressure-volume homeostasis. Unlike the situation in chronic heart failure, current strategies for treatment of acute heart failure are empirical and lack a strong evidence base. Management includes any of a combination of vasodilators, diuretics and ionotropic agents depending on the hemodynamic profile of the patient. Despite the improvement in the options available to improve outcomes in patients with chronic HF, for several decades little gain has been made in the treatment of the acute decompensated state. Morbidity and mortality rates remain high necessitating new therapeutic agents. The cardiac natriuretic peptides (NPs) are key hormones in pressure-volume homoeostasis. There are three isoforms of mammalian NPs, namely ANP, BNP and CNP. These peptides bind to membrane-bound NP receptors (NPRs) on the heart, vasculature and kidney to lower blood pressure and circulating volume. Intravenous infusion of NPs in HF patients improves hemodynamic status but is associated with occasional severe hypotension. Apart from mammalian NPs, snake venom NPs are an excellent source of pharmacologically distinct ligands that offer the possibility of engineering NPs for therapeutic purposes. Venom NPs have long half-lives, differential NPR activation profiles and varied NPR specificity. The scaffolds of venom NPs encode the molecular information for designing NPs with longer half-lives and improved and differential vascular and renal functions. This review focuses on the structure-function paradigm of mammalian and venom NPs and the different peptide engineering strategies that have been utilized in the design of clinically relevant new NP-analogues.

Investigating the cytotoxic effects of the venom proteome of two species of the Viperidae family (Cerastes cerastes and Cryptelytrops purpureomaculatus) from various habitats

Animal secretions are of great interest in terms of drug development due to their complex protein and peptide composition. Especially, in the field of therapeutic medications such as anti-cancer drugs snake venoms receive attention. In this study, we address two Viperidae species from various habitats with a particular focus on the cytotoxic potential along with the decomplexation of the venom proteome: the horned desert viper (Cerastes cerastes), native to desert regions of North Africa and the mangrove pit viper (Cryptelytrops purpureomaculatus), found in coastal forests of Southeast Asia. Initial cytotoxic screenings of the crude venoms revealed diverse activity, with the highest effect against SHSY5Y human glioblastoma carcinoma cells compared to other cancerous and non-cancerous cell lines. In-depth cytotoxicity studies of SHSY5Y cells with purified venom fractions revealed heterodimeric disintegrins from C. cerastes venom, which exerted a high cytotoxic activity with IC₅₀ values from 0.11 to 0.58 μM and a disintegrin-like effect on SHSY5Y morphology was observed due to cell detachment. Furthermore, two polyproline BPP-related peptides, one PLA₂ and a peptide-rich fraction were determined for C. purpureomaculatus with moderate IC₅₀ values between 3 and 51 μM. Additionally, the decryption of the venom proteomes by snake venomic mass spectrometry and comparison of the same species from different habitats revealed slight differences in the composition.

Morphometric characteristics and seasonal proximity to water of the Cypriot blunt-nosed viper Macrovipera lebetina lebetina (Linnaeus, 1758)

BACKGROUND

The blunt-nosed viper Macrovipera lebetina (Linnaeus, 1758) is a medically important snake species in the Middle East. Its nominate subspecies Macrovipera l. lebetina is confined to Cyprus, where it is the only dangerously venomous snake species and heavily pursued. Despite the viper's large size, data on its body mass and sex-specific morphological differences are scarce. It is commonly believed that M. l. lebetina prefers freshwater proximity during summer. Hence, we aimed at investigating M. l. lebetina sex-specific morphological differences and its possible attraction to freshwater bodies in late summer.

METHODS

Morphometric characteristics, proximity to water and conservation status of M. l. lebetina were investigated in Paphos district (Cyprus) in 2014, 2015 and 2017. Vipers were caught in different habitats, examined morphologically for metric and meristic characters, and released back into their habitat. Additionally, local people were interviewed about the conservation situation of the species.

RESULTS

Of 38 recorded blunt-nosed vipers, morphological characteristics were collected from 34 (10 adult males, 16 adult females, eight unsexed juveniles). Rounded total length (ToL) ranged from 23.5 cm to 133.0 cm and weight between 10 g and 1456 g. Adult males significantly exceeded adult females in tail length (TaL), ToL and head length (HL). No significant sex-specific differences were found in snout-vent length (SVL), head width (HW), weight or body condition index (BCI), nor for the ratios TaL / SVL, TaL / ToL, HL / SVL or HL / HW. Adult females from late summer (2015) had a significantly lower mean BCI than those from spring (2014).Distances of blunt-nosed vipers to the nearest water bodies (natural and artificial, respectively) did not differ significantly between spring (2014) and late summer (2015). There was also no significant difference between the distances of vipers to natural and to artificial water bodies in spring (and late summer).

CONCLUSIONS

Adult male blunt-nosed vipers exceed adult females in TaL, ToL and HL. Adult females are likely in a more vulnerable body condition in late summer than in spring. Periodic drying out of freshwater bodies in summer probably does not affect the species' occurrence. Educational workshops and habitat conservation are recommended for reducing human-viper conflict.

Does size matter? Venom proteomic and functional comparison between night adder species (Viperidae: Causus) with short and long venom glands

Night adders (Causus species within the Viperidae family) are amphibian specialists and a common source of snakebite in Africa. Some species are unique in that they have the longest venom glands of any viper, extending approximately 10% of the body length. Despite their potential medical importance and evolutionary novelty, their venom has received almost no research attention. In this study, venoms from a short-glanded species (C. lichtensteinii) and from a long-glanded species (C. rhombeatus) were compared using a series of proteomic and bioactivity testing techniques to investigate and compare the toxin composition and functioning of the venoms of these two species. Both C. rhombeatus and C. lichtensteinii were similar in overall venom composition and inhibition of blood coagulation through non-clotting proteolytic cleavage of fibrinogen. While the 1D gel profiles were very similar to each other in the toxin types present, 2D gel analyses revealed isoformic differences within each toxin classes. This variation was congruent with differential efficacy of South African Institute for Medical Research snake polyvalent antivenom, with C. lichtensteinii unaffected at the dose tested while C. rhombeatus was moderately but significantly neutralized. Despite the variation within toxin classes, the similarity in overall venom biochemistry suggests that the selection pressure for the evolution of long glands served to increase venom yield in order to subjugate proportionally large anurans as a unique form of niche partitioning, and is not linked to significant changes in venom function. These results not only contribute to the body of venom evolution knowledge but also highlight the limited clinical management outcomes for Causus envenomations.

Application of Metabolomic Tools for Studying Low Molecular-Weight Fraction of Animal Venoms and Poisons

Both venoms and poisonous secretions are complex mixtures that assist in defense, predation, communication, and competition in the animal world. They consist of variable bioactive molecules, such as proteins, peptides, salts and also metabolites. Metabolomics opens up new perspectives for the study of venoms and poisons as it gives an opportunity to investigate their previously unexplored low molecular-weight components. The aim of this article is to summarize the available literature where metabolomic technologies were used for examining the composition of animal venoms and poisons. The paper discusses only the low molecular-weight components of venoms and poisons collected from snakes, spiders, scorpions, toads, frogs, and ants. An overview is given of the analytical strategies used in the analysis of the metabolic content of the samples. We paid special attention to the classes of compounds identified in various venoms and poisons and potential applications of the small molecules (especially bufadienolides) discovered. The issues that should be more effectively addressed in the studies of animal venoms and poisons include challenges related to sample collection and preparation, species-related chemical diversity of compounds building the metabolome and a need of an online database that would enhance identification of small molecule components of these secretions.

Studying Smaller and Neglected Organisms in Modern Evolutionary Venomics Implementing RNASeq (Transcriptomics)-A Critical Guide

Venoms are evolutionary key adaptations that species employ for defense, predation or competition. However, the processes and forces that drive the evolution of venoms and their toxin components remain in many aspects understudied. In particular, the venoms of many smaller, neglected (mostly invertebrate) organisms are not characterized in detail, especially with modern methods. For the majority of these taxa, even their biology is only vaguely known. Modern evolutionary venomics addresses the question of how venoms evolve by applying a plethora of -omics methods. These recently became so sensitive and enhanced that smaller, neglected organisms are now more easily accessible to comparatively study their venoms. More knowledge about these taxa is essential to better understand venom evolution in general. The methodological core pillars of integrative evolutionary venomics are genomics, transcriptomics and proteomics, which are complemented by functional morphology and the field of protein synthesis and activity tests. This manuscript focuses on transcriptomics (or RNASeq) as one toolbox to describe venom evolution in smaller, neglected taxa. It provides a hands-on guide that discusses a generalized RNASeq workflow, which can be adapted, accordingly, to respective projects. For neglected and small taxa, generalized recommendations are difficult to give and conclusions need to be made individually from case to case. In the context of evolutionary venomics, this overview highlights critical points, but also promises of RNASeq analyses. Methodologically, these concern the impact of read processing, possible improvements by perfoming multiple and merged assemblies, and adequate quantification of expressed transcripts. Readers are guided to reappraise their hypotheses on venom evolution in smaller organisms and how robustly these are testable with the current transcriptomics toolbox. The complementary approach that combines particular proteomics but also genomics with transcriptomics is discussed as well. As recently shown, comparative proteomics is, for example, most important in preventing false positive identifications of possible toxin transcripts. Finally, future directions in transcriptomics, such as applying 3rd generation sequencing strategies to overcome difficulties by short read assemblies, are briefly addressed.

Combined venom profiling and cytotoxicity screening of the Radde's mountain viper (Montivipera raddei) and Mount Bulgar Viper (Montivipera bulgardaghica) with potent cytotoxicity against human A549 lung carcinoma cells

Here we report the first characterization of the endemic Mount Bulgar Viper (Montivipera bulgardaghica) and Radde's mountain viper (Montivipera raddei) venom by a combined approach using intact mass profiling and bottom-up proteomics. The cytotoxicity screening of crude venom as well as isolated serine proteases revealed a high activity against A549 human lung carcinoma cells. By means of intact mass profiling of native and reduced venom we observed basic and acidic phospholipases type A₂. Moreover, the analysis revealed snake venom metalloproteases, cysteine-rich secretory proteins, disintegrins, snake venom serine proteases, C-type lectins, a vascular endothelial growth factor and an L-amino acid oxidase.

Hemorrhagic metalloproteinase, Cc HSM-III, isolated from Cerastes cerastes venom: Purification and biochemical characterization

Snake venom metalloproteinases are the most abundant toxins in Viperidae venoms. In this study, a new hemorrhagin, Cc HSM-III (66 kDa), was purified from Cerastes cerastes venom by gel filtration, ion exchange, and reversed-phase high-performance liquid chromatographies. The analysis of Cc HSM-III by liquid chromatography with a tandem mass spectrometry revealed 32 peptides sharing a homology with P-III metalloproteinases from Echis ocellatus snake venom. Cc HSM-III displays hemorrhagic activity with a minimal hemorrhagic dose of 5 μg, which is abolished by ethylene diamine tetracetic acid but not by phenylmethylsulfonyl fluoride. The mechanism underlying Cc HSM-III hemorrhagic activity is probably due to its extensive proteolytic activity against type IV collagen. Cc HSM-III induces local tissue damage and an inflammatory response by upregulating both matrix metalloproteinase 2 and 9 in skin of mice. Thus, Cc HSM-III may play a key role in the pathogenesis of C. cerastes envenomation.

Metalloproteases Affecting Blood Coagulation, Fibrinolysis and Platelet Aggregation from Snake Venoms: Definition and Nomenclature of Interaction Sites

Snake venom metalloproteases, in addition to their contribution to the digestion of the prey, affect various physiological functions by cleaving specific proteins. They exhibit their activities through activation of zymogens of coagulation factors, and precursors of integrins or receptors. Based on their structure–function relationships and mechanism of action, we have defined classification and nomenclature of functional sites of proteases. These metalloproteases are useful as research tools and in diagnosis and treatment of various thrombotic and hemostatic conditions. They also contribute to our understanding of molecular details in the activation of specific factors involved in coagulation, platelet aggregation and matrix biology. This review provides a ready reference for metalloproteases that interfere in blood coagulation, fibrinolysis and platelet aggregation.

Polyamines as Snake Toxins and Their Probable Pharmacological Functions in Envenomation

While decades of research have focused on snake venom proteins, far less attention has been paid to small organic venom constituents. Using mostly pooled samples, we surveyed 31 venoms (six elapid, six viperid, and 19 crotalid) for spermine, spermidine, putrescine, and cadaverine. Most venoms contained all four polyamines, although some in essentially trace quantities. Spermine is a potentially significant component of many viperid and crotalid venoms (≤0.16% by mass, or 7.9 µmol/g); however, it is almost completely absent from elapid venoms assayed. All elapid venoms contained larger molar quantities of putrescine and cadaverine than spermine, but still at levels that are likely to be biologically insignificant. As with venom purines, polyamines impact numerous physiological targets in ways that are consistent with the objectives of prey envenomation, prey immobilization via hypotension and paralysis. Most venoms probably do not contain sufficient quantities of polyamines to induce systemic effects in prey; however, local effects seem probable. A review of the pharmacological literature suggests that spermine could contribute to prey hypotension and paralysis by interacting with N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, nicotinic and muscarinic acetylcholine receptors, γ-Aminobutyric acid (GABA) receptors, blood platelets, ryanodine receptors, and Ca²⁺-ATPase. It also blocks many types of cation-permeable channels by interacting with negatively charged amino acid residues in the channel mouths. The site of envenomation probably determines which physiological targets assume the greatest importance; however, venom-induced liberation of endogenous, intracellular stores of polyamines could potentially have systemic implications and may contribute significantly to envenomation sequelae.

Haemostasis disorders caused by envenomation by Cerastes cerastes and Macrovipera mauritanica vipers

Viper venoms are a real source of proteolytic enzymes causing clotting, bleeding, edema, necrosis, hemorrhage, pain at the bite site and systemic changes. This study was conducted to evaluate the changes induced in hematological and haemostatic parameters in rabbits after 1, 3, 6 and 24 h post-venom of subcutaneously administration of a sublethal dose of Cerastes cerastes and Macrovipera mauritanica venoms. Our results indicated that most hematological and haemostatic parameters showed significant changes 3 and 6 h after envenomation. The hemoglobin, hematocrit, red blood cells, platelets and prothrombin time were reduced significantly 3 h after envenomation. A very significant increase in the levels of white blood cells, lymphocytes, monocytes, activated thromboplastin time and fibrinogen were recorded 6 h following envenomation. However, no significant difference was found for the mean corpuscular volume, corpuscular hemoglobin content and mean corpuscular hemoglobin concentration throughout the whole duration of the experiment. These results suggest that severe hematological and haemostatic changes may be initiated during the early stages of envenomation leading to local and systemic hemorrhages and coagulopathies which are the main cause of death in case of vipers envenomation.

Biochemical and monolayer characterization of Tunisian snake venom phospholipases

The present study investigated the kinetic and interfacial properties of two secreted phospholipases isolated from Tunisian vipers'venoms: Cerastes cerastes (CC-PLA2) and Macrovipera lebetina transmediterranea (MVL-PLA2). Results show that these enzymes have great different abilities to bind and hydrolyse phospholipids. Using egg-yolk emulsions as substrate at pH 8, we found that MVL-PLA2 has a specific activity of 1473U/mg at 37°C in presence of 1mM CaCl2. Furthermore the interfacial kinetic and binding data indicate that MVL-PLA2 has a preference to the zwitterionic phosphatidylcholine monolayers (PC). Conversely, CC-PLA2 was found to be able to hydrolyse preferentially negatively charged head group phospholipids (PG and PS) and exhibits a specific activity 9 times more important (13333U/mg at 60°C in presence of 3mM CaCl2). Molecular models of both CC-PLA2 and MVL-PLA2 3D structures have been built and their electrostatic potentials surfaces have been calculated. A marked anisotropy of the overall electrostatic charge distribution leads to a significantly difference in the dipole moment intensity between the two enzymes explaining the great differences in catalytic and binding properties, which seems to be governed by the electrostatic and hydrophobic forces operative at the surface of the two phospholipases.

Heterodimeric l-amino acid oxidase enzymes from Egyptian Cerastes cerastes venom: Purification, biochemical characterization and partial amino acid sequencing

Two l-amino acid oxidase enzyme isoforms, Cc-LAAOI and Cc-LAAOII were purified to apparent homogeneity from Cerastes cerastes venom in a sequential two-step chromatographic protocol including; gel filtration and anion exchange chromatography. The native molecular weights of the isoforms were 115 kDa as determined by gel filtration on calibrated Sephacryl S-200 column, while the monomeric molecular weights of the enzymes were, 60, 56 kDa and 60, 53 kDa for LAAOI and LAAOII, respectively. The tryptic peptides of the two isoforms share high sequence homology with other snake venom l-amino acid oxidases. The optimal pH and temperature values of Cc-LAAOI and Cc-LAAOII were 7.8, 50 °C and 7, 60 °C, respectively. The two isoenzymes were thermally stable up to 70 °C. The K m and V max values were 0.67 mM, 0.135 μmol/min for LAAOI and 0.82 mM, 0.087 μmol/min for LAAOII. Both isoenzymes displayed high catalytic preference to long-chain, hydrophobic and aromatic amino acids. The Mn2 + ion markedly increased the LAAO activity for both purified isoforms, while Na+, K+, Ca2 +, Mg2 + and Ba2 + ions showed a non-significant increase in the enzymatic activity of both isoforms. Furthermore, Zn2 +, Ni2 +, Co2 +, Cu2 + and AL3 + ions markedly inhibited the LAAOI and LAAOII activities. l-Cysteine and reduced glutathione completely inhibited the LAAO activity of both isoenzymes, whereas, β-mercaptoethanol, O-phenanthroline and PMSF completely inhibited the enzymatic activity of LAAOII. Furthermore, iodoacitic acid inhibited the enzymatic activity of LAAOII by 46% and had no effect on the LAAOI activity.

Ecological venomics: How genomics, transcriptomics and proteomics can shed new light on the ecology and evolution of venom

Animal venom is a complex cocktail of bioactive chemicals that traditionally drew interest mostly from biochemists and pharmacologists. However, in recent years the evolutionary and ecological importance of venom is realized as this trait has direct and strong influence on interactions between species. Moreover, venom content can be modulated by environmental factors. Like many other fields of biology, venom research has been revolutionized in recent years by the introduction of systems biology approaches, i.e., genomics, transcriptomics and proteomics. The employment of these methods in venom research is known as 'venomics'. In this review we describe the history and recent advancements of venomics and discuss how they are employed in studying venom in general and in particular in the context of evolutionary ecology. We also discuss the pitfalls and challenges of venomics and what the future may hold for this emerging scientific field.

Detoxification of Echis ocellatus venom-induced toxicity by Annona senegalensis Pers

Different fractions (I-V) of the methanolic leaf extracts of Annona senegalensis were assessed for their anti-snake venom activities. Fractions III neutralized lethal toxicity induced by Echis ocellatus venom and manifested the same potency as the crude extracts against the venom. The anti-snake venom activity of fraction III was clearly shown by the complete abrogation of venom-induced haemorrhage and the 75% record of surviving mice which were injected with a pre-incubate of venom and extract in the ratio 1:30 w/w after a 24 h. Also, fraction III exhibited a weak inhibitory effect on fibrinogen clotting activity of this venom. The key phytochemicals mediating the activity of this fraction are flavonoids and tannins. The detoxification of this venom by fraction III and the possible mode of action in the pathology of snake envenoming is discussed in this report.

Disintegrins from snake venoms and their applications in cancer research and therapy

Integrins regulate diverse functions in cancer pathology and in tumor cell development and contribute to important processes such as cell shape, survival, proliferation, transcription, angiogenesis, migration, and invasion. A number of snake venom proteins have the ability to interact with integrins. Among these are the disintegrins, a family of small, non-enzymatic, and cysteine-rich proteins found in the venom of numerous snake families. The venom proteins may have a potential role in terms of novel therapeutic leads for cancer treatment. Disintegrin can target specific integrins and as such it is conceivable that they could interfere in important processes involved in carcinogenesis, tumor growth, invasion and migration. Herein we present a survey of studies involving the use of snake venom disintegrins for cancer detection and treatment. The aim of this review is to highlight the relationship of integrins with cancer and to present examples as to how certain disintegrins can detect and affect biological processes related to cancer. This in turn will illustrate the great potential of these molecules for cancer research. Furthermore, we also outline several new approaches being created to address problems commonly associated with the clinical application of peptide-based drugs such as instability, immunogenicity, and availability.

Immunological cross-reactivity and neutralisation of European viper venoms with the monospecific Vipera berus antivenom ViperaTAb

Medically important cases of snakebite in Europe are predominately caused by European vipers of the genus Vipera. The mainstay of snakebite therapy is polyclonal antibody therapy, referred to as antivenom. Here we investigate the capability of the monospecific V. berus antivenom, ViperaTAb^®, to cross-react with, and neutralise lethality induced by, a variety of European vipers. Using ELISA and immunoblotting, we find that ViperaTAb^® antibodies recognise and bind to the majority of toxic components found in the venoms of the Vipera species tested at comparably high levels to those observed with V. berus. Using in vivo pre-clinical efficacy studies, we demonstrate that ViperaTAb^® effectively neutralises lethality induced by V. berus, V. aspis, V. ammodytes and V. latastei venoms and at much higher levels than those outlined by regulatory pharmacopoeial guidelines. Notably, venom neutralisation was found to be superior to (V. berus, V. aspis and V. latastei), or as equally effective as (V. ammodytes), the monospecific V. ammodytes “Zagreb antivenom”, which has long been successfully used for treating European snake envenomings. This study suggests that ViperaTAb^® may be a valuable therapeutic product for treating snakebite by a variety of European vipers found throughout the continent.

Activation of J77A.1 macrophages by three phospholipases A2 isolated from Bothrops atrox snake venom

In the present study, we investigated the in vitro effects of two basic myotoxic phospholipases A2 (PLA2), BaTX-I, a catalytically inactive Lys-49 variant, and BaTX-II, a catalytically active Asp-49, and of one acidic myotoxic PLA2, BaPLA2, a catalytically active Asp-49, isolated from Bothrops atrox snake venom, on the activation of J774A.1 macrophages. At noncytotoxic concentrations, the toxins did not affect the adhesion of the macrophages, nor their ability to detach. The data obtained showed that only BaTX-I stimulated complement receptor-mediated phagocytosis. However, BaTX-I, BaTX-II, and BaPLA2 induced the release of the superoxide anion by J774A.1 macrophages. Additionally, only BaTX-I raised the lysosomal volume of macrophages after 15 min of incubation. After 30 min, all the phospholipases increased this parameter, which was not observed within 60 min. Moreover, BaTX-I, BaTX-II, and BaPLA2 increased the number of lipid bodies on macrophages submitted to phagocytosis and not submitted to phagocytosis. However, BaTX-II and BaPLA2 induced the release of TNF-α by J774A.1 macrophages. Taken together, the data show that, despite differences in enzymatic activity, the three toxins induced inflammatory events and whether the enzyme is acidic or basic does not seem to contribute to these effects.

Inhibitory effects of recombinant RTS-jerdostatin on integrin α1β1 function during adhesion, migration and proliferation of rat aortic smooth muscle cells and angiogenesis

Jerdostatin, a short RTS-disintegrin cloned from venom gland mRNA of Protobothrops jerdonii, selectively blocks the adhesion of α1β1 integrin to collagen IV. Integrin α1β1 is highly expressed in smooth muscle cells (SMC) surrounding small blood vessels and vascular endothelial cells. Vascular SMC adhesion, migration and proliferation are important processes during normal vascular development. Using recombinant jerdostatin we have investigated the role of the α1β1 integrin on the adhesion of vascular SMC to collagen IV, and the potential relevance of blocking this crucial component of focal adhesions as an anti-angiogenic strategy. Our results show that jerdostatin does not interact with canonical collagen-binding site on the isolated A-domain of the α1 integrin subunit. r-Jerdostatin inhibited the adhesion of RASMCs to immobilized CB3 fragment in a dose-dependent manner, triggering to round-up, retraction, and finally detachment of the cells. r-Jerdostatin did not affect the adhesion of human SMCs to CB3, presumably because the high expression of α2β1 integrin compensated for α1β1 integrin blockage by jerdostatin. r-Jerdostatin dose-dependently inhibited α1β1 integrin-dependent HUVEC tube formation. However, VEGF-driven tube formation in the matrigel assay was only completely abolished when binding of integrin α2β1 to collagen was also inhibited by the C-type lectin-like rhodocetin. As a whole, our work emphasizes the relevance of using specific inhibitors for dissecting the role of α1β1 integrin in physiological and pathological conditions.

Applications of snake venom components to modulate integrin activities in cell-matrix interactions

Snake venom proteins are broadly investigated in the different areas of life science. Direct interaction of these compounds with cells may involve a variety of mechanisms that result in diverse cellular responses leading to the activation or blocking of physiological functions of the cell. In this review, the snake venom components interacting with integrins will be characterized in context of their effect on cellular response. Currently, two major families of snake venom proteins are considered as integrin-binding molecules. The most attention has been devoted to the disintegrin family, which binds certain types of integrins through specific motifs recognized as a tri-peptide structurally localized on an integrin-binding loop. Other snake venom integrin-binding proteins belong to the C-type lectin family. Snake venom molecules bind to the cellular integrins resulting in a modulation of cell signaling and in consequence, the regulation of cell proliferation, migration and apoptosis. Therefore, snake venom research on the integrin-binding molecules may have significance in biomedicine and basic cell biology.

Isolated biomolecules of pharmacological interest in hemostasis from Cerastes cerastes venom

Biomolecules from Cerastes cerastes venom have been purified and characterized. Two phospholipases isolated from Cerastes cerastes venom share 51% of homology. CC2-PLA2 exhibits antiplatelet activity that blocks coagulation. CCSV-MPase, a non-hemorrhagic Zn²⁺-metalloproteinase, significantly reduced the plasmatic fibrinogen level and hydrolyzes only its Bβ chain. Serine proteinases such as RP34, afaâcytin and CC3-SPase hydrolyze the fibrinogen and are respectively α, αβ and αβ fibrinogenases. In deficient human plasma, afaâcytin replaces the missing factors VIII and IX, and activates purified human factor X into factor Xa. It releases serotonin from platelets and directly aggregates human (but not rabbit) blood platelets. RP34 proteinase also had no effect on both human and rabbit blood platelet aggregation. CC3-SPase revealed a pro-coagulant activity. However, the insolubility of the obtained clot indicates that CC3-SPase does not activate factor XIII. In addition, CC3-SPase clotting activity was carried out with human plasmas from volunteer patients deficient in clotting factors. Results showed that CC3-SPase shortens clotting time of plasma deficient in factors II and VII but with weaker clotting than normal plasma. The clotting time of plasma deficient in factor II is similar to that obtained with normal plasma; suggesting that CC3-SPase is able to replace both factors IIa and VII in the coagulation cascade and thus could be involved in the blood clotting process via an extrinsic pathway. These results imply that CC3-SPase and afaâcytin could repair hemostatic abnormalities and may replace some factors missing in pathological deficiency. Afaâcytin also exhibits α fibrinase property similar to a plasmin-like proteinase. Despite its thrombin-like characteristics, afaâcytin is not inhibited by plasmatic thrombin inhibitors. The procoagulant properties of afaâcytin might have potential clinical applications.

Antitumoral potential of Tunisian snake venoms secreted phospholipases A2

Phospholipases type A₂ (PLA₂s) are the most abundant proteins found in Viperidae snake venom. They are quite fascinating from both a biological and structural point of view. Despite similarity in their structures and common catalytic properties, they exhibit a wide spectrum of pharmacological activities. Besides being hydrolases, secreted phospholipases A₂ (sPLA₂) are an important group of toxins, whose action at the molecular level is still a matter of debate. These proteins can display toxic effects by different mechanisms. In addition to neurotoxicity, myotoxicity, hemolytic activity, antibacterial, anticoagulant, and antiplatelet effects, some venom PLA₂s show antitumor and antiangiogenic activities by mechanisms independent of their enzymatic activity. This paper aims to discuss original finding against anti-tumor and anti-angiogenic activities of sPLA₂ isolated from Tunisian vipers: Cerastes cerastes and Macrovipera lebetina, representing new tools to target specific integrins, mainly, α5β1 and αv integrins.

Recombinant expression of mutants of the Frankenstein disintegrin, RTS-ocellatusin. Evidence for the independent origin of RGD and KTS/RTS disintegrins

The requirements to transform a short disintegrin of the RGD clade into an RTS disintegrin, were investigated through the generation of recombinant mutants of ocellatusin in which the RGD tripeptide was substituted for RTS in different positions along the integrin-specificity loop. Any attempt to create an active integrin α(1)β(1) inhibitory motif within the specificity loop of ocellatusin was unsuccessful. Replacing the whole RGD-loop of ocellatusin by the RTS-loop of jerdostatin was neither sufficient for confering α(1)β(1) binding specificity to this ocellatusin-RTS Frankenstein(2) mutant. Factors other than the integrin-binding loop sequence per se are thus required to transform a disintegrin scaffold from the RGD clade into another scaffold from the RTS/KTS clade. Moreover, our results provide evidences, that the RTS/KTS short disintegrins have potentially been recruited into the venom gland of Eurasian vipers independently from the canonical neofunctionalization pathway of the RGD disintegrins. PCR-amplifications of jerdostatin-like sequences from a number of taxa across reptiles, including snakes (Crotalinae, Viperinae, and Elapidae taxa) and lizards (Lacertidae and Iguanidae) clearly showed that genes coding for RTS/KTS disintegrins existed long before the split of Lacertidae and Iguania, thus predating the recruitment of the SVMP precursors of disintegrins, providing strong support for the view of an independent evolutionary history of the RTS/KTS and the RGD clades of short disintegrins.