Antithrombotic activity of Batroxase, a metalloprotease from Bothrops atrox venom, in a model of venous thrombosis

Therapeutic applications of snake venoms: An invaluable potential of new drug candidates

Animal venoms and their chemical compounds have aroused both empirical and scientific attention for ages. However, there has been a significant increase in scientific investigations in recent decades, allowing the production of various formulations that are helping in the development of many important tools for biotechnological, diagnostic, or therapeutic use, both in human and animal health, as well as in plants. Venoms are composed of biomolecules and inorganic compounds that may have physiological and pharmacological activities that are not related to their principal actions (prey immobilization, digestion, and defense). Snake venom toxins, mainly enzymatic and non-enzymatic proteins, and peptides have been identified as potential prototypes for new drugs and/or models for the development of pharmacologically active structural domains for the treatment of cancer, cardiovascular diseases, neurodegenerative and autoimmune diseases, pain, and infectious-parasitic diseases. This minireview aims to provide an overview of the biotechnological potential of animal venoms, with a focus on snakes, and to introduce the reader to the fascinating world of Applied Toxinology, where animal biodiversity can be used to develop therapeutic and diagnostic applications for humans.

Neurotoxins Acting at Synaptic Sites: A Brief Review on Mechanisms and Clinical Applications

Neurotoxins generally inhibit or promote the release of neurotransmitters or bind to receptors that are located in the pre- or post-synaptic membranes, thereby affecting physiological functions of synapses and affecting biological processes. With more and more research on the toxins of various origins, many neurotoxins are now widely used in clinical treatment and have demonstrated good therapeutic outcomes. This review summarizes the structural properties and potential pharmacological effects of neurotoxins acting on different components of the synapse, as well as their important clinical applications, thus could be a useful reference for researchers and clinicians in the study of neurotoxins.

Bothrops atrox, the most important snake involved in human envenomings in the amazon: How venomics contributes to the knowledge of snake biology and clinical toxinology

Bothrops atrox snakes are mostly endemic of the Amazon rainforest and is certainly the South American pit viper responsible for most of the snakebites in the region. The composition of B. atrox venom is significantly known and has been used to trace the relevance of the venom phenotype for snake biology and for the impacts in the clinics of human patients involved in accidents by B. atrox. However, in spite of the wide distribution and the great medical relevance of B. atrox snakes, B. atrox taxonomy is not fully resolved and the impacts of the lack of taxonomic resolution on the studies focused on venom or envenoming are currently unknown. B. atrox venom presents different degrees of compositional variability and is generally coagulotoxic, inducing systemic hematological disturbances and local tissue damage in snakebite patients. Antivenoms are the effective therapy for attenuating the clinical signs. This review brings a comprehensive discussion of the literature concerning B. atrox snakes encompassing from snake taxonomy, diet and venom composition, towards clinical aspects of snakebite patients and efficacy of the antivenoms. This discussion is highly supported by the contributions that venomics and antivenomics added for the advancement of knowledge of B. atrox snakes, their venoms and the treatment of accidents they evoke.

Purification and characterization of a thrombin-like enzyme isolated from Vipera lebetina venom: its interaction with platelet receptor

: Snake venoms contain various molecules that can be used as tools in the diagnosis and in the treatment of hemostatic disorders. This study reports the isolation and functional characterization of a new thrombin-like enzyme and its role in the modulation of platelet aggregation and coagulation. The molecule was purified by gel filtration, anion exchange chromatography and reverse-phase-HPLC on C8 column; its molecular weight was determined. Natural and synthetic substrates were used to evaluate its enzymatic activities. The fibrinogenolytic activity was tested electrophoretically and by reverse-phase-HPLC on C18 column. Otherwise, the effect on blood coagulation and deficient plasma factors were also evaluated. The mechanism by which a thrombin-like enzyme VLCV (thrombin-like enzyme)-induced platelet aggregation was explored in presence of ticlopidin, clopidogrel and aspirin. VLCV (45 kDa) isolated from Vipera lebetina as a thrombin-like enzyme seems to be able to modulate platelet function. This enzyme showed an amidolytic activity by hydrolyzing the chromogenic-specific substrate of thrombin and the α-chain of fibrinogen. It is also able to clot human plasma and the deficient human plasma in factor X, suggesting that it is involved in the intrinsic and common pathways. The aggregating effect of VLCV is more sensitive to ticlopidine than to the clopidogrel suggesting the involvement of ADP/P2Y12/PI3K pathway. VLCV seems to be able to promote human platelet aggregation suggesting an interaction between P2Y12 and PAR1. Due to its ability to replace the missing factor X and its proaggregating activity, VLCV could be used as molecular tool to better understand the hemostasis mechanism.

Local and systemic effects of BtaMP-1, a new weakly hemorrhagic Snake Venom Metalloproteinase purified from Bothriopsis taeniata Snake Venom

A new weak hemorrhagic metalloproteinase named BtaMP-1 was purified from Bothriopsis taeniata snake venom by molecular exclusion followed by anion exchange chromatographies. This protein showed a molecular mass of 25,968.16 Da and is composed of 218 amino acid residues. The multiple alignments of its partial amino acid sequence showed high structural identity with other P-I class SVMP. BtaMP-1 showed caseinolytic activity that was enhanced by Ca²⁺ ion, completely inhibited by chelating and reducing agents and can be classified as an α-fibrinogenolytic enzyme. Locally, BtaMP-1 induces hemorrhage and edema, but not myotoxicity. These findings were confirmed by histological analysis of mouse gastrocnemius muscle. "In vitro" studies suggest that BtaMP-1 induce cytotoxicity in myoblast C2C12 but not in the myotubes cell line. BtaMP-1 induced systemic alterations in mice with one MHD and two hours exposure; histological analysis of lungs showed hemorrhagic areas, congestion, and increase the thickness of alveolar septum. Also, this protein induced mild effects on kidney and disruption of coagulation by depletion of fibrinogen plasma levels. This work provides insights into the importance of BtaMP-1 biological effects in envenomation by Bothropsis taeniata snake venom and providing further evidence to understand the role of P-I class SVMP in ophidian envenomation.

A fixed moderate-dose combination of tiletamine+zolazepam outperforms midazolam in induction of short-term immobilization of ball pythons (Python regius)

Laboratory animals are commonly anesthetized to prevent pain and distress and to provide safe handling. Anesthesia procedures are well-developed for common laboratory mammals, but not as well established in reptiles. We assessed the performance of intramuscularly injected tiletamine (dissociative anesthetic) and zolazepam (benzodiazepine sedative) in fixed combination (2 mg/kg and 3 mg/kg) in comparison to 2 mg/kg of midazolam (benzodiazepine sedative) in ball pythons (Python regius). We measured heart and respiratory rates and quantified induction parameters (i.e., time to loss of righting reflex, time to loss of withdrawal reflex) and recovery parameters (i.e., time to regain righting reflex, withdrawal reflex, normal behavior). Mild decreases in heart and respiratory rates (median decrease of <10 beats per minute and <5 breaths per minute) were observed for most time points among all three anesthetic dose groups. No statistically significant difference between the median time to loss of righting reflex was observed among animals of any group (p = 0.783). However, the withdrawal reflex was lost in all snakes receiving 3mg/kg of tiletamine+zolazepam but not in all animals of the other two groups (p = 0.0004). In addition, the time for animals to regain the righting reflex and resume normal behavior was longer in the drug combination dose groups compared to the midazolam group (p = 0.0055). Our results indicate that midazolam is an adequate sedative for ball pythons but does not suffice to achieve reliable immobilization or anesthesia, whereas tiletamine+zolazepam achieves short-term anesthesia in a dose-dependent manner.

Stress-Induced Mucus Secretion and Its Composition by a Combination of Proteomics and Metabolomics of the Jellyfish Aurelia coerulea

BACKGROUND

Jellyfish respond quickly to external stress that stimulates mucus secretion as a defense. Neither the composition of secreted mucus nor the process of secretion are well understood.

METHODS

Aurelia coerulea jellyfish were stimulated by removing them from environmental seawater. Secreted mucus and tissue samples were then collected within 60 min, and analyzed by a combination of proteomics and metabolomics using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS), respectively.

RESULTS

Two phases of sample collection displayed a quick decrease in volume, followed by a gradual increase. A total of 2421 and 1208 proteins were identified in tissue homogenate and secreted mucus, respectively. Gene Ontology (GO) analysis showed that the mucus-enriched proteins are mainly located in extracellular or membrane-associated regions, while the tissue-enriched proteins are distributed throughout intracellular compartments. Tryptamine, among 16 different metabolites, increased with the largest-fold change value of 7.8 in mucus, which is consistent with its involvement in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway 'tryptophan metabolism'. We identified 11 metalloproteinases, four serpins, three superoxide dismutases and three complements, and their presence was speculated to be related to self-protective defense.

CONCLUSIONS

Our results provide a composition profile of proteins and metabolites in stress-induced mucus and tissue homogenate of A. coerulea. This provides insight for the ongoing endeavors to discover novel bioactive compounds. The large increase of tryptamine in mucus may indicate a strong stress response when jellyfish were taken out of seawater and the active self-protective components such as enzymes, serpins and complements potentially play a key role in innate immunity of jellyfish.

Snakebites as cause of deaths in the Western Brazilian Amazon: Why and who dies? Deaths from snakebites in the Amazon

Snake envenoming represents a major burden for public health worldwide. In the Amazon, the official number of cases and deaths detected is probably underestimated because of the difficulty riverine and indigenous populations have reaching health centers in order to receive medical assistance. Thus, integrated analysis of health information systems must be used in order to improve adequate health policies. The aim of this work is to describe a series of deaths and identify risk factors for lethality from snakebites in the state of Amazonas, Brazil. All deaths from snakebites reported to the Brazilian Notifiable Diseases Surveillance System (SINAN) and to the Mortality Information System (SIM; ICD10-10th revision, X.29), from 2007 to 2015, were included. Variables were assessed by blocks with distal (ecological variables), intermediate (demographics) and proximal (clinical variables) components to identify predictors of case fatality. A total of 127 deaths from snakebites were recorded, with 58 pairs found through linkage of the SINAN and SIM databases (45.7%), 37 (29.1%) deaths found only in SINAN and 32 (25.2%) found only in the SIM. Deaths occurred mostly in males (95 cases; 74.8%) living in rural areas (78.6%). The most affected age group was the ≥61 years old (36 cases; 28.4%). Snakebites were presumably due to Bothrops snakes in 68.5% of the cases and Lachesis in 29.5% based on clinico-epidemiological diagnosis. A proportion of 26.2% of the cases received treatment over 24 h after the bite ocurred. On admission, cases were mostly classified as severe (65.6%). Overall, 28 patients (22.0%). Deceased without any medical assistance Antivenom was given to 53.5%. In the multivariate analysis, a distance from Manaus >300 km [OR = 3.40 (95%CI = 1.99-5.79); (p < 0.001)]; age ≥61 years [OR = 4.31 (95%CI = 1.22-15.21); (p = 0.023)] and Indigenous status [OR = 5.47 (95%CI = 2.37-12.66); (p < 0.001)] were independently associated with case fatality from snakebites. Severe snakebites [OR = 16.24 (95%CI = 4.37-60.39); (p < 0.001)] and a lack of antivenom administration [OR = 4.21 (95%CI = 1.30-13.19); (p = 0.014)] were also independently associated with case fatality. Respiratory failure/dyspnea, systemic bleeding, sepsis and shock were recorded only among fatal cases. In conclusion, i) death from snakebites was underreported in the mortality surveillance system; ii) older age groups living in remote municipalities and indigenous peoples were the population groups most prone to death; iii) lack or underdosage of antivenom resulted in higher case fatality and iv) systemic bleeding, circulatory shock, sepsis and acute respiratory failure were strongly associated to fatal outcome.

Poor efficacy of preemptive amoxicillin clavulanate for preventing secondary infection from Bothrops snakebites in the Brazilian Amazon: A randomized controlled clinical trial

BACKGROUND

Secondary bacterial infections from snakebites contribute to the high complication rates that can lead to permanent function loss and disabilities. Although common in endemic areas, routine empirical prophylactic use of antibiotics aiming to prevent secondary infection lacks a clearly defined policy. The aim of this work was to estimate the efficacy of amoxicillin clavulanate for reducing the secondary infection incidence in patients bitten by Bothrops snakes, and, secondarily, identify risk factors for secondary infections from snakebites in the Western Brazilian Amazon.

METHODS AND FINDINGS

This was an open-label, two-arm individually randomized superiority trial to prevent secondary infection from Bothrops snakebites. The antibiotic chosen for this clinical trial was oral amoxicillin clavulanate per seven days compared to no intervention. A total of 345 patients were assessed for eligibility in the study period. From this total, 187 accomplished the inclusion criteria and were randomized, 93 in the interventional group and 94 in the untreated control group. All randomized participants completed the 7 days follow-up period. Enzyme immunoassay confirmed Bothrops envenoming diagnosis in all participants. Primary outcome was defined as secondary infection (abscess and/or cellulitis) until day 7 after admission. Secondary infection incidence until 7 days after admission was 35.5% in the intervention group and 44.1% in the control group [RR = 0.80 (95%CI = 0.56 to 1.15; p = 0.235)]. Survival analysis demonstrated that the time from patient admission to the onset of secondary infection was not different between amoxicillin clavulanate treated and control group (Log-rank = 2.23; p = 0.789).Secondary infections incidence in 7 days of follow-up was independently associated to fibrinogen >400 mg/dL [AOR = 4.78 (95%CI = 2.17 to 10.55; p<0.001)], alanine transaminase >44 IU/L [AOR = 2.52 (95%CI = 1.06 to 5.98; p = 0.037)], C-reactive protein >6.5 mg/L [AOR = 2.98 (95%CI = 1.40 to 6.35; p = 0.005)], moderate pain [AOR = 24.30 (95%CI = 4.69 to 125.84; p<0.001)] and moderate snakebites [AOR = 2.43 (95%CI = 1.07 to 5.50; p = 0.034)].

CONCLUSIONS/SIGNIFICANCE

Preemptive amoxicillin clavulanate was not effective for preventing secondary infections from Bothrops snakebites. Laboratorial markers, such as high fibrinogen, alanine transaminase and C-reactive protein levels, and severity clinical grading of snakebites, may help to accurately diagnose secondary infections.

TRIAL REGISTRATION

Brazilian Clinical Trials Registry (ReBec): RBR-3h33wy; UTN Number: U1111-1169-1005.

Immune cells and mediators involved in the inflammatory responses induced by a P-I metalloprotease and a phospholipase A2 from Bothrops atrox venom

Bothrops envenomations can promote severe inflammatory responses by inducing edema, pain, leukocyte recruitment and release of chemical mediators by local cells. In the present study, two toxins from Bothrops atrox venom (the P-I metalloprotease Batroxase and the acidic phospholipase A₂ BatroxPLA₂) were evaluated in relation to their inflammatory effects induced in vivo and in vitro, mainly focusing on the participation of different immune cells and inflammatory mediators. Both toxins mainly promoted acute inflammatory responses with significant recruitment of neutrophils in the early hours (1-4h) after administration into the peritoneal cavity of C57BL/6 mice, and increased infiltration of mononuclear cells especially after 24h. Among the mediators induced by both toxins are IL-6, IL-10 and PGE₂, with Batroxase also inducing the release of L-1β, and BatroxPLA₂ of LTB₄ and CysLTs. These responses pointed to possible involvement of immune cells such as macrophages and mast cells, which were then evaluated in vitro. Mice peritoneal macrophages stimulated with Batroxase produced significant levels of IL-6, IL-1β, PGE₂ and LTB₄, whereas stimulus with BatroxPLA₂ induced increases of IL-6, PGE₂ and LTB₄. Furthermore, both toxins were able to stimulate degranulation of RBL-2H3 mast cells, but with distinct concentration-dependent effects. Altogether, these results indicated that Batroxase and BatroxPLA₂ promoted local and acute inflammatory responses related to macrophages and mast cells and to the production of several mediators. Our findings should contribute for better understanding the different mechanisms of toxicity induced by P-I metalloproteases and phospholipases A₂ after snakebite envenomations.