Pharmacological Study of Edema and Myonecrosis in Mice Induced by Venom of the Bushmaster Snake (Lachesis muta muta) and Its Basic Asp49 Phospholipase A2 (LmTX-I)

Hyperglycosylation impairs the inhibitory activity of rCdtPLI2, the first recombinant beta-phospholipase A2 inhibitor

Crotoxin, a phospholipase A2 (PLA2) complex and the major Crotalus venom component, is responsible for the main symptoms described in crotalic snakebite envenomings and a key target for PLA2 inhibitors (PLIs). PLIs comprise the alpha, beta and gamma families, and, due to a lack of reports on beta-PLIs, this study aimed to heterologously express CdtPLI2 from Crotalus durissus terrificus venom gland to improve the knowledge of the neglected beta-PLI family. Thereby, recombinant CdtPLI2 (rCdtPLI2) was produced in the eukaryotic Pichia pastoris system to keep some native post-translational modifications. rCdtPLI2 (~41 kDa) presents both N- and O-linked glycans. Alpha-mannosidase digested-rCdtPLI2 (1 mol) strongly inhibited (73%) CB-Cdc catalytic activity (5 moles), demonstrating that glycosylations performed by P. pastoris affect rCdtPLI2 action. Digested-rCdtPLI2 also inhibited PLA2s from diverse Brazilian snake venoms. Furthermore, rCdtPLI2 (1 mol) abolished the catalytic activity of Lmr-PLA2 (5 moles) and reduced the CTx-Cdc (5 moles) enzyme activity by 65%, suppressing basic and acidic snake venom PLA2s. Additionally, crotalic antivenom did not recognize rCdtPLI2, suggesting a lack of neutralization by antivenom antibodies. These findings demonstrate that studying snake venom components may reveal interesting novel molecules to be studied in the snakebite treatment and help to understand these underexplored inhibitors.

Indian Ornamental Tarantula (Poecilotheria regalis) Venom Affects Myoblast Function and Causes Skeletal Muscle Damage

Envenomation by the Indian ornamental tarantula (Poecilotheria regalis) is medically relevant to humans, both in its native India and worldwide, where they are kept as pets. Muscle-related symptoms such as cramps and pain are commonly reported in humans following envenomation by this species. There is no specific treatment, including antivenom, for its envenomation. Moreover, the scientific knowledge of the impact of this venom on skeletal muscle function is highly limited. Therefore, we carried out this study to better understand the myotoxic properties of Poecilotheria regalis venom by determining its effects in cultured myoblasts and in the tibialis anterior muscle in mice. While there was no effect found on undifferentiated myoblasts, the venom affected differentiated multinucleated myotubes resulting in the reduction of fusion and atrophy of myotubes. Similarly, intramuscular administration of this venom in the tibialis anterior muscle in mice resulted in extensive muscle damage on day 5. However, by day 10, the regeneration was evident, and the regeneration process continued until day 20. Nevertheless, some tissue abnormalities including reduced dystrophin expression and microthrombi presence were observed on day 20. Overall, this study demonstrates the ability of this venom to induce significant muscle damage and affect its regeneration in the early stages. These data provide novel mechanistic insights into this venom-induced muscle damage and guide future studies to isolate and characterise individual toxic component(s) that induce muscle damage and their significance in developing better therapeutics.

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.

The Colombian bushmasters Lachesis acrochorda (García, 1896) and Lachesis muta (Linnaeus, 1766): Snake species, venoms, envenomation, and its management

In Colombia, there are two species of bushmaster snakes, Lachesis acrochorda, which is distributed mainly in the west of the country (in the Choco region), and Lachesis muta in the southeast (in the Amazon and Orinoquia region), whose presence has been reduced due to the destruction of their habitats. Captive maintenance is challenging, making it difficult to obtain their venom for study and antivenom manufacturing. They are the largest vipers in the world. The occurrence of human envenomation is quite rare, but when it occurs, it is associated with high mortality. Bushmaster venom is necrotizing, hemorrhagic, myotoxic, hemolytic, and cardiovascular depressant. Due to the presence of bradycardia, hypotension, emesis, and diarrhea in some patients (Lachesis syndrome), the possibility of a vagal or cholinergic effect is raised. The treatment of envenomation is hindered by the scarcity of antivenom and the need to use high doses. A review of the most relevant biological and medical aspects of bushmaster snakes is presented, mainly for those occurring in Colombia, to facilitate their recognition and raise awareness about the need for special attention to improve their conservation and advance scientific knowledge, in particular, about their venom.

Proteomic and functional analyses of Lachesis acrochorda snake venom from the Valle del Cauca Department of Colombia

Lachesis acrochorda envenomation has a lethality rate of approximately 90%. Despite its high lethality, little is known about its local and systemic effects and its relationship with its protein content. Thus, to increase knowledge of L. acrochorda snake venom from the Southwestern ecoregion of Colombia, we developed a proteomic analysis using a "bottom-up shotgun proteomic profiling" approach. Besides, we evaluated toxinological properties and compared the effects with the Bothrops asper snake venom activities. The RP-HPLC profile showed similarities with the L. acrochorda snake venom from the Northwestern ecoregion of Colombia. However, the results displayed differences in the protein families identified, probably due to the proteomic identification strategy. The in vitro and in vivo tests showed a L. acrochorda snake venom with Phospholipase A₂ and metalloproteinase activities related to myotoxic, edematic, and hemorrhagic effects. Nevertheless, the L. acrochorda snake venom displayed a low lethality despite a large amount of inoculated venom. This investigation's results will help us improve the knowledge about the relationship between the clinical manifestations of L. acrochorda envenomation and the venom protein content.

Protective action of N-acetyl-L-cysteine associated with a polyvalent antivenom on the envenomation induced by Lachesis muta muta (South American bushmaster) in rats

In this study, we examined the potential use of N-acetyl-L-cysteine (NAC) in association with a polyvalent antivenom and as stand-alone therapy to reduce the acute local and systemic effects induced by Lachesis muta muta venom in rats. Male Wistar rats (300-350 g) were exposed to L. m. muta venom (1.5 mg/kg - i.m.) and subsequently treated with anti-Bothrops/Lachesis serum (antivenom:venom ratio 1:3 'v/w' - i.p.) and NAC (150 mg/kg - i.p.) separately or in association; the animals were monitored for 120 min to assess changes in temperature, locomotor activity, local oedema formation and the prevalence of haemorrhaging. After this time, animals were anesthetized in order to collect blood samples through intracardiac puncture and then euthanized for collecting tissue samples; the hematological-biochemical and histopathological analyses were performed through conventional methods. L. m. muta venom produced pronounced local oedema, subcutaneous haemorrhage and myonecrosis, with both antivenom and NAC successfully reducing the extent of the myonecrotic lesion when individually administered; their association also prevented the occurrence of subcutaneous haemorrhage. Venom-induced creatine kinase (CK) release was significantly prevented by NAC alone or in combination with antivenom; NAC alone failed to reduce the release of hepatotoxic (alanine aminotransferase) and nephrotoxic (creatinine) serum biomarkers induced by L. m. muta venom. Venom induced significant increase of leucocytes which was also associated with an increase of neutrophils, eosinophils and monocytes; antivenom and NAC partially reduced these alterations, with NAC alone significantly preventing the increase of eosinophils whereas neither NAC or antivenom prevented the increase in monocytes. Venom did not induce changes in the erythrogram parameters. In the absence of a suitable antivenom, NAC has the potential to reduce a number of local and systemic effects caused by L. m. muta venom.

Structural, enzymatic and pharmacological profiles of AplTX-II - A basic sPLA2 (D49) isolated from the Agkistrodon piscivorus leucostoma snake venom

A basic sPLA₂ (D49) from the venom of snake Agkistrodon piscivorus leucostoma (AplTX-II) was isolated, purified and characterized. We determined the enzymatic and pharmacological profiles of this toxin. AplTX-II was isolated with a high level of purity through reverse phase chromatography and molecular exclusion. The enzyme showed pI 9.48 and molecular weight of 14,003 Da. The enzymatic activity of the AplTX-II depended on Ca²⁺ pH and temperature. The comparison of the primary structure with other sPLA₂s revealed that AplTX-II presented all the structural reasons expected for a basic sPLA₂s. Additionally, we have resolved its structure with the docked synthetic substrate NOBA (4-nitro-3-octanoyloxy benzoic acid) by homology modeling, and performed MD simulations with explicit solvent. Structural similarities were found between the enzyme's modeled structure and other snake sPLA₂ X-Ray structures, available in the PDB database. NOBA and active-site water molecules spontaneously adopted stable positions and established interactions in full agreement with the reaction mechanism, proposed for the physiological substrate, suggesting that NOBA hydrolysis is an excellent model to study phospholipid hydrolysis.

Biochemical characterization of Bothrops roedingeri Mertens, 1942 snake venom and its edematogenic, hemorrhagic, and myotoxic activities

Introduction: Snakebite envenoming is considered by the World Health Organization (WHO) as a neglected tropical disease. Currently, Bothrops snake venoms are being studied intensively, but there is little knowledge about Bothrops roedingeri venom. Objectives: To biochemically characterize B. roedingeri total venom and evaluate its myotoxic, edematogenic, and hemorrhagic activity. Materials and methods: We characterized B. roedingeri venom enzymatic activity by determining the phospholipase A2 and the proteolytic and fibrinogenolytic action using SDSPAGE electrophoresis while we characterized its venom toxicity by determining the minimum hemorrhagic dose, the minimum edema dose, and the local and systemic myotoxic effects. Results: Bothrops roedingeri venom showed a PLA2 activity of 3.45 ± 0.11 nmoles/min, proteolytic activity of 0.145 ± 0.009 nmoles/min, and a fibrinogen coagulation index of 6.67 ± 1.33 seconds. On the other hand, it produced an minimum hemorrhagic dose of 24.5 μg, an minimum edema dose of 15.6 μg, and a pronounced local myotoxic effect evidenced by the elevation of plasma creatine kinase levels after intramuscular inoculation. The venom showed no systemic myotoxicity. Conclusions: Bothrops roedingeri venom has local hemorrhagic, edematogenic, and myotoxic activity. Enzymatically, it has high PLA2 activity, which would be responsible for the myotoxic and edematogenic effects. It also has proteolytic activity, which could affect coagulation given its ability to degrade fibrinogen, and it causes bleeding through the metalloproteases.

A brief review on the natural history, venomics and the medical importance of bushmaster (Lachesis) pit viper snakes

Snakes of the genus Lachesis, commonly known as bushmasters, are the largest venomous snakes in the Americas. Because these snakes have their habitats in areas of remote forests they are difficult to find, and consequently there are few studies of Lachesis taxa in their natural ecosystems. Bushmasters are distributed in tropical forest areas of South and Central America. In Brazil they can be found in the Amazon Rainforest and the Atlantic Forest. Despite the low incidence of cases, laquetic envenoming causes severe permanent sequelae due to the high amount of inoculated venom. These accidents are characterized by local pain, hemorrhage and myonecrosis that can be confused with bothropic envenomings. However, victims of Lachesis bites develop symptoms characteristic of Lachesis envenoming, known as vagal syndrome. An important message of this bibliographic synthesis exercise is that, despite having the proteomic profiles of all the taxa of the genus available, very few structure-function correlation studies have been carried out. Therefore the motivation for this review was to fill a gap in the literature on the genus Lachesis, about which there is no recent review. Here we discuss data scattered in a number of original articles published in specialized journals, spanning the evolutionary history and extant phylogeographic distribution of the bushmasters, their venom composition and diet, as well as the pathophysiology of their bites to humans and the biological activities and possible biotechnological applicability of their venom toxins.

The protective effect exerted by ascorbic acid on DNA fragmentation of human leukocytes induced by Lachesis muta muta venom

The objective of this study was to evaluate the genotoxic and mutagenic effects of the toxins present in Lachesis muta muta's venom on human peripheral blood leukocytes and the protective potential of ascorbic acid on DNA fragmentation. The venom of L. muta muta was incubated in different concentrations (1, 2.5, 5, 7.5, 10, 15, 20, 30, 40, 50, 60, and 120 µg/mL) with human blood to evaluate DNA fragmentation using the comet, agarose gel electrophoresis, and micronucleus assays. In these concentrations evaluated, the venom of L. muta muta induced genotoxicity (comet assay and agarose gel electrophoresis) and mutagenicity (micronucleus test), but they were not cytotoxic, as they did not change the rate of cell proliferation after cytokinesis blockade with cytochalasin B. The ascorbic acid significantly inhibited the genotoxicity induced by L. muta muta venom in the proportions evaluated (1:0.1 and 1:0.5, venom/ascorbic acid - w/w). Thus, future studies are needed to elucidate the protective mechanisms of ascorbic acid on the genotoxic effects induced by toxins present in snake venoms.

Structural Insight into Binding Mode of 9-Hydroxy Aristolochic Acid, Diclofenac and Indomethacin to PLA2

Phospholipase A₂ (PLA₂) catalyzes the hydrolysis of phospholipids into arachidonic acid and lysophospholipids. Arachidonic acid is modified by cyclooxygenases into active compounds called eicosanoids that act as signaling molecules in a number of physiological processes. Excessive production of eicosanoids leads to several pathological conditions such as inflammation. In order to block the inflammatory effect of these compounds, upstream enzymes such as PLA₂ are valid targets. In the present contribution, molecular dynamic analysis was performed to evaluate the binding of diclofenac, 9-hydroxy aristolochic acid (9-HAA) and indomethacin to PLA₂. Obtained results revealed that 9-HAA could form a more stable complex with PLA₂ when compared to diclofenac and indomethacin. Furthermore, analysis of intermolecular binding energy components indicated that hydrophobic interactions were dominant in binding process. On the basis of obtained data, inhibitors bearing fused rings with hydrogen acceptor/donor substituent(s) interacted with His48 and Asp49 residues of the active site. More affinity toward PLA₂ might be envisaged through negatively charged moieties via interaction with Trp31, Lys34 and Lys69.

Isolation and biochemical characterization of a gamma-type phospholipase A2 inhibitor from Macropisthodon rudis snake serum

A novel phospholipaseA₂ (PLA₂) inhibitory protein (PLI) was purified from the serum of Macropisthodon rudis, a non-venomous snake mainly found in southern China. The molecular mass of the purified PLI was 160 kDa as determined by Superdex 200HR; however, the PLI protein had only one subunit of 25.4 kDa as determined by 12% SDS-PAGE, indicating an oligomeric protein. PLI cDNA obtained by PCR from the liver of Macropisthodon rudis, revealed 549 bps coding for a mature protein of 183 amino acid residues. Based on an amino acid sequence alignment with venomous and non-venomous snakes, this inhibitor was determined to be in the γ type family of PLI. In vitro experiments showed that PLIγ inhibited enzymatic, inflammatory, and antibacterial activities of snake venom PLA₂ isolated from Agkistrodon acutus.

PhTX-II a basic myotoxic phospholipase A₂ from Porthidium hyoprora snake venom, pharmacological characterization and amino acid sequence by mass spectrometry

A monomeric basic PLA₂ (PhTX-II) of 14149.08 Da molecular weight was purified to homogeneity from Porthidium hyoprora venom. Amino acid sequence by in tandem mass spectrometry revealed that PhTX-II belongs to Asp49 PLA₂ enzyme class and displays conserved domains as the catalytic network, Ca²⁺-binding loop and the hydrophobic channel of access to the catalytic site, reflected in the high catalytic activity displayed by the enzyme. Moreover, PhTX-II PLA₂ showed an allosteric behavior and its enzymatic activity was dependent on Ca²⁺. Examination of PhTX-II PLA₂ by CD spectroscopy indicated a high content of alpha-helical structures, similar to the known structure of secreted phospholipase IIA group suggesting a similar folding. PhTX-II PLA₂ causes neuromuscular blockade in avian neuromuscular preparations with a significant direct action on skeletal muscle function, as well as, induced local edema and myotoxicity, in mice. The treatment of PhTX-II by BPB resulted in complete loss of their catalytic activity that was accompanied by loss of their edematogenic effect. On the other hand, enzymatic activity of PhTX-II contributes to this neuromuscular blockade and local myotoxicity is dependent not only on enzymatic activity. These results show that PhTX-II is a myotoxic Asp49 PLA₂ that contributes with toxic actions caused by P. hyoprora venom.

Alkylation of histidine residues of Bothrops jararacussu venom proteins and isolated phospholipases A2: a biotechnological tool to improve the production of antibodies

Crude venom of Bothrops jararacussu and isolated phospholipases A₂ (PLA₂) of this toxin (BthTX-I and BthTX-II) were chemically modified (alkylation) by p-bromophenacyl bromide (BPB) in order to study antibody production capacity in function of the structure-function relationship of these substances (crude venom and PLA₂ native and alkylated). BthTX-II showed enzymatic activity, while BthTX-I did not. Alkylation reduced BthTX-II activity by 50% while this process abolished the catalytic and myotoxic activities of BthTX-I, while reducing its edema-inducing activity by about 50%. Antibody production against the native and alkylated forms of BthTX-I and -II and the cross-reactivity of antibodies to native and alkylated toxins did not show any apparent differences and these observations were reinforced by surface plasmon resonance (SPR) data. Histopathological analysis of mouse gastrocnemius muscle sections after injection of PBS, BthTX-I, BthTX-II, or both myotoxins previously incubated with neutralizing antibody showed inhibition of the toxin-induced myotoxicity. These results reveal that the chemical modification of the phospholipases A₂ (PLA₂) diminished their toxicity but did not alter their antigenicity. This observation indicates that the modified PLA₂ may provide a biotechnological tool to attenuate the toxicity of the crude venom, by improving the production of antibodies and decreasing the local toxic effects of this poisonous substance in animals used to produce antivenom.

A novel phospholipase A2 (D49) from the venom of the Crotalus oreganus abyssus (North American Grand canyon rattlesnake)

Currently, Crotalus viridis was divided into two species: Crotalus viridis and Crotalus oreganus. The current classification divides "the old" Crotalus viridis into two new and independent species: Crotalus viridis (subspecies: viridis and nuntius) and Crotalus oreganus (subspecies: abyssus, lutosus, concolor, oreganus, helleri, cerberus, and caliginis). The analysis of a product from cDNA (E6d), derived from the gland of a specie Crotalus viridis viridis, was found to produce an acid phospholipase A2. In this study we isolated and characterized a PLA2 (D49) from Crotalus oreganus abyssus venom. Our studies show that the PLA2 produced from the cDNA of Crotalus viridis viridis (named E6d) is exactly the same PLA2 primary sequence of amino acids isolated from the venom of Crotalus oreganus abyssus. Thus, the PLA2 from E6d cDNA is actually the same PLA2 presented in the venom of Crotalus oreganus abyssus and does not correspond to the venom from Crotalus viridis viridis. These facts highlight the importance of performing more studies on subspecies of Crotalus oreganus and Crotalus viridis, since the old classification may have led to mixed results or mistaken data.

Snake venom PLA2s inhibitors isolated from Brazilian plants: synthetic and natural molecules

Ophidian envenomation is an important health problem in Brazil and other South American countries. In folk medicine, especially in developing countries, several vegetal species are employed for the treatment of snakebites in communities that lack prompt access to serum therapy. However, the identification and characterization of the effects of several new plants or their isolated compounds, which are able to inhibit the activities of snake venom, are extremely important and such studies are imperative. Snake venom contains several organic and inorganic compounds; phospholipases A₂ (PLA₂s) are one of the principal toxic components of venom. PLA₂s display a wide variety of pharmacological activities, such as neurotoxicity, myotoxicity, cardiotoxicity, anticoagulant, hemorrhagic, and edema-inducing effects. PLA₂ inhibition is of pharmacological and therapeutic interests as these enzymes are involved in several inflammatory diseases. This review describes the results of several studies of plant extracts and their isolated active principles, when used against crude snake venoms or their toxic fractions. Isolated inhibitors, such as steroids, terpenoids, and phenolic compounds, are able to inhibit PLA₂s from different snake venoms. The design of specific inhibitors of PLA₂s might help in the development of new pharmaceutical drugs, more specific antivenom, or even as alternative approaches for treating snakebites.