Coagulopathy and haemorrhage in human victims of Bothrops jararaca envenoming in Brazil

Bothrops venom-induced hemostasis disorders in the rat: Between Scylla and Charybdis

Hemostasis impairment represents the most threatening consequence of Viperidae envenoming, notably with Bothrops genus. In the French departments of America, B. atrox envenomation in French Guiana may lead to bleeding while B. lanceolatus envenomation in Martinique to thrombosis. Bleeding related to B. atrox envenomation is attributed to vascular damage mediated by venom metalloproteinases and blood uncoagulable state resulting from thrombocytopenia and consumptive coagulopathy. Thrombosis related to B. lanceolatus envenomation are poorly understood. We aimed to compare the effects of B. atrox and B. lanceolatus venoms in the rat to identify the determinants of the hemorrhagic versus thrombotic complications. Viscoelastometry (ROTEM), platelet count, plasma fibrinogen, thrombin generation assay, fibrinography, endothelial (von Willebrand factor, ADAMTS13 activity, ICAM-1, and soluble E-selectin), and inflammatory biomarkers (IL-1β, IL-6, TNF-α, MCP-1, and PAI-1) were determined in blood samples obtained at H3, H6, and H24 after the subcutaneous venom versus saline injection. In comparison to the control, initial fibrinogen consumption was observed with the two venoms while thrombocytopenia and reduction in the clot amplitude only with B. atrox venom. Moreover, we showed an increase in thrombin generation at H3 with the two venoms, an increase in fibrin generation accompanied with hyperfibrinogenemia at H24 and an increase in inflammatory biomarkers with B. lanceolatus venom. No endothelial damage was found with the two venoms. To conclude, our data support two-sided hemostasis complications in Bothrops envenoming with an initial risk of hemorrhage related to platelet consumption and hypocoagulability followed by an increased risk of thrombosis promoted by the activated inflammatory response and rapid-onset fibrinogen restoration.

Crosstalk of Inflammation and Coagulation in Bothrops Snakebite Envenoming: Endogenous Signaling Pathways and Pathophysiology

Snakebite envenoming represents a major health problem in tropical and subtropical countries. Considering the elevated number of accidents and high morbidity and mortality rates, the World Health Organization reclassified this disease to category A of neglected diseases. In Latin America, Bothrops genus snakes are mainly responsible for snakebites in humans, whose pathophysiology is characterized by local and systemic inflammatory and degradative processes, triggering prothrombotic and hemorrhagic events, which lead to various complications, organ damage, tissue loss, amputations, and death. The activation of the multicellular blood system, hemostatic alterations, and activation of the inflammatory response are all well-documented in Bothrops envenomings. However, the interface between inflammation and coagulation is still a neglected issue in the toxinology field. Thromboinflammatory pathways can play a significant role in some of the major complications of snakebite envenoming, such as stroke, venous thromboembolism, and acute kidney injury. In addition to exacerbating inflammation and cell interactions that trigger vaso-occlusion, ischemia-reperfusion processes, and, eventually, organic damage and necrosis. In this review, we discuss the role of inflammatory pathways in modulating coagulation and inducing platelet and leukocyte activation, as well as the inflammatory production mediators and induction of innate immune responses, among other mechanisms that are altered by Bothrops venoms.

The Venom Composition of the Snake Tribe Philodryadini: 'Omic' Techniques Reveal Intergeneric Variability among South American Racers

Snakes of the Philodryadini tribe are included in the Dipsadidae family, which is a diverse group of rear-fanged snakes widespread in different ecological conditions, including habitats and diet. However, little is known about the composition and effects of their venoms despite their relevance for understanding the evolution of these snakes or even their impact on the occasional cases of human envenoming. In this study, we integrated venom gland transcriptomics, venom proteomics and functional assays to characterize the venoms from eight species of the Philodryadini tribe, which includes the genus Philodryas, Chlorosoma and Xenoxybelis. The most abundant components identified in the venoms were snake venom metalloproteinases (SVMPs), cysteine-rich secretory proteins (CRISPs), C-type lectins (CTLs), snake endogenous matrix metalloproteinases type 9 (seMMP-9) and snake venom serinoproteinases (SVSPs). These protein families showed a variable expression profile in each genus. SVMPs were the most abundant components in Philodryas, while seMMP-9 and CRISPs were the most expressed in Chlorosoma and Xenoxybelis, respectively. Lineage-specific differences in venom composition were also observed among Philodryas species, whereas P. olfersii presented the highest amount of SVSPs and P. agassizii was the only species to express significant amounts of 3FTx. The variability observed in venom composition was confirmed by the venom functional assays. Philodryas species presented the highest SVMP activity, whereas Chlorosoma species showed higher levels of gelatin activity, which may correlate to the seMMP-9 enzymes. The variability observed in the composition of these venoms may be related to the tribe phylogeny and influenced by their diets. In the presented study, we expanded the set of venomics studies of the Philodryadini tribe, which paves new roads for further studies on the evolution and ecology of Dipsadidae snakes.

The Bioflavonoids Rutin and Rutin Succinate Neutralize the Toxins of B. jararaca Venom and Inhibit its Lethality

The venom of the Brazilian pit viper Bothrops jararaca (BjV) is a complex mixture of molecules, and snake venom metalloproteinases (SVMP) and serine proteinases (SVSP) are the most abundant protein families found therein. Toxins present in BjV trigger most of the deleterious disturbances in hemostasis observed in snakebites, i.e., thrombocytopenia, hypofibrinogenemia and bleedings. The treatment of patients bitten by snakes still poses challenges and the bioflavonoid rutin has already been shown to improve hemostasis in an experimental model of snakebite envenomation. However, rutin is poorly soluble in water; in this study, it was succinylated to generate its water-soluble form, rutin succinate (RS), which was analyzed comparatively regarding the chemical structure and characteristic features of rutin. Biological activities of rutin and RS were compared on hemostatic parameters, and against toxic activities of crude BjV in vitro. In vivo, C57BL/6 mice were injected i.p. with either BjV alone or pre-incubated with rutin, RS or 1,10-phenanthroline (o-phe, an SVMP inhibitor), and the survival rates and hemostatic parameters were analyzed 48 h after envenomation. RS showed the characteristic activities described for rutin – i.e., antioxidant and inhibitor of protein disulfide isomerase – but also prolonged the clotting time of fibrinogen and plasma in vitro. Differently from rutin, RS inhibited typical proteolytic activities of SVMP, as well as the coagulant activity of BjV. Importantly, both rutin and RS completely abrogated the lethal activity of BjV, in the same degree as o-phe. BjV induced hemorrhages, falls in RBC counts, thrombocytopenia and hypofibrinogenemia in mice. Rutin and RS also improved the recovery of platelet counts and fibrinogen levels, and the development of hemorrhages was totally blocked in mice injected with BjV incubated with RS. In conclusion, RS has anticoagulant properties and is a novel SVMP inhibitor. Rutin and RS showed different mechanisms of action on hemostasis. Only RS inhibited directly BjV biological activities, even though both flavonoids neutralized B. jararaca toxicity in vivo. Our results showed clearly that rutin and RS show a great potential to be used as therapeutic compounds for snakebite envenomation.

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.

Involvement of von Willebrand factor and botrocetin in the thrombocytopenia induced by Bothrops jararaca snake venom

Patients bitten by snakes consistently manifest a bleeding tendency, in which thrombocytopenia, consumption coagulopathy, mucous bleeding, and, more rarely, thrombotic microangiopathy, are observed. Von Willebrand factor (VWF) is required for primary hemostasis, and some venom proteins, such as botrocetin (a C-type lectin-like protein) and snake venom metalloproteinases (SVMP), disturb the normal interaction between platelets and VWF, possibly contributing to snakebite-induced bleedings. To understand the relationship among plasma VWF, platelets, botrocetin and SVMP from Bothrops jararaca snake venom (BjV) in the development of thrombocytopenia, we used (a) Wistar rats injected s.c. with BjV preincubated with anti-botrocetin antibodies (ABA) and/or Na2-EDTA (a SVMP inhibitor), and (b) VWF knockout mice (Vwf-/-) injected with BjV. Under all conditions, BjV induced a rapid and intense thrombocytopenia. In rats, BjV alone reduced the levels of VWF:Ag, VWF:CB, high molecular weight multimers of VWF, ADAMTS13 activity, and factor VIII. Moreover, VWF:Ag levels in rats that received BjV preincubated with Na2-EDTA and/or ABA tended to recover faster. In mice, BjV caused thrombocytopenia in both Vwf-/- and C57BL/6 (background control) strains, and VWF:Ag levels tended to decrease in C57BL/6, demonstrating that thrombocytopenia was independent of the presence of plasma VWF. These findings showed that botrocetin present in BjV failed to affect the extent or the time course of thrombocytopenia induced by envenomation, but it contributed to decrease the levels and function of plasma VWF. Thus, VWF alterations during B. jararaca envenomation are an ancillary event, and not the main mechanism leading to decreased platelet counts.

Synergistic effect of serine protease inhibitors and a bothropic antivenom in reducing local hemorrhage and coagulopathy caused by Bothrops jararaca venom

Snakebite accidents are a public health problem that affects the whole world, causing thousands of deaths and amputations each year. In Brazil, snakebite envenomations are caused mostly by snakes from the Bothrops genus. The local symptoms are characterized by pain, swelling, ecchymosis, and hemorrhages. Systemic disturbances can lead to necrosis and amputations. The present treatment consists of intravenous administration of bothropic antivenom, which is capable of reversing most of the systemic symptoms, while presenting limitations to treat the local effects, such as hemorrhage and to neutralize the snake venom serine protease (SVSP). In this context, we aimed to evaluate the activity of selective serine protease inhibitors (pepC and pepB) in combination with the bothropic antivenom in vivo. Further, we assessed their possible synergistic effect in the treatment of coagulopathy and hemorrhage induced by Bothrops jararaca venom. For this, we evaluated the in vivo activity in mouse models of local hemorrhage and a series of in vitro hemostasis assays. Our results showed that pepC and pepB, when combinated with the antivenom, increase its protective activity in vivo and decrease the hemostatic disturbances in vitro with high selectivity, possibly by inhibiting botropic proteases. These data suggest that the addition of serine protease inhibitor to the antivenom can improve its overall potential.

Jararhagin, a snake venom metalloproteinase, induces mechanical hyperalgesia in mice with the neuroinflammatory contribution of spinal cord microglia and astrocytes

Jararhagin is a hyperalgesic metalloproteinase from Bothrops jararaca venom. In rodents, jararhagin induces nociceptive behaviors that correlate with an increase in peripheral cytokine levels. However, the role of the spinal cord glia in pain processing after peripheral stimulus of jararhagin has not been investigated. Aiming to explore this proposal, mice received intraplantar (i.pl.) injection of jararhagin and the following parameters were evaluated: hyperalgesia, spinal cord TNF-α, IL-1β levels, and CX3CR1, GFAP and p-NFκB activation. The effects of intrathecal (i.t.) injection of TNF-α soluble receptor (etanercept), IL-1 receptor antagonist (IL-1Ra), and inhibitors of NFκB (PDTC), microglia (minocycline) and astrocytes (α-aminoadipate) were investigated. Jararhagin inoculation induced cytokine production (TNF-α and IL-1β) in the spinal cord, which was reduced by treatment with PDTC (40% and 50%, respectively). Jararhagin mechanical hyperalgesia and cytokine production were inhibited by treatment with etanercept (67%), IL-1Ra (60%), PDTC (70%), minocycline (60%) and α-aminoadipate (45%). Furthermore, jararhagin induced an increase in p-NFκB, CX3CR1 and GFAP detection in the spinal cord indicating activation of NFκB, microglia and astrocytes. These results demonstrate for the first time that jararhagin-induced mechanical hyperalgesia is dependent on spinal cord activation of glial cells, consequent NFκB activation, and cytokine production in mice.

Comparison of venom from wild and long-term captive Gloydius caucasicus and the neutralization capacity of antivenom produced in rabbits immunized with captive venom

Gloydius caucasicus (NIKOLSKY, 1916) is a member of the Viperidae family in Iran. Comprehensive understanding of the toxigenic characteristics of snake venom is important for clinical monitoring of snakebite patients and effective therapy. We compared the toxic activities of venoms and the neutralization capacity of antivenoms produced with venoms from wild adult (WA) with long-term captive adult (LCA) of G. caucasicus in order to obtain more effective antivenom from LCA in therapy, and subsequently protect G. caucasicus from overharvesting for its venom, which poses a real threat of extinction for the species. Our results showed that LD50 of WA and LCA were 16.8 μg/dose and 17.7 μg/dose, respectively. Lower hemorrhagic and necrotic (p ≥ 0.05), and higher coagulative and edematogenic activities (p ≤ 0.05) were observed in WA compared with LCA venom. Also, captive-born neonates exhibited weaker toxic activities compared with captive adult snakes, which could be an age-related difference. Study data illustrated that effective capacity of LCA antivenom to neutralize the toxic activities of WA viper venom. According to the results, about 0.4-4 μl of LCA antivenom is required to neutralize the toxic activities of 1 μg of WA venom, indicating its efficacy in treatment of snakebites in humans. On this basis, it is recommended that capture of wild snakes for their venom be discontinued to reduce their future extinction risk.

Bedside Coagulation Tests in Diagnosing Venom-Induced Consumption Coagulopathy in Snakebite

Venom-induced consumption coagulopathy is the most important systemic effect of snake envenoming. Coagulation tests are helpful to accurately and promptly diagnose venom-induced consumption coagulopathy and administer antivenom, which is the only specific treatment available. However, bedside clotting tests play a major role in diagnosing coagulopathy in low-income settings, where the majority of snakebites occur. We conducted a literature search in MEDLINE^® from 1946 to 30 November 2019, looking for research articles describing clinical studies on bedside coagulation tests in snakebite patients. Out of 442 articles identified, 147 articles describing bedside clotting assays were included in the review. Three main bedside clotting tests were identified, namely the Lee–White clotting test, 20-min whole blood clotting time and venous clotting time. Although the original Lee–White clotting test has never been validated for snake envenoming, a recently validated version has been used in some South American countries. The 20-min whole blood clotting time test is the most commonly used test in a wide range of settings and for taxonomically diverse snake species. Venous clotting time is almost exclusively used in Thailand. Many validation studies have methodological limitations, including small sample size, lack of case-authentication, the inclusion of a heterogeneous mix of snakebites and inappropriate uses of gold standard tests. The observation times for bedside clotting tests were arbitrary, without proper scientific justification. Future research needs to focus on improving the existing 20-min whole blood clotting test, and also on looking for alternative bedside coagulation tests which are cheap, reliable and quicker.

Bleeding Disorders in Bothrops atrox Envenomations in the Brazilian Amazon: Participation of Hemostatic Factors and the Impact of Tissue Factor

Bleeding is a common hemostatic disorder that occurs in Bothrops envenomations. We evaluated the changes in coagulation, fibrinolysis components, and platelets in Bothrops atrox envenomations with bleeding. This is an observational study with B. atrox snakebite patients (n = 100) treated in Manaus, Brazilian Amazon. Bleeding was recorded on admission and during hospitalization. We found that the platelet count in our patients presented a weak correlation to tissue factor, factor II, and plasminogen. Tissue factor presented weak correlation to factor V, II, D-dimer, plasminogen, alpha 2-antiplasmin, and moderate correlation to fibrinogen and fibrin/fibrinogen degradation product (FDP). Patients with systemic bleeding (n = 20) presented low levels of factor V, II, fibrinogen, plasminogen, and alpha 2-antiplasmin, and high levels of tissue factor and FDP compared to those without bleeding. Patients with only local bleeding (n = 41) and without bleeding showed similar levels of hemostatic factors. Thrombocytopenia was observed mainly in patients with systemic bleeding and increased levels of serum venom. No association was found between venom levels and systemic bleeding, or between venom levels and clinical severity of envenomation. This is the first report that shows the participation of the extrinsic coagulation pathway in the consumption coagulopathy of B. atrox envenomations with systemic bleeding due to tissue factor release.

Thrombotic microangiopathy due to Bothrops erythromelas: a case report in Northeast Brazil

Bothrops erythromelas are serpents that belong to the Viperidae family, which are the main species responsible for human snakebites in Ceara State, Northeast Brazil. Thrombotic microangiopathy (TMA) is an uncommon group of disorders characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia and acute kidney injury (AKI), and occurrence after snakebites have been rarely reported. In this report, we described the case of a 57 year-old-man without comorbidities who was bitten by a Bothrops erythromelas on his right ankle. He presented with pain, edema and local bleeding. Symptomatology and laboratory tests were compatible with the diagnosis of TMA. He received specific antivenom and fluids replacement without any anaphylactic reaction. The conservative treatment was effective and there was no need for red blood cells transfusion or plasmapheresis. The aim of this report was to describe the first case of thrombotic microangiopathy following Bothrops erythromelas envenoming in the Northeast Brazil, providing insights about important mechanistic pathways of Bothrops snakebite-associated TMA and how to change the prognosis of the disease.

Liver gene regulation of hemostasis-related factors is altered by experimental snake envenomation in mice

Few studies have addressed gene expression of hemostasis-related factors during acute thrombo-hemorrhagic diseases. Bites by the lanced-headed viper Bothrops jaracaca induce rapid hemostatic disturbances in victims, leading to systemic bleedings, thrombocytopenia and consumption coagulopathy. Although circulating levels of coagulation factors recover rapidly after administration of specific antivenom therapy, it is unclear if B. jararaca venom (BjV) upregulates the mRNA synthesis of hepatic hemostasis-related factors, or if the recovery occurs under basal conditions after the neutralization of venom components by antivenom. Thus, we aimed to investigate if BjV regulates gene expression of important hemostasis-related factors synthetized by the liver. On that account, Swiss mice were injected with saline or BjV (1.6 mg/kg b.w, s.c.), and after 3, 6 and 24 h blood samples and liver fragments were collected to analyze mRNA expression by real-time qPCR. Increased gene expression of fibrinogen chains, haptoglobin and STAT3 was observed during envenomation, particularly at 3 and 6 h. At 24h, mRNA levels of F10 were raised, while those of Serpinc1, Proc and Adamts13 were diminished. Surprisingly, F3 mRNA levels were steadily decreased at 3 h. Gene expression of Thpo, F7, F5 Tfpi, Mug1 was unaltered. mRNA levels of Vwf, P4hb, F8, F2, Plg, and Serpinf2 were minimally altered, but showed important associations with Nfkb1 gene expression. In conclusion, snakebite envenomation upregulates hepatic mRNA synthesis particularly of fibrinogen chains, and acute-phase markers. This response explains the fast recovery of fibrinogen levels after antivenom administration to patients bitten by B. jararaca snakes.

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 

Biochemical, Hematological Effects and Complications of Pseudosynanceia Melanostigma Envenoming

Objectives

Venomous fishes have different pharmacological effects and are useful. Among the venomous fish, stonefishes; especially Pseudosynanceia melanostigma has various pharmacological effects on the nervous, muscular and cardiovascular system of humans. In this study, toxicological characteristics, some blood effects, pharmacological and enzymatic properties of Pseudosynanceia melanostigma venom was investigated.

Methods

Crude venom purified by using gel filtration chromatography and the molecular weights of the venom and its fractions were estimated. The approximate LD values of this venom were determinedand the effects of LD50 dose on the blood of rabbits were studied. Hemolytic and Hemorrhagic activity of the venom sample was determined. In this case coagulation tests were performed.

Results

The LD50 of the Pseudosynanceia melanostigma crude venom was also determined to be 194.54 μg/mouse. The effect of two doses of LD50 showed a non-significant differences decrease in RBCs and MCV. In other cases, the results showed significant differences in WBC, Plt, Hb, MCH, MCHC and HCT; also it’s showed a significant decrease. WBC count showed a significant increase with two doses of LD50 groups. The prothrombin time and partial prothrombin time were increased after venom treatment. As well as bleeding and clotting time were increased. According to the results, a minimum dose for Haemorrhagic effect 40 μg was obtained.

Conclusion

Venom of Pseudosynanceia melanostigma has inhibitory effect on platelet aggregation that can be used to design and develop of anticoagulant drugs.

Bothrops snakebites in the Amazon: recovery from hemostatic disorders after Brazilian antivenom therapy

Introduction: Bothrops atrox snakebites are a major public health problem in the Amazon region and also cause hemostatic disorders. In this study, we assessed the recovery from hemostatic disorders in Bothrops snakebite patients after being given antivenom therapy.Methods: This is a prospective study of Bothrops snakebite patients (n = 100) treated at the Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazilian Amazon, between January 2016 and December 2017. Blood samples were taken for the measurement of venom concentrations, platelets, clotting time and factors of patients on admission, 12, 24 and 48 h after antivenom therapy, and taken again on discharge. The presence of systemic bleeding was recorded during the follow-up.Results: On admission, systemic bleeding was observed in 14% of the patients. Thrombocytopenia was noted in 10% of the patients. A total of 54% of the patients presented unclottable blood with low levels of fibrinogen and alpha 2-antiplasmin, and high levels of fibrin/fibrinogen degradation product (FDP) and D-dimers. Unclottable blood and systemic bleeding were overcome in most patients 12 h after the antivenom therapy. Three patients developed systemic bleeding 48 h after antivenom therapy. Levels of fibrinogen and alpha 2-antiplasmin, FDP and D-dimer returned to normal around 48 h after the treatment or on discharge. The frequency of thrombocytopenia with high mean platelet volume increased in the first 24 h after antivenom therapy, and decreased on discharge. Bothrops venom levels in patients decreased 12 h after antivenom therapy and were not correlated with coagulation and fibrinolytic parameters. There were no deaths.Conclusion: Laboratorial parameters of coagulopathy returned to normal values within 48 h after the antivenom therapy until discharge. A few patients still presented bleeding signs within 48 h after beginning antivenom therapy. However, the Brazilian antivenom was able to overcome the hemostatic disorders in these cases of envenomation.

Elevated plasma levels of hepatocyte growth factor in rats experimentally envenomated with Bothrops jararaca venom: Role of snake venom metalloproteases

The hepatocyte growth factor (HGF)/c-met pathway, which mainly consists of HGF activator (HGFA) and its substrate HGF, protects various types of cells via anti-apoptotic and anti-inflammatory signals. Thrombin is the main physiological activator of such plasmatic pathway, and increased plasma concentrations of HGF have been considered as a molecular marker for some pathological conditions, such as disseminated intravascular coagulation. Since thrombin generation is often linked to tissue injury, and these events are common during snake venom-induced consumption coagulopathies (VICC), our goals were to examine whether Bothrops jararaca venom (Bjv), which induces VICC in vivo: (i) activates the HGF/c-met pathway in vivo and (ii) cleaves zymogen forms of HGFA and HGF (proHGFA and proHGF, respectively) in vitro. Two experimental groups (n = 6, each) of male adult Wistar rats were subcutaneously injected with 500 μL of 0.9% NaCl solution (control) or sub-lethal doses (1.6 mg/kg) of Bjv. Three hours after envenomation, whole blood samples were collected from the carotid arteries to evaluate relevant coagulation parameters using rotational thromboelastometry and fibrinogen level (colorimetric assay). Additionally, the plasma concentration of HGF was assayed (ELISA). Thromboelastometric assays showed that blood clotting and fibrin polymerization were severely impaired 3 h after Bjv injection. Total plasma HGF concentrations were almost 6-fold higher in the Bjv-injected group (410.0 ± 91) compared with control values (68 ± 18 pg/mL, p < 0.05). Western blotting assay showed that Bjv processed proHGFA and proHGF, generating bands resembling those generated by thrombin and kallikrein, respectively. In contrast to the serine protease inhibitor 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF), the metalloprotease inhibitor ethylenediaminetetraacetic acid disodium salt (Na₂-EDTA) strongly reduced the ability of Bjv to process proHGFA and generated one active band similar to that of thrombin. Since Bjv contains prothrombin and factor X activators, increased intravascular thrombin formation might partly explain the increased HGF levels after bothropic envenomation. In conclusion, these findings suggest that snake venom metalloproteases may be determinant for elevation of plasma levels of HGF in rats experimentally envenomated with Bjv.

Optimization of von Willebrand factor multimer analysis in vertical mini-gel electrophoresis systems: A rapid procedure

Von Willebrand disease (VWD) is a common cause of bleeding worldwide. Analysis of von Willebrand factor (VWF) multimer distribution (VWF:MD) is essential to properly classify and treat different types of VWD, and it is performed using a SDS agarose gel electrophoresis followed by Western blotting, a handmade technique that demands days to be completed and requires skillful execution. Aiming both to facilitate gel production and to shorten the preparation time, we developed an uncomplicated technique to provide agility in the analysis of VWF:MD, so that it can be easily accomplished in the routine practice of hemostasis laboratories. On that account, we used a commercial vertical mini-gel electrophoresis system for SDS-PAGE and a semi-dry transfer system, which allowed us to analyze VWF:MD of various samples in a period shorter than 12 h. This technique differentiated VWF:MD in human and animal plasmas under normal, congenital and acquired (experimental envenomation by Bothrops jararaca snake) conditions. This optimized method is cheap, rapid, reproducible, easy to be performed, and uses electrophoresis and Western blotting systems available in most laboratories. All these advantages encourage hemostasis professionals to use it in their routine practices. In order to facilitate the setup and accomplishment of the whole procedure step by step, videos were appended to the article.

Lapachol and synthetic derivatives: in vitro and in vivo activities against Bothrops snake venoms

Background

It is known that local tissue injuries incurred by snakebites are quickly instilled causing extensive, irreversible, tissue destruction that may include loss of limb function or even amputation. Such injuries are not completely neutralized by the available antivenins, which in general are focused on halting systemic effects. Therefore it is prudent to investigate the potential antiophidic effects of natural and synthetic compounds, perhaps combining them with serum therapy, to potentially attenuate or eliminate the adverse local and systemic effects of snake venom. This study assessed a group of quinones that are widely distributed in nature and constitute an important class of natural products that exhibit a range of biological activities. Of these quinones, lapachol is one of the most important compounds, having been first isolated in 1882 from the bark of Tabebuia avellanedae.

Methodology/Principal findings

It was investigated the ability of lapachol and some new potential active analogues based on the 2-hydroxi-naphthoquinone scaffold to antagonize important activities of Bothrops venoms (Bothrops atrox and Bothrops jararaca) under different experimental protocols in vitro and in vivo. The bioassays used to test the compounds were: procoagulant, phospholipase A₂, collagenase and proteolytic activities in vitro, venom-induced hemorrhage, edematogenic, and myotoxic effects in mice. Proteolytic and collagenase activities of Bothrops atrox venom were shown to be inhibited by lapachol and its analogues 3a, 3b, 3c, 3e. The inhibition of these enzymatic activities might help to explain the effects of the analogue 3a in vivo, which decreased skin hemorrhage induced by Bothrops venom. Lapachol and the synthetic analogues 3a and 3b did not inhibit the myotoxic activity induced by Bothrops atrox venom. The negative protective effect of these compounds against the myotoxicity can be partially explained by their lack of ability to effectively inhibit phospholipase A₂ venom activity. Bothrops atrox venom also induced edema, which was significantly reduced by the analogue 3a.

Conclusions

This research using a natural quinone and some related synthetic quinone compounds has shown that they exhibit antivenom activity; especially the compound 3a. The data from 3a showed a decrease in inflammatory venom effects, presumably those that are metalloproteinase-derived. Its ability to counteract such snake venom activities contributes to the search for improving the management of venomous snakebites.

Factors Associated with Systemic Bleeding in Bothrops Envenomation in a Tertiary Hospital in the Brazilian Amazon

Bothrops snakebites usually present systemic bleeding, and the clinical–epidemiological and laboratorial factors associated with the development of this manifestation are not well established. In this study, we assessed the prevalence of Bothrops snakebites with systemic bleeding reported at the Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, in Manaus, Amazonas State, Brazil, and the clinical–epidemiological and laboratorial factors associated with systemic bleeding. This is an observational, cross-sectional study carried out between August, 2013 and July, 2016. Patients who developed systemic bleeding on admission or during hospitalization were considered cases, and those with non-systemic bleeding were included in the control group. Systemic bleeding was observed in 63 (15.3%) of the 442 Bothrops snakebites evaluated. Bothrops snakebites mostly occurred in males (78.2%), in rural areas (89.0%) and in the age group of 11 to 30 years old (40.4%). It took most of the patients (59.8%) less than 3 h to receive medical assistance. Unclottable blood (AOR = 3.11 (95% CI = 1.53 to 6.31; p = 0.002)) and thrombocytopenia (AOR = 4.52 (95% CI = 2.03 to 10.09; p < 0.001)) on admission were independently associated with systemic bleeding during hospitalization. These hemostatic disorders on admission increase the chances of systemic bleeding during hospitalization. Prospective studies are needed to clarify the pathophysiology of systemic bleeding in Bothrops snakebites in the Amazon region.

Thrombotic microangiopathy following Bothrops jararaca snakebite: case report

CONTEXT

Thrombotic microangiopathy (TMA) is an uncommon and severe complication of snakebites, and is similar, in general, to hemolytic-uremic syndrome (HUS). We describe a case of TMA following envenomation by Bothrops jararaca.

CASE DETAILS

A 56-y-old-woman with controlled hypertension was transferred from a primary hospital to our ER ∼7 h after being bitten by B. jararaca in the distal left leg. She developed edema extending from the bite site to the proximal thigh, associated with intense radiating local pain, local paresthesia and ecchymosis at the bite site. Laboratory features upon admission revealed coagulopathy (20 min whole blood clotting time - WBCT20 > 20 min), thrombocytopenia (76,000 platelets/mm³) and slight increase in serum creatinine (1.58 mg/dL; RV < 1.2 mg/dL). Upon admission, the patient was treated with bothropic antivenom and fluids replacement. During evolution, her thrombocytopenia and anemia worsened, with blood films showing fragmented red cells, haptoglobin consumption, increase in serum lactate dehydrogenase, and progressive increase of serum creatinine (KDIGO stage = 3). No RBC transfusion, renal replacement therapy or plasmapheresis was done. The patient showed progressive improvement from day nine (D9) onwards and was discharged on D20; there was complete recovery of hemoglobin levels at follow-up (D50). ADAMTS-13 activity, assayed 10 months post-bite, was within reference values.

DISCUSSION

TMA following snakebite has been reported mainly in India, Sri Lanka and Australia, with several patients needing renal replacement therapy. Although controversial, plasmapheresis has also been used in some cases. Our patient developed microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury, a triad of features compatible with TMA similar to HUS. Despite the severity, the outcome following conservative treatment was good, with complete recovery.

Predicting acute renal failure in Bothrops snakebite patients in a tertiary reference center, Western Brazilian Amazon

Acute Kidney Injury (AKI) is the main systemic complication and cause of death in viperid envenomation. Although there are hypotheses for the development of AKI, the mechanisms involved are still not established. The aim of this study was to evaluate the clinical-laboratorial-epidemiological factors associated with AKI in victims of Bothrops sp envenomation. This is an observational study carried out at the Fundação de Medicina Tropical Dr. Heitor Vieira Dourado. AKI was defined according to the guidelines of the Acute Kidney Injury Network (AKIN). Among the 186 patients evaluated, AKI was observed in 24 (12.9%) after 48 hours of admission. Stage I was present in 17 (70.8%) patients, II in 3 (12.5%) and III in 4 (16.7%). Epidemiological characterization showed predominance of men, occurrence in rural areas, aged between 16–60 years, feet as the most affected anatomical region, and time to medical assistance less than 3 hours. Hypertension and diabetes were the comorbidities identified. Most of the accidents were classified as moderate, and clinical manifestations included severe pain, mild edema, local bleeding and headache. Laboratory results showed blood uncoagulability, hypofibrinogenemia, leukocytosis, increase of creatine kinase, and high lactate dehydrogenase levels. Multivariate analysis showed an association with high LDH levels [AOR = 1.01 (95% CI = 1.01–1.01, p<0.002)], local bleeding [AOR = 0.13 (95%CI = 0.027–0.59, p<0.009)], and the presence of comorbidities [AOR = 60.96 (95%CI = 9.69–383.30; p<0.000)]. Herein, laboratory markers such as high LDH levels along with local bleeding and comorbidities may aid in the diagnosis of AKI.

Disseminated intravascular coagulation caused by moojenactivase, a procoagulant snake venom metalloprotease

Snake venom toxins that activate coagulation factors are key players in the process of venom-induced coagulopathy, and account for severe clinical manifestations. The present study applies a variety of biochemical, hematological, and histopathological approaches to broadly investigate the intravascular and systemic effects of moojenactivase (MooA), the first described PIIId subclass metalloprotease isolated from Bothrops sp. venom that activates coagulation factors. MooA induced consumption coagulopathy with high toxic potency, characterized by prolongation of prothrombin and activated partial thromboplastin time, consumption of fibrinogen and the plasma coagulation factors X and II, and thrombocytopenia. MooA promoted leukocytosis and expression of the proinflammatory cytokines interleukin-6 and tumor necrosis factor-α, accompanied by tissue factor-dependent procoagulant activity in peripheral blood mononuclear cells. This metalloprotease also caused intravascular hemolysis, elevated plasma levels of creatine kinase-MB, aspartate transaminase, and urea/creatinine, and induced morphopathological alterations in erythrocytes, heart, kidney, and lungs associated with thrombosis and hemorrhage. Diagnosis of MooA-induced disseminated intravascular coagulation represents an important approach to better understand the pathophysiology of Bothrops envenomation and develop novel therapeutic strategies targeting hemostatic disturbances.

Processing of Snake Venom Metalloproteinases: Generation of Toxin Diversity and Enzyme Inactivation

Snake venom metalloproteinases (SVMPs) are abundant in the venoms of vipers and rattlesnakes, playing important roles for the snake adaptation to different environments, and are related to most of the pathological effects of these venoms in human victims. The effectiveness of SVMPs is greatly due to their functional diversity, targeting important physiological proteins or receptors in different tissues and in the coagulation system. Functional diversity is often related to the genetic diversification of the snake venom. In this review, we discuss some published evidence that posit that processing and post-translational modifications are great contributors for the generation of functional diversity and for maintaining latency or inactivation of enzymes belonging to this relevant family of venom toxins.

Counteraction of Bothrops snake venoms by Combretum leprosum root extract and arjunolic acid

ETHNOPHARMACOLOGICAL RELEVANCE

Serotherapy against snakebite is often unavailable in some regions over Brazil, where people make use of plants from folk medicine to deal with ophidic accidents. About 10% of Combretum species have some ethnopharmacological use, including treatment of snakebites.

MATERIALS AND METHODS

We evaluated the ability of the extract of Combretum leprosum and its component arjunolic acid to reduce some in vivo and in vitro effects of Bothrops jararacussu and Bothrops jararaca venoms. The protocols investigated include phospholipase, proteolytic, collagenase, hyaluronidase, procoagulant, hemorrhagic, edematogenic, myotoxic and lethal activities induced by these venoms in Swiss mice.

RESULTS

Oral pre-treatment with arjunolic acid reduced the Bothrops jararacussu lethality in up to 75%, while preincubation prevented the death of all the animals. Hemoconcentration effect of Bothrops jararacussu venom was confirmed two hours after i.p. injection, while preincubation with arjunolic acid preserved the hematocrit levels. Both Combretum leprosum extract and arjunolic acid abolished the myotoxic action of Bothrops jararacussu venom. Preincubation of Bothrops jararacussu venom with the extract or arjunolic acid prevented the increase of plasma creatine kinase activity in mice. The hemorrhagic activity of Bothrops jararaca crude venom was reduced down to about 90% and completely inhibited by preincubation with 10 mg/kg or 100 mg/kg Combretum leprosum extract, respectively, while the preincubation and the pretreatment with 30 mg/kg of arjunolic acid reduced the venom hemorrhagic activity down to about 12% and 58%, respectively. The preincubation of the venom with both extract and 30 mg/kg arjunolic acid significantly reduced the bleeding amount induced by Bothrops jararacussu venom. The extract of Combretum leprosum decreased the edema formation induced by Bothrops jararacussu venom both in preincubation and pretreatment, but not in posttreatment. Similarly, arjunolic acid preincubated with the venom abolished edema formation, while pre- and posttreatment have been partially effective. Some enzymatic activities of Bothrops jararacussu and Bothrops jararaca venoms, i.e. phospholipase A2, collagenase, proteolytic and hyaluronidase activities, were to some extent inhibited by the extract and arjunolic acid in a concentration-dependent manner.

CONCLUSIONS

Altogether, our results show that Combretum leprosum extract can inhibit different activities of two important Brazilian snake venoms, giving support for its popular use in folk medicine in the management of venomous snakebites.

Bothrops jararaca venom metalloproteinases are essential for coagulopathy and increase plasma tissue factor levels during envenomation

BACKGROUND/AIMS

Bleeding tendency, coagulopathy and platelet disorders are recurrent manifestations in snakebites occurring worldwide. We reasoned that by damaging tissues and/or activating cells at the site of the bite and systemically, snake venom toxins might release or decrypt tissue factor (TF), resulting in activation of blood coagulation and aggravation of the bleeding tendency. Thus, we addressed (a) whether TF and protein disulfide isomerase (PDI), an oxireductase involved in TF encryption/decryption, were altered in experimental snake envenomation; (b) the involvement and significance of snake venom metalloproteinases (SVMP) and serine proteinases (SVSP) to hemostatic disturbances.

METHODS/PRINCIPAL FINDINGS

Crude Bothrops jararaca venom (BjV) was preincubated with Na2-EDTA or AEBSF, which are inhibitors of SVMP and SVSP, respectively, and injected subcutaneously or intravenously into rats to analyze the contribution of local lesion to the development of hemostatic disturbances. Samples of blood, lung and skin were collected and analyzed at 3 and 6 h. Platelet counts were markedly diminished in rats, and neither Na2-EDTA nor AEBSF could effectively abrogate this fall. However, Na2-EDTA markedly reduced plasma fibrinogen consumption and hemorrhage at the site of BjV inoculation. Na2-EDTA also abolished the marked elevation in TF levels in plasma at 3 and 6 h, by both administration routes. Moreover, increased TF activity was also noticed in lung and skin tissue samples at 6 h. However, factor VII levels did not decrease over time. PDI expression in skin was normal at 3 h, and downregulated at 6 h in all groups treated with BjV.

CONCLUSIONS

SVMP induce coagulopathy, hemorrhage and increased TF levels in plasma, but neither SVMP nor SVSP are directly involved in thrombocytopenia. High levels of TF in plasma and TF decryption occur during snake envenomation, like true disseminated intravascular coagulation syndrome, and might be implicated in engendering bleeding manifestations in severely-envenomed patients.

Unmasking snake venom of Bothrops leucurus: purification and pharmacological and structural characterization of new PLA2 Bleu TX-III

Bleu TX-III was isolated from Bothrops leucurus snake venom on one-step analytical chromatography reverse phase HPLC, was homogeneous on SDS-PAGE, and was confirmed by Q-Tof Ultima API ESI/MS (TOF MS mode) mass spectrometry in 14243.8 Da. Multiple alignments of Bleu TX-III show high degree of homology with basic PLA2 myotoxins from other Bothrops venoms. Our studies on local and systemic myotoxicity "in vivo" reveal that Bleu TX-III is myotoxin with local but not systemic action due to the decrease in the plasmatic CK levels when Bleu TX-III is administrated by intravenous route in mice (dose 1 and 5  μg). And at a dose of 20  μg myotoxin behaves like a local and systemic action. Bleu TX-III induced moderate marked paw edema, evidencing the local increase in vascular permeability. The inflammatory events induced in the mice (I.M.) were investigated. The increase in the levels of IL-1, IL-6, and TNF-α was observed in the plasma. It is concluded that Bleu TX-III induces inflammatory events in this model. The enzymatic phospholipid hydrolysis may be relevant to these phenomena. Bothrops leucurus venom is still not extensively explored, and the knowledge of its toxins separately through the study of structure/function will contribute for a better understanding of its action mechanism.

Antiophidic activity of the extract of the Amazon plant Humirianthera ampla and constituents

ETHNOPHARMACOLOGICAL RELEVANCE

Although serotherapy against snakebite has been discovered more than one hundred years ago, antivenom is not available all over Brazil. The use of plants from folk medicine is common mainly in the Brazilian Amazon area. One of these plants is named Humirianthera ampla (HA).

MATERIALS AND METHODS

We have investigated HA extract and constituents' antiophidic activity in different experimental protocols against some Bothrops snake venoms (Bothrops jararacussu, Bothrops atrox and Bothrops jararaca). The protocols investigated include phospholipase, proteolytic, pro-coagulant, hemorrhagic, edematogenic and myotoxic activities induced by these venoms in Swiss mice.

RESULTS

All the venoms caused an increase in the rate of creatine kinase (CK) release from isolated muscles, indicating damage to the sarcolemma. The crude extract of HA decreased the myotoxic activity in a concentration-dependent fashion. The presence of HA 300 μg/mL decreased up to 96% of Bothrops jararacussu and 94% of Bothrops atrox myotoxicity after 90 min of exposure. In vivo myotoxicity of Bothrops atrox venom was decreased in 75% when the venom was preincubated with HA 500 mg/kg. Similar results were observed with lupeol against Bothrops jararacussu and Bothrops atrox venoms. The hemorrhagic activity was evaluated by intradermal injection of Bothrops atrox venom. Preincubation and oral pre- and posttreatment with HA decreased hemorrhage by 100%, 45% and 45%, respectively. Bothrops atrox venom also induced formation of edema, which was significantly inhibited by pre- and posttreatment with HA. All the venoms showed extensive pro-coagulating properties, and these activities were inhibited by up to 90% with HA, which presented concentration-dependent inhibition. Finally, proteolytic and phospholipase activities of the venoms were all inhibited by increasing concentrations of HA, lupeol and sitosterol. The inhibition of these activities might help explain the actions against in vivo myotoxicity and the in vivo effects observed, i.e., edema, myotoxicity, pro-coagulation and hemorrhage.

CONCLUSIONS

Altogether, our results give support for the popular use of HA extracts in cases of accidents with snakes, suggesting that it can be used as an adjunct in the management of venomous snakebites.

Jararhagin, a hemorrhagic snake venom metalloproteinase from Bothrops jararaca

Jararhagin is a metalloproteinase isolated from Bothrops jararaca snake venom, which has been extensively studied. These studies showed its involvement on most of the systemic and local damaging effects of snakebite envenomings. In this review we comment on the major targets of jararhagin as the vascular endothelium, platelets and coagulation factors and also its action on other cell systems as inflammatory cells and their mediators, cancer and cell signaling. The mechanisms of jararhagin action are discussed together with structural features essential for the expression of its biological activities. The studies reviewed here denote jararhagin as a prototype for studies of snake venom metalloproteinases, bringing new insights into cellular-matrix interactions and adding for the improvement of snakebite treatment.

Intraspecific variation of biological activities in venoms from wild and captive Bothrops jararaca

The venom of Bothrops jararaca is composed of complex mixture of molecules, mainly lectins, metalloproteinases, serinoproteinases, desintegrins, phospholipases, and peptides. This composition may vary according to the snake's age, gender, and region of origin. The aim of the was to determine individual variation in Bothrops jararaca venom in the Botucatu region, Sao Paulo State, Brazil, by means of enzymatic, biochemical, and pharmacological characterization, utilizing in vitro tests and biological assays. The activities were compared with those of Brazilian Reference Venom (BRV). Protein concentration varied between adult and juvenile groups. The electrophoretic profiles were similar, with molecular masses ranging between 25 and 50 kD, but with intraspecific variations. Reverse-phase high-performance liquid chromatography (RP-HPLC) revealed protein concentration differences. Coagulant activity did not differ significantly among adult groups, but there was a large variation between juvenile venom and BRV, which coagulated more extensively. Venoms from adults displayed greater hemorrhagic activity, especially in males recently obtained from the wild. In contrast, juveniles kept in captivity and adult males showed higher values. Edematogenic activity displayed an increase in edema in all groups. At the mean lethal dose (LD₅₀), toxicity varied significantly between groups, with venom from captive females being threefold more toxic than juvenile venom. Data illustrate the intra- and interspecific complexity that occurs in snake venoms, which may be attributed to ontogenetic, sexual, and environmental factors that affect variability in Bothrops jararaca venom. Further, it is proposed that Brazilian public health authorities document the constitution of pooled venom employed in the immunization of serum-producing animals due to this variability in venom properties. Given the large Brazilian territory, this variability requires regional monitoring and evaluation of the efficacy of bothropic antivenom in treatment of snakebite and consequent permanent sequelae observed.

Involvement of circulating platelets on the hyperalgesic response evoked by carrageenan and Bothrops jararaca snake venom

BACKGROUND

The role of platelets in hemostasis is well known, but few papers have reported their role in pain and edema induced by inflammatory agents.

OBJECTIVE

To evaluate the role of circulating platelets in the local injury induced by two diverse inflammatory agents, Bothrops jararaca venom (Bjv) and carrageenan.

METHODS

Rats were (i) rendered thrombocytopenic by administration of polyclonal anti-rat platelet IgG (ARPI) or busulfan, or (ii) treated with platelet inhibitors (aspirin or clopidogrel). Edema formation, local hemorrhage and the pain threshold were assessed after intraplantar injection of Bjv or carrageenan in rat hind paws. Additionally, whole platelets or platelet releasate were tested whether they directly induced hyperalgesia.

RESULTS

Platelet counts were markedly diminished in rats administered with either ARPI (± 88%) or busulfan (± 96%). Previous treatment with ARPI or busulfan slightly reduced edema induced by Bjv or carrageenan. Injection of Bjv, but not of carrageenan, induced a statistically significance increase in hemorrhage in the hind paws of thrombocytopenic rats. Remarkably, hyperalgesia evoked by Bjv or carrageenan was completely blocked in animals treated with ARPI or busulfan, or pre-treated with aspirin or clopidogrel. On the other hand, intraplantar administration of whole platelets or platelet releasate evoked hyperalgesia, which was inhibited by pre-incubation with alkaline phosphatase.

CONCLUSIONS

Thrombocytopenia or inhibition of platelet function drastically reduced hyperalgesia induced by injection of carrageenan or Bjv; moreover, platelets per se secrete phosphorylated compounds involved in pain mediation. Thus, blood platelets are crucial cells involved in the pain genesis, and their role therein has been underestimated.

Ability of a synthetic coumestan to antagonize Bothrops snake venom activities

We investigated a synthetic coumestan named LQB93 and similar compounds abilities to antagonize activities of Bothrops jararacussu and Bothrops jararaca crude venoms in different protocols. The antimyotoxic activity was evaluated in vitro by the rate of release of creatine kinase (CK) from isolated mouse extensor digitorum longus muscle (EDL) induced by B. jararacussu (25 g/ml). For in vivo studies, B. jararacussu venom (1.0 mg/kg) was preincubated with LQB93 (0.1-30 mg/kg), during 30 min, for later injection in mouse tight and evaluation of the antimyotoxic and anti-edematogenic effects. LQB93 antagonized in vitro, the increase of CK release from the EDL muscle (IC(50)=0.0291 M). It also showed in vivo, antimyotoxic and anti-edematogenic effects that were dose-dependent with ID50 of 0.17 mg/kg and 0.14 mg/kg, respectively. The hemorrhage induced by B. jararaca (1.0 mg/kg) venom in the mouse skin, was abolished by LQB93 (10.0 mg/kg) preincubated with venom. Like wedelolactone, LQB93 protected rat isolated heart on a Langendorff preparation, from the cardiotoxicity of B. jararacussu venom. LQB93 inhibit the effects of Bothrops venoms like wedelolactone, a natural compound isolated from the plant Eclipta prostrata.

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.

Bothrops snakebite on the head: case report and review of the literature

A previously healthy, 21-year-old female was admitted 5 h after being bitten in the occipital region by a pitviper presumed to be Bothrops jararaca. Physical examination revealed marked cranial and facial oedema extending to the neck and dorsum, bilateral eyelid ecchymosis, and local conjunctival and gingival bleeding. The patient was alert and complained of mild, local pain and nausea. There were no signs of neurological involvement. The main laboratory findings on admission included incoagulable blood, a platelet count of 4000/microl, and an ELISA-estimated serum venom concentration of 62.6 ng/ml. Sequential serum creatinine, urea nitrogen, sodium and potassium concentrations were normal. The case was classified as severe and, after the intravenous administration of ranitidine, chlorpheniramine and hydrocortisone, the intravenous infusion of 12 vials of undiluted bothropic equine antivenom [F(ab)(2); 10 ml/vial] was initiated. The antivenom infusion was halted after 10 vials because the patient developed a severe early reaction, although this was successfully treated with subcutaneous adrenaline and intravenous hydrocortisone. Platelet replacement (seven units) was performed and 24 h after the antivenom infusion, normal results in blood-coagulation tests and an increase in the platelet count (to 100,000/microl) were observed. No circulating venom was detected in blood samples collected 6, 12, 24 or 48 h post-admission. The patient was discharged after 4 days, with clinical improvement and no signs of local infection, and subsequent follow-up revealed no sequelae.

Hemorrhagic, coagulant and fibrino(geno)lytic activities of crude venom and fractions from mapanare (Bothrops colombiensis) snakes

Bothrops colombiensis venom from two similar geographical locations were tested for their hemostatic functions and characterized by gel-filtration chromatography and SDS-PAGE electrophoresis. The snakes were from Caucagua and El Guapo towns of the Venezuelan state of Miranda. Fibrino(geno)lytic, procoagulant, hemorrhagic, lethal activities, gel-filtration chromatography and SDS-PAGE profiles were analyzed and compared for both venoms. The highest hemorrhagic activity of 5.3 mug was seen in El Guapo venom while Caucagua venom had the lowest LD(50) of 5.8 mg/kg. Both venoms presented similar thrombin-like activity. El Guapo showed a factor Xa-like activity two times higher than Caucagua. Differences were observed in kallikrein-like and t-PA activities, being highest in El Guapo. Caucagua venom showed the maximum fibrin lysis. Both crude venom runs on Sephadex G-100 chromatography gave fraction SII with the high fibrinolytic activity. Proteases presented in SII fractions and eluted from Benzamidine-Sepharose (not bound to the column) provoked a fast degradation of fibrinogen alpha chains and a slower degradation of beta chains, which could possibly be due to a higher content of alpha fibrinogenases in these venoms. The fibrinogenolytic activity was decreased by metalloprotease inhibitors. The results suggested that metalloproteases in SII fractions were responsible for the fibrinolytic activity. The analysis of samples for fibrin-zymography of SII fractions showed an active band with a molecular mass of approximately 30 kDa. These results reiterate the importance of using pools of venoms for antivenom immunization, to facilitate the neutralization of the maximum potential number of toxins.

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.

Evaluation of three Brazilian antivenom ability to antagonize myonecrosis and hemorrhage induced by Bothrops snake venoms in a mouse model

Despite preventing death after snakebites, there is little evidence that polyvalent antivenoms (PAVs) protect against myotoxicity and local damages. We evaluated antibothropic Brazilian PAVs from three manufacturers against the myotoxicity and hemorrhagic activity of Bothrops jararacussu and B. jararaca venoms, respectively, by using two protocols: preincubation of PAVs with venom, and i.v. pretreatment with PAVs, prior to the venom inoculation. In this investigation, we used doses of PAVs ranging from 0.4 to 4.0mL/mg of venom equivalent up to 10 times the amount recommended by the producers for the clinical practice in Brazil. In our preincubation protocol in vivo, PAVs antagonized myotoxicity of B. jararacussu venom by 40-95%, while our pretreatment protocol antagonized myotoxic activity by 0-60%. Preincubation of antivenoms with B. jararaca venom antagonized its hemorrhagic activity by 70-95%, while pretreatment antagonized hemorrhagic activity by 10-50%. Although all PAVs demonstrated partial antagonism against both venoms, the magnitude of these effects varied greatly among the manufactures. The results suggest that the current clinical doses of these PAVs may have negligible antimyotoxic effect.

Suramin counteracts the haemostatic disturbances produced by Bothrops jararaca snake venom

Snakebite accidents produced by Bothrops jararaca typically results in haemostatic changes including pro- and anticoagulant disturbs as well as interference with platelets. Suramin is a hexasulfonated naphthylurea derivative that was recently characterized as a thrombin inhibitor (Monteiro et al., 2004. Suramin interaction with human alpha-thrombin: inhibitory effects and binding studies. Int. J. Biochem. Cell Biol. 36(10), 2077-2085). Here, we evaluated the ability of suramin to counteract some of the haemostatic disturbs produced by B. jararaca venom. In vitro assays showed that suramin inhibited venom-induced hydrolysis of a number of synthetic substrates: S-2238, S-2266, S-2302 and S-2288, being this ability more prominent towards the thrombin substrate S-2238 (IC(50)=4.3 microM). It was also observed that suramin impaired the fibrinogen clotting induced by B. jararaca venom (IC(50)=124 microM). Accordingly, increasing concentrations of suramin progressively delayed venom-induced plasma clotting, with complete inhibition attained at concentrations above 1.0 mM. In addition, the platelet-aggregating properties of B. jararaca venom were inhibited by suramin in a dose-dependent fashion (IC(50)=127 microM). Suramin showed no effect in the in vivo hemorrhagic effect of venom in mouse skin. The in vivo effect of suramin was further tested using a previously established venous thrombosis model in rats induced by intravenous administration of B. jararaca venom combined with stasis. Venom doses of 100 microg/kg produced 100% of thrombus incidence (10.6+/-1.7 mg). On the other hand, previous administration of suramin partially inhibited thrombus formation. Thus, 12.5 or 25 mg/kg of suramin decreased thrombus weight by 24% and 40%, respectively. Remarkably, co-administration of 3 microL/kg of antibothropic serum (which has no effect on thrombus formation) and 12.5 mg/kg of suramin decreased thrombus weight by 75%, suggesting a synergic effect. Altogether, we demonstrate here that suramin inhibits in vitro and in vivo haemostatic changes caused by B. jararaca venom. At this point, this drug could be of potential interest for association with conventional antiserum therapy.

A comparative analysis of the clotting and fibrinolytic activities of the snake venom (Bothrops atrox) from different geographical areas in Venezuela

Venom constitution within the same snake species can present considerable geographical variations. Bothrops atrox venoms were obtained from adult snakes captured at different geographical locations: Parguasa (Bolívar state); Puerto Ayacucho 1, Serranía del Cuao and Puerto Ayacucho 2 (Amazon state). The coagulant and fibrinolytic activities of these venoms were compared. Amidolytic activity of crude snake venom was measured by a micromethod designed in our laboratory. Coagulant activity on plasma and fibrinogen due to thrombin-like activity in venoms was also determined. Crude snake venom fibrinolytic activity by the fibrin plate method was assayed. Chromatographic studies were developed on Protein-Pack 300 column. Polyacrylamide gel electrophoresis was carried out under reduced conditions. After SDS-PAGE of samples, the fibrin-zymography was tested on agarose-fibrin plates. The results demonstrated several differences among B. atrox venoms from different geographical areas. Chromatograms and SDS-PAGE profiles indicated that venoms from the same species presented differences in the molecular mass of their components. The procoagulant activity depended on the utilized method (amidolytic versus clotting). Parguasa and Puerto Ayacucho 2 venoms presented procoagulant activity for both methods. Furthermore, Parguasa venom had also the highest hemorrhagic activity and the lowest LD50. In relation to the fibrinolytic activity, Puerto Ayacucho 1 venom was the most active, equally for fibrin plates as for the amidolytic method (t-PA like). This venom had the lowest coagulant activity, which induced us to think that probably its procoagulant activity was interfered by its fibrinolytic activity.