Differential mode of attack on membrane phospholipids by an acidic phospholipase A2 (RVVA-PLA2-I) from Daboia russelli venom

Monitoring Snake Venom-Induced Extracellular Matrix Degradation and Identifying Proteolytically Active Venom Toxins Using Fluorescently Labeled Substrates

Snakebite envenoming is an important public health issue with devastating consequences and annual mortality rates that range between 81,000 and 138,000. Snake venoms may cause a range of pathophysiological effects affecting the nervous system and the cardiovascular system. Moreover, snake venom may have tissue-damaging activities that result in lifelong morbidities such as amputations, muscle degeneration, and organ malfunctioning. The tissue-damaging components in snake venoms comprise multiple toxin classes with various molecular targets including cellular membranes and the extracellular matrix (ECM). In this study, we present multiple assay formats that enable investigation of snake venom-induced ECM degradation using a variety of (dye-quenched) fluorescently labeled ECM components. Using a combinatorial approach, we were able to characterise different proteolytic profiles for different medically relevant snake venoms, followed by identification of the responsible components within the snake venoms. This workflow could provide valuable insights into the key mechanisms by which proteolytic venom components exert their effects and could therefore prove useful for the development of effective snakebite treatments against this severe pathology.

Unlocking the potential of snake venom-based molecules against the malaria, Chagas disease, and leishmaniasis triad

Malaria, leishmaniasis and Chagas disease are vector-borne protozoal infections with a disproportionately high impact on the most fragile societies in the world, and despite malaria-focused research gained momentum in the past two decades, both trypanosomiases and leishmaniases remain neglected tropical diseases. Affordable effective drugs remain the mainstay of tackling this burden, but toxicicty, inneficiency against later stage disease, and drug resistance issues are serious shortcomings. One strategy to overcome these hurdles is to get new therapeutics or inspiration in nature. Indeed, snake venoms have been recognized as valuable sources of biomacromolecules, like peptides and proteins, with antiprotozoal activity. This review highlights major snake venom components active against at least one of the three aforementioned diseases, which include phospholipases A2, metalloproteases, L-amino acid oxidases, lectins, and oligopeptides. The relevance of this repertoire of biomacromolecules and the bottlenecks in their clinical translation are discussed considering approaches that should increase the success rate in this arduous task. Overall, this review underlines how venom-derived biomacromolecules could lead to pioneering antiprotozoal treatments and how the drug landscape for neglected diseases may be revolutionized by a closer look at venoms. Further investigations on poorly studied venoms is needed and could add new therapeutics to the pipeline.

Neutrophil-mediated erythrophagocytosis following Russell's viper (Daboia russelii) bite

Snakebite envenomation is regarded as a high-priority neglected tropical disease by the World Health Organisation, as it results in significant loss of lives and permanent disabilities. Russell's viper is one of the snakes that causes morbidities, mortalities and disabilities in India. The clinical presentation of Russell's viper envenomation is characterised by local envenoming effects, tissue damage, venom-induced coagulopathy, neurotoxicity, and kidney injury. However, venom composition and its mechanisms of toxicity are highly variable even within snakes of the same species including Russell's viper. This variation in venom composition results in a broad range of clinical complications. Here we present a previously undocumented case of neutrophil-mediated erythrophagocytosis in a healthy 28-year-old female following Russell's viper bite. Systemic envenomation effects and bleeding abnormalities in this patient were corrected by the administration of polyvalent antivenom. Two days later, the patient developed progressive swelling and ecchymosis in the bitten limb. Observed abnormal limits within blood testing were followed up by a peripheral blood smear where it was found that 30% of neutrophils had phagocytosed erythrocytes as they were found within the cytoplasm. The patient underwent a fasciotomy for compartmental syndrome and received packed red cells and a course of corticosteroids. Following this treatment, the patient made a full recovery. This case report outlines a previously undocumented pathological event induced by Russell's viper envenomation, guiding diagnosis and treatment. Clinicians' knowledge of the mechanisms of toxicity of Russell's viper envenomation and its clinical manifestations are essential for improving the treatment of snakebites to achieve positive outcomes.

A strategy for the enrichment and characterization of disulfide bond-contained proteins from Chinese cobra (Naja atra) venom

A new strategy combined gold-coated magnetic nanocomposites assisted enrichment with mass spectrometry was developed for the characterization of disulfide bond-contained proteins from Chinese cobra (Naja atra) venom. In this work, core-shell nanocomposites were synthesized by the seed-mediated growth method and used for the enrichment of snake venom proteins containing disulfide bonds. A total of 3545 tryptic digested peptides derived from 96 venom proteins in Naja atra venom were identified. The venom proteins comprised 14 toxin families including three-finger toxins, phospholipase A₂ , snake venom metalloproteinase, cobra venom factor, and so forth. Extra 16 venom proteins were detected exclusively in the nanocomposites set, among which 11 venom proteins were from the three-finger toxins family. In the present study, the proposed simple and efficient protocol replaced the tedious and laborious technologies commonly used for pre-separating crude snake venom, suggesting widely implementation in low-abundance or trace disulfide bond-contained proteins or peptides characterization.

Assessment of quality and pre-clinical efficacy of a newly developed polyvalent antivenom against the medically important snakes of Sri Lanka

Snake envenomation is a severe problem in Sri Lanka (SL) and Indian polyvalent antivenom (PAV) is mostly used for treating snakebite albeit due to geographical variation in venom composition, Indian PAV shows poor efficacy in neutralizing the lethality and toxicity of venom from the same species of snakes in SL. Therefore, the quality and in vivo venom neutralization potency of a country-specific PAV produced against the venom of the five most medically important snakes of SL (Daboia russelii, Echis carinatus, Hypnale hypnale, Naja naja, Bungarus caeruleus) was assessed. LC-MS/MS analysis of two batches of PAV showed the presence of 88.7-97.2% IgG and traces of other plasma proteins. The tested PAVs contained minor amounts of undigested IgG and F(ab')2 aggregates, showed complement activation, were devoid of IgE, endotoxin, and content of preservative was below the threshold level. Immunological cross-reactivity and in vitro neutralization of enzymatic activities, pharmacological properties demonstrated superior efficacy of SL PAV compared to Indian PAV against SL snake venoms. The in vivo neutralization study showed that the tested PAVs are potent to neutralize the lethality and venom-induced toxicity of SL snake venoms. Therefore, our study suggests that introduction of SL-specific PAV will improve snakebite management in SL.

Biogeographic venom variation in Russell's viper (Daboia russelii) and the preclinical inefficacy of antivenom therapy in snakebite hotspots

BACKGROUND

Snakebite in India results in over 58,000 fatalities and a vast number of morbidities annually. The majority of these clinically severe envenomings are attributed to Russell's viper (Daboia russelii), which has a near pan-India distribution. Unfortunately, despite its medical significance, the influence of biogeography on the composition and potency of venom from disparate D. russelii populations, and the repercussions of venom variation on the neutralisation efficacy of marketed Indian antivenoms, remain elusive.

METHODS

Here, we employ an integrative approach comprising proteomic characterisation, biochemical analyses, pharmacological assessment, and venom toxicity profiling to elucidate the influence of varying ecology and environment on the pan-Indian populations of D. russelii. We then conducted in vitro venom recognition experiments and in vivo neutralisation assays to evaluate the efficacy of the commercial Indian antivenoms against the geographically disparate D. russelii populations.

FINDINGS

We reveal significant intraspecific variation in the composition, biochemical and pharmacological activities and potencies of D. russelii venoms sourced from five distinct biogeographic zones across India. Contrary to our understanding of the consequences of venom variation on the effectiveness of snakebite therapy, commercial antivenom exhibited surprisingly similar neutralisation potencies against the majority of the investigated populations, with the exception of low preclinical efficacy against the semi-arid population from northern India. However, the ability of Indian antivenoms to counter the severe morbid effects of Daboia envenoming remains to be evaluated.

CONCLUSION

The concerning lack of antivenom efficacy against the north Indian population of D. russelii, as well as against two other 'big four' snake species in nearby locations, underscores the pressing need to develop pan-India effective antivenoms with improved efficacy in high snakebite burden locales.

Binding of a Naja naja venom acidic phospholipase A2 cognate complex to membrane-bound vimentin of rat L6 cells: Implications in cobra venom-induced cytotoxicity

An acidic phospholipase A₂ enzyme (NnPLA₂-I) interacts with three finger toxins (cytotoxin and neurotoxin) from Naja naja venom to form cognate complexes to enhance its cytotoxicity towards rat L6 myogenic cells. The cytotoxicity was further enhanced in presence of trace quantity of venom nerve growth factor. The purified rat myoblast cell membrane protein showing interaction with NnPLA₂-I was identified as vimentin by LC-MS/MS analysis. The ELISA, immunoblot and spectrofluorometric analyses showed greater binding of NnPLA₂-I cognate complex to vimentin as compared to the binding of individual NnPLA₂-I. The immunofluorescence and confocal microscopy studies evidenced the internalization of NnPLA₂-I to partially differentiated myoblasts post binding with vimentin in a time-dependent manner. Pre-incubation of polyvalent antivenom with NnPLA₂-I cognate complex demonstrated better neutralization of cytotoxicity towards L6 cells as compared to exogenous addition of polyvalent antivenom 60-240 min post treatment of L6 cells with cognate complex suggesting clinical advantage of early antivenom treatment to prevent cobra venom-induced cytotoxicity. The in silico analysis showed that 19-22 residues, inclusive of Asp48 residue, of NnPLA₂-I preferentially binds with the rod domain (99-189 and 261-335 regions) of vimentin with a predicted free binding energy (ΔG) and dissociation constant (K_D) values of -12.86 kcal/mol and 3.67 × 10^-10 M, respectively; however, NnPLA₂-I cognate complex showed greater binding with the same regions of vimentin indicating the pathophysiological significance of cognate complex in cobra venom-induced cytotoxicity.

First Report of Plant-Derived β-Sitosterol with Antithrombotic, in Vivo Anticoagulant, and Thrombus-Preventing Activities in a Mouse Model

Inhibitors of thrombin, a key enzyme in the blood coagulation cascade, are of great interest because of their selective specificity and effectiveness in anticoagulation therapy against cardiovascular disorders. The natural soybean phytosterol, β-sitosterol (BSS) demonstrated anticoagulant activity by dose-dependent inhibition of thrombin in an uncompetitive manner with a K_i value of 0.267 μM as well as by partial inhibition of thrombin-catalyzed platelet aggregation with a half-maximal inhibitory concentration (IC₅₀) value of 10.45 ± 2.88 μM against platelet-rich plasma and 9.2 ± 1.2 μM against washed platelets. An in silico study indicated binding of BSS to thrombin, which was experimentally verified by spectrofluorometric and isothermal calorimetric analyses. Under in vitro conditions, BSS demonstrated thrombolytic activity by activating plasminogen, albeit it is devoid of protease (fibrinogenolytic) activity. BSS was noncytotoxic to mammalian cells, nonhemolytic, demonstrated its in vivo anticoagulant activity when administered orally, and inhibited k-carrageen-induced thrombus formation in the tails of mice. Our results suggest that dietary supplementation of BSS may help to prevent thrombosis-associated cardiovascular disorders.

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

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

Proteomic analysis reveals geographic variation in venom composition of Russell's Viper in the Indian subcontinent: implications for clinical manifestations post-envenomation and antivenom treatment

INTRODUCTION

The Russell's Viper (RV) (Daboia russelii), a category I medically important snake, is responsible for a significant level of morbidity and mortality in the Indian sub-continent. Areas covered: The current review highlights the variation in RV venom (RVV) composition from different geographical locales on the Indian sub-continent, as revealed by biochemical and proteomic analyses. A comparison of these RVV proteomes revealed significant differences in the number of toxin isoforms and relative toxin abundances, highlighting the impact of geographic location on RVV composition. Antivenom efficacy studies have shown differential neutralization of toxicity and enzymatic activity of different RVV samples from the Indian sub-continent by commercial polyvalent antivenom (PAV). The proteome analysis has provided deeper insights into the variation of RVV composition leading to differences in antivenom efficacy and severity of clinical manifestations post RV-envenomation across the Indian sub-continent. Expert commentary: Variation in RVV antigenicity due to geographical differences and poor recognition of low molecular mass (<20 kDa) RVV toxins by PAV are serious concerns for effective antivenom treatment against RV envenomation. Improvements in immunization protocols that take into account the poorly immunogenic components and geographic variation in RVV composition, can lead to better hospital management of RV bite patients.

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

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

First report of the characterization of a snake venom apyrase (Ruviapyrase) from Indian Russell's viper (Daboia russelii) venom

A novel apyrase from Russell's viper venom (RVV) was purified and characterized, and it was named Ruviapyrase (Russell's viper apyrase). It is a high molecular weight (79.4 kDa) monomeric glycoprotein that contains 2.4% neutral sugars and 58.4% N-linked oligosaccharides and strongly binds to Concanavalin A. The LC-MS/MS analysis did not identify any protein in NCBI protein database, nevertheless some de novo sequences of Ruviapyrase showed putative conserved domain of apyrase superfamily. Ruviapyrase hydrolysed adenosine triphosphate (ATP) to a significantly greater extent (p < .05) as compared to adenosine diphosphate (ADP); however, it was devoid of 5'-nucleotidase and phosphodiesterase activities. The Km and Vmax values for Ruviapyrase towards ATP were 2.54 μM and 615 μM of Pi released min-1, respectively with a turnover number (Kcat) of 24,600 min-1. Spectrofluorometric analysis demonstrated interaction of Ruviapyrase with ATP and ADP at Kd values of 0.92 nM and 1.25 nM, respectively. Ruviapyrase did not show cytotoxicity against breast cancer (MCF-7) cells and haemolytic activity, it exhibited marginal anticoagulant and strong antiplatelet activity, and dose-dependently reversed the ADP-induced platelet aggregation. The catalytic activity and platelet deaggregation property of Ruviapyrase was significantly inhibited by EDTA, DTT and IAA, and neutralized by commercial monovalent and polyvalent antivenom.

Single Chain Antibody Fragment against Venom from the Snake Daboia russelii formosensis

Russell's vipers containing hemotoxic and neurotoxic venom commonly cause snake envenomation. Horse-derived antivenom is a specific antidote, but its production is expensive and has side effects. Developing a cost-effective and more tolerable therapeutic strategy is favorable. In this study, using glutaraldehyde-attenuated Daboia russelii formosensis (DRF) venom proteins to immunize chickens, polyclonal yolk-immunoglobulin (IgY) antibodies were generated and showed a specific binding affinity. Phage display technology was used to generate two antibody libraries of single-chain variable fragments (scFvs) containing 3.4 × 10⁷ and 5.5 × 10⁷ transformants, respectively. Phage-based ELISA indicated that specific clones were enriched after bio-panning. The nucleotide sequences of scFv-expressing clones were analyzed and classified into six groups in the short linker and four groups in the long linker. These scFv antibodies specifically bound to DRF proteins, but not other venom proteins. Mass spectrometric data suggested that these scFv antibodies may recognize phospholipase A2 RV-4 or RV-7. In vivo studies showed that anti-DRF IgY exhibited complete protective effects and mixed scFv antibodies increased the survival rate and time of mice challenged with a lethal dose of DRF proteins. These antibodies can be potentially applied in a rapid diagnostic method or for treatment in the future.

Unraveling the Proteome Composition and Immuno-profiling of Western India Russell's Viper Venom for In-Depth Understanding of Its Pharmacological Properties, Clinical Manifestations, and Effective Antivenom Treatment

The proteome composition of western India (WI) Russell's viper venom (RVV) was correlated with pharmacological properties and pathological manifestations of RV envenomation. Proteins in the 5-19 and 100-110 kDa mass ranges were the most predominate (∼35.1%) and least abundant (∼3.4%) components, respectively, of WI RVV. Non-reduced SDS-PAGE indicated the occurrence of multiple subunits, non-covalent oligomers, self-aggregation, and/or interactions among the RVV proteins. A total of 55 proteins belonging to 13 distinct snake venom families were unambiguously identified by ESI-LC-MS/MS analysis. Phospholipase A2 (32.5%) and Kunitz-type serine protease inhibitors (12.5%) represented the most abundant enzymatic and non-enzymatic proteins, respectively. However, ATPase, ADPase, and hyaluronidase, detected by enzyme assays, were not identified by proteomic analysis owing to limitations in protein database deposition. Several biochemical and pharmacological properties of WI RVV were also investigated. Neurological symptoms exhibited by some RV-bite patients in WI may be correlated to the presence of neurotoxic phospholipase A2 enzymes and Kunitz-type serine protease inhibitor complex in this venom. Monovalent antivenom was found to be better than polyvalent antivenom in immuno-recognition and neutralization of the tested pharmacological properties and enzyme activities of WI RVV; nevertheless, both antivenoms demonstrated poor cross-reactivity and neutralization of pharmacological activities shown by low-molecular-mass proteins (<18 kDa) of this venom.

Proteomic analysis to unravel the complex venom proteome of eastern India Naja naja: Correlation of venom composition with its biochemical and pharmacological properties

The complex venom proteome of the eastern India (EI) spectacled cobra (Naja naja) was analyzed using tandem mass spectrometry of cation-exchange venom fractions. About 75% of EI N. naja venom proteins were <18kDa and cationic at physiological pH of blood. SDS-PAGE (non-reduced) analysis indicated that in the native state venom proteins either interacted with each-other or self-aggregated resulting in the formation of higher molecular mass complexes. Proteomic analysis revealed that 43 enzymatic and non-enzymatic proteins in EI N. naja venom with a percent composition of about 28.4% and 71.6% respectively were distributed over 15 venom protein families. The three finger toxins (63.8%) and phospholipase A₂s (11.4%) were the most abundant families of non-enzymatic and enzymatic proteins, respectively. nanoLC-ESI-MS/MS analysis demonstrated the occurrence of acetylcholinesterase, phosphodiesterase, cholinesterase and snake venom serine proteases in N. naja venom previously not detected by proteomic analysis. ATPase, ADPase, hyaluronidase, TAME, and BAEE-esterase activities were detected by biochemical analysis; however, due to a limitation in the protein database depository they were not identified in EI N. naja venom by proteomic analysis. The proteome composition of EI N. naja venom was well correlated with its in vitro and in vivo pharmacological properties in experimental animals and envenomed human.

BIOLOGICAL SIGNIFICANCE

Proteomic analysis reveals the complex and diverse protein profile of EI N. naja venom which collectively contributes to the severe pathophysiological manifestation upon cobra envenomation. The study has also aided in comprehending the compositional variation in venom proteins of N. naja within the Indian sub-continent. In addition, this study has also identified several enzymes in EI N. naja venom which were previously uncharacterized by proteomic analysis of Naja venom.

A proteomic analysis of Pakistan Daboia russelii russelii venom and assessment of potency of Indian polyvalent and monovalent antivenom

To address the dearth of knowledge on the biochemical composition of Pakistan Russell's Viper (Daboia russelii russelii) venom (RVV), the venom proteome has been analyzed and several biochemical and pharmacological properties of the venom were investigated. SDS-PAGE (reduced) analysis indicated that proteins/peptides in the molecular mass range of ~56.0-105.0kDa, 31.6-51.0kDa, 15.6-30.0kDa, 9.0-14.2kDa and 5.6-7.2kDa contribute approximately 9.8%, 12.1%, 13.4%, 34.1% and 30.5%, respectively of Pakistan RVV. Proteomics analysis of gel-filtration peaks of RVV resulted in identification of 75 proteins/peptides which belong to 14 distinct snake venom protein families. Phospholipases A2 (32.8%), Kunitz type serine protease inhibitors (28.4%), and snake venom metalloproteases (21.8%) comprised the majority of Pakistan RVV proteins, while 11 additional families accounted for 6.5-0.2%. Occurrence of aminotransferase, endo-β-glycosidase, and disintegrins is reported for the first time in RVV. Several of RVV proteins/peptides share significant sequence homology across Viperidae subfamilies. Pakistan RVV was well recognized by both the polyvalent (PAV) and monovalent (MAV) antivenom manufactured in India; nonetheless, immunological cross-reactivity determined by ELISA and neutralization of pro-coagulant/anticoagulant activity of RVV and its fractions by MAV surpassed that of PAV.

BIOLOGICAL SIGNIFICANCE

The study establishes the proteome profile of the Pakistan RVV, thereby indicating the presence of diverse proteins and peptides that play a significant role in the pathophysiology of RVV bite. Further, the proteomic findings will contribute to understand the variation in venom composition owing to different geographical location and identification of pharmacologically important proteins in Pakistan RVV.

Biochemical and monolayer characterization of Tunisian snake venom phospholipases

The present study investigated the kinetic and interfacial properties of two secreted phospholipases isolated from Tunisian vipers'venoms: Cerastes cerastes (CC-PLA2) and Macrovipera lebetina transmediterranea (MVL-PLA2). Results show that these enzymes have great different abilities to bind and hydrolyse phospholipids. Using egg-yolk emulsions as substrate at pH 8, we found that MVL-PLA2 has a specific activity of 1473U/mg at 37°C in presence of 1mM CaCl2. Furthermore the interfacial kinetic and binding data indicate that MVL-PLA2 has a preference to the zwitterionic phosphatidylcholine monolayers (PC). Conversely, CC-PLA2 was found to be able to hydrolyse preferentially negatively charged head group phospholipids (PG and PS) and exhibits a specific activity 9 times more important (13333U/mg at 60°C in presence of 3mM CaCl2). Molecular models of both CC-PLA2 and MVL-PLA2 3D structures have been built and their electrostatic potentials surfaces have been calculated. A marked anisotropy of the overall electrostatic charge distribution leads to a significantly difference in the dipole moment intensity between the two enzymes explaining the great differences in catalytic and binding properties, which seems to be governed by the electrostatic and hydrophobic forces operative at the surface of the two phospholipases.

Anticancer properties of phospholipase A2 from Daboia siamensis venom on human skin melanoma cells

Background

Phospholipase A₂ (PLA₂) is a major component of the Daboia siamensis venom, which is able to hydrolyse the membrane of various cells. For this reason, the activity of PLA₂ was investigated regarding its pharmaceutical properties. This study was conducted to explore the pharmacological properties of a PLA₂ from Daboia siamensis (dssPLA₂) venom on human skin melanoma cell line (SK-MEL-28).

Methods

dssPLA₂ was isolated by ion exchange and gel filtration columns. Various concentrations of dssPLA₂ were investigated for cytotoxic activity and inhibition of migration on SK-MEL-28 cells. Cell death analysis, mRNA expression levels of Notch I-III and BRAF V600E genes were also determined.

Results

dssPLA₂ exhibited cytotoxicity on SK-MEL-28 for 24 and 72 h as compared with untreated cells. However, it had no toxic effects on CCD-1064sk cells under the same conditions. dssPLA₂ (0.25 and 0.5 μg/mL) induced 17.16 and 30.60 % of apoptosis, while activated 6.53 and 7.05 % of necrotic cells. dssPLA₂ at 0.25, 0.5, 1 and 2 μg/mL could inhibit migration on SK-MEL-28 cells for 24 h by 31.06, 41.66, 50 and 68.75 %, respectively. The action of dssPLA₂ significantly reduced the levels of Notch I and BRAF V600E genes expression on SK-MEL-28 cells compared with untreated cells at 72 h.

Conclusions

This study indicates that dssPLA₂ had potential effects of apoptosis, necrosis, cytotoxicity and inhibition of migration on SK-MEL-28 cells. dssPLA₂ could possibly be a selective agent that targets cancer cells without affecting normal cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s40409-016-0061-z) contains supplementary material, which is available to authorized users.

Antibacterial activity of an acidic phospholipase A2 (NN-XIb-PLA2) from the venom of Naja naja (Indian cobra)

The resistance of bacteria against the use of conventional antibiotics has become a serious threat to public health and considering the associated side effect with antibiotics; new strategies to find and develop new molecules with novel modes of action has received grate attention in recent years. In this study, when the antibacterial potential of an acidic protein—NN-XIb-PLA₂ (Naja naja venom phospholipase A₂ fraction—XIb) of Naja naja venom was evaluated, it showed significant bactericidal action against the human pathogenic strains tested. It inhibited more effectively the gram positive bacteria like Staphylococcus aureus and Bacillus subtilis, when compared to gram negative bacteria like Escherichia coli, Vibrio cholerae, Klebsiell pneumoniae and Salmonella paratyphi. It inhibited the bacterial growth, with a MIC values ranging from 17 to 20 µg/ml. It was interesting to observe that NN-XIb-PLA₂ showed comparable antibacterial activity to the used standards antibiotics. It was found that their was a strong correlation between PLA₂ activities, hemolytic and antibacterial activity. Furthermore, it is found that in the presence of p-bromophenacyl bromide (p-BPB), there is a significant decrease in enzymatic activity and associated antibacterial activities, suggesting that a strong association exists between catalytic activity and antimicrobial effects, which thereby destabilize the membrane bilayer. These studies encourage further in dept study on molecular mechanisms of bactericidal properties of NN-XIb-PLA₂ and thereby help in development of this protein into a possible therapeutic lead molecule for treating bacterial infections.

Cytolytic and systemic toxic effects induced by the aqueous extract of the fire coral Millepora alcicornis collected in the Mexican Caribbean and detection of two types of cytolisins

BACKGROUND

Millepora alcicornis is a branching hydrocoral common throughout the Caribbean Sea. Like other members of this genus, this species is capable of inducing skin eruptions and blisters with severe pain after contact. In the present study, we investigated the toxicity of the M. alcicornis aqueous extract on several animal models. Considering that some cnidarian hemolysins have been associated to local tissue damage, since they also induce lysis of other cell types, we also made a partial characterization of the hemolytic activity of M. alcicornis aqueous extract. This information is important for understanding the defense mechanisms of the "fire corals".

METHODS

The effects of pH, temperature, and some divalent cations on the hemolytic activity of the extract were assayed, followed by a zymogram analysis to detect the cytolysins and determine their approximate molecular weight. The toxicity of the aqueous extract was assayed in mice, by intravenous administration, and histopathological changes on several tissues were analyzed by light microscopy. The toxicity of the extract was also tested in Artemia salina nauplii, and the damages caused on the crustaceans were analyzed by transmission and scanning electron microscopy.

RESULTS

The hemolytic activity of the hydrocoral extract was enhanced in the presence of Ca(2+) (≥2 mM), Mg(2+) (≥6 mM), and Ba(2+) (≥0.1 mM); however, it was reduced in the presence of Cu(2+) (≥0.1 mM), Zn(2+) (≥6 mM), and EDTA (≥0.34 mM). Differences in the pH did not affect the hemolytic activity, but it was temperature-sensitive, since preincubation at ≥ 50 °C sharply reduced hemolysis. The zymogram showed the presence of two types of hemolysins: ~ 28-30 kDa proteins with phospholipase A2 activity and ~ 200 kDa proteins that do not elicit enzymatic activity. The aqueous extract of this cnidarian was lethal to mice (LD50 = 17 μg protein/g), and induced kidney, liver, and lung damages. Under denaturing conditions, the aqueous extract completely lost its toxic and hemolytic activities.

CONCLUSIONS

The results showed that the M. alcicornis aqueous extract contains two types of thermolabile hemolysins: proteins of approximately 28-30 kDa with PLA2 activity, while the others are larger proteins of approximately 200 kDa, which do not possess PLA2 activity. Those thermolabile cytolysins, which are stable to pH changes and whose activity is calcium dependent, are capable of inducing damage in lung, kidney and liver tissues, resulting in a slow death of mice. M. alcicornis cytolysins also provoke tissue dissociation in Artemia salina nauplii that might be attributed to pore forming mechanisms.

Elucidation of procoagulant mechanism and pathophysiological significance of a new prothrombin activating metalloprotease purified from Daboia russelii russelii venom

The procoagulant proteases present in Russell's Viper venom (RVV) are responsible for promoting consumption coagulopathy in victims. In this study, a procoagulant metalloprotease (Rusviprotease) possessing prothrombin activating and α-fibrinogenase properties has been purified and characterized from RVV. Rusviprotease is a 26.8 kDa glycoprotein which also exists in other multimeric forms. The peptide mass fingerprinting and secondary structure analyses of Rusviprotease revealed its similarity with snake venom prothrombin activators and metalloproteases. Similar to group A prothrombin activators, Rusviprotease cleaved prothrombin independent of any co-factor requirement generating meizothrombin which is further cleaved to form thrombin. The Km and Vmax values of Rusviprotease towards prothrombin were determined to be 1.73 μM, and 153.5 nM thrombin generated/min/μmoles of Rusviprotease, respectively. The Km and Vmax values of Rusviprotease towards fibrinogen were calculated to be 3.14 μM and 78.7 nmol/min, respectively. Spectrofluorometric study provided the evidence of interaction between Rusviprotease and factor Xa with a Kd value of 6.64 nM. This interaction augmented the prothrombin activating property of the factor Xa-prothrombinase-Rusviprotease complex by 2.5 fold. Intravenous injection of Rusviprotease to BALB/c mice (0.1 mg/kg) resulted in in vivo defibrinogenation rendering the blood incoagulable. In conclusion, Rusviprotease is the first example of a prothrombin activator with fibrinogenolytic property purified from Daboia russelii russelii venom.

Antibacterial potential of a basic phospholipase A2 (VRV-PL-VIIIa) from Daboia russelii pulchella (Russell's viper) venom

Background

Microbial/bacterial resistance against antibiotics poses a serious threat to public health. Furthermore, the side effects of these antibiotics have stimulated tremendous interest in developing new molecules from diverse organisms as therapeutic agents. This study evaluates the antibacterial potential of a basic protein, Vipera russellii venom phospholipase A₂ fraction VIIIa (VRV-PL-VIIIa), from Daboia russelii pulchella venom against gram-positive and gram-negative bacteria.

Methods

The antibacterial potential of VRV-PL-VIIIa in the presence and absence of an inhibitor (p-bromophenacyl bromide) was tested against gram-positive and gram-negative bacteria and the minimum inhibitory concentration was determined by microdilution tests.

Results

VRV-PL-VIIIa demonstrated potent antibacterial activities against all the human pathogenic strains tested. It more effectively inhibited such gram-positive bacteria as Staphylococcus aureus and Bacillus subtilis, when compared to the gram-negative bacteria Escherichia coli, Vibrio cholerae, Klebsiella pneumoniae and Salmonella paratyphi. It inhibited bacterial growth at minimum inhibitory concentration values ranging from 11.1 to 19.2 μg/mL. The anti-bacterial potential of VRV-PL-VIIIa was comparable to the standards gentamycin, chlorophenicol and streptomycin. The PLA₂’s hemolytic and antibacterial activities were strongly correlated. Furthermore, even in the presence of p-bromophenacyl bromide, intense antibacterial activity was observed, suggesting a dissociation or partial overlapping of the bactericidal/antimicrobial domains.

Conclusion

VRV-PL-VIIIa demonstrated potent antibacterial activities against all the human pathogenic strains tested. The study shows that despite a strong correlation between enzymatic and antimicrobial activities of VRV-PL-VIIIa, it may possess additional properties that mimic the bactericidal/membrane permeability-increasing protein. This study encourages further in-depth studies on the molecular mechanisms of antibacterial properties of VRV-PL-VIIIa, which would thereby facilitate development of this protein into a possible therapeutic lead molecule for treating bacterial infections.

Biochemical and pharmacological characterization of a toxic fraction and its cytotoxin-like component isolated from Russell's viper (Daboia russelii russelii) venom

The pathophysiological significance of a toxic fraction (GF-VI DEAE-II) isolated from Russell's viper venom (RVV) is characterized. GF-VI DEAE-II represents 1.6% of the total RVV protein and it comprises of a 27.6kDa minor component (RP-I) (0.04%, w/w) and a major 6.6kDa non-enzymatic peptide (1.11%, w/w), named Rusvitoxin. The LC-MS/MS analysis of RP-I showed its identity to snake venom serine proteases, whereas Rusvitoxin demonstrated its close identity with snake venom three finger toxins, cytotoxins and cardiotoxins particularly from Naja sp. GF-VI DEAE-II was found to be non-cytotoxic to the tested mammalian cancer cells and non-hemolytic; nevertheless, it demonstrated α-fibrin(ogen)ase activity and in vivo toxicity in BALB/c mice with an LD50 (i.p.) of 2.3mg/kg. GF-VI DEAE-II induced lethargy and hind-leg paralysis in mice within 10min of i.p. injection. GF-VI DEAE-II induced hyperfibrinogenomia, and significantly altered (p<0.05) the plasma levels of factor X, pro- and anti-inflammatory cytokines viz. TNF-α, IL-6 and IL-10 in treated mice. Histological observations of tissues and biochemical properties of serum from GF-VI DEAE-II-treated mice suggested multiple organ dysfunctions. Conversely, Rusvitoxin at a dose of 5mg/kg did not induce toxicity in BALB/c mice. At 1:15 (antigen: antivenom, w/w) ratio, commercially polyvalent and monovalent antivenoms neutralized more than 80% of the fibrinolytic and anticoagulant activities of GF-VI DEAE-II. The present study suggests the significant role of GF-VI DEAE-II in RVV-induced pathogenesis in victim/prey.

Anticoagulant mechanism and platelet deaggregation property of a non-cytotoxic, acidic phospholipase A2 purified from Indian cobra (Naja naja) venom: inhibition of anticoagulant activity by low molecular weight heparin

In the present study, anticoagulant and platelet modulating activities of an acidic phospholipase A2 (NnPLA2-I) purified from Indian cobra Naja naja venom was investigated. The NnPLA2-I displayed a mass of 15.2 kDa and 14,186.0 Da when analyzed by SDS-PAGE and MALDI-TOF-MS, respectively. Peptide mass fingerprinting analysis of the NnPLA2-I showed its significant similarity with phospholipase A2 enzymes purified from cobra venom. BLAST analysis of one tryptic peptide sequence of NnPLA2-I demonstrated putative conserved domains of the PLA2-like superfamily. The Km and Vmax values of NnPLA2-I toward hydrolysis of its most preferred substrate-phosphotidylcholine (PC)-were determined to be 0.72 mM and 29.3 μmol min(-1) mg(-1), respectively. The anticoagulant activity of NnPLA2-I was found to be higher than the anticoagulant activity of heparin/AT-III or warfarin. The histidine modifying reagent, monovalent and polyvalent antivenom differentially inhibited the catalytic and anticoagulant activities of NnPLA2-I. Low molecular weight heparin did not inhibit the catalytic and platelet deaggregation activity of NnPLA2-I, albeit its anticoagulant activity was significantly reduced. The NnPLA2-I showed a non-enzymatic, mixed inhibition of thrombin with a Ki value of 9.3 nM. Heparin significantly decreased, with an IC50 value of 15.23 mIU, the thrombin inhibitory activity of NnPLA2-I. The NnPLA2-I uniquely increased the amidolytic activity of FXa without influencing its prothrombin activating property. NnPLA2-I showed dose-dependent deaggregation of platelet rich plasma (PRP) and inhibited the collagen and thrombin-induced aggregation of PRP. However, deaggregation of washed platelets by NnPLA2-I demonstrated in presence of PC or platelet poor plasma. Alkylation of histidine residue of NnPLA2-I resulted in 95% and 21% reduction of its platelet deaggregation and platelet binding properties, respectively. NnPLA2-I did not show cytotoxicity against human glioblastoma U87MG cells, bactericidal or hemolytic activity. The future therapeutic application of NnPLA2-I for treatment and prevention of cardiovascular disorders is therefore suggested.

Antibacterial potential of a basic phospholipase A2 (VRV-PL-V) of Daboia russellii pulchella (Russell's Viper) venom

Microbial/bacterial resistance against antibiotics is considered as a potentially serious threat to public health. Further, as these antibiotics elicit side effects, there is interest in developing new molecules with novel modes of action from diverse organisms. Along these lines, in this study the antibacterial potential of the basic protein VRV-PL-V (Vipera russellii venom phospholipase A2 fraction V) of Daboia russellii pulchella venom was evaluated. VRV-PL-V demonstrated a potent antibacterial activity against all the human pathogenic strains tested. It inhibited more effectively Gram-positive bacteria like Staphylococcus aureus and Bacillus subtilis when compared to Gram-negative bacteria like Escherichia coli, Vibrio cholerae, Klebsiella pneumoniae, and Salmonella paratyphi. It inhibited bacterial growth with MIC values ranging from 13 to 24 µg/ml. The antibacterial potential of VRV-PL-V was comparable to the standards used like gentamycin, chloramphenicol, and streptomycin. There was a strong correlation between PLA2 activities and hemolytic and antibacterial activity. It was found that even in the presence of p-bromophenacyl bromide (an inhibitor of PLA2 enzymatic activity), there was marked antibacterial activity, suggesting dissociation or partial overlapping of the bactericidal/antimicrobial domains. Therefore, this study shows that although there is a strong correlation between enzymatic and antimicrobial activities of VRV-PL-V, it may also possess other properties that mimic bactericidal/membrane permeability-increasing protein.

Two acidic, anticoagulant PLA2 isoenzymes purified from the venom of monocled cobra Naja kaouthia exhibit different potency to inhibit thrombin and factor Xa via phospholipids independent, non-enzymatic mechanism

Background

The monocled cobra (Naja kaouthia) is responsible for snakebite fatality in Indian subcontinent and in south-western China. Phospholipase A₂ (PLA₂; EC 3.1.1.4) is one of the toxic components of snake venom. The present study explores the mechanism and rationale(s) for the differences in anticoagulant potency of two acidic PLA₂ isoenzymes, Nk-PLA₂α (13463.91 Da) and Nk-PLA₂β (13282.38 Da) purified from the venom of N. kaouthia.

Principal Findings

By LC-MS/MS analysis, these PLA₂s showed highest similarity (23.5% sequence coverage) with PLA₂ III isolated from monocled cobra venom. The catalytic activity of Nk-PLA₂β exceeds that of Nk-PLA₂α. Heparin differentially regulated the catalytic and anticoagulant activities of these Nk-PLA₂ isoenzymes. The anticoagulant potency of Nk-PLA₂α was comparable to commercial anticoagulants warfarin, and heparin/antithrombin-III albeit Nk-PLA₂β demonstrated highest anticoagulant activity. The anticoagulant action of these PLA₂s was partially contributed by a small but specific hydrolysis of plasma phospholipids. The strong anticoagulant effect of Nk-PLA₂α and Nk-PLA₂β was achieved via preferential, non-enzymatic inhibition of FXa (Ki = 43 nM) and thrombin (Ki = 8.3 nM), respectively. Kinetics study suggests that the Nk-PLA₂ isoenzymes inhibit their “pharmacological target(s)” by uncompetitive mechanism without the requirement of phospholipids/Ca²⁺. The anticoagulant potency of Nk-PLA₂β which is higher than that of Nk-PLA₂α is corroborated by its superior catalytic activity, its higher capacity for binding to phosphatidylcholine, and its greater strength of thrombin inhibition. These PLA₂ isoenzymes thus have evolved to affect haemostasis by different mechanisms. The Nk-PLA₂β partially inhibited the thrombin-induced aggregation of mammalian platelets suggesting its therapeutic application in the prevention of unwanted clot formation.

Conclusion/Significance

In order to develop peptide-based superior anticoagulant therapeutics, future application of Nk-PLA₂α and Nk-PLA₂β for the treatment and/or prevention of cardiovascular disorders are proposed.

A major phospholipase A2 from Daboia russelii russelii venom shows potent anticoagulant action via thrombin inhibition and binding with plasma phospholipids

This is the first report on antithrombin effects of a phospholipase A2 (RVAPLA2) purified from venom of Daboia russelii russelii. The N-terminal sequence as well as in-gel tryptic digested peptides of RVAPLA2 showed significant homology with PLA2s from Russell's viper venom. RVAPLA2 demonstrated highest specific activity in hydrolyzing phosphatidylcholine (1.8 × 10(6) U/mg) with Km and Vmax values of 0.61 mM and 132.3 μmol/min, respectively. RVAPLA2 exerted dose-dependent catalytic and strong anticoagulant activities; however, studies indicated dissociation of its catalytic and anticoagulant sites. The anticoagulant action of RVAPLA2 was partially contributed by catalytic hydrolysis of plasma phospholipids. RVAPLA2 showed strong anticoagulant effect via thrombin inhibition with a Ki value of 380 nM as well as by binding to pro-coagulant phospholipids of plasma. In ex-vivo conditions, RVAPLA2 (1.0 μM) was non-hemolytic and non-cytotoxic to mammalian cells. It did not inhibit the collagen-induced aggregation of platelets. RVAPLA2 at a dose of 5 mg/kg was not lethal to mice after 48 h of injection. It demonstrated in vivo anticoagulant activity possibly due to targeting thrombin and binding with plasma phospholipids.

Mechanism of in vivo anticoagulant and haemolytic activity by a neutral phospholipase A(2) purified from Daboia russelii russelii venom: correlation with clinical manifestations in Russell's Viper envenomed patients

A 13.0 kDa neutral phospholipase A2 (NEUPHOLIPASE) purified from venom of Daboia russelii russelii from eastern India was identified by peptide mass fingerprinting analysis. It exerted dose-dependent PLA2, anticoagulant and indirect haemolytic activities. NEUPHOLIPASE showed preferential binding followed by hydrolysis of phosphatidylserine > phosphatidylcholine >> phosphatidylethanolamine. Circular dichroism analysis of NEUPHOLIPASE showed a high content of alpha helix (54.6%) followed by beta-turn (29.7%) in its secondary structure. Gas-chromatographic analysis of plasma from PLA2-treated mice suggested preferential hydrolysis of pro-coagulant phospholipid PS was the primary mechanism to account for in vivo anticoagulant effect of NEUPHOLIPASE. The NEUPHOLIPASE-treated mice blood showed a significant decrease (p < 0.01) in WBC as well as RBC counts with a corresponding decline in Hb content due to indirect damage to erythrocyte membranes by plasma phospholipids hydrolysis products rather than the direct haemolytic activity of PLA2 under study. NEUPHOLIPASE was non-lethal to BALB/c mice, however; it was detrimental to liver of treated-mice. Pathological symptoms observed in NEUPHOLIPASE-treated mice were correlated with the actual clinical manifestations in Russell's Viper envenomed patients from eastern India indicating some contribution of NEUPHOLIPASE in Russell's Viper venom induced toxicity and pathogenesis.