Experimental pathophysiology of systemic alterations induced by Bothrops asper snake venom

Anti-inflammatory and antiophidic effects of extract of Hymenaea eriogyne benth and structure-activity relationship prediction of the major markers in silico

ETHNOPHARMACOLOGICAL RELEVANCE

Hymenaea eriogyne Benth (Fabaceae) is popularly known as "Jatobá". Despite its use in folk medicine to treat inflammatory disorders, there are no descriptions that show its anti-inflammatory potential.

AIM OF THE STUDY

In this sense, this study aimed to evaluate the anti-inflammatory and antivenom action of bark and leaves extract of H. eriogyne.

MATERIALS AND METHODS

The in vivo anti-inflammatory activity was conducted by carrageenan-induced paw edema and zymosan-induced air pouch models, evaluating the edematogenic effect, leukocyte migration, protein concentration, levels of pro-inflammatory cytokines, malondialdehyde (MDA) and myeloperoxidase (MPO) activity. The antivenom potential was investigated in vitro on the enzymatic action (proteolytic, phospholipase and hyaluronidase) of Bothrops brazili and B. leucurus venom, as well as in vivo on the paw edema model induced by B. leucurus. Furthermore, the influence of its markers (astilbin and rutin) on MPO activity was investigated in silico. For molecular docking, AutodockVina, Biovia Discovery Studio, and Chimera 1.16 software were used.

RESULTS

The extracts and bark and leaves of H. eriogyne revealed a high anti-inflammatory effect, with a reduction in all inflammatory parameters evaluated. The bark extract showed superior results when compared to the leaf extract, suggesting the influence of the astilbin concentration, higher in the bark, on the anti-inflammatory action. In addition, only the H. eriogyne bark extract was able to reduce MDA, indicating an associated antioxidant effect. Regarding the in vitro antivenom action, the extracts (bark and leaves) revealed the ability to inhibit the proteolytic, phospholipase and hyaluronidase action of both bothropic venom, with a greater effect against B. leucurus venom. In vivo, extracts from the bark and leaves of H. eriogyne (50-200 mg/kg) showed antiedematogenic activity, reducing the release of MPO and pro-inflammatory cytokines, indicating the presence of bioactive components useful in controlling the inflammatory process induced by the venom. In the in silico assays, astilbin and rutin showed reversible interactions of 9 possible positions and orientations towards MPO, with affinities of -9.5 and -10.4 kcal/mol and interactions with Phe407, Gln91, His95 and Arg239, important active pockets of MPO. Rutin demonstrated more effective types of interactions with MPO.

CONCLUSION

This approach reveals for the first time the anti-inflammatory action of H. eriogyne bark and leaf extracts in vivo, as well as its antiophidic potential. Moreover, the distinct effect of pharmacogens as antioxidant agents and distinct effect of astilbin and rutin under MPO sheds light on the different anti-inflammatory mechanisms of bioactive compounds present in H. eriogyne extracts, with high potential for the prospection of new pharmacological agents.

Photobiomodulation mitigates Bothrops jararacussu venom-induced damage in myoblast cells by enhancing myogenic factors and reducing cytokine production

BACKGROUND

Photobiomodulation has exhibited promise in mitigating the local effects induced by Bothrops snakebite envenoming; however, the mechanisms underlying this protection are not yet fully understood. Herein, the effectiveness of photobiomodulation effects on regenerative response of C2C12 myoblast cells following exposure to Bothrops jararacussu venom (BjsuV), as well as the mechanisms involved was investigated.

METHODOLOGY/PRINCIPAL FINDINGS

C2C12 myoblast cells were exposed to BjsuV (12.5 μg/mL) and irradiated once for 10 seconds with laser light of 660 nm (14.08 mW; 0.04 cm2; 352 mW/cm2) or 780 nm (17.6 mW; 0.04 cm2; 440 mW/ cm2) to provide energy densities of 3.52 and 4.4 J/cm2, and total energies of 0.1408 and 0.176 J, respectively. Cell migration was assessed through a wound-healing assay. The expression of MAPK p38-α, NF-Кβ, Myf5, Pax-7, MyoD, and myogenin proteins were assessed by western blotting analysis. In addition, interleukin IL1-β, IL-6, TNF-alfa and IL-10 levels were measured in the supernatant by ELISA. The PBM applied to C2C12 cells exposed to BjsuV promoted cell migration, increase the expression of myogenic factors (Pax7, MyF5, MyoD and myogenin), reduced the levels of proinflammatory cytokines, IL1-β, IL-6, TNF-alfa, and increased the levels of anti-inflammatory cytokine IL-10. In addition, PBM downregulates the expression of NF-kB, and had no effect on p38 MAKP.

CONCLUSION/SIGNIFICANCE

These data demonstrated that protection of the muscle cell by PBM seems to be related to the increase of myogenic factors as well as the modulation of inflammatory mediators. PBM therapy may offer a new therapeutic strategy to address the local effects of snakebite envenoming by promoting muscle regeneration and reducing the inflammatory process.

A Cytotoxicity Assay as an Alternative to the Murine Model for the Potency Testing of Bothrops jararaca Venom and Antivenom: An Intralaboratory Pre-validation Study

Antivenom therapy is the only specific treatment for snakebite envenomation, and antivenom potency determination is key in the efficacy assurance quality control process. Nowadays, this process relies on the in vivo murine model - thus, the development of alternative in vitro methods is imperative. In the current study, the principle of the proposed method is the ability of Bothrops venom to induce cytotoxic effects in Vero cells, and the capacity to evaluate the inhibition of this cytotoxicity by the respective antivenom. After exposure to the venom/antivenom, the relative proportions of adherent (viable) cells were evaluated by direct staining with Coomassie Blue. The optical density (OD) of the lysed cell eluate was directly proportional to the number of adherent cells. This cytotoxicity-based alternative method could represent a potential candidate for validation as a replacement for the current in vivo test. The in vitro-determined cytotoxicity of the Brazilian Bothrops reference venom (expressed as the 50% effective concentration; EC50) was 3.61 μg/ml; the in vitro-determined 50% inhibitory concentration (IC50) of the Brazilian Bothrops reference antivenom was 0.133 μl/ml. From these two values, it was possible to calculate the potency of the reference antivenom. The results from the assays exhibited a good linear response, indicating that the method could be a potential candidate replacement method for use in antivenom quality control prior to lot release, subject to further validation.

Toxinological profile and histopathological alterations induced by Bothrocophias campbelli venom from Colombia

Snakebite envenomings most frequently reported in Colombia are caused by snakes of the genera Bothrops, Bothriechis, Bothrocophias, and Porthidium. Their venoms induce local and systemic pathophysiological effects, sometimes leading to permanent sequelae such as reduced mobility of the limbs, amputations, besides the risk of death. The genus Bothrocophias includes nine species, among which B. campbelli has a distribution restricted to the department of Nariño in Colombia. In this work we determined the toxinological profile its venom, by performing assays for the lethal, hemorrhagic, edematogenic, and myotoxic activities in mouse models, as well as for in vitro coagulant activity on human plasma. The lethal toxicity of the venom was 142.7 µg venom/mouse (111.4-179.8 µg/mouse; 6.6-10.6 µg/g body weight) by intraperitoneal route. Its hemorrhagic activity (minimum hemorrhagic dose: 12.7 ± 2.3 µg) is generally weaker compared to other South American vipers, but edematogenic (minimum edematogenic dose 1.0 ± 0.3 µg), and myotoxic (minimum myotoxic dose 3.9 ± 2.5 µg) activities are very potent. Histopathological examination of the injected mouse gastrocnemius muscle showed prominent disorganization of the myofibrils, myonecrosis, and an intense inflammatory leukocyte infiltrate. In vitro, the minimal coagulant dose was 12.3 ± 0.5 µg. Overall, this toxinological profile would predict that the clinical picture of envenomings by B. campbelli might be characterized by moderate disturbances in the coagulation cascade, mild local hemorrhage, and, conversely, severe myonecrosis and edema, which could potentially lead to compartment syndrome and gangrene.

In vitro and in vivo anti-inflammatory and antiophidic effects of the extract and fraction of Eugenia uniflora

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia uniflora Linn, popularly known as 'pitanga', is a native plant endemic to Brazil that belongs to the Myrtaceae family. Its traditional use (leaves infusion) has been reported for the treatment of different diseases, including hypertension, inflammation, and as a diuretic agent. Considering the snakebite problem and the rich molecule repertoire of this herbal species, studies that evaluate its antiophidic potential are relevant for a broad social impact.

AIM OF THE STUDY

This approach aims to evaluate the anti-inflammatory and antiophidic potential in vitro and in vivo of the extract (aqueous) and a fraction (ethyl acetate) of E. uniflora leaves against Bothrops leucurus and Bothrops brazili venoms.

MATERIALS AND METHODS

Extract and fraction from E. uniflora leaves were obtained by turbo-extraction and partitioning. The cytotoxicity was assayed on normal cell lines (Vero E6 and 3T3) using the 3-methyl-[4-5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide method. The anti-inflammatory activity of the aqueous extract was analyzed in vivo in the zymosan-induced air pouch model, and the leukocytes migration and other molecular inflammatory mediators quantified (myeloperoxidase, total protein, pro-inflammatory cytokine, malondialdehyde, and glutathione). In vitro, the antiophidic effect was evaluated by the ability of the E. uniflora extract and fraction to inhibit the enzymatic action (proteolytic, phospholipase A2, and hyaluronidase) of B. leucurus and B. brazili venoms. In addition, the antiophidic action in vivo was investigated after treatment with E. uniflora extract and fraction (50, 100, and 200 mg/kg) in the B. leucurus venom-induced paw edema with an evaluation of the antiedematogenic effect and quantification of myeloperoxidase (MPO) and pro-inflammatory cytokine levels.

RESULTS

The E. uniflora leaves extract (7.8-125 mg/mL) revealed no toxicity in cell culture, but reduced MTT by 47% at the highest concentration (250 mg/mL) in Vero E6 cells. In contrast, the E. uniflora fraction (7.8-250 mg/mL) showed no cytotoxicity for both cell lines. In the air pouch model, E. uniflora leaves extract demonstrated anti-inflammatory activity, reducing cell migration, MPO activity, protein, malondialdehyde, and proinflammatory cytokines, and increased glutathione levels. Evaluating the antiophidic action in vitro, E. uniflora extract and fraction inhibited the proteolytic, phospholipase, and hyaluronidase effects of B. leucurus and B. brazili venoms at low concentrations. In addition, the extract and fraction also demonstrated in vivo antiophidic activity by reducing edema in the first 0.5 h after treatment, besides reducing MPO and pro-inflammatory cytokines levels.

CONCLUSION

E. uniflora leaves extract showed cytotoxicity only at the highest concentration while the fraction revealed no toxic effect in vitro. This approach showed for the first time that the aqueous extract and ethyl acetate fraction of E. uniflora leaves has similar antiophidic action in vitro and in vivo, with antiedematogenic and anti-inflammatory effects and the ability to inhibit the enzymatic action of B. leucurus and B. brazili venoms. Therefore, this study points to the presence of bioactive components in the leaves of E. uniflora useful for the treatment of inflammatory disorders and ophidian accidents, expanding the therapeutic potential of this herbal species.

Systemic toxicity of snake venom metalloproteinases: Multi-omics analyses of kidney and blood plasma disturbances in a mouse model

Snakebite envenomation is classified as a Neglected Tropical Disease. Bothrops jararaca venom induces kidney injury and coagulopathy. HF3, a hemorrhagic metalloproteinase of B. jararaca venom, participates in the envenomation pathogenesis. We evaluated the effects of HF3 in mouse kidney and blood plasma after injection in the thigh muscle, mimicking a snakebite. Transcriptomic analysis showed differential expression of 31 and 137 genes related to kidney pathology after 2 h and 6 h, respectively. However, only subtle changes were observed in kidney proteome, with differential abundance of 15 proteins after 6 h, including kidney injury markers. N-terminomic analysis of kidney proteins showed 420 proteinase-generated peptides compatible with meprin specificity, indicating activation of host proteinases. Plasma analysis revealed differential abundance of 90 and 219 proteins, respectively, after 2 h and 6 h, including coagulation-cascade and complement-system components, and creatine-kinase, whereas a semi-specific search of N-terminal peptides indicated activation of endogenous proteinases. HF3 promoted host reactions, altering the gene expression and the proteolytic profile of kidney tissue, and inducing plasma proteome imbalance driven by changes in abundance and proteolysis. The overall response of the mouse underscores the systemic action of a hemorrhagic toxin that transcends local tissue damage and is related to known venom-induced systemic effects.

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

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

A retrospective study of clinical and epidemiological characteristics of snakebite in Napo Province, Ecuadorian Amazon

BACKGROUND

Snakebite envenoming remains a relevant public health problem in tropical and subtropical countries. In Ecuador, this is particularly true in an area of great diversity like the Amazon region. Nevertheless, there is scarce information about epidemiological and clinical characteristics of these accidents in this area.

METHODS

This was a descriptive and retrospective study of snakebite cases treated at a tertiary hospital in the Napo Province, Ecuadorian Amazon, from 2015 to 2019. We collected sociodemographic and snakebite-related information, clinical aspects and the use of antivenom and antibiotics from medical records.

RESULTS

Information from 133 snakebite accidents was reviewed in this time period. Reports of snakebite envenoming decreased over the years. In total, 67% of those bitten were from nearby indigenous communities, which were the most affected groups. When a species was identified, Bothrops atrox was responsible for the highest number of cases registered. Local clinical manifestations were more frequent than systemic signs, in keeping with the typical effects produced by bothropic venoms. Additionally, data showed that more antivenom vials were given than those suggested by the protocol of the Ecuadorian Ministry of Health, in proportion to the grade of severity. Finally, we identified a low incidence of adverse reactions with antivenom administration, as well as a frequent use of antibiotics.

CONCLUSIONS

The profile of snakebite accidents in the Napo Province is very similar to that described for other localities in the Amazon region of Ecuador and neighboring countries, with its challenges and limitations. Such aspects underlie the importance of establishing a robust and science-based public health program to respond to this frequent, but neglected, tropical disease.

Longitudinal Metabolomics and Lipidomics Analyses Reveal Alterations Associated with Envenoming by Bothrops asper and Daboia russelii in an Experimental Murine Model

Longitudinal metabolomics and lipidomics analyses were carried out on the blood plasma of mice injected intramuscularly with venoms of the viperid species Bothrops asper or Daboia russelii. Blood samples were collected 1, 3, 6, and 24 h after venom injection, and a control group of non-envenomed mice was included. Significant perturbations in metabolomics and lipidomics were observed at 1, 3, and 6 h, while values returned close to those of control mice by 24 h, hence reflecting a transient pattern of metabolic disturbance. Both venoms induced significant changes in amino acids, as well as in several purines and pyrimidines, and in some metabolites of the tricarboxylic acid cycle. KEGG analysis of metabolic pathways that showed those with the greatest change included aminoacyl tRNA synthesis and amino acid biosynthesis and metabolism pathways. With regard to lipid metabolism, there was an increase in triglycerides and some acyl carnitines and a concomitant drop in the levels of some phospholipids. In addition, envenomed mice had higher levels of cortisol, heme, and some oxidative stress markers. The overall pattern of metabolic changes in envenomed mice bears similarities with the patterns described in several traumatic injuries, thus underscoring a metabolic response/adaptation to the injurious action of the venoms.

Delayed Recognition of Severe Systemic Envenomation after Copperhead Bite: A Case Report

Introduction

We report a case of severe systemic copperhead, Agkistrodon contortrix, envenomation that resulted in long-term sequelae.

Case Report

A 72-year-old man presented to the emergency department after suffering a copperhead snakebite. He developed severe systemic toxicity before local tissue injury developed. Clinicians did not initially recognize his envenomation syndrome and sought alternative explanations for his systemic symptoms before polyvalent immune fab (ovine) antivenom was administered. Although the patient improved, he was discharged with new stage three chronic kidney disease.

Conclusion

Although rare, copperhead envenomation can cause severe systemic toxicity. Envenomation should be promptly treated with antivenom.

A First Look at the Inhibitory Potential of Urospatha sagittifolia (Araceae) Ethanolic Extract for Bothrops atrox Snakebite Envenomation

Bothrops atrox snakebites are a relevant problem in the Amazon basin. In this biodiverse region, the ethnomedicinal approach plays an important role as an alternative to antivenom therapy. Urospatha sagittifolia (Araceae) is a plant used for this purpose; however, its neutralizing properties have not been scientifically accessed. To fill this gap, we investigated the ability of U. sagittifolia to modulate the catalytic activity of Bothrops atrox venom, and their toxic consequences, such as local damage and lethality. The venom profile of B. atrox was assessed by chromatography and electrophoresis. Inhibition of the three main enzymatic and medically important toxins from the venom was evaluated using synthetic substrates and quantified by chromogenic activity assays. Additionally, the neutralization of lethality, hemorrhage and edema were investigated by in vivo assays. The possible interactions between venom proteins and plant molecules were visualized by polyacrylamide gel electrophoresis. Finally, the phytochemical constituents present in the ethanolic extract were determined by qualitative and quantitative analyses. The ethanolic extract reduced the activity of the three main enzymes of venom target, achieving ranges from 19% to 81% of inhibition. Our in vivo venom neuralizations assays showed a significant inhibition of edema (38.72%) and hemorrhage (42.90%). Additionally, lethality was remarkably counteracted. The highest extract ratio evaluated had a 75% survival rate. Our data support the biomedical value of U. sagittifolia as a source of natural enzyme inhibitors able to neutralize catalytically active B. atrox venom toxins and their toxic effects.

Inhibition of enzymatic activities of Bothrops asper snake venom and docking analysis of compounds from plants used in Central America to treat snakebite envenoming

ETHNOPHARMACOLOGICAL RELEVANCE

Snakebite envenoming is a public health problem of high impact in Central America. Bothrops asper, known as barba amarilla, terciopelo, and equis, is the snake species responsible for most snakebites in Central America. In this region, there is a long-standing tradition on the use of plants in the management of snakebites, especially in indigenous communities. Ethnomedical use of Eryngium foetidum L., Neurolaena lobata (L.) Cass. and Pimenta dioica (L.) Merr. to treat snakebite envenoming has been reported in Belice, Guatemala, Nicaragua, and Costa Rica. Extracts of the leaves of these plants have shown anti-venom activities in in vitro assays in previous studies.

AIM OF THE STUDY

To assess the ability of organic fractions from these three plants to inhibit enzymatic activities associated with toxicity of the venom of B. asper, and to study, by docking analysis, the interaction of metalloproteinase and phospholipases A₂ (PLA₂) from B. asper venom with secondary metabolites previously described in these plants.

MATERIALS AND METHODS

Organic fractions were obtained from these three plant species and their ability to neutralize proteolytic, PLA₂ and in vitro coagulant activities of B. asper venom was assessed. A phytochemical analysis was carried out in these fractions. The interaction of secondary metabolites previously described in these plants with three toxins from B. asper venom (a metalloproteinase, a PLA₂ and a PLA₂ homologue) was investigated by docking analysis.

RESULTS

The inhibitory activity of plants was mainly concentrated in their polar fractions. Acetonic fraction from P. dioica was the most active against PLA₂ activity, while the acetonic fraction of E. foetidum completely inhibited the proteolytic activity of the venom. Coagulant activity was partially inhibited only by the acetone and ethyl acetate fractions of P. dioica. Phytochemical analysis of the most bioactive fractions identified flavonoids, saponins, essential oils, coumarins, alkaloids, tannins and sesquiterpene lactones. Docking analysis revealed high affinity interactions of several secondary metabolites of these plants with residues in the vicinity of the catalytic site of these enzymes and, in the case of PLA₂ homologue myotoxin II, in the hydrophobic channel.

CONCLUSIONS

Various fractions from these plants have inhibitory activity against enzymatic actions of B. asper venom which are directly associated with toxicological effects. Docking analysis showed structural evidence of the interaction of secondary metabolites with three toxins. These observations provide support to the potential of these plants to inhibit relevant toxic components of this snake venom.

Evaluation of the systemic alterations triggers by Porthidium lansbergii lansbergii snake venom

The systemic effects generated by Porthidium lansbergii lansbergii envenoming, a species found in the northern region of Colombia, is poorly known. The present study aimed to analyze for the first time the mice's behavior, the histological alterations, and changes in biochemical markers levels resulting from the intraperitoneal injection of an LD₅₀ of P. lansbergii lansbergii snake venom on mice. The envenoming mice displayed hypodynamic condition, clonic head movements, accompanied by bradypnea and thoracoabdominal imbalance. After 7 h of envenoming, the mice showed an ecchymotic region at the injection site, including bleeding in the pleural, liver, and kidney capsules. The effect on the brain revealed a micro-hemorrhage in the sensorimotor cortex with substantial loss of neurons. The venom caused dilated blood vessels in lung tissue, with endothelial necrosis associated with alveolar rupture. The liver showed parenchyma alteration with many extravasated erythrocytes. The kidneys exhibited renal tubules necrosis and a statistically significant increase in creatinine concentration. ALP and ALT's enzymatic activities remained constant at 7 h after envenoming but increased at 12 h. AST and LDH were significantly increased at 7 h but decreased to the near baseline 12 h after venom administration. Massive hemorrhages could trigger a hypovolemic shock, which could lead to death after several h without treatment. Knowledge of P. lansbergii lansbergii snake bites' injuries is essential to make the appropriate diagnostic in human envenoming cases by this snake.

Bleeding and Thrombosis: Insights into Pathophysiology of Bothrops Venom-Related Hemostasis Disorders

Toxins from Bothrops venoms targeting hemostasis are responsible for a broad range of clinical and biological syndromes including local and systemic bleeding, incoagulability, thrombotic microangiopathy and macrothrombosis. Beyond hemostais disorders, toxins are also involved in the pathogenesis of edema and in most complications such as hypovolemia, cardiovascular collapse, acute kidney injury, myonecrosis, compartmental syndrome and superinfection. These toxins can be classified as enzymatic proteins (snake venom metalloproteinases, snake venom serine proteases, phospholipases A₂ and L-amino acid oxidases) and non-enzymatic proteins (desintegrins and C-type lectin proteins). Bleeding is due to a multifocal toxicity targeting vessels, platelets and coagulation factors. Vessel damage due to the degradation of basement membrane and the subsequent disruption of endothelial cell integrity under hydrostatic pressure and tangential shear stress is primarily responsible for bleeding. Hemorrhage is promoted by thrombocytopenia, platelet hypoaggregation, consumption coagulopathy and fibrin(ogen)olysis. Onset of thrombotic microangiopathy is probably due to the switch of endothelium to a prothrombotic phenotype with overexpression of tissue factor and other pro-aggregating biomarkers in association with activation of platelets and coagulation. Thrombosis involving large-caliber vessels in B. lanceolatus envenomation remains a unique entity, which exact pathophysiology remains poorly understood.

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

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

Snakebite envenoming in different national contexts: Costa Rica, Sri Lanka, and Nigeria

Snakebite envenoming is a neglected tropical disease that predominantly affects impoverished rural communities in sub-Saharan Africa, Asia, and Latin America. The global efforts to reduce the impact of this disease must consider the local national contexts and, therefore, comparative studies on envenomings in different countries are necessary to identify strengths, weaknesses and needs. This work presents a comparative analysis of snakebite envenomings in Costa Rica, Sri Lanka, and Nigeria. The comparison included the following aspects: (a) burden of envenomings, (b) historical background of national efforts to confront envenomings, (c) national health systems, (d) antivenom availability and accessibility including local production, (e) training of physicians and nurses in the diagnosis and management of envenomings, (f) prevention campaigns and community-based work, (g) scientific and technological platforms in these topics, and (h) international cooperation programs. Strengths and weaknesses were identified in the three contexts and several urgent tasks to improve the management of this disease in these countries are highlighted. This comparative analysis could be of benefit for similar studies in other national and regional contexts.

Les envenimations vipérines en Guyane française

L’OMS classe l’envenimation vipérine comme pathologie négligée. Elle représente un problème de santé publique associé à des taux de mortalité et de morbidité importants. Notre objectif est de faire une mise au point sur les données récentes de la littérature sur l’épidémiologie et la prise en charge de l’envenimation vipérine en Guyane française. La Guyane est un département français presque entièrement recouvert par une forêt tropicale. Elle abrite une herpétofaune très riche comportant notamment les espèces du genre Bothrops (famille des Viperidae) qui provoquent le plus grand nombre de morsures et d’envenimations. La gestion des envenimations vipérines représente un défi de santé publique. En effet, la plupart des envenimations se produisent dans des zones rurales éloignées où l’accès aux soins est le plus compliqué, avec la présence d’un personnel médical peu formé à la prise en charge et l’indisponibilité de l’antivenin, ce qui constitue une véritable perte de chance pour les patients. En conclusion, dans un contexte d’efforts mondiaux visant à réduire l’impact des envenimations vipérines, la coopération internationale et l’engagement des autorités locales de santé et de la société civile sont nécessaires. En Guyane, la mise en place d’une véritable filière de soins et la mise à disposition de l’antivenin dans les structures sanitaires les plus isolées constitueraient un réel progrès sanitaire.

Fatal brain hemorrhage after Bothrops asper bite in the Catatumbo region of Colombia

Las mordeduras de serpientes son un problema de salud pública en regiones tropicales y subtropicales del mundo. Ocurren, especialmente, en trabajadores rurales, y son una importante fuente de discapacidad y mortalidad.

Se presenta el caso de un hombre de 59 años, agricultor de la región del Catatumbo (Colombia), quien sufrió la mordedura de una serpiente Bothrops asper, la cual le produjo una hemorragia cerebral fatal.

Se llama la atención sobre el grave trastorno hemorrágico en contraste con los leves cambios en el sitio de la mordedura, así como sobre la necesidad del tratamiento temprano de la intoxicación con el suero antiofídico, incluso, en ausencia de manifestaciones cutáneas significativas.

Proteomic Investigations of Two Pakistani Naja Snake Venoms Species Unravel the Venom Complexity, Posttranslational Modifications, and Presence of Extracellular Vesicles

Latest advancement of omics technologies allows in-depth characterization of venom compositions. In the present work we present a proteomic study of two snake venoms of the genus Naja i.e., Naja naja (black cobra) and Naja oxiana (brown cobra) of Pakistani origin. The present study has shown that these snake venoms consist of a highly diversified proteome. Furthermore, the data also revealed variation among closely related species. High throughput mass spectrometric analysis of the venom proteome allowed to identify for the N. naja venom 34 protein families and for the N. oxiana 24 protein families. The comparative evaluation of the two venoms showed that N. naja consists of a more complex venom proteome than N. oxiana venom. Analysis also showed N-terminal acetylation (N-ace) of a few proteins in both venoms. To the best of our knowledge, this is the first study revealing this posttranslational modification in snake venom. N-ace can shed light on the mechanism of regulation of venom proteins inside the venom gland. Furthermore, our data showed the presence of other body proteins, e.g., ankyrin repeats, leucine repeats, zinc finger, cobra serum albumin, transferrin, insulin, deoxyribonuclease-2-alpha, and other regulatory proteins in these venoms. Interestingly, our data identified Ras-GTpase type of proteins, which indicate the presence of extracellular vesicles in the venom. The data can support the production of distinct and specific anti-venoms and also allow a better understanding of the envenomation and mechanism of distribution of toxins. Data are available via ProteomeXchange with identifier PXD018726.

Clinical Features and Management of Snakebite Envenoming in French Guiana

The management of snakebite (SB) envenoming in French Guiana (FG) is based on symptomatic measures and antivenom (AV) administration (Antivipmyn Tri®; Instituto Bioclon-Mexico). Our study aimed to assess clinical manifestations, the efficacy, and safety of Antivipmyn Tri® in the management of SB. Our study is a prospective observational work. It was conducted in the Intensive Care Unit (ICU) of Cayenne General Hospital between 1 January 2016 and 31 December 2019. We included all patients hospitalized for SB envenoming. Our study contained three groups (without AV, three vials, and six vials Antivipmyn Tri®). During the study period, 133 patients were included. The main clinical symptoms were edema (98.5%), pain (97.7%), systemic hemorrhage (18%), blister (14.3%), and local hemorrhage (14.3%). AV was prescribed for 83 patients (62.3%), and 17 of them (20%) developed early adverse reactions. Biological parameters at admission showed defibrinogenation in 124 cases (93.2%), International Normalized Ratio (INR) > 2 in 104 cases (78.2%), and partial thromboplastin time (PTT) > 1.5 in 74 cases (55.6%). The time from SB to AV was 9:00 (5:22-20:40). The median time from SB to achieve a normal dosage of fibrinogen was 47:00 vs. 25:30, that of Factor II was 24:55 vs. 15:10, that of Factor V was 31:42 vs. 19:42, and that of Factor VIII was 21:30 vs. 10:20 in patients without and with AV, respectively, (p < 0.001 for all factors). Patients receiving Antivipmyn Tri® showed a reduction in the time to return to normal clotting tests, as compared to those who did not. We suggest assessing other antivenoms available in the region to compare their efficacy and safety with Antivipmyn Tri® in FG.

Catechin and epicatechin as an adjuvant in the therapy of hemostasis disorders induced by snake venoms

Snake toxins, such as phospholipases A₂ and proteases, are used as research tools to evaluate biological activities and to understand physiopathological processes of natural compounds better. In the present study, the phenolic compounds catechin and epicatechin were incubated with snake venoms to evaluate their inhibition against different substrates. Catechin and epicatechin exerted inhibitions between 20% and 95% on the activity of phospholipases A₂ present in the venom of Bothrops alternatus. In the hemolytic activity, catechin exerted inhibitions between 20% and 25% in all proportions evaluated on the B. jararacussu venom, whereas epicatechin inhibited 20% of the venom activity. Coagulation induced by B. atrox and B. jararacussu venoms was significantly inhibited by catechin and epicatechin, where the time for coagulation was two to three times higher after previous incubation of the venoms with the compounds. The most significant inhibitions for the proteolytic activity on casein were 17% and 27%, respectively, by both compounds. Catechin inhibited serine protease activity induced by B. atrox venom by 64% and epicatechin by 65%. Regarding B. atrox-induced thrombolysis, catechin exerted 40% inhibition and epicatechin around 30%. The fibrinogen proteolysis was completely inhibited by catechin acting on the B. atrox venom in the proportion of 1:1 and by epicatechin on B. jararacussu venom. Catechin and epicatechin showed promising inhibitory action on proteases and phospholipases A₂ . Therefore, these compounds can be explored as an adjuvant for serum therapy or pharmaceutical purposes, once they act on homologous enzymes that are present in humans.

Clinical assessment and pathophysiology of Bothrops venom-related acute kidney injury: a scoping review

Bothrops are one of the most common medically important snakes found in Latin America. Its venom is predominantly hemotoxic and proteolytic, which means that local lesion (edema and redness) and hemorrhagic symptoms are recurrent in envenoming by this snake. Although hemorrhage is usually the major cause of death, snakebite-related acute kidney injury is another potentially fatal clinical complication that may lead to chronic kidney disease. The present review highlights the main studies on Bothrops venom-related acute kidney injury, including observational, cross-sectional, case-control and cohort human studies available up to December 2019. The following descriptors were used according to Medical Subject Headings (MeSH): on Medline/Pubmed and Google Scholar "acute kidney injury" or "kidney disease" and "Bothrops"; on Lilacs and SciELO "kidney disease" or "acute kidney injury" and "Bothrops". Newcastle-Ottawa quality assessment scale was used to appraise the quality of the cross-sectional and cohort studies included. The selection of more severe patients who looked for health care units and tertiary centers is a risk of bias. Due to the methodological heterogeneity of the studies, a critical analysis of the results was performed based on the hypothesis that the design of the included studies influences the incidence of acute kidney injury. Fifteen human studies (total participants 4624) were included according to stablished criteria. The coagulation abnormalities (hemorrhagic symptoms, abnormal fibrinogen and activated partial thromboplastin time) were associated with acute kidney injury in the most recent studies reported. The findings observed in this review provide up-to-date evidence about the acute kidney injury pathogenesis following Bothrops syndrome. Studies pointed out that coagulation abnormalities comprise the major pathway for acute kidney injury development. This review may improve patient management by primary healthcare providers, allowing earlier diagnosis and treatment of Bothrops venom-related acute kidney injury.

Bothrops leucurus venom induces acute hypotension in rats by means of its phospholipase A2 (blD-PLA2)

Cardiovascular effects induced by snake venoms, in spite of having a crucial role in the outcome of the envenomation, have been less studied than other toxic activities displayed by these venoms. In this study we evaluated acute cardiovascular responses to Bothrops leucurus venom - Bl-V - both in vivo, in anesthetized rats, and in vitro, in isolated rat mesenteric resistance arteries. Bl-V (10-100 μg protein/kg) caused dose-dependent hypotension, followed by gradual recovery (2-20 min) to basal levels, and induced dose-dependent (1-20 μg/mL) vasodilation in pre-contracted arteries, what was more pronounced when the endothelium remained intact. These effects were partially counteracted by pre-treatment with indomethacin (cyclooxygenase inhibitor). Prior incubation of Bl-V with commercial pentavalent Bothrops antivenom also attenuated the cardiovascular effects induced by the venom, in spite of it not being among the venoms used for the development of the bothropic antivenom. Through an approach based on two chromatographic steps and mass spectrometry (MALDI-ToF and MALDI-ISD), a component with acute cardiovascular effects was isolated and identified as the basic phospholipase blD-PLA₂, previously purified from the venom of B. leucurus. Taken together, our results show that, at low doses, the venom of B. leucurus induces transient, acute hypotension in anesthetized rats following systemic vasodilation in a dose-dependent way. In addition, we provide clear evidence of the involvement of the enzymatic activity of blD-PLA₂ in this cardiovascular response, acting via the production of vasodilating prostanoids.

Vanillic acid as phospholipase A2 and proteases inhibitor: In vitro and computational analyses

Enzymatic inhibition by natural compounds may represent a valuable adjuvant in snakebite serum therapy. The objective in this work was to evaluate possible in vitro interactions between vanillic acid and enzymes from Bothrops spp. and Crotalus durissus terrificus venoms, and also suggest a theory as how they interact based on molecular docking. Vanillic acid inhibited the phospholipase activity induced by Bothrops alternatus (∼25% inhibition); the caseinolytic activity induced by Bothrops atrox (∼30%), Bothrops jararacussu (∼44%), and C. d. terrificus (∼33%); the fibrinogenolysis induced by B. jararacussu, B. atrox, and C. d. terrificus (100%); the serine protease activity induced by Bothrops moojeni (∼45%) and Bothrops jararaca (∼66%); the hemolytic activity induced by B. moojeni (∼26%); the thrombolysis activity induced by B. atrox (∼30%) and B. jararacussu (∼20%); and the thrombotic activity induced by C. d. terrificus (∼8%). The compound was also capable of delaying the coagulation time in citrated plasma by 60, 35, and 75 Sec, when incubated with B. moojeni, B. atrox, and B. jararaca, respectively. The results obtained expand the possibilities for future pharmaceutical use of vanillic acid, considering the high homology degree among human and snake venom phospholipases A₂ and proteases (involved in chronic inflammatory diseases). Also, this compound can be used as adjuvant to improve currently available treatments for ophidism victims.

Toxicological profile of medically relevant Crotalus species from Mexico and their neutralization by a Crotalus basiliscus/Bothrops asper antivenom

Specimens of the Crotalus genus represent a potential snakebite problem in Mexico, and despite the great number of species of Crotalus present in this country, only a few of them are relevant from a medical point of view. Crotalus envenomed patients can present a range of signs and symptoms, depending on the species involved, and their treatment is indistinctly with either of the anti-viperid antivenoms available in the Mexican Public Health System. One of these antivenoms is produced by immunization of horses with a mixture of only two venoms: Crotalus basiliscus and Bothrops asper venoms. In light of the high variability found in Crotalus species venom composition, it is important to demonstrate the cross-neutralization of this antivenom against other Crotalus species. Therefore, in this work the toxic variability of eight medically important Crotalus venoms from Mexico and its neutralization by the Crotalus basiliscus/Bothrops asper antivenom were assessed. The present study evidenced the variability of toxic and enzymatic activities among the following Crotalus venoms: (1) Crotalus atrox, (2) Crotalus basiliscus, (3) Crotalus culminatus, (4) Crotalus simus, (5) Crotalus tzabcan, (6) Crotalus scutulatus salvini, (7) Crotalus scutulatus scutulatus-A, and (8) Crotalus scutulatus scutulatus-B. All venoms studied possess lethal and hemorrhagic activity on a murine model, although there are important variations among the species; in contrast, the PLA₂ activity was similar for all venoms. Interestingly, only C. simus venom exhibited coagulant activity on human plasma under 100 μg. The antivenom neutralized the lethality and all the other assessed activities for all venoms tested. However, the dose required varied depending on the venom and the evaluated activity. Our preclinical data support the recommendation of using this antivenom to clinically manage Crotalus snakebites produced by the species assessed in this study. Nonetheless, only clinical trials could categorically validate these results.

BoaγPLI: Structural and functional characterization of the gamma phospholipase A2 plasma inhibitor from the non-venomous Brazilian snake Boa constrictor

Plasma in several organisms has components that promote resistance to envenomation by inhibiting specific proteins from snake venoms, such as phospholipases A2 (PLA2s). The major hypothesis for inhibitor's presence would be the protection against self-envenomation in venomous snakes, but the occurrence of inhibitors in non-venomous snakes and other animals has opened new perspectives for this molecule. Thus, this study showed for the first time the structural and functional characterization of the PLA2 inhibitor from the Boa constrictor serum (BoaγPLI), a non-venomous snake that dwells extensively the Brazilian territory. Therefore, the inhibitor was isolated from B. constrictor serum, with 0.63% of recovery. SDS-PAGE showed a band at ~25 kDa under reducing conditions and ~20 kDa under non-reducing conditions. Chromatographic analyses showed the presence of oligomers formed by BoaγPLI. Primary structure of BoaγPLI suggested an estimated molecular mass of 22 kDa. When BoaγPLI was incubated with Asp-49 and Lys-49 PLA2 there was no severe change in its dichroism spectrum, suggesting a non-covalent interaction. The enzymatic assay showed a dose-dependent inhibition, up to 48.2%, when BoaγPLI was incubated with Asp-49 PLA2, since Lys-49 PLA2 has a lack of enzymatic activity. The edematogenic and myotoxic effects of PLA2s were also inhibited by BoaγPLI. In summary, the present work provides new insights into inhibitors from non-venomous snakes, which possess PLIs in their plasma, although the contact with venom is unlikely.

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.

Comparación de la eficacia, la seguridad y la farmacocinética de los antivenenos antiofídicos: revisión de literatura

En Colombia se presentan anualmente alrededor de 5000 casos de mordedura de serpiente y su tratamiento se basa en la neutralización con inmunoglobulinas completas purificadas, sin embargo, globalmente se utilizan antivenenos faboterápicos. Objetivo: Dar a conocer diferencias entre las generaciones de antivenenos, la importancia del veneno en la producción de anticuerpos, comparar aspectos farmacocinéticos y los efectos adversos en pacientes. Materiales Métodos: Se realizó una búsqueda de literatura en bases de datos utilizando combinaciones de los descriptores y términos Mesh, en inglés y español. Se cotejaron parámetros farmacocinéticos en estudios preclínicos y los efectos adversos en estudios clínicos. Resultados: Se encontraron diferencias debidas al tamaño de la fracción de la inmunoglobulina que la compone, así entre más pequeña es ésta, se observa mayor distribución a los tejidos y una vida media más corta, comparada con las moléculas más pesadas. Se encontraron estudios con disminución de efectos adversos con antivenenos faboterápicos 

Venom Composition in a Phenotypically Variable Pit Viper ( Trimeresurus insularis) across the Lesser Sunda Archipelago

The genus Trimeresurus comprises a group of venomous pitvipers endemic to Southeast Asia and the Pacific Islands. Of these, Trimeresurus insularis, the White-lipped Island Pitviper, is a nocturnal, arboreal species that occurs on nearly every major island of the Lesser Sunda archipelago. In the current study, venom phenotypic characteristics of T. insularis sampled from eight Lesser Sunda Islands (Flores, Lembata, Lombok, Pantar, Sumba, Sumbawa, Timor, and Wetar) were evaluated via SDS-PAGE, enzymatic activity assays, fibrinogenolytic assays, gelatin zymography, and RP-HPLC, and the Sumbawa sample was characterized by venomic analysis. For additional comparative analyses, venoms were also examined from several species in the Trimeresurus complex, including T. borneensis, T. gramineus, T. puniceus, T. purpureomaculatus, T. stejnegeri, and Protobothrops flavoviridis. Despite the geographical isolation, T. insularis venoms from all eight islands demonstrated remarkable similarities in gel electrophoretic profiles and RP-HPLC patterns, and all populations had protein bands in the mass ranges of phosphodiesterases (PDE), l-amino acid oxidases (LAAO), P-III snake venom metalloproteinases (SVMP), serine proteases, cysteine-rich secretory proteins (CRISP), phospholipases A₂ (PLA₂), and C-type lectins. An exception was observed in the Lombok sample, which lacked protein bands in the mass range of serine protease and CRISP. Venomic analysis of the Sumbawa venom also identified these protein families, in addition to several proteins of lesser abundance (<1%), including glutaminyl cyclase, aminopeptidase, PLA₂ inhibitor, phospholipase B, cobra venom factor, 5'-nucleotidase, vascular endothelial growth factor, and hyaluronidase. All T. insularis venoms exhibited similarities in thrombin-like and PDE activities, while significant differences were observed for LAAO, SVMP, and kallikrein-like activities, though these differences were only observed for a few islands. Slight but noticeable differences were also observed with fibrinogen and gelatin digestion activities. Trimeresurus insularis venoms exhibited overall similarity to the other Trimeresurus complex species examined, with the exception of P. flavoviridis venom, which showed the greatest overall differentiation. Western blot analysis revealed that all major T. insularis venom proteins were recognized by Green Pitviper ( T. albolabris) antivenom, and reactivity was also seen with most venom proteins of the other Trimeresurus species, but incomplete antivenom-venom recognition was observed against P. flavoviridis venom proteins. These results demonstrate significant conservation in the venom composition of T. insularis across the Lesser Sunda archipelago relative to the other Trimeresurus species examined.

Case Report: Hemothorax in Envenomation by the Viperid Snake Bothrops asper

Bothrops asper, a highly venomous pit viper distributed from Colombia and northwestern Peru in South America to southern Mexico, is responsible for most snake bites in Central America, affecting especially young agricultural workers. A 17-year-old male from a rural area in northern Honduras was admitted at San Francisco Hospital after a B. asper bite that had occurred 3 days earlier. The puncture wounds were located on the first toe of the right foot. On the second day of admission, the patient developed dyspnea. A physical examination revealed hypoventilation of the left lung with dullness on 75% of the left lung. Left pleural effusion, approximately 90%, was observed on the chest X-ray. The patient was diagnosed with hemothorax, and a thoracostomy drained 1,350 mL of serosanguineous fluid, followed by the installation of a wet suction control system (Pleur-evac®). After 10 days, the patient was discharged. This case illustrates the diversity of hemorrhagic manifestations in envenomations by B. asper.

Inhibition of a Snake Venom Metalloproteinase by the Flavonoid Myricetin

Most of the snakebite envenomations in Central and South America are caused by species belonging to Bothrops genus. Their venom is composed mainly by zinc-dependent metalloproteinases, responsible of the hemorrhage characteristic of these envenomations. The aim of this study was to determine the inhibitory ability of ten flavonoids on the in-vitro proteolytic activity of Bothrops atrox venom and on the hemorrhagic, edema-forming and myonecrotic activities of Batx-I, the most abundant metalloproteinase isolated from this venom. Myricetin was the most active compound, exhibiting an IC 50 value of 150 μ M and 1021 μ M for the inhibition of proteolytic and hemorrhagic activity, respectively. Independent injection experiments, with a concentration of 1600 μ M of myricetin administered locally, immediately after toxin injection, demonstrated a reduction of 28 ± 6 % in the hemorrhagic lesion. Additionally, myricetin at concentrations 800, 1200 and 1600 μ M promoted a reduction in plasma creatine kinase activity induced by Batx-I of 21 ± 2 % , 60 ± 5 % and 63 ± 2 % , respectively. Molecular dynamics simulations coupled with the adaptive biasing method suggest that myricetin can bind to the metalloproteinase active site via formation of hydrogen bonds between the hydroxyl groups 3', 4' and 5' of the benzyl moiety and amino acid Glu143 of the metalloproteinase. The hydroxyl substitution pattern of myricetin appears to be essential for its inhibitory activity. Based on this evidence, myricetin constitutes a candidate for the development of inhibitors to reduce local tissue damage in snakebite envenomations.

Quantitative proteomic analysis and antivenom study revealing that neurotoxic phospholipase A2 enzymes, the major toxin class of Russell's viper venom from southern India, shows the least immuno-recognition and neutralization by commercial polyvalent antivenom

The proteome composition of Russell's viper venom (RVV) from southern India (SI) was investigated by 1D-SDS-PAGE of venom followed by tandem mass spectrometry analysis of protein bands. A total of 66 proteins belonging to 14 snake venom protein families were identified by LC-MS/MS analysis against Viperidae (taxid 8689) protein entries from the non-redundant NCBI database. Phospholipase A2 (43.25%) and snaclec (14.57%) represented the most abundant enzymatic and non-enzymatic proteins, respectively. SI RVV was characterized as containing a higher quantity of PLA2 and a lower amount of Kunitz-type serine protease inhibitors, in comparison to RVV from other regions of the Indian subcontinent. The enzymatic activities, pharmacological properties, and clinical manifestations of RV envenomation in SI were well correlated with its proteome composition; however, ATPase, ADPase, and hyaluronidase enzymes were not identified by LC-MS/MS analysis, owing to paucity of the existing database. Neurological symptoms exhibited by RV-bite patients in SI were correlated to the presence of abundant neurotoxic phospholipase A2 enzymes (15.66%) in SI RVV. Neutralization studies, immunological cross-reactivity, and antivenomics studies unequivocally demonstrated the poor recognition and lowest neutralization of PLA2 enzymes by commercial polyvalent antivenom, which is a major concern for the treatment of RV-envenomed patients in SI.

Proteomic Analysis and Immuno-Profiling of Eastern India Russell's Viper ( Daboia russelii) Venom: Correlation between RVV Composition and Clinical Manifestations Post RV Bite

The proteomes of Russell's viper venom (RVV) from Burdwan (RVV B) and Nadia (RVV N), the two districts of West Bengal, eastern India (EI), were investigated by gel-filtration chromatography (GFC) followed by tandem mass spectrometry of tryptic fragments of the fractions. A total of 73 and 69 proteins belonging to 15 snake venom protein families were identified in RVV B and RVV N, respectively, by MS/MS search against Viperidae (taxid 8689) protein entries of the nonredundant NCBI database. The minor differences in venom composition of both the EI RV were established unequivocally by their biochemical and pharmacological properties and by SDS-PAGE, gel filtration chromatography, and LC-MS/MS analyses. The composition of EI RVVs was well correlated with published reports on the pathophysiology of RV-envenomed patients from this part of the country. Venom-antivenom cross-reactivity determined by ELISA, Western blotting, and antivenomics approaches demonstrated poor recognition of low molecular mass (<20 kDa) RVV proteins by commercial polyvalent antivenoms, which was substantiated by neutralization of RVV enzymes by antivenom.

Inactivation of Venom PLA₂ Alleviates Myonecrosis and Facilitates Muscle Regeneration in Envenomed Mice: A Time Course Observation

Snake venom is a complex cocktail of toxins which induces a series of clinical and pathophysiological manifestations in victims, including severe local tissue damage and systemic alterations. Deinagkistrodon acutus (D. acutus) ranks among the “big four” life-threatening venomous species in China, whose venom possesses strong myotoxicity and hematotoxicity that often lead to permanent disability or muscle atrophy. Varespladib, an inhibitor of mammalian phospholipase A₂ (PLA₂), has been recently reproposed as an effective antidote against snakebite envenomation. The present study aimed at evaluating the protective role of varespladib on muscle regeneration in envenomed mice. Mice were grouped and subjected to inoculation with D. acutus venom or a mixture of venom and varespladib or control vehicle in the gastrocnemius muscle. Local injuries including hemorrhage, myonecrosis, ulceration, and systemic damages including general dysfunction, visceral failure, and inflammatory responses were observed at 1, 3, 7, 14, and 21 days. The results indicated that most of the muscle myonecrosis and hemorrhage were alleviated by varespladib. Besides, the pretreated mice recovered rapidly with lesser atrophy and muscle fibrosis. In conclusion, the findings of the present study suggested that varespladib is an effective antidote that could neutralize D. acutus venom and allow for earlier and improved rehabilitation outcome.

Severe snakebite envenomation in French Guiana: When antivenom is not available

In French Guiana, Bothrops atrox, Bothrops brazili, Bothrops bilineatus, Lachesis muta and Micrurus sp are responsible for most cases of snakebite envenomation. The clinical features in patients suffering from envenomations by viperid snakes involve local tissue damage and systemic manifestations, such as hemorrhage, coagulopathies and hemodynamic instability. We report a severe case of envenomation in a patient bitten by a large unidentified pit viper in French Guiana. Due to lack of antivenom, the patient only received symptomatic management. Severe manifestations of local and systemic envenomation developed, and the patient needed multiple debridement procedures and ultimately required a transfemoral amputation. In addition, Aeromonas hydrophila was cultivated from the affected tissue, suggesting that infection contributed to necrotizing fasciitis. This case highlights the clinical features of a severe viperid snakebite envenomation, and illustrates the urgent need to ensure accessibility of effective and safe polyvalent viperid antivenom in French Guiana.

Purification and characterization of the first γ-phospholipase inhibitor (γPLI) from Bothrops jararaca snake serum

Phospholipases A₂ (PLA₂) are enzymes acting on the cell membrane phospholipids resulting in fatty acids and lysophospholipids and deconstructing the cell membrane. This protein is commonly found in snake venoms, causing tissue inflammation in the affected area. Evidence indicates that snakes have natural resistance to their own venom due to protective properties in plasma, that inhibit the action of proteins present in their venom. Given that, this study aimed to purify and characterize a γPLI from Bothrops jararaca serum, named γBjPLI. PLA₂ inhibitor was isolated using two chromatographic steps: an ion exchange column (DEAE), followed by an affinity column (crotoxin coupled to a CNBr-activated Sepharose resin). The purity and biochemical characterization of the isolated protein were analyzed by RP-HPLC, SEC, SDS-PAGE, circular dichroism and mass spectrometry. The ability to inhibit PLA₂ was determined by enzymatic activity, neutralization of paw edema and myonecrosis. The protein purity was confirmed by RP-HPLC and SEC, whilst an apparent molecular mass of 25 kDa and 20 kDa was obtained by SDS-PAGE, under reducing and non-reducing conditions, respectively. According to mass spectrometry analysis, this protein showed 72% and 68% of coverage when aligned to amino acid sequences of two proteins already described as PLIs. Thus, the inhibitory activity of enzymatic, edema and myonecrotic activities by γBjPLI suggests a role of this inhibitor for protection of these snakes against self-envenomation.

Betulinic, oleanolic and ursolic acids inhibit the enzymatic and biological effects induced by a P-I snake venom metalloproteinase

Betulinic acid (BA), Oleanolic acid (OA) and Ursolic acid (UA), are pentacyclic triterpenoids with widespread occurrence throughout the plant kingdom, these compounds are widely recognized by their pharmacological and biological properties, such as, anti-tumoral, anti-inflammatory, anti-microbial and hepatoprotective activity. In this work we determined the inhibitory ability of these compounds on the enzymatic, hemorrhagic, myotoxic and edema-inducing activities of Batx-I, a P-I metalloproteinase isolated from Bothrops atrox venom. BA, UA and OA inhibited the proteolytic activity of Batx-I on gelatin with IC50 values of 115.3, 223.0 and 357.3 μM, respectively. Additionally, these compounds showed inhibition of the hemorrhagic activity of Batx-I in skin with IC50 345.7, 643.5 and 1077.0 μM for BA, UA and OA in preincubation experiments. In studies with independent-injection, in which Batx-I was injected and then, at the same site, a concentration of 600 μM of each compound were administered at either 0, 5 or 10 min, BA showed a significant reduction of hemorrhage at 0 and 5 min. In addition, these compounds inhibited myotoxicity and edema-forming activity of Batx-I at 600 μM concentration. Molecular docking studies suggested that these compounds could occupy part of the substrate binding cleft of the enzyme affecting its catalytic cycle. In this manner, triterpenic acids are candidates for the development of inhibitors for the prevention of local tissue damage in snakebite envenomation.

Proteomics and antivenomics of Echis carinatus carinatus venom: Correlation with pharmacological properties and pathophysiology of envenomation

The proteome composition of Echis carinatus carinatus venom (ECV) from India was studied for the first time by tandem mass spectrometry analysis. A total of 90, 47, and 22 distinct enzymatic and non-enzymatic proteins belonging to 15, 10, and 6 snake venom protein families were identified in ECV by searching the ESI-LC-MS/MS data against non-redundant protein databases of Viperidae (taxid 8689), Echis (taxid 8699) and Echis carinatus (taxid 40353), respectively. However, analysis of MS/MS data against the Transcriptome Shotgun Assembly sequences (87 entries) of conger E. coloratus identified only 14 proteins in ECV. Snake venom metalloproteases and snaclecs, the most abundant enzymatic and non-enzymatic proteins, respectively in ECV account for defibrinogenation and the strong in vitro pro-coagulant activity. Further, glutaminyl cyclase, aspartic protease, aminopeptidase, phospholipase B, vascular endothelial growth factor, and nerve growth factor were reported for the first time in ECV. The proteome composition of ECV was well correlated with its biochemical and pharmacological properties and clinical manifestations observed in Echis envenomed patients. Neutralization of enzymes and pharmacological properties of ECV, and immuno-cross-reactivity studies unequivocally point to the poor recognition of <20 kDa ECV proteins, such as PLA₂, subunits of snaclec, and disintegrin by commercial polyvalent antivenom.

Allopurinol attenuates acute kidney injury following Bothrops jararaca envenomation

Snakebites have been recognized as a neglected public health problem in several tropical and subtropical countries. Bothrops snakebites frequently complicate with acute kidney injury (AKI) with relevant morbidity and mortality. To date, the only treatment available for Bothrops envenomation is the intravenous administration of antivenom despite its several limitations. Therefore, the study of novel therapies in Bothrops envenomation is compelling. The aim of this study was to evaluate the protective effect of Allopurinol (Allo) in an experimental model of Bothrops jararaca venom (BJ)-associated AKI. Five groups of Wistar rats were studied: Sham, Allo, BJ, BJ+Allo, BJ+ipAllo. BJ (0.25 mg/kg) was intravenously injected during 40'. Saline at same dose and infusion rate was administered to Sham and Allo groups. Allo and BJ+Allo groups received Allo (300 mg/L) in the drinking water 7 days prior to Saline or BJ infusion respectively. BJ+ipAllo rats received intraperitoneal Allo (25 mg/Kg) 40' after BJ infusion. BJ rats showed markedly reduced glomerular filtration rate (GFR, inulin clearance) associated with intense renal vasoconstriction, hemolysis, hemoglobinuria, reduced glutathione and increased systemic and renal markers of nitro-oxidative stress (Nitrotyrosine). Allo ameliorated GFR, renal blood flow (RBF), renal vascular resistance and arterial lactate levels. In addition, Allo was associated with increased serum glutathione as well as reduced levels of plasma and renal Nitrotyrosine. Our data show that Allo attenuated BJ-associated AKI, reduced oxidative stress, improved renal hemodynamics and organ perfusion. It might represent a novel adjuvant approach for Bothrops envenomation, a new use for an old and widely available drug.