Effects of crotamine in human prostate cancer cell line.

Our study presents the anticancer potential of crotamine from Crotalus durissus terrificus in human prostate cancer cell line DU-145. Crotamine isolation was conducted through RP-FPLC, its molecular mass analyzed by MALDI-TOF was 4881.4 kDa, and N-terminal sequencing confirmed crotamine identity. Crotamine demonstrated no toxicity and did not inhibit migration in HUVEC cells. Although no cell death occurred in DU-145 cells, crotamine inhibited their migration. Thus, crotamine presented potential to be a prototype of anticancer drug.

Harnessing the Cross-Neutralisation Potential of Existing Antivenoms for Mitigating the Outcomes of Snakebite in Sub-Saharan Africa.

Over 32,000 individuals succumb to snake envenoming in sub-Saharan Africa (sSA) annually. This results from several factors, including a lack of antivenom products capable of neutralising the venoms of diverse snake species in this region. Most manufacturers produce polyvalent antivenoms targeting 3 to 16 clinically important snake species in sSA. However, specific products are unavailable for many others, especially those with a restricted geographic distribution. While next-generation antivenoms, comprising a cocktail of broadly neutralising antibodies, may offer an effective solution to this problem, given the need for their clinical validation, recombinant antivenoms are far from being available to snakebite victims. One of the strategies that could immediately address this issue involves harnessing the cross-neutralisation potential of existing products. Therefore, we assessed the neutralisation potency of PANAF-Premium antivenom towards the venoms of 14 medically important snakes from 13 countries across sSA for which specific antivenom products are unavailable. Preclinical assays in a murine model of snake envenoming revealed that the venoms of most snake species under investigation were effectively neutralised by this antivenom. Thus, this finding highlights the potential use of PANAF-Premium antivenom in treating bites from diverse snakes across sSA and the utility of harnessing the cross-neutralisation potential of antivenoms.

Analysis of intra-specific variations in the venom of individual snakes based on Raman spectroscopy.

The knowledge of variations in the composition of venoms from different snakes is important from both theoretical and practical points of view, in particular, at developing and selecting an antivenom. Many studies on this topic are conducted with pooled venoms, while the existence and significance of variations in the composition of venoms between individual snakes of the same species are emphasized by many authors. It is important to study both inter- and intra-specific, including intra-population, venom variations, because intra-specific variations in the venom composition may affect the effectiveness of antivenoms as strongly as inter-specific. In this work, based on venom Raman spectroscopy with principal component analysis, we assessed the variations in venoms of individual snakes of the Vipera nikolskii species from two populations and compared these intra-specific variations with inter-specific variations (with regard to the other related species). We demonstrated intra-specific (inter- and intra-population) differences in venom compositions which are smaller than inter-specific variations. We also assessed the compositions of V. nikolskii venoms from two populations to explain inter-population differences. The method used is rapid and requires virtually no preparation of samples, used in extremely small quantities, allowing the venoms of individual snakes to be analyzed. In addition, the method is informative and capable of detecting fairly subtle differences in the composition of venoms.

Venom Composition of Neglected Bothropoid Snakes from the Amazon Rainforest: Ecological and Toxinological Implications.

Snake venoms have evolved in several families of Caenophidae, and their toxins have been assumed to be biochemical weapons with a role as a trophic adaptation. However, it remains unclear how venom contributes to the success of venomous species for adaptation to different environments. Here we compared the venoms from Bothrocophias hyoprora, Bothrops taeniatus, Bothrops bilineatus smaragdinus, Bothrops brazili, and Bothrops atrox collected in the Amazon Rainforest, aiming to understand the ecological and toxinological consequences of venom composition. Transcriptomic and proteomic analyses indicated that the venoms presented the same toxin groups characteristic from bothropoids, but with distinct isoforms with variable qualitative and quantitative abundances, contributing to distinct enzymatic and toxic effects. Despite the particularities of each venom, commercial Bothrops antivenom recognized the venom components and neutralized the lethality of all species. No clear features could be observed between venoms from arboreal and terrestrial habitats, nor in the dispersion of the species throughout the Amazon habitats, supporting the notion that venom composition may not shape the ecological or toxinological characteristics of these snake species and that other factors influence their foraging or dispersal in different ecological niches.

Immunological Cross-Reactivity and Preclinical Assessment of a Colombian Anticoral Antivenom against the Venoms of Three Micrurus Species.

Snakebite accident treatment requires the administration of antivenoms that provide efficacy and effectiveness against several snake venoms of the same genus or family. The low number of immunogenic components in venom mixtures that allow the production of antivenoms consequently gives them partial neutralization and a suboptimal pharmacological response. This study evaluates the immunorecognition and neutralizing efficacy of the polyvalent anticoral antivenom from the Instituto Nacional de Salud (INS) of Colombia against the heterologous endemic venoms of Micrurus medemi, and M. sangilensis, and M. helleri by assessing immunoreactivity through affinity chromatography, ELISA, Western blot, and neutralization capability. Immunorecognition towards the venoms of M. medemi and M. sangilensis showed values of 62% and 68% of the protein composition according to the immunoaffinity matrix, respectively. The analysis by Western blot depicted the highest recognition patterns for M. medemi, followed by M. sangilensis, and finally by M. helleri. These findings suggest that the venom compositions are closely related and exhibit similar recognition by the antivenom. According to enzyme immunoassays, M. helleri requires a higher amount of antivenom to achieve recognition than the others. Besides reinforcing the evaluation of INS antivenom capability, this work recommends the use of M. helleri in the production of Colombian antisera.

A novel metalloproteinase-derived cryptide from Bothrops cotiara venom inhibits angiotensin-converting enzyme activity.

Snake venoms are primarily composed of proteins and peptides, which selectively interact with specific molecular targets, disrupting prey homeostasis. Identifying toxins and the mechanisms involved in envenoming can lead to the discovery of new drugs based on natural peptide scaffolds. In this study, we used mass spectrometry-based peptidomics to sequence 197 peptides in the venom of Bothrops cotiara, including a novel 7-residue peptide derived from a snake venom metalloproteinase. This peptide, named Bc-7a, features a pyroglutamic acid at the N-terminal and a PFR motif at the C-terminal, homologous to bradykinin. Using FRET (fluorescence resonance energy transfer) substrate assays, we demonstrated that Bc-7a strongly inhibits the two domains of angiotensin converting enzyme (Ki < 1 µM). Our findings contribute to the repertoire of biologically active peptides from snake venoms capable of inhibiting angiotensin-converting enzyme (ACE), beyond current known structural motifs and precursors. In summary, we report a novel snake venom peptide with ACE inhibitory activity, suggesting its potential contribution to the hypotensive effect observed in envenomation.

Bothrops Moojeni Snake Venom: A Source of Potential Therapeutic Agents Against Hemostatic Disorders

Abstract Hemostasis is a complex set of biological processes responsible for blood fluidity within normal vessels and for the physiological interruption of bleeding in cases of vascular injury. Bothrops moojeni snake venom is rich in bioactive compounds of pharmacological and clinical interest since its protein components are capable of interfering with many points of the hemostatic process. Here, we present the B. moojeni venom proteins that affect hemostasis and discuss their pharmacological and clinical potential. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Data were obtained from the CAPES Journal Portal database, using the terms "Bothrops" AND "hemostasis", in a search for scientific articles made available in the last 20 years. Many components isolated from B. moojeni snake venom are characterized for their effect on hemostasis and possible application in the diagnosis and treatment of hemostatic disorders.

Snake and arthropod venoms: Search for inflammatory activity in human cells involved in joint diseases.

Most anti-inflammatory drugs currently adopted to treat chronic inflammatory joint diseases can alleviate symptoms but they do not lead to remission. Therefore, new and more efficient drugs are needed to block the course of joint inflammatory diseases. Animal venoms, rich in bioactive compounds, can contribute as valuable tools in this field of research. In this study, we first demonstrate the direct action of venoms on cells that constitute the articular joints. We established a platform consisting of cell-based assays to evaluate the release of cytokines (IL-6, IL-8, TNFα, IL-1ß, and IL-10) by human chondrocytes, synoviocytes and THP1 macrophages, as well as the release of neuropeptides (substance-P and ß-endorphin) by differentiated sensory neuron-like cells, 24 h after stimulation of cells with 21 animal venoms from snake and arthropod species, sourced from different taxonomic families and geographic origins. Results demonstrated that at non-cytotoxic concentrations, the venoms activate at varying degrees the secretion of inflammatory mediators involved in the pathology of articular diseases, such as IL-6, IL-8, and TNF-α by chondrocytes, synoviocytes, and macrophages and of substance P by neuron-like cells. Venoms of the Viperidae snake family were more inflammatory than those of the Elapidae family, while venoms of Arthropods were less inflammatory than snake venoms. Notably, some venoms also induced the release of the anti-inflammatory IL-10 by macrophages. However, the scorpion Buthus occitanus venom induced the release of IL-10 without increasing the release of inflammatory cytokines by macrophages. Since the cell types used in the experiments are crucial elements in joint inflammatory processes, the results of this work may guide future research on the activation of receptors and inflammatory signaling pathways by selected venoms in these particular cells, aiming at discovering new targets for therapeutic intervention.

Venom composition of neglected Bothropoid snakes from the Amazon Rainforest: ecological and toxinological implications

Snake venoms have evolved in several families of Caenophidae, and their toxins have been assumed to be biochemical weapons with a role as a trophic adaptation. However, it remains unclear how venom contributes to the success of venomous species for adaptation to different environments. Here we compared the venoms from Bothrocophias hyoprora, Bothrops taeniatus, Bothrops bilineatus smaragdinus, Bothrops brazili, and Bothrops atrox collected in the Amazon Rainforest, aiming to understand the ecological and toxinological consequences of venom composition. Transcriptomic and proteomic analyses indicated that the venoms presented the same toxin groups characteristic from bothropoids, but with distinct isoforms with variable qualitative and quantitative abundances, contributing to distinct enzymatic and toxic effects. Despite the particularities of each venom, commercial Bothrops antivenom recognized the venom components and neutralized the lethality of all species. No clear features could be observed between venoms from arboreal and terrestrial habitats, nor in the dispersion of the species throughout the Amazon habitats, supporting the notion that venom composition may not shape the ecological or toxinological characteristics of these snake species and that other factors influence their foraging or dispersal in different ecological niches.

Snake and arthropod venoms: search for inflammatory activity in human cells involved in joint diseases

Most anti-inflammatory drugs currently adopted to treat chronic inflammatory joint diseases can alleviate symptoms but they do not lead to remission. Therefore, new and more efficient drugs are needed to block the course of joint inflammatory diseases. Animal venoms, rich in bioactive compounds, can contribute as valuable tools in this field of research. In this study, we first demonstrate the direct action of venoms on cells that constitute the articular joints. We established a platform consisting of cell-based assays to evaluate the release of cytokines (IL-6, IL-8, TNFα, IL-1β, and IL-10) by human chondrocytes, synoviocytes and THP1 macrophages, as well as the release of neuropeptides (substance-P and β-endorphin) by differentiated sensory neuron-like cells, 24 h after stimulation of cells with 21 animal venoms from snake and arthropod species, sourced from different taxonomic families and geographic origins. Results demonstrated that at non-cytotoxic concentrations, the venoms activate at varying degrees the secretion of inflammatory mediators involved in the pathology of articular diseases, such as IL-6, IL-8, and TNF-α by chondrocytes, synoviocytes, and macrophages and of substance P by neuron-like cells. Venoms of the Viperidae snake family were more inflammatory than those of the Elapidae family, while venoms of Arthropods were less inflammatory than snake venoms. Notably, some venoms also induced the release of the anti-inflammatory IL-10 by macrophages. However, the scorpion Buthus occitanus venom induced the release of IL-10 without increasing the release of inflammatory cytokines by macrophages. Since the cell types used in the experiments are crucial elements in joint inflammatory processes, the results of this work may guide future research on the activation of receptors and inflammatory signaling pathways by selected venoms in these particular cells, aiming at discovering new targets for therapeutic intervention.

A novel metalloproteinase-derived cryptide from Bothrops cotiara venom inhibits angiotensin-converting enzyme activity

Snake venoms are primarily composed of proteins and peptides, which selectively interact with specific molecular targets, disrupting prey homeostasis. Identifying toxins and the mechanisms involved in envenoming can lead to the discovery of new drugs based on natural peptide scaffolds. In this study, we used mass spectrometry-based peptidomics to sequence 197 peptides in the venom of Bothrops cotiara, including a novel 7-residue peptide derived from a snake venom metalloproteinase. This peptide, named Bc-7a, features a pyroglutamic acid at the N-terminal and a PFR motif at the C-terminal, homologous to bradykinin. Using FRET (fluorescence resonance energy transfer) substrate assays, we demonstrated that Bc-7a strongly inhibits the two domains of angiotensin converting enzyme (Ki < 1 μM). Our findings contribute to the repertoire of biologically active peptides from snake venoms capable of inhibiting angiotensin-converting enzyme (ACE), beyond current known structural motifs and precursors. In summary, we report a novel snake venom peptide with ACE inhibitory activity, suggesting its potential contribution to the hypotensive effect observed in envenomation.

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.

Immune response to neurotoxic South American snake venoms.

South American rattlesnakes (Crotalus durissus spp) and coral snakes (Micrurus sp) venoms are characterized by inducing a limited inflammatory innate immune response, in contrast to Bothrops sp snake venoms which exert a prominent inflammatory activity. Some Crotalus durissus spp venoms, in addition, exert immunosuppressive activities that hamper the development of neutralizing antibodies in animals immunized for antivenom production. Micrurus sp venoms are rich in low molecular mass neurotoxins that elicit a limited immune response. These characteristics make it difficult to generate antivenoms of high neutralizing activity. Therefore, the study of the mechanisms operating behind this limited immune response to venoms is relevant from both fundamental and practical perspectives. This review summarizes key aspects of the immune response to these venoms and discusses some pending challenges to further understand these phenomena and to improve antivenom production.

The Royal Armoury: Venomics and antivenomics of king cobra (Ophiophagus hannah) from the Indian Western Ghats.

Despite being famous as 'the king' of the snake world, the king cobra (Ophiophagus hannah) has remained a mysterious species, particularly with respect to its venom ecology. In contrast, venom research has largely focussed on the 'big four' snakes that are greatly responsible for the burden of snakebite in the Indian subcontinent. This study aims to bridge the current void in our understanding of the O. hannah venom by investigating its proteomic, biochemical, pharmacological, and toxinological profiles via interdisciplinary approaches. Considering their physical resemblance, the king cobra is often compared to the spectacled cobra (Naja naja). Comparative venomics of O. hannah and N. naja in this study provided interesting insights into their venom compositions, activities, and potencies. Our findings suggest that the O. hannah venom, despite being relatively less complex than the N. naja venom, is equally potent. Finally, our in vitro and in vivo assays revealed that both Indian polyvalent and Thai Red Cross monovalent antivenoms completely fail to neutralise the O. hannah venom. Our findings provide guidelines for the management of bites from this clinically important yet neglected snake species in India.

Unlocking the potential of snake venom-based molecules against the malaria, Chagas disease, and leishmaniasis triad.

Malaria, leishmaniasis and Chagas disease are vector-borne protozoal infections with a disproportionately high impact on the most fragile societies in the world, and despite malaria-focused research gained momentum in the past two decades, both trypanosomiases and leishmaniases remain neglected tropical diseases. Affordable effective drugs remain the mainstay of tackling this burden, but toxicicty, inneficiency against later stage disease, and drug resistance issues are serious shortcomings. One strategy to overcome these hurdles is to get new therapeutics or inspiration in nature. Indeed, snake venoms have been recognized as valuable sources of biomacromolecules, like peptides and proteins, with antiprotozoal activity. This review highlights major snake venom components active against at least one of the three aforementioned diseases, which include phospholipases A2, metalloproteases, L-amino acid oxidases, lectins, and oligopeptides. The relevance of this repertoire of biomacromolecules and the bottlenecks in their clinical translation are discussed considering approaches that should increase the success rate in this arduous task. Overall, this review underlines how venom-derived biomacromolecules could lead to pioneering antiprotozoal treatments and how the drug landscape for neglected diseases may be revolutionized by a closer look at venoms. Further investigations on poorly studied venoms is needed and could add new therapeutics to the pipeline.

Pictolysin-III, a Hemorrhagic Type-III Metalloproteinase Isolated from Bothrops pictus (Serpentes: Viperidae) Venom, Reduces Mitochondrial Respiration and Induces Cytokine Secretion in Epithelial and Stromal Cell Lines.

From the venom of the Bothrops pictus snake, an endemic species from Peru, we recently have described toxins that inhibited platelet aggregation and cancer cell migration. In this work, we characterize a novel P-III class snake venom metalloproteinase, called pictolysin-III (Pic-III). It is a 62 kDa proteinase that hydrolyzes dimethyl casein, azocasein, gelatin, fibrinogen, and fibrin. The cations Mg2+ and Ca2+ enhanced its enzymatic activity, whereas Zn2+ inhibited it. In addition, EDTA and marimastat were also effective inhibitors. The amino acid sequence deduced from cDNA shows a multidomain structure that includes a proprotein, metalloproteinase, disintegrin-like, and cysteine-rich domains. Additionally, Pic-III reduces the convulxin- and thrombin-stimulated platelet aggregation and in vivo, it has hemorrhagic activity (DHM = 0.3 µg). In epithelial cell lines (MDA-MB-231 and Caco-2) and RMF-621 fibroblast, it triggers morphological changes that are accompanied by a decrease in mitochondrial respiration, glycolysis, and ATP levels, and an increase in NAD(P)H, mitochondrial ROS, and cytokine secretion. Moreover, Pic-III sensitizes to the cytotoxic BH3 mimetic drug ABT-199 (Venetoclax) in MDA-MB-231 cells. To our knowledge, Pic-III is the first SVMP reported with action on mitochondrial bioenergetics and may offer novel opportunities for promising lead compounds that inhibit platelet aggregation or ECM-cancer-cell interactions.

In Silico Evaluation of Quercetin Methylated Derivatives on the Interaction with Secretory Phospholipases A2 from Crotalus durissus terrificus and Bothrops jararacussu.

Quercetin derivatives have already shown their anti-inflammatory potential, inhibiting essential enzymes involved in this process. Among diverse pro-inflammatory toxins from snake venoms, phospholipase A2 is one of the most abundant in some species, such as Crotalus durissus terrificus and Bothrops jararacussu from the Viperidae family. These enzymes can induce the inflammatory process through hydrolysis at the sn-2 position of glycerophospholipids. Hence, elucidating the main residues involved in the biological effects of these macromolecules can help to identify potential compounds with inhibitory activity. In silico tools were used in this study to evaluate the potential of quercetin methylated derivatives in the inhibition of bothropstoxin I (BthTX-I) and II (BthTX-II) from Bothrops jararacussu and phospholipase A2 from Crotalus durissus terrificus. The use of a transitional analogous and two classical inhibitors of phospholipase A2 guided this work to find the role of residues involved in the phospholipid anchoring and the subsequent development of the inflammatory process. First, main cavities were studied, revealing the best regions to be inhibited by a compound. Focusing on these regions, molecular docking assays were made to show main interactions between each compound. Results reveal that analogue and inhibitors, Varespladib (Var) and p-bromophenacyl bromide (BPB), guided quercetins derivatives analysis, revealing that Leu2, Phe5, Tyr28, glycine in the calcium-binding loop, His48, Asp49 of BthTX-II and Cdtspla2 were the main residues to be inhibited. 3MQ exhibited great interaction with the active site, similar to Var results, while Q anchored better in the BthTX-II active site. However, strong interactions in the C-terminal region, highlighting His120, seem to be crucial to decreasing contacts with phospholipid and BthTX-II. Hence, quercetin derivatives anchor differently with each toxin and further in vitro and in vivo studies are essential to elucidate these data.

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 ß-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 ß-defensin sequences of Sistrurus miliarius that can lead to novel peptide-based antimicrobial agents, using a multidisciplinary approach that includes sequence phylogeny.

Caracterização estrutural e funcional de uma metaloproteinase de classe P-I do veneno de Lachesis muta rhombeata

Rhomb-I, a 23-kDa metalloproteinase was isolated from L. m. rhombeata venom. Its dimethylcasein proteolysis was abolished by metal chelators, and slightly enhanced by Ca2+ and Mg2+ ions, but inhibited by Co2+ , Zn2+ and α2-macroglobulin. In aqueous solution, rhomb-I autoproteolyzed to a 20- and 11-kDa fragments at 37 oC. The amino acid sequence showed high homology with other SVMPs. Rhomb-I causes hemorrhage that may be ascribed to hydrolysis of essential BM, ECM and plasma proteins. It preferentially cleaves the α-chains of fibrin(ogen). Rhomb-I inhibited convulxin- and vWF-induced aggregation on human platelets without significant effect on collagen-stimulated aggregation or other effectors. It digests vWF into a low- molecular-mass multimers of vWF and a rvWF-A1 domain to a 27-kDa fragment as revealed by western blotting with mouse anti-rvWF A1-domain IgG. Incubation of platelets with rhomb-I resulted in adhesion to and cleavage of platelet receptors GPIbα and GPVI to release a 130-kDa and 55-kDa soluble form. Both membrane glycoproteins, GPIbα that binds vWF, together with GPVI which binds collagen, play a key role in mediating platelet adhesion/activation and can initiate (patho)physiological thrombus formation. Conclusions: rhomb-I is implicated in the pathophysiology of Lachesis envenoming by disrupting vasculature, hemostasis and platelet aggregation through impairing vWF-GPIb axis and blocking GPVI-collagen binding.

Rhomb-I, uma metaloproteinase de 23 kDa foi isolada do veneno de L. m. rhombata. Sua ação proteolítica sobre dimetilcaseína foi inibida por α2-macroglobulina, quelantes de metais e por cátions Co2+ e Zn2+ e levemente estimulada por Ca2+ e Mg2+ . Em solução aquosa a 37 oC, rhomb-I sofreu autoproteólise gerando fragmentos de aproximadamente 20 e 11 kDa. A sequência de aminoácidos apresentou alta similaridade com outras SVMPs P-I. Rhomb-I causa hemorragia que pode ser atribuída à hidrólise de proteínas da membrana basal, da matriz extracelular e proteínas plasmáticas. Rhomb-I cliva, preferencialmente, as cadeias Aα da fibrina e do fibrinogênio. Rhomb-I inibiu a agregação induzida por convulxina e pelo fator de von Willebrand (vWF) em plaquetas humanas, sem efeito significativo na agregação estimulada por colágeno ou outros agonistas. Ela digere vWF em multímeros de massas moleculares menores bem como o domínio A1 recombinante de vWF (rvWF- A1) gerando um fragmento de aproximadamente 27 kDa, conforme evidenciado por western blot com IgG anti-rvWF-A1, produzido em camundongos. Após incubar plaquetas lavadas com rhomb-I, foi possível observar por western blot que a proteína liga e cliva as glicoproteínas de plaquetas GPIb e GPVI, liberando as formas solúveis de 130 kDa e 55 kDa, respectivamente. Ambas glicoproteínas, GPIbα que se liga ao vWF, e GPVI que se liga ao colágeno, desempenham um papel fundamental na mediação da adesão/ativação plaquetária e podem iniciar a formação fisiológica ou patológica de trombos. Conclusões: Rhomb-I é uma metaloproteinase classe P-I, hemorrágica, fibrino(geno)lítica que degrada proteínas da matriz extracelular e interfere na função plaquetária pela clivagem de vWF, GPIb e GPVI. Estes resultados indicam que rhomb-I pode estar envolvida na fisiopatologia do envenenamento por Lachesis, perturbando a hemostasia e agregação plaquetária e causando danos à vasculatura.