Biochemical and biological characterization of a PLA2 from crotoxin complex of Crotalus durissus cumanensis

A Review of Rattlesnake Venoms

Venom components are invaluable in biomedical research owing to their specificity and potency. Many of these components exist in two genera of rattlesnakes, Crotalus and Sistrurus, with high toxicity and proteolytic activity variation. This review focuses on venom components within rattlesnakes, and offers a comparison and itemized list of factors dictating venom composition, as well as presenting their known characteristics, activities, and significant applications in biosciences. There are 64 families and subfamilies of proteins present in Crotalus and Sistrurus venom. Snake venom serine proteases (SVSP), snake venom metalloproteases (SVMP), and phospholipases A2 (PLA2) are the standard components in Crotalus and Sistrurus venom. Through this review, we highlight gaps in the knowledge of rattlesnake venom; there needs to be more information on the venom composition of three Crotalus species and one Sistrurus subspecies. We discuss the activity and importance of both major and minor components in biomedical research and drug development.

Knowledge about Snake Venoms and Toxins from Colombia: A Systematic Review

Colombia encompasses three mountain ranges that divide the country into five natural regions: Andes, Pacific, Caribbean, Amazon, and Orinoquia. These regions offer an impressive range of climates, altitudes, and landscapes, which lead to a high snake biodiversity. Of the almost 300 snake species reported in Colombia, nearly 50 are categorized as venomous. This high diversity of species contrasts with the small number of studies to characterize their venom compositions and natural history in the different ecoregions. This work reviews the available information about the venom composition, isolated toxins, and potential applications of snake species found in Colombia. Data compilation was conducted according to the PRISMA guidelines, and the systematic literature search was carried out in Pubmed/MEDLINE. Venom proteomes from nine Viperidae and three Elapidae species have been described using quantitative analytical strategies. In addition, venoms of three Colubridae species have been studied. Bioactivities reported for some of the venoms or isolated components-such as antibacterial, cytotoxicity on tumoral cell lines, and antiplasmodial properties-may be of interest to develop potential applications. Overall, this review indicates that, despite recent progress in the characterization of venoms from several Colombian snakes, it is necessary to perform further studies on the many species whose venoms remain essentially unexplored, especially those of the poorly known genus Micrurus.

Continuous Electrospray Ionization Mass Spectrometry Assay for Measuring Phospholipase Activity against Liposomes

Phospholipases have diverse roles in lipid and cell membrane biology. In animal venoms, they can have roles as neurotoxins or myotoxins that disrupt the integrity of cell membranes. In this work, we describe a temperature-controlled, continuous electrospray ionization mass spectrometry (ESI-MS) assay for measuring phospholipase A₂ activity against liposomes. The enzyme used in this assay was paradoxin, which is a neurotoxic trimeric phospholipase A₂ from inland taipan snake venom. Previously developed ESI-MS-based phospholipase assays have been discontinuous and analyzed hydrolysis of single lipid molecules by liquid chromatography ESI-MS. In this work, a continuous assay was developed against liposomes, a more complex substrate that more closely reflects the natural substrate for paradoxin. The assay confirmed the requirement for Ca²⁺ and allowed measurement of Michaelis-Menten-type parameters. The use of ESI-MS for lipid detection enabled nuanced insights into the effect of changing assay conditions not only on the enzyme but also on the liposome substrate. Changing the metal ion concentrations did not significantly change the liposomes but did affect enzymatic activity. Increasing temperature did not substantially affect the secondary structure of paradoxin but affected liposome size, resulting in increased enzymatic activity consistent with the disruption of the phosphatidylcholine membrane, increasing accessibility of sn-2 ester bonds. The continuous ESI-MS method described herein can be applied to other enzyme reactions, particularly those which utilize complex lipid substrates.

Biological and Medical Aspects Related to South American Rattlesnake Crotalus durissus (Linnaeus, 1758): A View from Colombia

In Colombia, South America, there is a subspecies of the South American rattlesnake Crotalus durissus, C. d. cumanensis, a snake of the Viperidae family, whose presence has been reduced due to the destruction of its habitat. It is an enigmatic snake from the group of pit vipers, venomous, with large articulated front fangs, special designs on its body, and a characteristic rattle on its tail. Unlike in Brazil, the occurrence of human envenomation by C. durisus in Colombia is very rare and contributes to less than 1% of envenomation caused by snakes. Its venom is a complex cocktail of proteins with different biological effects, which evolved with the purpose of paralyzing the prey, killing it, and starting its digestive process, as well as having defense functions. When its venom is injected into humans as the result of a bite, the victim presents with both local tissue damage and with systemic involvement, including a diverse degree of neurotoxic, myotoxic, nephrotoxic, and coagulopathic effects, among others. Its biological effects are being studied for use in human health, including the possible development of analgesic, muscle relaxant, anti-inflammatory, immunosuppressive, anti-infection, and antineoplastic drugs. Several groups of researchers in Brazil are very active in their contributions in this regard. In this work, a review is made of the most relevant biological and medical aspects related to the South American rattlesnake and of what may be of importance for a better understanding of the snake C. d. cumanensis, present in Colombia and Venezuela.

Inhibitory Effects of Varespladib, CP471474, and Their Potential Synergistic Activity on Bothrops asper and Crotalus durissus cumanensis Venoms

Snakebite is a neglected tropical disease that causes extensive mortality and morbidity in rural communities. Antivenim sera are the currently approved therapy for snake bites; however, they have some therapeutic limitations that have been extensively documented. Recently, small molecule toxin inhibitors have received significant attention as potential alternatives or co-adjuvant to immunoglobulin-based snakebite therapies. Thus, in this study, we evaluated the inhibitory effects of the phospholipase A2 inhibitor varespladib and the metalloproteinase inhibitor CP471474 and their synergistic effects on the lethal, edema-forming, hemorrhagic, and myotoxic activities of Bothrops asper and Crotalus durissus cumanensis venoms from Colombia. Except for the preincubation assay of the lethal activity with B. asper venom, the mixture showed the best inhibitory activity. Nevertheless, the mix did not display statistically significant differences to varespladib and CP471474 used separately in all assays. In preincubation assays, varespladib showed the best inhibitory activity against the lethal effect induced by B. asper venom. However, in independent injection assays, the mix of the compounds partially inhibited the lethal activity of both venoms (50%). In addition, in the assays to test the inhibition of edema-forming activity, the mixture exhibited the best inhibitory activity, followed by Varespladib, but without statistically significant differences (p > 0.05). The combination also decreased the myotoxic activity of evaluated venoms. In these assays, the mix showed statistical differences regarding CP471474 (p < 0.05). The mixture also abolished the hemorrhagic activity of B. asper venom in preincubation assays, with no statistical differences to CP471474. Finally, the mixture showed inhibition in studies with independent administration in a time-dependent manner. To propose a mode of action of varespladib and CP471474, molecular docking was performed. PLA2s and SVMPs from tested venoms were used as targets. In all cases, our molecular modeling results suggested that inhibitors may occupy the substrate-binding cleft of the enzymes, which was supported by specific interaction with amino acids from the active site, such as His48 for PLA2s and Glu143 for the metalloproteinase. In addition, varespladib and CP471474 also showed interaction with residues from the hydrophobic channel in PLA2s and substrate binding subsites in the SVMP. Our results suggest a synergistic action of the mixed inhibitors and show the potential of varespladib, CP471474, and their mixture to generate new treatments for snakebite envenoming with application in the field or as antivenom co-adjuvants.

Molecular Characterization and In Silico Analyses of Maurolipin Structure as a Secretory Phospholipase A 2 ( sPLA 2 ) from Venom Glands of Iranian Scorpio maurus (Arachnida: Scorpionida)

The venom is a mixture of various compounds with specific biological activities, such as the phospholipase  A₂ (PLA₂) enzyme present in scorpion venom. PLA₂ plays a key role in inhibiting ryanodine receptor channels and has neurotoxic activity. This study is the first investigation of molecular characterization, cloning, and in silico analyses of PLA₂ from Iranian Scorpio maurus, named Maurolipin. After RNA extraction from S. maurus venom glands, cDNA was synthesized and amplified through RT-PCR using specific primers. Amplified Maurolipin was cloned in TA cloning vector, pTG19. For in silico analyses, the characterized gene was analyzed utilizing different software. Maurolipin coding gene with 432 base pair nucleotide length encoded a protein of 144 amino acid residues and 16.34 kilodaltons. Comparing the coding sequence of Maurolipin with other characterized PLA₂ from different species of scorpions showed that this protein was a member of the PLA₂ superfamily. According to SWISS-MODEL prediction, Maurolipin had 38.83% identity with bee venom PLA₂ with 100% confidence and 39% identity with insect phospholipase A₂ family, which Phyre2 predicted. According to the three-dimensional structure prediction, Maurolipin with five disulfide bonds has a very high similarity to the structure of PLA₂ that belonged to the group III subfamily. The in silico analyses showed that phospholipase A₂ coding gene and protein structure is different based on scorpion species and geographical condition in which they live.

Intraspecific Differences in the Venom of Crotalus durissus cumanensis from Colombia

Biochemical and biological differences in the venom of Crotalus durissus cumanensis from three ecoregions of Colombia were evaluated. Rattlesnakes were collected from the geographic areas of Magdalena Medio (MM), Caribe (CA) and Orinoquía (OR). All three regionally distributed venoms contain proteases, PLA₂s and the basic subunit of crotoxin. However, only crotamine was detected in the CA venom. The highest lethality, coagulant, phospholipase A₂ and hyaluronidase activities were found in the MM venom. Also, some differences, observed by western blot and immunoaffinity, were found in all three venoms when using commercial antivenoms. Furthermore, all three eco-regional venoms showed intraspecific variability, considering the differences in the abundance and intensity of their components, in addition to the activity and response to commercial antivenoms.

Purification, Characterization and Evaluation of the Antitumoral Activity of a Phospholipase A2 from the Snake Bothrops moojeni

Nature presents a wide range of biomolecules with pharmacological potential, including venomous animal proteins. Among the protein components from snake venoms, phospholipases (PLA₂) are of great importance for the development of new anticancer compounds. Thus, we aimed to evaluate the PLA₂ anticancer properties from Bothrops moojeni venom. The crude venom was purified through three chromatographic steps, monitored by enzymatic activity and SDS-PAGE (12%). The purified PLA₂ denominated BmPLA2 had its molecular mass and N-terminal sequence identified by mass spectrometry and Edman degradation, respectively. BmPLA2 was assayed against human epithelial colorectal adenocarcinoma cells (Caco-2), human rhabdomyosarcoma cells (RD) and mucoepidermoid carcinoma of the lung (NCI-H292), using human fibroblast cells (MRC-5) and microglia cells (BV-2) as a cytotoxicity control. BmPLA2 presented 13,836 Da and a 24 amino acid-residue homologue with snake PLA₂, which showed a 90% similarity with other Bothrops moojeni PLA₂. BmPLA2 displayed an IC₅₀ of 0.6 µM against Caco-2, and demonstrated a selectivity index of 1.85 (compared to MRC-5) and 6.33 (compared to BV-2), supporting its selectivity for cancer cells. In conclusion, we describe a new acidic phospholipase, which showed antitumor activity and is a potential candidate in the development of new biotechnological tools.

Immunorecognition and Neutralization of Crotalus durissus cumanensis Venom by a Commercial Antivenom Produced in Colombia

In Colombia, on average 2.9% of the nearly 5600 snakebite events that occur annually involve the rattlesnake Crotalus durissus cumanensis. The envenomation by this snake is mainly characterized by neurotoxicity and the main toxin is crotoxin (~64.7% of the total venom). The Instituto Nacional de Salud (INS) produces a polyvalent antivenom aimed at the treatment of bothropic, crotalid, and lachesic envenomations; nonetheless, its immune reactivity profile and neutralizing capacity over biological activities of the C. d. cumanensis venom has been poorly evaluated. In this sense, the study aims: (1) to describe an in-depth exploration of its immunoreactivity through second-generation antivenomics and HPLC fraction-specific ELISA immunoprofiles; and (2) to evaluate the neutralization pattern of the rattlesnake venom in vitro and in vivo biological activities. The results obtained showed a variable recognition of crotoxin subunits, in addition to a molecular mass-dependent immunoreactivity pattern in which the disintegrins were not recognized, and snake venom metalloproteinases and L-amino acid oxidases were the most recognized. Additionally, a high neutralization of proteolytic and coagulant activities was observed, but not over the PLA₂ activity. Further, the median effective dose against C. d. cumanensis venom lethality was 962 μL of antivenom per mg of venom. In conclusion, (1) the antivenom recognition over the crotoxin and the disintegrins of the C. d. cumanensis should be improved, thus aiming upcoming efforts for the exploration of new techniques and approaches in antivenom production in Colombia, and (2) the neutralization activity of the antivenom seems to follow the molecular mass-dependent recognition pattern, although other explanations should be explored.

Isolation and Characterization of A2-EPTX-Nsm1a, a Secretory Phospholipase A2 from Malaysian Spitting Cobra (Naja sumatrana) Venom

Phospholipase A₂ (PLA₂) toxins are one of the main toxin families found in snake venom. PLA₂ toxins are associated with various detrimental effects, including neurotoxicity, myotoxicity, hemostatic disturbances, nephrotoxicity, edema, and inflammation. Although Naja sumatrana venom contains substantial quantities of PLA₂ components_, there is limited information on the function and activities of PLA₂ toxins from the venom. In this study, a secretory PLA₂ from the venom of Malaysian N. sumatrana, subsequently named A2-EPTX-Nsm1a, was isolated, purified, and characterized. A2-EPTX-Nsm1a was purified using a mass spectrometry-guided approach and multiple chromatography steps. Based on LC-MSMS, A2-EPTX-Nsm1a was found to show high sequence similarity with PLA₂ from venoms of other Naja species. The PLA₂ activity of A2-EPTX-Nsm1 was inhibited by 4-BPB and EDTA. A2-EPTX-Nsm1a was significantly less cytotoxic in a neuroblastoma cell line (SH-SY5Y) compared to crude venom and did not show a concentration-dependent cytotoxic activity. To our knowledge, this is the first study that characterizes and investigates the cytotoxicity of an Asp49 PLA₂ isolated from Malaysian N. sumatrana venom in a human neuroblastoma cell line.

A Meta-Analysis of the Protein Components in Rattlesnake Venom

The specificity and potency of venom components give them a unique advantage in developing various pharmaceutical drugs. Though venom is a cocktail of proteins, rarely are the synergy and association between various venom components studied. Understanding the relationship between various components of venom is critical in medical research. Using meta-analysis, we observed underlying patterns and associations in the appearance of the toxin families. For Crotalus, Dis has the most associations with the following toxins: PDE; BPP; CRL; CRiSP; LAAO; SVMP P-I and LAAO; SVMP P-III and LAAO. In Sistrurus venom, CTL and NGF have the most associations. These associations can predict the presence of proteins in novel venom and understand synergies between venom components for enhanced bioactivity. Using this approach, the need to revisit the classification of proteins as major components or minor components is highlighted. The revised classification of venom components is based on ubiquity, bioactivity, the number of associations, and synergies. The revised classification can be expected to trigger increased research on venom components, such as NGF, which have high biomedical significance. Using hierarchical clustering, we observed that the genera's venom compositions were similar, based on functional characteristics rather than phylogenetic relationships.

Biochemical characterization and inhibition of thermolabile hemolysin from Vibrio parahaemolyticus by phenolic compounds

Vibrio parahaemolyticus (Vp), a typical microorganism inhabiting marine ecosystems, uses pathogenic virulence molecules such as hemolysins to cause bacterial infections of both human and marine animals. The thermolabile hemolysin VpTLH lyses human erythrocytes by a phospholipase B/A2 enzymatic activity in egg-yolk lecithin. However, few studies have been characterized the biochemical properties and the use of VpTLH as a molecular target for natural compounds as an alternative to control Vp infection. Here, we evaluated the biochemical and inhibition parameters of the recombinant VpTLH using enzymatic and hemolytic assays and determined the molecular interactions by in silico docking analysis. The highest enzymatic activity was at pH 8 and 50 °C, and it was inactivated by 20 min at 60 °C with Tm = 50.9 °C. Additionally, the flavonoids quercetin, epigallocatechin gallate, and morin inhibited the VpTLH activity with IC50 values of 4.5 µM, 6.3 µM, and 9.9 µM, respectively; while phenolics acids were not effective inhibitors for this enzyme. Boltzmann and Arrhenius equation analysis indicate that VpTLH is a thermolabile enzyme. The inhibition of both enzymatic and hemolytic activities by flavonoids agrees with molecular docking, suggesting that flavonoids could interact with the active site’s amino acids. Future research is necessary to evaluate the antibacterial activity of flavonoids against Vp in vivo.

Immunotoxicological effects triggered by the rattlesnake Crotalus durissus cumanensis, mapanare (Bothrops colombiensis) venoms and its purified fractions on spleen and lymph nodes cells

Purpose: The snakes in Venezuela vary in their different venom composition amid the species. In this sense, studies have been carried out elucidating mechanisms related to their immunostimulatory and/or immunosuppressive effects in vitro, measuring inhibition or stimulation on the mice spleen and lymph nodes lymphocytes under the rattlesnake (Crotalus durissus cumanensis) (Cdc) and mapanare (Bothrops colombiensis) crude venoms actions, and also its purified fraction crotoxin (CTX) (Cdc) and a semi-purified fraction (SPF) (Bc) activities. Material and methods: The stimulation of lymphocyte proliferation was carried out in the presence or absence of Concanavalin A (ConA) and lipopolysaccharides (LPS). Results: The lymphocyte response was measured by the Alamar Blue^® (Resazurin) assay, observing that the Crotalus crude venom increased basal proliferation in the spleen and lymph nodes, being also increased with ConA and LPS. CTX slightly decreased the proliferative response in the presence of mitogens. Both Bc venom and its SPF fraction had no significant effect on basal proliferation in the spleen and lymph nodes, but a decrease in the response with ConA was observed. These results suggest that CTX has an inhibitory action on lymphocyte proliferation, while Cdc crude venom has a stimulatory action on T and B cell populations. Bothrops colombiensis venom had no effect on these two types of cell populations. As it is known, lymphocytes are cells of enormous flexibility and can operate in diverse aspects, warranting that the correct immune response persists controlled. Conclusions: These results suggested that these different toxins can modulate lymphocyte functional activation toward an inhibitory or stimulatory state.

Sulfur Compounds as Inhibitors of Enzymatic Activity of a Snake Venom Phospholipase A2: Benzyl 4-nitrobenzenecarbodithioate as a Case of Study

Snakebite is a neglected disease with a high impact in tropical and subtropical countries. Therapy based on antivenom has limited efficacy in local tissue damage caused by venoms. Phospholipases A2 (PLA2) are enzymes that abundantly occur in snake venoms and induce several systemic and local effects. Furthermore, sulfur compounds such as thioesters have an inhibitory capacity against a snake venom PLA2. Hence, the objective of this work was to obtain a carbodithioate from a thioester with known activity against PLA2 and test its ability to inhibit the same enzyme. Benzyl 4-nitrobenzenecarbodithioate (I) was synthesized, purified, and characterized using as precursor 4-nitrothiobenzoic acid S-benzyl ester (II). Compound I showed inhibition of the enzymatic activity a PLA2 isolated from the venom of the Colombian rattlesnake Crotalus durissus cumanensis with an IC50 of 55.58 μM. This result is comparable with the reported inhibition obtained for II. Computational calculations were performed to support the study, and molecular docking results suggested that compounds I and II interact with the active site residues of the enzyme, impeding the normal catalysis cycle and attachment of the substrate to the active site of the PLA2.

Bioactive Compounds Isolated from Marine Bacterium Vibrio neocaledonicus and Their Enzyme Inhibitory Activities

Marine organisms are recognized as a source of compounds with interesting biological activities. Vibrio neocaledonicus has been reported on for its high effectiveness against corrosion in metals but it has been little studied for its chemical and biological activities. In this study, four compounds were isolated from V. neocaledonicus: indole (1); 1H-indole-3-carboxaldehyde (2); 4-hydroxybenzaldehyde (3) and Cyclo (-Pro-Tyr) (4); using a bioassay-guided method, since in a previous study it was found that the ethyl acetate extract was active on the enzymes acetylcholinesterase (AChE), alpha-glucosidase (AG) and xanthine oxidase (XO). The inhibitory activities of the three compounds against AChE, AG and XO was also evaluated. In addition, the enzymatic inhibitory activity of indole to the toxins from the venom of Bothrops asper was tested. Results showed that indole exhibited strong inhibitory activity to AG (IC50 = 18.65 ± 1.1 μM), to AChE, and XO (51.3% and 44.3% at 50 μg/mL, respectively). 1H-indole-3-carboxaldehyde displayed strong activity to XO (IC50 = 13.36 ± 0.39 μM). 4-hydroxybenzaldehyde showed moderate activity to XO (50.75% at 50 μg/mL) and weak activity to AChE (25.7% at 50 μg/mL). Furthermore, indole showed a significant in vitro inhibition to the coagulant effect induced by 1.0 μg of venom. The findings were supported by molecular docking. This is the first comprehensive report on the chemistry of V. neocaledonicus and the bioactivity of its metabolites.

Synthetic Inhibitors of Snake Venom Enzymes: Thioesters Derived from 2-Sulfenyl Ethylacetate

Snakebite envenomings are a global public health issue. The therapy based on the administration of animal-derived antivenoms has limited efficacy against the venom-induced local tissue damage, which often leads to permanent disability. Therefore, there is a need to find inhibitors against toxins responsible for local damage. This work aimed to synthesize thioesters derived from 2-sulfenyl ethylacetate and to evaluate the inhibitory effects on two snake venom toxins. Ethyl 2-((4-chlorobenzoyl)thio)acetate (I), Ethyl 2-((3-nitrobenzoyl)thio)acetate (II) and Ethyl 2-((4-nitrobenzoyl)thio)acetate (III) were synthesized and spectroscopically characterized. Computational calculations were performed to support the study. The inhibitory capacity of compounds (I–III) was evaluated on a phospholipase A₂ (Cdcum6) isolated from the venom of the Colombian rattlesnake Crotalus durissus cumanensis and the P-I type metalloproteinase Batx-I isolated from Bothrops atrox. I–III inhibited PLA₂ with IC₅₀ values of 193.2, 305.4 and 132.7 µM, respectively. Otherwise, compounds II and III inhibited the proteolytic activity of Batx-I with IC₅₀ of 2774 and 1879 µM. Molecular docking studies show that inhibition of PLA₂ may be due to interactions of the studied compounds with amino acids in the catalytic site and the cofactor Ca²⁺. Probably, a blockage of the hydrophobic channel and some amino acids of the interfacial binding surface of PLA₂ may occur.

Biochemical and pharmacological characterization of Trimersurus malabaricus snake venom

Trimeresurus malabaricus is a venomous pit viper species endemic to southwestern part of India. In earlier reports, we have shown that envenomation by T. malabaricus venom leading to strong local tissue damage but the mechanism of action is not clearly revealed. Local tissue damage affected by T. malabaricus venom is of great importance since the poison has serious systemic effects including death in the case of multiple attacks. The present study details the major manifestations of T. malabaricus venom and the induction of local tissue damage, which suggests that most toxins are present in the form of hydrolytic enzymes. Hydrolytic activity of the enzymes was measured and the data indicated that protease and phospholipase A₂ activity was high which is responsible for local tissue damage. Furthermore, the role of hydrolytic enzymes in the induction of pathological events such as hemorrhage, edema, myotoxicity, and blood coagulation examination were assessed through animal models.

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

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

Inhibitory effect of pinostrobin from Renealmia alpinia, on the enzymatic and biological activities of a PLA2

Pinostrobin is a flavanone isolated from Renealmia alpinia, a plant used in folk medicine to treat snakebites. We tested the inhibitory ability of pinostrobin on the enzymatic, anticoagulant, myotoxic and edema-inducing activities of a PLA2 isolated from Crotalus durissus cumanensis venom. The compound displayed IC50 values of 1.76mM and 1.85mM (95% Confidence intervals: 1.34-2.18 and 1.21-2.45) on the PLA2 enzymatic activity, when either aggregated or monodispersed substrates were used, respectively. When mice were injected with PLA2 preincubated with 0.4, 2.0 and 4.0mM of pinostrobin, myotoxic activity induced by the PLA2 was inhibited up to 87%. Nevertheless, these values decreased up to 56% when the pinostrobin was injected into muscle after PLA2. Pinostrobin inhibited edema-forming and anticoagulant activities of the PLA2. In order to have insights on the mode of action of pinostrobin, intrinsic fluorescence and ultraviolet studies were performed. Results suggest that pinostrobin interacts directly with the PLA2. These findings were supported by molecular docking results, which suggested that pinostrobin forms hydrogen bonds with residues His48 and Asp49 of PLA2, besides, a π-π stacking interactions with those of residues Phe5 and Trp31, and rings C of flavanone and Tyr52 of the toxin.

Novel acidic phospholipase A2 from Porthidium hyoprora causes inflammation with mast cell rich infiltrate

Phospholipases A₂ (PLA₂) are a group of enzymes that hydrolyze phospholipids at the sn-2 position, being present in all nature. In venomous animals, these proteins assume a special role, being able to exert diverse pharmacological effects. In this work, authors identified a new isoform of PLA₂ in the venom of Porthidium hyoprora, which was isolated through sequential chromatographic steps and named PhTX-III. The enzyme was characterized biochemically and structurally. Structural studies using mass spectrometry confirmed an acidic secretory PLA₂, family IIA, with molecular mass of 13,620.9 Da and identification of 86% of its primary sequence. PhTX-III did not exhibit myotoxic, anticoagulant or antibacterial effects, often present in this class of enzymes. Although, it was capable of initiate inflammatory response, with local edema and release of cytokines IL-1α, IL-6 and TNF-α, probably due to mast cell degranulation.

Neuromuscular effects of venoms and crotoxin-like proteins from Crotalus durissus ruruima and Crotalus durissus cumanensis

A myographic study was performed to compare the neuromuscular effects of venoms and crotoxin-like proteins from Crotalus durissus ruruima and Crotalus durissus cumanensis in mice phrenic-diaphragm preparation. It was concluded that both venoms present neurotoxic activity as a consequence of their crotoxin content. Furthermore, crotoxin from C.d. cumanensis is more potent than that from C.d. ruruima venom. At the concentration range in which both venoms express neurotoxic activity, only C.d. cumanensis venom also manifest a direct myotoxic effect that probably involves the synergic participation of other components than crotoxin.

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.

The biflavonoid morelloflavone inhibits the enzymatic and biological activities of a snake venom phospholipase A2

The biflavonoid morelloflavone has been reported as inhibitor of secretory PLA2s (phospholipases A2 from human synovial and bee venom sources); however, its capacity to interact and inhibit snake venom PLA2 activities has not been described. In this work we tested the inhibitory ability of morelloflavone on the enzymatic, anticoagulant, myotoxic and edema-inducing activities of a PLA2 isolated from Crotalus durissus cumanensis venom. The biflavonoid displayed IC50 values of 0.48 mM (95% Confidence intervals: 0.45-0.51) and 0.38 mM (95% Confidence intervals: 0.36-0.40) on the PLA2 enzymatic activity, when either aggregated or monodispersed substrates were used, respectively. In addition, morelloflavone inhibited in a time-dependent manner and irreversibly the PLA2 enzymatic activity. When mice were injected with PLA2 preincubated (preincubation assay) with 0.13, 0.63 and 1.26 mM of the biflavonoid, the myotoxic activity induced by the PLA2 was inhibited up to 63%. Nevertheless, these values decreased up to 38% when the morelloflavone was injected into muscle after PLA2. Moreover, morelloflavone inhibited, in a concentration-dependent manner, edema-forming activity of the PLA2 in the footpad. Morelloflavone also inhibited the anticoagulant activities of the PLA2 in concentration-dependent mode. In order to have insights on the mode of action of morelloflavone, intrinsic fluorescence studies were performed. Results of these assays suggest that morelloflavone interacts directly with the PLA2. These findings were supported by molecular docking results, which suggested that morelloflavone forms hydrogen bonds with residues Gly33, Asp49, Gly53 and Thr68 of the enzyme. In addition, our results suggested a π-π stacking interaction between rings A of morelloflavone with that of the residue Tyr52, and Van der Waals interactions with Gly32, His48 and Ala56. Our molecular modeling results suggest that morelloflavone may occupy part of substrate binding cleft of the PLA2. Morelloflavone is a candidate for the development of inhibitors to be used in snakebite envenomation.

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.

Antiplasmodial effect of the venom of Crotalus durissus cumanensis, crotoxin complex and Crotoxin B

The antiplasmodial activity of phospholipases A(2) (PLA(2)) isolated from different animals has been studied. We explored the in vitro anti Plasmodium falciparum effect of a fraction containing crotoxin, Crotoxin B and whole venom of the rattlesnake Crotalus durissus cumanensis. Fraction II (crotoxin complex) was obtained by size exclusion chromatography, whereas Crotoxin B was purified by RP-HPLC. The whole venom is active against the parasite at concentrations of 0.17±0.03 μg/ml, fraction II at 0.76±0.17 μg/ml and Crotoxin B at 0.6±0.04 μg/ml. Differences were observed in the cytotoxic activity against peripheral mononuclear cells, with Crotoxin B exhibiting the highest cytotoxicity. The concentration of Crotoxin B required to exert cytotoxic activity was higher than that required to exert antiplasmodial activity. Lethality in mice confirmed the higher toxicity and neurotoxicity of whole venom and fraction II, whereas Crotoxin B was not lethal at the doses tested. These results suggest the potential of Crotoxin B as a lead compound for antimalarial activity.

Relationship between the structure and the enzymatic activity of crotoxin complex and its phospholipase A2 subunit: an in silico approach

Crotoxin, one of the major toxins of South American rattlesnake Crotalus durissus subspecies, is an heterodimeric complex composed of two distinct subunits: a basic phospholipase A(2) (PLA(2), CB) and an acidic nontoxic catalytically inactive protein, crotapotin (CA). It's well known that CB has a high enzymatic activity; however the molecular aspects that determine this fact remain unknown. In this study, an in silico approach was used to predict the CA structure by homology modeling, and the crotoxin structure by means of molecular docking. CA structure was built using the software Modeller taking Crotalus atrox PLA(2) (1PP2:R) as a template. Different criteria measured by Procheck, Verify 3D and ProSA were indicative of the reliability and the proper fold for the predicted structural model of CA. Then, a combination of this model and CB crystal structure was used to build the structure of crotoxin complex through rigid-body protein-protein docking. The crotoxin-3D model suggested that by means of hydrophobic and π-π stacking interactions, CA-Y24 and CA-F119 interact with CB-F24 and CB-F119, respectively. Those interactions could prevent the interfacial adsorption of the CB onto the lipid/water interface by blocking part of the interfacial binding surface of the PLA(2). This fact could explain the differences regarding to enzymatic activity between the crotoxin complex and CB. In addition, the crotoxin-3D model showed solvent-exposed regions of CA that could bind the receptor expressed in target cells.

Inhibitory effects of bile acids on enzymatic and pharmacological activities of a snake venom phospholipase A(2) from group IIA

Bile acids, such as cholic acid (CA) and ursodeoxycholic acid (UDCA) have shown to decrease or increase the enzymatic activity of group IB pancreatic PLA(2), depending on the concentration used. Studies suggest that the inhibition of hydrolysis rate of the substrate is due to formation in aqueous phase of a complex between bile acid and PLA(2), which is catalytically inert. For this reason, we tested the inhibition of the enzymatic activity of group IIA snake venom PLA(2) by bile acids, using an aqueous phase model. In addition, we measured the ability of bile acids to inhibit the toxic effects caused by the mentioned toxin. UDCA and CA inhibited the enzymatic activity of the PLA(2) in a competitive mode. Moreover, these compounds inhibited myotoxic, cytotoxic and edema-forming activities induced by the toxin, but UDCA was more efficient than CA. It was demonstrated that bile acids interact directly with this protein by causing slight changes in the intrinsic fluorescence spectra. Preliminary molecular docking studies suggest that bile acids interact with amino acids at the active site of the PLA(2) through different interactions, CA showed hydrogen bonds with His48, whereas, UDCA displayed with Asp49. Results obtained herein may turn UDCA and CA into promising models for the development of new molecules with anti-inflammatory and anti-snake venom PLA(2) properties.

Biochemical and pharmacological characterization of PhTX-I a new myotoxic phospholipase A2 isolated from Porthidium hyoprora snake venom

This paper reports the biochemical and pharmacological characterization of a new myotoxic PLA(2) (EC 3.1.1.4) called PhTX-I, purified from Porthidium hyoprora venom by one step analytical chromatography reverse phase HPLC. The homogeneity of the PhTX-I fraction and its molecular mass were initially evaluated by SDS-PAGE and confirmed by MALDI-TOF spectrometry, indicating a molecular mass of 14.249Da and constituted of a single polipeptidic chain. Amino acid sequence was determined by "de novo sequencing," in tandem mass spectrometry, belonging to D49-PLA(2) enzyme class and exhibiting high identity (44-90%) with other myotoxics PLA(2) from snake venoms. The enzymatic investigation showed maximal activity at pH 8 and 35-45°C. This activity was dependent on Ca(2+), other cations (Mg(2+), Mn(2+), Cd(2+) and Zn(2+)) reduced notably the enzymatic activity, suggesting that the arrangement of the catalytic site presents an exclusive structure for Ca(2+). Ex vivo, whole venom and PhTX-I PLA(2) caused blockade of the neuromuscular transmission in young chick biventer cervicis preparations similar to other isolated snake venom toxins from the Bothrops genus. In vivo, both induced local myotoxicity and systemic interleukin-6 response upon intramuscular injection, additionally, induced moderate footpad edema. In vitro, both induced low cytotoxicity in skeletal muscle myoblasts, however PhTX-I PLA(2) was able to lyse myotubes.

Biological and biochemical characterization of two new PLA2 isoforms Cdc-9 and Cdc-10 from Crotalus durissus cumanensis snake venom

This work reports the purification, biological characterization and amino acid sequence of two new basic PLA(2) isoforms, Cdc-9 and Cdc-10, purified from the Crotalus durissus cumanensis venom by one step analytical chromatography reverse phase HPLC. The molecular masses of the PLA(2) were 14,175+/-2.7 Da for Cdc-9 and 14,228+/-3.5 Da for Cdc-10 both deduced by primary structure and confirmed by MALDI-TOF. The isoforms presented an amino acid sequence of 122 amino acid residues, being Cdc-9: SLVQFNKMIK FETRKSGLPF YAAYGCYCGW GGQRPKDATD RCCFVHDCCY GKVAKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLS TYKNEYMFYP DSRCREPPEY TC with pI value of 8.25 and Cdc-10: SLLQFNKMIK FETRKSGVPF YAAYGCYCGW GGRRPKDPTD RCCFVHDCCY GKLTKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLN TYKNEYMFYP DSRCRGPPEY TC with a pI value of 8.46, showing highly conserved Ca(2+)-binding and catalytic sites. The PLA(2) activity decreased when the isoforms Cdc-9 and Cdc-10 were incubated with 4-bromophenacyl bromide (p-BPB), anhydrous acetic acid and p-nitrobenzene sulfonyl fluoride (NBSF) when compared with the activity of both native isoforms. In mice, the PLA(2) isoforms Cdc-9 and Cdc-10 induced myonecrosis and edema. Myotoxic and edema activities were reduced after treatment of the isoforms with p-BPB; acetylation of the lysine residues and the treatment of PLA(2) with NBSF have also induced edema reduction. However, p-BPB strongly diminishes the local and systemic myotoxic effects.