Isolation and comparison of myotoxins isolated from venoms of different species of Bothrops snakes

Phenotypic, functional and plasticity features of human PBMCs induced by venom secreted PLA2s

Bothrops venom contains a high amount of secreted phospholipase A₂ (sPLA₂s) enzymes responsible for the inflammatory reaction and activation of leukocytes in cases of envenoming. PLA₂s are proteins that have enzymatic activity and can hydrolyze phospholipids at the sn-2 position, thereby releasing fatty acids and lysophospholipids precursors of eicosanoids, which are significant mediators of inflammatory conditions. Whether these enzymes have a role in the activation and function of peripheral blood mononuclear cells (PBMCs) is not known. Here we show for the first time how two secreted PLA₂s (BthTX-I and BthTX-II) isolated from the venom of Bothrops jararacussu affect the function and polarization of PBMCs. Neither BthTX-I nor BthTX-II exhibited significant cytotoxicity to isolated PBMCs compared with the control at any of the time points studied. RT-qPCR and enzyme-linked immunosorbent assays were used to determine changes in gene expression and the release of pro-inflammatory (TNF-α, IL-6, and IL-12) and anti-inflammatory (TGF-β and IL-10) cytokines, respectively, during the cell differentiation process. Lipid droplets formation and phagocytosis were also investigated. Monocytes/macrophages were labeled with anti-CD14, -CD163, and -CD206 antibodies to assay cell polarization. Both toxins caused a heterogeneous morphology (M1 and M2) on days 1 and 7 based on immunofluorescence analysis, revealing the considerable flexibility of these cells even in the presence of typical polarization stimuli. Thus, these findings indicate that the two sPLA₂s trigger both immune response profiles in PBMCs indicating a significant degree of cell plasticity, which may be crucial for understanding the consequences of snake envenoming.

The bioprospecting potential of Clusia fluminensis Planch. & Triana: a scoping review

Many biological activities are described for the Clusiaceae family. Clusia fluminensis, a species from Brazilian flora, is mainly employed for ornamental purposes. This review aimed to depict the current knowledge of C. fluminensis from a bioprospecting standpoint. "Clusia fluminensis" search term was applied in Scopus, Web of Science, PubMed and Bireme databases according to PRISMA-ScR statement. Selected papers on Phytochemistry or Bioactivity followed hand searching procedures. Bioactivity preclinical studies considered in vitro or in vivo biological systems, treated with plant extracts or isolated compounds. The outcomes were compared with standard or no treatment control groups. Critical appraisal of individual trials considered completeness in the research fields. Our results showed that 81% of the selected papers presented high level of completeness, 69% revealed phytochemical parameters and 31% biological applications of plant extracts and isolated compounds. Polyisoprenylated benzophenones, terpenoids, sterols and phenolic compounds were identified. Antiviral, insecticidal and snake antivenom activities were reported. In conclusion, the phytochemical data reinforce the reported activities. Potential applications in personal care, nutritional supplementation and pharmaceutical, food, chemical or textile industries were also identified. Toxicological and phytochemical complementary studies may be required.

Doxycycline treatment reestablishes renal function of Wistar rats in experimental envenomation with Bothrops jararacussu venom

Acute kidney injury is one of the main complications of ophidian accidents and the leading cause of death in patients who survive the initial damage effects of venom. The hypothesis proposed in this investigation is that the pharmacological repositioning of doxycycline (doxy) attenuates renal injury provoked by Bothrops jararacussu (Bj) venom. Male Wistar rats were subjected or not (control) to experimental envenomation with Bj venom (3.5 mg/kg, im). Doxy (3 mg/kg, ip) was administered 2 h after envenoming. Envenomation with Bj venom promoted tissue damage in the renal cortex (moderate degree, score 3) in 24 h associated with decreased glomerular and tubular function, which promoted proteinuria and polyuria. Doxy treatment prevented the increase in urinary volume in 3 times, the increase in plasma creatinine in 33%, the increase in blood urea-nitrogen accumulation in 65%, the increase in urinary Na⁺ excretion in 2 times, marked proteinuria and kidney cortex injury induced by Bj envenomation. Bj venom promoted increase in protein content (66%) and reduction of 45% (Na⁺+K⁺)-ATPase activity in the renal cortex. The enzyme was detected mainly in the luminal membrane. Doxy treatment was effective in preventing the mentioned alterations, maintaining (Na⁺+K⁺)-ATPase in the basolateral membranes.

Inflammatory effect of Bothropstoxin-I from Bothrops jararacussu venom mediated by NLRP3 inflammasome involves ATP and P2X7 receptor

Muscle tissue damage is one of the local effects described in bothropic envenomations. Bothropstoxin-I (BthTX-I), from Bothrops jararacussu venom, is a K49-phospholipase A2 (PLA2) that induces a massive muscle tissue injury, and, consequently, local inflammatory reaction. The NLRP3 inflammasome is a sensor that triggers inflammation by activating caspase 1 and releasing interleukin (IL)-1β and/or inducing pyroptotic cell death in response to tissue damage. We, therefore, aimed to address activation of NLRP3 inflammasome by BthTX-I-associated injury and the mechanism involved in this process. Intramuscular injection of BthTX-I results in infiltration of neutrophils and macrophages in gastrocnemius muscle, which is reduced in NLRP3- and Caspase-1-deficient mice. The in vitro IL-1β production induced by BthTX-I in peritoneal macrophages (PMs) requires caspase 1/11, ASC and NLRP3 and is dependent on adenosine 5'-triphosphate (ATP)-induced K+ efflux and P2X7 receptor (P2X7R). BthTX-I induces a dramatic release of ATP from C2C12 myotubes, therefore representing the major mechanism for P2X7R-dependent inflammasome activation in macrophages. A similar result was obtained when human monocyte-derived macrophages (HMDMs) were treated with BthTX-I. These findings demonstrated the inflammatory effect of BthTX-I on muscle tissue, pointing out a role for the ATP released by damaged cells for the NLRP3 activation on macrophages, contributing to the understanding of the microenvironment of the tissue damage of the Bothrops envenomation.

Differential Macrophage Subsets in Muscle Damage Induced by a K49-PLA2 from Bothrops jararacussu Venom Modulate the Time Course of the Regeneration Process

Bothrops snakes cause around 80% of snakebites in Brazil, with muscle tissue damage as an important consequence, which may cause dysfunction on the affected limb. Bothropstoxin-I (BthTX-I) from Bothrops jararacussu is a K49-phospholipase A₂, involved in the injury and envenomation's inflammatory response. Immune system components act in the resolution of tissue damage and regeneration. Thus, macrophages exert a crucial role in the elimination of dead tissue and muscle repair. Here, we studied the cellular influx and presence of classical and alternative macrophages (M1 and M2) during muscle injury induced by BthTX-I and the regeneration process. BthTX-I elicited intense inflammatory response characterized by neutrophil migration, then increased influx of M1 macrophages followed by M2 population that declined, resulting in tissue regeneration. The high expressions of TNF-α and IL6 were changed by increased TGF-β expression after BthTX-I injection, coinciding with the iNOs and arginase expression and the peaks of M1 and M2 macrophages in muscle tissue. A coordinated sequence of PAX7, MyoD, and myogenin expression involved in muscle regenerative process appeared after BthTX-I injection. Together, these results demonstrate a direct correlation between the macrophage subsets, cytokine microenvironment, and the myogenesis process. This information may be useful for new envenomation and muscular dysfunction therapies.

Morphological alterations caused by manual venom extraction on the main venom gland of Bothrops asper and Crotalus simus snakes (Serpentes: Viperidae): Long-term implications for antivenom production

The only scientifically validated treatment for snakebite envenomation is the administration of antivenoms. For their production, small quantities of snake venom are injected in animals to elicit a specific antibody response. Snakes are kept in captivity, and their venom is regularly extracted to assure antivenom access. It has already been reported that the pressure exerted upon the venom gland during this extraction can cause tissue damage and fibrosis, leading to a decrease in the venom yield. We described the histopathology of venom glands for B. asper and C. simus snakes used for antivenom production. Based on these reported tissue abnormalities, we quantify the tissue injury by a generated damage-SCORE and fibrosis. A variety of histopathological damages were found such as fibrosis, edema, necrosis, hemorrhage, and formation of anomalous structures, especially in C. simus, which is more prone to suffer severe damage. The level and severity of the damage depend on the frequency and the number of venom extractions. Furthermore, we design an experimental intensive venom extraction scheme with which we could confirm the causality of these effects. In addition to the histopathological damages, the LD₅₀ and biochemical venom composition were also affected giving experimental evidence that the venom extraction not only causes tissue damage but also affects the composition stability and toxicity of the venom. In order to produce quality and effective antivenoms, an improvement of the management of snake collections could be established, such as rotation groups to assure the quality of the venom yielded.

An overview of Bothrops erythromelas venom

This review discusses studies on the venom of Bothrops erythromelas published over the past 36 years. During this period, many contributions have been made to understand the venomous snake, its venom, and its experimental and clinical effects better. The following chronological overview is based on 29 articles that were published between 1979 and 2015, with emphasis on diverse areas. The complexity of this task demands an integration of multidisciplinary research tools to study toxinology. This science is in need of renewed conceptual and experimental platforms aimed at obtaining a profound understanding of the highly complex pathophysiology of snakebite envenoming and toxins isolated from snakes.

Bp-13 PLA2: Purification and Neuromuscular Activity of a New Asp49 Toxin Isolated from Bothrops pauloensis Snake Venom

A new PLA₂ (Bp-13) was purified from Bothrops pauloensis snake venom after a single chromatographic step of RP-HPLC on μ-Bondapak C-18. Amino acid analysis showed a high content of hydrophobic and basic amino acids and 14 half-cysteine residues. The N-terminal sequence showed a high degree of homology with basic Asp49 PLA₂ myotoxins from other Bothrops venoms. Bp-13 showed allosteric enzymatic behavior and maximal activity at pH 8.1, 36°–45°C. Full Bp-13 PLA₂ activity required Ca²⁺; its PLA₂ activity was inhibited by Mg²⁺, Mn²⁺, Sr²⁺, and Cd²⁺ in the presence and absence of 1 mM Ca²⁺. In the mouse phrenic nerve-diaphragm (PND) preparation, the time for 50% paralysis was concentration-dependent (P < 0.05). Both the replacement of Ca²⁺ by Sr²⁺ and temperature lowering (24°C) inhibited the Bp-13 PLA₂-induced twitch-tension blockade. Bp-13 PLA₂ inhibited the contractile response to direct electrical stimulation in curarized mouse PND preparation corroborating its contracture effect. In biventer cervicis preparations, Bp-13 induced irreversible twitch-tension blockade and the KCl evoked contracture was partially, but significantly, inhibited (P > 0.05). The main effect of this new Asp49 PLA₂ of Bothrops pauloensis venom is on muscle fiber sarcolemma, with avian preparation being less responsive than rodent preparation. The study enhances biochemical and pharmacological characterization of B. pauloensis venom.

Venomics and antivenomics of Bothrops erythromelas from five geographic populations within the Caatinga ecoregion of northeastern Brazil

The Caatinga lancehead, Bothrops erythromelas, is a medically relevant species, responsible for most of the snakebite accidents in most parts of its distribution range in northeastern Brazil. The spectrum and geographic variability of its venom toxins were investigated applying a venomics approach to venom pools from five geographic areas within the Caatinga ecoregion. Despite its wide habitat, populations of B. erythromelas from Ceará, Pernambuco, Juazeiro, Paraiba, and Ilha de Itaparica exhibit highly conserved venom proteomes. Mirroring their compositional conservation, the five geographic venom pools also showed qualitatively and quantitatively overlapping antivenomic profiles against antivenoms generated in Vital Brazil (BR) and Clodomiro Picado (CR) Institutes, using different venoms in the immunization mixtures. The paraspecificity exhibited by the Brazilian SAB and the Costa Rican BCL antivenoms against venom toxins from B. erythromelas indicates large immunoreactive epitope conservation across genus Bothrops during the last ~14 million years, thus offering promise for the possibility of generating a broad-spectrum bothropic antivenom. Biological Significance Accidental snakebite envenomings represent an important public health hazard in Brazil. Ninety per cent of the yearly estimated 20-30,000 snakebite accidents are caused by species of the Bothrops genus. Bothrops erythromelas, a small, moderately stocky terrestrial venomous snake, is responsible for most of the snakebite accidents in its broad distribution range in the Caatinga, a large ecoregion in northeastern Brazil. To gain a deeper insight into the spectrum of medically important toxins present in the venom of the Caatinga lancehead, we applied a venomics approach to define the proteome and geographic variability of adult B. erythromelas venoms from five geographic regions. Although intraspecific compositional variation between venoms among specimens from different geographic regions has long been appreciated by herpetologists and toxinologists as a general feature of highly adaptable and widely distributed snake species, the five B. erythromelas populations investigated exhibit highly conserved venom proteomes. The overall toxin profile of the Caatinga lancehead's venom explains the local and systemic effects observed in envenomations by B. erythromelas. The five geographic venom pools sampled also showed qualitatively and quantitatively overlapping antivenomic profiles against antivenoms generated using different bothropic venoms in the immunization mixtures. The large immunoreactive epitope conservation across genus Bothrops offers promise for the generation of a broad-spectrum bothropic antivenom.

Functional variability of snake venom metalloproteinases: adaptive advantages in targeting different prey and implications for human envenomation

Snake venom metalloproteinases (SVMPs) are major components in most viperid venoms that induce disturbances in the hemostatic system and tissues of animals envenomated by snakes. These disturbances are involved in human pathology of snake bites and appear to be essential for the capture and digestion of snake's prey and avoidance of predators. SVMPs are a versatile family of venom toxins acting on different hemostatic targets which are present in venoms in distinct structural forms. However, the reason why a large number of different SVMPs are expressed in some venoms is still unclear. In this study, we evaluated the interference of five isolated SVMPs in blood coagulation of humans, birds and small rodents. P-III class SVMPs (fractions Ic, IIb and IIc) possess gelatinolytic and hemorrhagic activities, and, of these, two also show fibrinolytic activity. P-I class SVMPs (fractions IVa and IVb) are only fibrinolytic. P-III class SVMPs reduced clotting time of human plasma. Fraction IIc was characterized as prothrombin activator and fraction Ic as factor X activator. In the absence of Ca²⁺, a firm clot was observed in chicken blood samples with fractions Ic, IIb and partially with fraction IIc. In contrast, without Ca²⁺, only fraction IIc was able to induce a firm clot in rat blood. In conclusion, functionally distinct forms of SVMPs were found in B. neuwiedi venom that affect distinct mechanisms in the coagulation system of humans, birds and small rodents. Distinct SVMPs appear to be more specialized to rat or chicken blood, strengthening the current hypothesis that toxin diversity enhances the possibilities of the snakes for hunting different prey or evading different predators. This functional diversity also impacts the complexity of human envenoming since different hemostatic mechanisms will be targeted by SVMPs accounting for the complexity of the response of humans to venoms.

Comparison of phylogeny, venom composition and neutralization by antivenom in diverse species of bothrops complex

In Latin America, Bothrops snakes account for most snake bites in humans, and the recommended treatment is administration of multispecific Bothrops antivenom (SAB – soro antibotrópico). However, Bothrops snakes are very diverse with regard to their venom composition, which raises the issue of which venoms should be used as immunizing antigens for the production of pan-specific Bothrops antivenoms. In this study, we simultaneously compared the composition and reactivity with SAB of venoms collected from six species of snakes, distributed in pairs from three distinct phylogenetic clades: Bothrops, Bothropoides and Rhinocerophis. We also evaluated the neutralization of Bothrops atrox venom, which is the species responsible for most snake bites in the Amazon region, but not included in the immunization antigen mixture used to produce SAB. Using mass spectrometric and chromatographic approaches, we observed a lack of similarity in protein composition between the venoms from closely related snakes and a high similarity between the venoms of phylogenetically more distant snakes, suggesting little connection between taxonomic position and venom composition. P-III snake venom metalloproteinases (SVMPs) are the most antigenic toxins in the venoms of snakes from the Bothrops complex, whereas class P-I SVMPs, snake venom serine proteinases and phospholipases A₂ reacted with antibodies in lower levels. Low molecular size toxins, such as disintegrins and bradykinin-potentiating peptides, were poorly antigenic. Toxins from the same protein family showed antigenic cross-reactivity among venoms from different species; SAB was efficient in neutralizing the B. atrox venom major toxins. Thus, we suggest that it is possible to obtain pan-specific effective antivenoms for Bothrops envenomations through immunization with venoms from only a few species of snakes, if these venoms contain protein classes that are representative of all species to which the antivenom is targeted.

Snakebite envenomation is a serious health issue in Latin America, particularly in the Amazon, where antivenom administration may be delayed due to logistic constraints. Bothrops snakes are involved in most of the snakebite-related accidents in Brazil. This work reports a comparative study of the toxin composition and antigenicity of the Bothrops venoms used to prepare the commercial antivenom and its effectiveness against the venom from Bothrops atrox, a prevalent Amazon species that is not included in the pool. Our data show a lack of connection between Bothrops taxonomic identity and venom composition. We also show that different toxins display distinct reactivity with the tested antivenom. However, the antivenom reacted similarly with each class of toxin present in the venoms of the different snakes studied. Important evidence was the neutralization of the major toxic effects of B. atrox venom, not included in the mixture of antigens used to produce the antivenom. Based on the observed antigenicity of the distinct protein classes of toxins, we suggest that it is possible to obtain pan-specific and efficient Bothrops antivenoms via immunization with venoms from a few species of snakes that are representative of the protein composition of a large number of targeted species.

In vitro comparison of enzymatic effects among Brazilian Bothrops spp. venoms

In various types of snake venom, the major toxic components are proteinases and members of the phospholipase A2 family, although other enzymes also contribute to the toxicity. In this study, we evaluated the proteolytic, phospholipase, and L-Amino acid oxidase activities in the venom of five Bothrops species-Bothrops jararaca, Bothrops jararacussu, Bothrops moojeni, Bothrops neuwiedi, and Bothrops alternatus-all of which are used in the production of commercial antivenom, prepared in horses. The enzymatic activities of each species' venom were classified as high, moderate, or low. B. moojeni venom demonstrated the highest enzymatic activity profile, followed by the venom of B. neuwiedi, B. jararacussu, B. jararaca, and B. alternatus. To our knowledge, this is the first study to compare all of these enzymes from multiple species, which is significant in view of the activity of L-amino acid oxidase across Bothrops species.

A transcriptomic analysis of gene expression in the venom gland of the snake Bothrops alternatus (urutu)

Background

The genus Bothrops is widespread throughout Central and South America and is the principal cause of snakebite in these regions. Transcriptomic and proteomic studies have examined the venom composition of several species in this genus, but many others remain to be studied. In this work, we used a transcriptomic approach to examine the venom gland genes of Bothrops alternatus, a clinically important species found in southeastern and southern Brazil, Uruguay, northern Argentina and eastern Paraguay.

Results

A cDNA library of 5,350 expressed sequence tags (ESTs) was produced and assembled into 838 contigs and 4512 singletons. BLAST searches of relevant databases showed 30% hits and 70% no-hits, with toxin-related transcripts accounting for 23% and 78% of the total transcripts and hits, respectively. Gene ontology analysis identified non-toxin genes related to general metabolism, transcription and translation, processing and sorting, (polypeptide) degradation, structural functions and cell regulation. The major groups of toxin transcripts identified were metalloproteinases (81%), bradykinin-potentiating peptides/C-type natriuretic peptides (8.8%), phospholipases A₂ (5.6%), serine proteinases (1.9%) and C-type lectins (1.5%). Metalloproteinases were almost exclusively type PIII proteins, with few type PII and no type PI proteins. Phospholipases A₂ were essentially acidic; no basic PLA₂ were detected. Minor toxin transcripts were related to L-amino acid oxidase, cysteine-rich secretory proteins, dipeptidylpeptidase IV, hyaluronidase, three-finger toxins and ohanin. Two non-toxic proteins, thioredoxin and double-specificity phosphatase Dusp6, showed high sequence identity to similar proteins from other snakes. In addition to the above features, single-nucleotide polymorphisms, microsatellites, transposable elements and inverted repeats that could contribute to toxin diversity were observed.

Conclusions

Bothrops alternatus venom gland contains the major toxin classes described for other Bothrops venoms based on trancriptomic and proteomic studies. The predominance of type PIII metalloproteinases agrees with the well-known hemorrhagic activity of this venom, whereas the lower content of serine proteases and C-type lectins could contribute to less marked coagulopathy following envenoming by this species. The lack of basic PLA₂ agrees with the lower myotoxicity of this venom compared to other Bothrops species with these toxins. Together, these results contribute to our understanding of the physiopathology of envenoming by this species.

Isolation and characterization of two new Lys49 PLA2s with heparin neutralizing properties from Bothrops moojeni snake venom

Among the proteins and peptides already characterized in Bothrops moojeni venom, two novel phospholipases A(2) (PLA(2)) have been purified and fully sequenced by ESI-MS/MS techniques. Both of them belong to the enzymatically non-active Lys49 variants of PLA(2). They consist of 122 amino acids and share a characteristic sequence in their C-terminal region composed of clusters of basic amino acids known to interact with heparin. Thus, as already established, heparin can be used as an antidote to antagonize some myotoxic PLA(2)s from venoms of Bothrops genus. The two PLA(2) variants were shown to interact in vitro with unfractionated heparin (UFH) and low molecular weight heparin (LMWH), neutralizing their anticoagulant properties. Although the influences of PLA(2)s from snake venoms on the blood coagulation system are known, their use to antagonize the anticoagulant effect of heparin in vitro or in vivo has never been proposed. These finding recommend diagnostic and therapeutic applications, which are currently investigated.

Myotoxic phospholipases A(2) isolated from Bothrops brazili snake venom and synthetic peptides derived from their C-terminal region: cytotoxic effect on microorganism and tumor cells

This paper reports the purification and biochemical/pharmacological characterization of two myotoxic phospholipases A(2) (PLA(2)s) from Bothrops brazili venom, a native snake from Brazil. Both myotoxins (MTX-I and II) were purified by a single chromatographic step on a CM-Sepharose ion-exchange column up to a high purity level, showing M(r) approximately 14,000 for the monomer and 28,000Da for the dimer. The N-terminal and internal peptide amino acid sequences showed similarity with other myotoxic PLA(2)s from snake venoms, MTX-I belonging to Asp49 PLA(2) class, enzymatically active, and MTX-II to Lys49 PLA(2)s, catalytically inactive. Treatment of MTX-I with BPB and EDTA reduced drastically its PLA(2) and anticoagulant activities, corroborating the importance of residue His48 and Ca(2+) ions for the enzymatic catalysis. Both PLA(2)s induced myotoxic activity and dose-time dependent edema similar to other isolated snake venom toxins from Bothrops and Crotalus genus. The results also demonstrated that MTXs and cationic synthetic peptides derived from their 115-129 C-terminal region displayed cytotoxic activity on human T-cell leukemia (JURKAT) lines and microbicidal effects against Escherichia coli, Candida albicans and Leishmania sp. Thus, these PLA(2) proteins and C-terminal synthetic peptides present multifunctional properties that might be of interest in the development of therapeutic strategies against parasites, bacteria and cancer.

Cytoskeletal rearrangement and cell death induced by Bothrops alternatus snake venom in cultured Madin–Darby canine kidney cells

Bothrops snake venoms cause renal damage, with renal failure being the main cause of death in humans bitten by these snakes. In this work, we investigated the cytoskeletal rearrangement and cytotoxicity caused by Bothrops alternatus venom in cultured Madin–Darby canine kidney (MDCK) cells. Incubation with venom (10 and 100 µg/mL) significantly (p <0.05) decreased the cellular uptake of neutral red dye after 1 and 3 h. Venom (100 µg/mL) also markedly decreased the transepithelial electrical resistance (RT) across MDCK monolayers. Staining with rhodamine-conjugated phalloidin revealed disarray of the cytoskeleton that involved the stress fibers at the basal cell surface and focal adhesion-associated F-actin in the cell–matrix contact region. Feulgen staining showed a significant decrease in the number of cells undergoing mitosis and an increase in the frequency of altered nuclei. Scanning electron microscopy revealed a decrease in the number of microvilli and the presence of cells with a fusiform format. Flow cytometry with annexin V and propidium iodide showed that cell death occurred by necrosis, with little apoptosis, a conclusion supported by the lack of DNA fragmentation characteristic of apoptosis. Pretreating the cells with catalase significantly attenuated the venom-induced loss of viability, indicating a possible involvement of H2O2 in the cellular damage; less protection was observed with superoxide dismutase or Nω-nitro-l-arginine methyl ester. These results indicate that Bothrops alternatus venom is cytotoxic to cultured MDCK cells, possibly via the action of reactive oxygen species. This cytotoxicity could contribute to nephrotoxicity after envenoming by this species.

Neuromuscular and phospholipase activities of venoms from three subspecies of Bothrops neuwiedi (B. n. goyazensis, B. n. paranaensis and B. n. diporus)

The Bothrops neuwiedi (Neuwied's lancehead) species complex consists of a variety of subspecies with a wide distribution in South America. In this work, we compared the neuromuscular blockade caused by venoms from three subspecies (B. n. goyazensis, B. n. paranaensis and B. n. diporus) of this complex using chick biventer cervicis (BC) and mouse phrenic nerve-diaphragm (PND) preparations and investigated their phospholipase A2 (PLA2) activities and electrophoretic profiles. The order of potency of PLA2 activity was B. n. diporus>B. n. paranaensis>B. n. goyazensis. In BC preparations, B. n. goyazensis venom (50 microg/mL) was significantly (p<0.05) more active than B. n. paranaensis and B. n. diporus venoms, which did not produce a significant blockade at this time interval; after 120 min, B. n. goyazensis, B. n. paranaensis and B. n. diporus venoms (100 microg/mL) produced blockades of 57.4+/-5%, 30+/-3% and 17.4+/-7% (n=3-6 each), respectively. The three venoms inhibited contractures in response to ACh, indicating interference with postsynaptic neurotransmission. Only B. n. goyazensis and B. n. paranaensis venoms caused a long-lasting, concentration-dependent muscle contracture prior to blockade. In PND preparations, all of the venoms blocked the twitch-tension responses within 45-100 min, indicating that these preparations were more sensitive than avian preparations. There was a correlation between PLA2 activity and the time for 50% blockade in PND but not in BC preparations. SDS-PAGE showed quantitative rather than qualitative differences among the venoms. These results indicate that the venoms of the three subspecies had similar profiles of neuromuscular activity, although the relationship with PLA2 activity varied with the preparation used.

Biochemical and biological characterization of the venoms of Bothriopsis bilineata and Bothriopsis taeniata (Serpentes: Viperidae)

Snake venom is a complex mixture containing diverse protein components with different structures and functions that are used for prey immobilization and death. Snake venoms from the family Viperidae cause pronounced local and systemic effects, such as pain, edema, hemorrhage and necrosis. Here, we investigated the enzymatic and biological activities of venoms from two Amazonian snakes, Bothriopsis bilineata and Bothriopsis taeniata. Both venoms presented high enzymatic activities for proteases kallikrein, thrombin and plasmin, low levels of trypsin, cathepsin C and leucine aminopeptidase activities, while lacked acetylcholinesterase activity. B. taeniata and B. bilineata crude venoms caused inflammation inducing neutrophil recruitment into peritoneal cavity of mice 4h after injection. Neutrophil recruitment induced by B. taeniata venom was accompanied by hemorrhage. EDTA treatment profoundly impaired neutrophil recruitment, suggesting the involvement of a metalloproteinase on venoms-induced neutrophil recruitment. Pretreatment with dexamethasone and zileuton, a 5-lipoxygenase inhibitor, significantly reduced neutrophil migration, but indomethacin and montelukast, a cysteinyl leukotriene receptor antagonist, had no effect, suggesting the involvement of lipoxygenase-derived metabolites, probably LTB(4). Together, these results show that B. bilineata and B. taeniata venoms induce a marked inflammatory reaction, with leukocyte recruitment, and hemorrhage, which parallels to a high proteolytic activity found in these venoms.

Enzymatic and immunochemical characterization of Bothrops insularis venom and its neutralization by polyspecific Bothrops antivenom

Herein we compared the biological activities of Bothrops insularis and Bothrops jararaca venoms as well as their neutralization by polyspecific Bothrops antivenom (PBA). On account of that, we investigated their antigenic cross-reactivity and the neutralization of lethal, myotoxic and defibrinating activities by polyspecific and species-specific antivenoms. Silver-stained SDS-PAGE gels evidenced many common bands particularly above 47 kDa between B. jararaca and B. insularis venoms. However, some protein bands between 46 and 28 kDa were observed exclusively in B. jararaca venom. Both venoms presented gelatinolytic, caseinolytic, fibrinogenolytic and phospholipase A(2) activities. No hyaluronidase activity was detected in both venoms by zymography. Polyspecific and species-specific antivenoms showed similar titers to B. jararaca and B. insularis venoms by ELISA, and recognized similar components by immunoblotting. The PBA was effective in neutralizing the lethal, myotoxic and defibrinating activities of both venoms as well as to abrogate microcirculatory disturbances induced by B. insularis venom. No statistically significant difference was observed for minimal hemorrhagic doses between both venoms. Antigenic cross-reactivity was evident between both venoms. Since toxic and enzymatic activities were similar, we speculate that B. insularis venoms can induce a local damage in humans comparable to that observed in other Bothrops venoms. Besides, the PBA was effective in neutralizing the toxic activities of B. insularis venom.

Sexual dimorphism in venom of Bothrops jararaca(Serpentes: Viperidae)

Bothrops jararaca is an abundant snake in Brazil, and its venom has been studied exhaustively. The species exhibits adult size dimorphism in which female are larger. We registered the growth in Snout-Vent Length and weight of one litter (with 11 females and 12 males). We compared growth curves and venom profile between male and female of B. jararaca in order to establish the relationship of those characters and sex. Their venoms were analyzed when they were 36 months old, concerning SDS PAGE, protein content, proteolytic, hyaluronidasic, phospholipasic, blood-clotting, edematogenic, hemorrhagic, myotoxic activities, and lethality. Differences in the growth curves of the females and the males were significantly different after the 12th month of age, with the females growing faster. Females produced five times more venom than males. The electrophoretic patterns were variable: the venom from males had more protein bands than females. Venom composition varied significantly between males and females. Venom from females is more potent for hyaluronidasic, hemorrhagic, and lethality activities, whereas venom from males is more potent for coagulant, phospholipasic, and myotoxic activities. The variability of proteolytic and edematogenic activities were not significant. The important sexual dimorphism in body size and mass, amount of venom produced, and venom composition in B. jararaca may reflect a divergence in niche partitioning.

Caracterização individual do veneno de Bothrops alternatus Duméril, Bibron & Duméril em função da distribuição geográfica no Brasil (Serpentes,Viperidae)

Bothrops alternatus Duméril, Bibron & Duméril, 1854 é uma serpente de importância em saúde pública, com ampla distribuição geográfica, desde o Mato Grosso do Sul até o sudeste do Brasil, chegando até a Argentina e Uruguai, ocupando vários domínios morfoclimáticos. Neste trabalho investigou-se a variação do veneno de adultos de Bothrops alternatus, em função de sua distribuição geográfica no Brasil, comparativamente ao veneno elaborado sob a forma de "pool" desta espécie (veneno referência), que inclui serpentes, em sua maioria, da região do estado de São Paulo. Foram analisadas as atividades letal, coagulante sobre o plasma, proteolítica sobre a caseína e miotóxica, bem como os padrões eletroforéticos de 61 amostras individuais de veneno contrapostas ao "pool". Os resultados mostraram que o veneno de B. alternatus é pouco ativo, comparativamente ao de outros Bothrops Wagler, 1824. A variação individual prevaleceu, não apresentando correlação com as áreas de distribuição geográfica e domínios morfoclimáticos, porém a atividade coagulante das amostras de veneno provenientes do nordeste da distribuição geográfica apresentaram-se menos ativas comparativamente às da porção central da distribuição. Os venenos provenientes das bordas da distribuição apresentaram ações proteolíticas e miotóxicas mais intensas, que estatisticamente não foram significativamente diferentes. As variações individuais prevaleceram.

Comparison of the neurotoxic and myotoxic effects of Brazilian Bothrops venoms and their neutralization by commercial antivenom

The venoms of some Bothrops species produce neuromuscular blockade in avian and mammalian nerve-muscle preparations in vitro. In this study, we compared the neuromuscular activities (myotoxicity and neurotoxicity) of venoms from several Brazilian species of Bothrops (B. jararaca, B. jararacussu, B. moojeni, B. erythromelas and B. neuwiedi) in chick isolated biventer cervicis muscle preparations and examined their neutralization by commercial antivenom. All of the venoms (50-200 microg/ml, n = 3 - 7 each) induced long-lasting, concentration-dependent muscle contracture and twitch-tension blockade, and also inhibited the muscle responses to acetylcholine and KCl. Preincubation of the venoms (200 microg/ml) with bothropic antivenom (0.2 ml) for 30 min at 37 degrees C prevented the twitch-tension blockade to different extents, with the protection varying from 0.5% (B. neuwiedi) to 88% (B. moojeni). Complete protection against the neuromuscular action of B. neuwiedi venom was observed only with a mixture of bothropic and crotalic antivenoms. The venoms caused either high (B. jararacussu, B. neuwiedi and B. moojeni) or low (B. jararaca and B. erythromelas) creatine kinase release. Morphologically, myonecrosis was greatest with B. jararacussu venom (98-100% of fibers damaged) and least with B. jararaca venom (74% damage). The extent of neutralization by bothropic antivenom was B. jararaca (93%)>B. erythromelas (65.8%)>B. moojeni (30.7%)>B. neuwiedi (20%)>B. jararacussu (no neutralization). Despite this variation in neutralization, enzyme-linked immunosorbent assays indicated similar immunoreactivities for the venoms, although immunoblots revealed quantitative variations in the bands detected. These results show that Bothrops venoms produce varying degrees of neuromuscular blockade in chick nerve-muscle preparations. The variable protection by antivenom against neuromuscular activity indicates that the components responsible for the neuromuscular action may differ among the venoms.

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

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

Pharmacological evidence for a presynaptic action of venoms from Bothrops insularis (jararaca ilhoa) and Bothrops neuwiedi (jararaca pintada)

Whereas the presynaptic action of Crotalus durissus terrificus venom is well-established, Bothrops venoms have historically been considered to have only postsynaptic and muscular effects. However, some studies have also suggested a presynaptic action for these venoms. In this work, we used chick biventer cervicis preparations to compare the presynaptic actions of two Bothrops venoms (B. insularis and B. neuwiedi) with that of C. d. terrificus venom. At 10 microg/ml, all venoms produced irreversible blockade of the twitch tension responses, with no reduction in acetylcholine (ACh)-induced contractures and only a slight decrease in potassium induced-contractures. The times (in min) required to produce 50% neuromuscular blockade (C. d. terrificus: 16.3+/-0.7, n = 8; B. insularis: 30.0+/-1.9, n = 5; B. neuwiedi: 42.0+/-2.0, n = 8; mean +/- SEM) were significantly different among the venoms (p < 0.01). Lowering the temperature at which the experiments were done (from 37 to 24 degrees C) prevented neuromuscular blockade by the three venoms, indicating that enzyme activity may be involved in this response. At concentrations capable of causing complete neuromuscular blockade, creatine kinase release remained close to levels seen in control preparations incubated with Krebs solution alone (500-1200 IU/l). Commercial crotalic antivenom, but not bothropic antivenom, protected against the neuromuscular blockade caused by B. insularis and B. neuwiedi venoms. These observations indicate that bothropic venoms may contain components which act presynaptically in a manner similar to C. d. terrificus venom, and that at low venom concentrations a direct action on skeletal muscle does not contribute to this presynaptic neurotoxicity.

An overview of lysine-49 phospholipase A2 myotoxins from crotalid snake venoms and their structural determinants of myotoxic action

In 1984, the first venom phospholipase A2 (PLA2) with a lysine substituting for the highly conserved aspartate 49 was discovered, in the North American crotalid snake Agkistrodon p. piscivorus [J. Biol. Chem. 259 (1984) 13839]. Ten years later, the first mapping of a 'toxic region' on a Lys49 PLA2 was reported, in Bothrops asper myotoxin II [J. Biol. Chem. 269 (1994) 29867]. After a further decade of research on the Lys49 PLA2s, a better understanding of their structural determinants of toxicity and mode of action is rapidly emerging, with myotoxic effector sites identified at the C-terminal region in at least four proteins: B. asper myotoxin II, A. p. piscivorus K49 PLA2, A. c. laticinctus ACL myotoxin, and B. jararacussu bothropstoxin I. Although important features still remain to be established, their toxic mode of action has now been understood in its more general concepts, and a consistent working hypothesis can be experimentally supported. It is proposed that all the toxic activities of Lys49 PLA2s are related to their ability to destabilize natural (eukaryotic and prokaryotic) and artificial membranes, using a cationic/hydrophobic effector site located at their C-terminal loop. This review summarizes the general properties of the Lys49 PLA2 myotoxins, emphasizing the development of current concepts and hypotheses concerning the molecular basis of their toxic activities.

Myotoxicity induced by an acidic Asp-49 phospholipase A(2) isolated from Lachesis muta snake venom. Comparison with lysophosphatidylcholine

In a previous report we showed that Lachesis muta crude venom displays potent indirect hemolytic activity and myotoxicity when injected into mice. Then, a phospholipase A(2) (PLA(2)) (LM-PLA(2)-I) responsible for these activities was isolated. More recently, a catalytically active isoenzyme (LM-PLA(2)-II) with molecular mass of 18 kDa and isoeletric point at pH 5.4 was isolated from the same snake venom. LM-PLA(2)-II inhibited ADP- and collagen-induced platelet aggregation as well as induced a potent paw edema reaction in rats. Here we show that LM-PLA(2)-II induced myotoxic effects both in vitro characterized by an increase on the rate of creatine kinase (CK) release from isolated mice extensor digitorum longus (EDL) muscles and in vivo by increasing plasma CK activity of injected mice. Histological analysis showed an intense damage in muscle cells injected with LM-PLA(2)-II. It was also shown that exogenous lysophosphatidylcholine (lyso-pc) behaved as a typical myotoxin damaging muscle cells, producing myonecrosis characterized by local infiltration of inflammatory cells similarly to that observed for LM-PLA(2)-II. Hemorrhage and lethal effects were not observed neither with LM-PLA(2)-II nor lyso-pc. As previously observed for other biological activities, pretreatment of LM-PLA(2)-II with p-bromophenacyl bromide (p-BPB) or acetic anhydride abolished all the enzyme's actions. The data confirms that biological activities displayed by LM-PLA(2)-II, including the myotoxic effects reported here, are all dependent on its enzymatic activity where the product formed (lyso-pc) may play an important function on such myotoxicity.

Effect of Bothrops leucurus venom in chick biventer cervicis preparations

Bothrops leucurus is a poorly studied pitviper found in northeastern Brazil. We examined the action of B. leucurus venom (5-100 microg/ml) on contractile responses in chick biventer cervicis preparations. Muscle damage was assessed by quantifying the release of creatine kinase (CK) and by histological analysis. B. leucurus venom dose-dependently inhibited the contractile responses of indirectly stimulated preparations, the maximum inhibition with 100 microg of venom/ml being 74.0+/-6.6% (mean+/-SEM) after 120 min. The venom also reduced contractures to exogenous acetylcholine (55 and 110 microM) and K(+) (13.4mM) (85-100% reduction with 100 microg of venom/ml) and increased the release of CK (348+/-139 U/ml in controls vs 1260+/-263 U/ml with 20 microg of venom/ml after 120 min, p<0.05). The accompanying morphological changes included multivacuolated, swollen, amorphous fibers and agglutinated myofibrils. These results indicate that B. leucurus venom can adversely affect neuromuscular transmission and produce muscle damage in avian preparations.

Myotoxic phospholipases A(2) in bothrops snake venoms: effect of chemical modifications on the enzymatic and pharmacological properties of bothropstoxins from Bothrops jararacussu

Venoms from eight Bothrops spp. were fractionated by ion-exchange chromatography on CM-Sepharose at pH 8.0 for the purification of myotoxins. Chromatographic profiles showed differences regarding myotoxic components among these venoms. B. alternatus, B. atrox and B. jararaca venoms did not show the major basic myotoxic fractions identified in the other venoms. Polyacrylamide gel electrophoresis for basic proteins also showed distinct patterns for these toxins. In vivo, all the isolated myotoxins induced release of creatine kinase due to necrosis of muscle fibers, accompanied by polymorphonuclear cell infiltration, and edema in the mouse paw. In addition, the toxins showed cytotoxic and liposome-disrupting activities in vitro. B. jararacussu bothropstoxins-I (BthTX-I) and II (BthTX-II) were submitted to chemical modifications of: His, by 4-bromophenacyl bromide (BPB) or photooxidation by Rose Bengal (RB); Tyr, by 2-nitrobenzenesulphonyl fluoride (NBSF); and Trp, by o-nitrophenylsulphenyl chloride (NPSC). The myotoxic and cytotoxic activities of BthTX-I, a Lys49 PLA(2) homologue, after modification by BPB, RB, NBSF and NPSC, were reduced to 50%, 20%, 75%, 65% and 13%, 0.5%, 76%, 58%, respectively. However, the edema-inducing and liposome-disrupting activities were not significantly reduced by the above modifications. BPB-treated BthTX-II, an Asp49 PLA(2) homologue, lost most of its catalytic, indirect hemolytic, anticoagulant, myotoxic and cytotoxic activities. The edema-inducing and liposome-disrupting activities were reduced to 50% and 80%, respectively. Lethality caused by BthTX-I and -II was strongly reduced after treatment with BPB or RB, but only partially with NBSF or NPSC. BthTX-I and -II, both native or modified, migrated similarly in a charge-shift electrophoresis. Antibodies raised against BthTX-I or -II, B. asper Basp-II and the C-terminal 115-129 peptide from Basp-II did not show significant differences in their cross-reactivity with the modified toxins, except with RB photooxidized toxins.

Bothrops lanceolatus (Fer de lance) venom induces oedema formation and increases vascular permeability in the mouse hind paw

The ability of snake venoms to increase vascular permeability and to induce oedema through the release of pharmacologically active substances is well known. We have studied the oedema and vascular permeability induced by Bothrops lanceolatus venom in male Swiss white mice. Paw oedema was induced by the subplantar injection of B. lanceolatus venom (125-1000 ng/paw) and was quantified as the increase in paw weight. Changes in vascular permeability were assessed by measuring the amount of Evans blue dye extravasation. The oedema and the increase in vascular permeability were maximal within 2 h and had resolved after 24 h. The administration of the vasodilator iloprost (20 ng/paw) immediately after B. lanceolatus venom potentiated the oedema and the increase in vascular permeability by approximately four-fold. Pretreating the mice with indomethacin, dexamethasone, NDGA or BW A4C inhibited the venom-induced oedema and the increase in vascular permeability. In contrast, histamine, serotonin and PAF-acether antagonists (mepyramine, cyproheptadine and WEB 2086, respectively) were ineffective. Histological examination showed that B. lanceolatus venom (250 ng and 500 ng/paw) caused thickening of the inner dermal layers which was accompanied by extensive intercellular spaces indicative of oedema. In addition, there was a marked infiltration of inflammatory cells, particularly neutrophils, into the underlying muscle layer. The latter, however, remained morphologically unaffected during the 3 h of observation. Venom doses larger than 500 ng/paw produced intense haemorrhage. These results indicate that B. lanceolatus venom induces oedema and increases vascular permeability in the mouse hind paw. The principal mediators of this inflammatory response are cyclooxygenase and lipoxygenase products.

Characterization of a basic phospholipase A2-homologeu myotoxin isolated from the venom of the snake Bothrops neuwiedii (yarará chica) from Argentina

A basic protein was isolated by CM-Sephadex C-25 chromatography from the venom of Bothrops neuwiedii from Argentina, and named B. neuwiedii myotoxin I. This protein exerted local myotoxic and edema-forming effects in mice, with potencies comparable to other myotoxins isolated from Bothrops spp. venoms. When injected by i.v. route at doses up to 4.7 mg/kg of body weight, the toxin was not lethal. In vitro, the toxin had no detectable phospholipase A2 activity on egg yolk phospholipids. B. neuwiedii myotoxin I appeared as a homodimer in sodium dodecylsulphate-polyacrylamide gel electrophoresis, with a subunit molecular weight of 15 kD. Gel immunodiffusion revealed a pattern of partial antigenic identity between the newly isolated myotoxin and myotoxin II from Bothrops asper venom. The sequence of B. neuwiedii myotoxin I was determined for the first 40 amino acid residues, showing high homology to several class II phospholipase A2 myotoxins of the Lys-49 family from crotalids. Altogether, results suggest that this toxin is a new member of the Lys-49 phospholipase A2-homologues with myotoxic, cytolytic, and edema-inducing activities.

Distribution of 131I-labeled Bothrops erythromelas venom in mice

Bothrops erythromelas is responsible for many snake bites in northeastern Brazil. In the present study we determined the in vivo distribution of the venom following its subcutaneous injection into mice. B. erythromelas venom and albumin were labeled individually with 131I by the chloramine T method, and separated in a Sephacryl S-200 column. The efficiency of labeling was 68%. Male Swiss mice (40-45 g), which had been provided with drinking water containing 0.05% KI over a period of 10 days prior to the experiment, were inoculated dorsally (s.c.) with 0.3 ml (2.35 x 10(5) cpm/mouse) of 131I-venom (N = 42), 131I-albumin or 131I (controls, N = 28 each). Thirty minutes and 1, 3, 6, 12, 18 and 24 h after inoculation, the animals were perfused with 0.85% NaCl and skin and various organs were collected in order to determine radioactivity content. There was a high rate of venom absorption in the skin (51%) within the first 30 min compared to albumin (20.1%) and free iodine (8.2%). Up to the third hour after injection there was a tendency for venom and albumin to concentrate in the stomach (3rd h), small intestine (3rd h) and large intestine (6th h). Both control groups had more radioactivity in the digestive tract, especially in the stomach, but these levels decreased essentially to baseline by 12-18 h postinjection. In the kidneys, the distribution profiles of venom, albumin and iodine were similar. Counts at 30 min postinjection were low in all three groups (1.37, 1.86 and 0.77, respectively), and diminished to essentially 0% by 12-18 h. Albumin tended to concentrate in muscle until the 3rd h postinjection (1.98%). There was a low binding of labeled venom in the liver (< 0.54%), thyroid (< 0.11%) and lungs (< 0.08%), and no iodinated venom was detected in brain, heart, diaphragm, spleen or bladder. The low venom binding observed in most internal organs, comparable to that of albumin, suggests that B. erythromelas venom does not specifically target most internal organs. That is, the systemic effects of envenomation are mainly due to an indirect action.

Phospholipase A2 myotoxins from Bothrops snake venoms

Several myotoxins have been isolated from Bothrops snake venoms during the last 10 years. All of them are group II basic phospholipases A2, although some lack enzymatic activity (i.e. Lys-49 variants). These myotoxins appear as an antigenically related family of proteins occurring in many, but not all, Bothrops venoms, bearing a close structural and antigenic relationship to toxins found in other crotalid venoms of the genera Agkistrodon and Trimeresurus. Myotoxins are quantitatively important venom components in some Bothrops species. Intramuscular injection of Bothrops myotoxins leads to a rapid series of drastic degenerative events, probably initiated at the plasma membrane level, which culminate in a selective skeletal muscle necrosis. This in vivo specificity contrasts with the ability of myotoxins to lyse many types of cells in culture. Muscle damage, as well as cytolysis and liposome disruption, occur in conditions where phospholipase A2 activity is inhibited, although enzymatic activity might enhance myotoxin actions. A membrane receptor for Bothrops myotoxins has not been identified yet. A working hypothesis on the mechanism of action is proposed. Current evidence suggests that these toxins interact with biological membranes via a molecular region distinct from their known catalytic site. The active region is likely to be formed by a combination of basic and hydrophobic amino acid residues near the C-terminus of the protein, which allow electrostatic interaction and bilayer penetration. These events may lead to membrane destabilization and loss of selective permeability to ions such as calcium, both of which appear to be important mediators in the process of muscle necrosis.

Hyperalgesia induced by Bothrops jararaca venom in rats: role of eicosanoids and platelet activating factor (PAF)

In this study we investigated the ability of Bothrops jararaca venom (BjV) to induce hyperalgesia and the modulation of this effect by lipid mediators. It was found that intraplantar injection of BjV (1 to 25 micrograms) caused a dose and time-related hyperalgesia. The peak of the hyperalgesic response was 1 hr after injection of the venom and persisted for 24 hr with the higher dose. The BjV-induced hyperalgesia was markedly attenuated by dexamethasone. Dexamethasone blocks the generation of biologically active metabolites from arachidonic acid by inhibiting PLA2 activation. Inhibition of the cyclo-oxygenase pathway by indomethacin, or inhibition of lipoxygenases by NDGA both significantly inhibited BjV-induced hyperalgesia. Two antagonists of PAF, WEB2170 and BN52021, also significantly inhibited the initial phase of the hyperalgesia. These results suggest that hyperalgesia induced by BjV is, at least partially, mediated by lipid mediators such as prostaglandins, leukotrienes and PAF.

Effects on cultured mammalian cells of myotoxin III, a phospholipase A2 isolated from Bothrops asper (terciopelo) venom

Myotoxin III (MT-III), a myotoxic phospholipase A2 from Bothrops asper, was studied with respect to interactions with cultured mammalian cells and red blood cells. Tests of the cytopathogenic effect of MT-III on different cell lines indicated that rat skeletal muscle L6 myoblasts were more sensitive to the toxin than chinese hamster ovary cells, human lung fibroblasts, mouse adrenal tumour cells and rat intestinal epithelial cells. Specific plasma-membrane permeabilization was assayed as release of a cytosolic [3H]uridine nucleotide marker from toxin-treated L6 cells. A dose- and time-related membrane permeabilization was induced at 37 degrees C, but not at 0 degree C. A half-maximal effect was obtained after 20 min. 30 micrograms/ml MT-III induced 50% marker release in 1 h, and the effect was not reversed by post-incubation for up to 48 h in toxin-free medium. The membrane permeabilization in L6 cells did not seem to require cellular internalisation of the toxin. The catalytic site of the toxin was inactivated by alkylation with p-bromophenacyl bromide (BPB). This treatment abolished the toxin's specific PLA2 activity, as assayed in vitro, and reduced the PLA2 activity on the myoblast membrane by more than 95%, as measured by release of [14C]arachidonic acid from prelabelled cells. However, the membrane-permeabilizing effect (release of cytosolic marker) was reduced only by 70% upon modification with BPB. We also report that MT-III is not directly haemolytic, and one reason for this is the inability of the toxin to associate with the membranes of human or mouse erythrocytes. Taken together, the data suggest that MT-III at 37 degrees C binds to and penetrates the plasma membrane of cultured myoblasts, thereby inducing a rapid, direct and irreversible membrane permeabilization. This effect apparently depends in part on the PLA2 activity of the toxin and in part on a molecular region which is separate from the catalytic site.

p-Bromophenacyl bromide modification of Bothrops asper myotoxin II, a lysine-49 phospholipase A2, affects its pharmacological activities

Modification of Bothrops asper myotoxin II, a lysine-49 phospholipase A2 variant, was carried out with p-bromophenacyl bromide. Modified toxin did not show changes in its charge and immunological properties but two of its pharmacological activities were modified. Myotoxic activity, measured by histology and by increment of creatine kinase levels in plasma of mice, was significantly reduced after toxin modification. In addition, liposome disruption activity was also significantly lower with the modified toxin both at 3 and 24 hr of incubation with the alkylating reagent. Some of the implications of these results on the structure-function relationship of myotoxins are discussed.

Neutralization of different activities of venoms from nine species of Bothrops snakes by Bothrops jararaca antivenom

Antivenoms are the usual treatment in cases of systemic envenoming by Bothrops snakes. However, the neutralization of each venom component by the antivenom is not well established. Bothrops jararaca antivenom, produced in rabbits, recognizes the venoms of nine different Bothrops species with high ELISA antibody titres. Western blot analysis showed that almost all antigens present on both homologous and heterologous venoms are recognized. Neutralization tests were performed using whole antivenom or its IgG fraction. The antivenom was able to neutralize the haemorrhagic, coagulant and necrotizing activities of the heterologous venoms in the same antivenom/venom proportion as for the homologous venom. Myotoxic activity was only partially neutralized. Neutralization of the proteolytic activity of heterologous venoms required higher amounts of antivenom than for the homologous venom. Phospholipase and oedema-inducing activities were completely neutralized only in the homologous system.

Isolation and characterization of basic myotoxic phospholipases A2 from Bothrops godmani (Godman's pit viper) snake venom

Two basic myotoxic phospholipases A2 were purified to homogeneity from the venom of Bothrops godmani from Costa Rica by ion-exchange chromatography on CM-Sephadex. They have molecular weights of 14,300 (myotoxin I) and 13,400 (myotoxin II) and isoelectric points of 8.2 (myotoxin I) and 8.9 (myotoxin II). They behave as amphiphilic proteins in charge-shift electrophoresis and have similar amino acid compositions. Both toxins induce drastic myotoxic effects when injected in the gastrocnemius muscle of mice and induce release of peroxidase trapped in negatively charged liposomes. In addition, myotoxin I has high phospholipase A2 activity and is anticoagulant at doses higher than 0.3 microgram/ml, whereas myotoxin II has a very low phospholipase A2 activity and exerts anticoagulant effect only at concentrations higher than 50 micrograms/ml. Immunochemical data indicate that both toxins are immunologically related to Bothrops asper myotoxins, although B. godmani myotoxin II gives a stronger cross-reactivity when tested with antisera raised against B. asper myotoxins I and II.

Characterization of the snake venoms from seven Brazilian species of Bothrops by FPLC anion-exchange chromatography

1. The elution profiles and the caseinolytic, myotoxic, coagulant and hemorrhagic activities of the venoms of seven Bothrops species fractionated on a Mono-Q FPLC column were analyzed. 2. Each venom separated into 16-20 peaks, with good reproducibility and the activities were concentrated in virtually discrete regions of the chromatogram. 3. There is a considerable overlap of active proteins in the different species venoms and our results indicate that a venom pool with the species B. jararaca, B. jararacussu, B. moojeni, B. neuwiedi and B. atrox venoms would contain the major active proteins determined in the seven species.

Effect of a proteinase inhibitor from the plasma of Bothrops jararaca on coagulant and myotoxic activities of Bothrops venoms

A proteinase inhibitor purified from the plasma of Bothrops jararaca was tested for the neutralization of total blood clotting activity, prothrombin activating factor and thrombin-like activity of B. jararaca venom and also myotoxic activity of B. jararacussu venom. This inhibitor was also tested for neutralization of the lethality induced by the venom of B. jararaca and B. jararacussu. The inhibitor markedly reduced the total blood clotting activity (95%) and the prothrombin activating factor (98%), and partially decreased the thrombin-like activity of B. jararaca venom. The proteinase inhibitor failed to neutralize the myotoxic activity of B. jararacussu. Lethality induced by the venom of B. jararaca in mice was inhibited by the proteinase inhibitor, whereas the protection on B. jararacussu venom was only partial. These results show that the proteinase inhibitor purified from the plasma of B. jararaca inhibits different proteinases but not myotoxins of Bothrops venoms, and consequently neutralizes the toxic effect due to these proteins.