A [Lys 49 ]phospholipase A 2 from Protobothrops flavoviridis Venom Induces Caspase-Independent Apoptotic Cell Death Accompanied by Rapid Plasma-Membrane Rupture in Human Leukemia Cells

Comparative in vitro immunoreactivity and protein analysis of Trimeresurus albolabris and Tropidolaemus wagleri venoms

Snakebite envenomation remains a significant global health concern, with antivenoms being the primary treatment. However, variations in venom composition can affect antivenom efficacy, leading to differences in immunoreactivity. This study aimed to evaluate and compare the immunological reactivity of venom components in Trimeresurus albolabris and Tropidolaemus wagleri venoms and further investigate the differences in antigenic properties of a key protein between two species that may influence antivenom recognition. The levels of immunological reactivity of monovalent (homospecific) antivenom and hemato polyvalent antivenom to Trimeresurus albolabris and Tropidolaemus wagleri venoms were evaluated using indirect ELISA. The immunoreactive levels of both antivenoms to antigenic proteins in Trimeresurus albolabris venom were comparable. In addition, both antivenoms reacted immunologically with antigens in Tropidolaemus wagleri venom. However, the hemato polyvalent antivenom showed greater reactivity to Tropidolaemus wagleri venom than the monovalent antivenom. The overall reactivity of the antivenoms to Trimeresurus albolabris venom was higher than that to Tropidolaemus wagleri venom. Using two-dimensional (2DE) immunoblotting and liquid chromatography mass-spectrometry-based proteomic technology (LC-MS/MS), immunoreactive and non-reactive proteins in both pit viper venoms were characterized and identified. Trimeresurus albolabris venom comprised a total of 235 spots, while Tropidolaemus wagleri venom contained 72 spots. Immunorecognition between the polyvalent antivenom and specific proteins in both venoms was mostly detected in proteins with a size over 30 kDa. Among the nine protein families identified in both venoms, the most frequently reactive proteins found in Trimeresurus albolabris venom were snake venom metalloproteinases (SVMP) and snake venom serine proteases (SVSP), while in Tropidolaemus wagleri venom, the most frequent were members of the L-amino acid oxidase (LAAO) family. For the non-immunoreactive proteins, we detected the highest identity numbers of phospholipase A2 (PLA2) in Trimeresurus albolabris venom and SVSP in Tropidolaemus wagleri venom. The distinctive characteristics between the non-reactive SVSP in Tropidolaemus wagleri venom and the reactive SVSP in Trimeresurus albolabris venom were investigated. The antigenic properties and predicted B cell epitopes were further analyzed using a computational approach. Structural and physicochemical analyses indicated that Loop 2 (residues 100-110) in the immunoreactive SVSP from Trimeresurus albolabris venom exhibited higher hydrophilicity and surface accessibility compared to the non-immunoreactive SVSP from Tropidolaemus wagleri venom. These findings provide important insights into the differences in antivenom reactivity to specific proteins across different snake venoms and may contribute to future research aimed at optimizing antivenom formulations.

Supramolecular Hybrids of Proteins from Habu Snake Venom with Discrete [Pt(CN)4]2- Complex

The venom of the Habu snake Protobothrops flavoviridis (P. flavoviridis) is known to contain a diverse array of proteins and peptides, with a notable presence of phospholipase A2 (PLA2) enzymes. These PLA2 enzymes have been extensively studied for their function and molecular evolution. Nevertheless, several aspects, such as the physical properties and the self-assembly mechanism of hierarchical structure from the nanoscale to the microscale with different chemical compounds, remain poorly understood. This study aims to fill this knowledge gap by investigating the behavior of enzyme components purified from P. flavoviridis venom in the presence of anionic [Pt(CN)4]2- complexes, which have the potential for soft metallophilic interactions and interesting optical properties. The purified PLA2 isozymes were diluted in Dulbecco's phosphate buffered saline (D-PBS (-)) and combined with the anionic metal complex, resulting in the formation of microstructures several micrometers in size, which further grew to form fibrous structures. This novel approach of combining PLA2 enzymes with discrete functional metal complexes opens up exciting possibilities for designing flexible and functional supramolecular and biomolecular hybrid systems in aqueous environments. These findings shed light on the potential applications of snake venom enzymes in nanotechnology and bioengineering.

Proteomic Analysis and Biochemical Characterization of the Nematocyst Extract of the Hydrozoan Velella velella

The venom contained within cnidarian nematocysts has a complex composition and holds significant potential for biotechnological applications. In this context, one of the most effective methods for studying nematocyst contents is the proteomic approach, which can detect even trace amounts of compounds while minimizing the need for large-scale animal collection, thus helping to preserve ecosystem integrity. This study aimed to provide a comprehensive proteomic and biochemical characterization of the crude nematocyst extract from the common hydrozoan Velella velella. Despite not being harmful to humans, the analysis of the crude venom extract from V. velella brought to the identification of 783 different proteins, categorized into structural components, enzymes, and potential toxins, revealing a qualitative composition of the venom similar to that of other more toxic cnidarians. Biochemical assays confirmed the presence of various active hydrolytic enzymes within the extract, including proteases, phospholipases, hyaluronidases, DNases, and chitinases. These findings pave the road for future studies involving the pharmacological applications of Velella velella venom components through recombinant production and functional testing.

Emerging anticancer potential and mechanisms of snake venom toxins: A review

Animal-derived venom, like snake venom, has been proven to be valuable natural resources for the drug development. Previously, snake venom was mainly investigated in its pharmacological activities in regulating coagulation, vasodilation, and cardiovascular function, and several marketed cardiovascular drugs were successfully developed from snake venom. In recent years, snake venom fractions have been demonstrated with anticancer properties of inducing apoptotic and autophagic cell death, restraining proliferation, suppressing angiogenesis, inhibiting cell adhesion and migration, improving immunity, and so on. A number of active anticancer enzymes and peptides have been identified from snake venom toxins, such as L-amino acid oxidases (LAAOs), phospholipase A2 (PLA2), metalloproteinases (MPs), three-finger toxins (3FTxs), serine proteinases (SPs), disintegrins, C-type lectin-like proteins (CTLPs), cell-penetrating peptides, cysteine-rich secretory proteins (CRISPs). In this review, we focus on summarizing these snake venom-derived anticancer components on their anticancer activities and underlying mechanisms. We will also discuss their potential to be developed as anticancer drugs in the future.

Cytotoxic effect of crotoxin on cancer cells and its antitumoral effects correlated to tumor microenvironment: A review

Cancer is the second leading cause of death worldwide, and despite the effort of standard treatments, the search for new tools against this disease is necessary. Importantly, it is known that the tumor microenvironment plays a crucial role in tumor initiation, progression, and response to therapies. Therefore, studies of potential drugs that act on these components are as critical as studies regarding antiproliferative substances. Through the years, studies of several natural products, including animal toxins, have been conducted to guide the development of medical compounds. In this review, we present the remarkable antitumor activities of crotoxin, a toxin from the rattlesnake Crotalus durissus terrificus, highlighting its effects on cancer cells and in the modulation of relevant elements in the tumor microenvironment as well as the clinical trials conducted with this compound. In summary, crotoxin acts through several mechanisms of action, such as activation of apoptosis, induction of cell cycle arrest, inhibition of metastasis, and decrease of tumor growth, in different tumor types. Crotoxin also modulates tumor-associated fibroblasts, endothelial cells, and immune cells, which contribute to its antitumoral effects. In addition, preliminary clinical studies confirm the promising results of crotoxin and support its potential future use as an anticancer drug.

Lys49 myotoxins, secreted phospholipase A2-like proteins of viperid venoms: A comprehensive review

Muscle necrosis is a potential clinical complication of snakebite envenomings, which in severe cases can lead to functional or physical sequelae such as disability or amputation. Snake venom proteins with the ability to directly damage skeletal muscle fibers are collectively referred to as myotoxins, and include three main types: cytolysins of the "three-finger toxin" protein family expressed in many elapid venoms, the so-called "small" myotoxins found in a number of rattlesnake venoms, and the widespread secreted phospholipase A₂ (sPLA₂) molecules. Among the latter, protein variants that conserve the sPLA₂ structure, but lack such enzymatic activity, have been increasingly found in the venoms of many viperid species. Intriguingly, these sPLA₂-like proteins are able to induce muscle necrosis by a mechanism independent of phospholipid hydrolysis. They are commonly referred to as "Lys49 myotoxins" since they most often present, among other substitutions, the replacement of the otherwise invariant residue Asp49 of sPLA₂s by Lys. This work comprehensively reviews the historical developments and current knowledge towards deciphering the mechanism of action of Lys49 sPLA₂-like myotoxins, and points out main gaps to be filled for a better understanding of these multifaceted snake venom proteins, to hopefully lead to improved treatments for snakebites.

SDS-induced oligomerization of Lys49-phospholipase A2 from snake venom

Phospholipase A₂ (PLA₂) is one of the representative toxic components of snake venom. PLA₂s are categorized into several subgroups according to the amino acid at position 49, which comprises either Asp49, Lys49, Arg49 or Ser49. Previous studies suggested that the Lys49-PLA₂ assembles into an extremely stable dimer. Although the behavior on Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing or non-reducing conditions suggested the presence of intermolecular disulfide bonds, these bonds were not observed in the crystal structure of Lys49-PLA₂. The reason for this discrepancy between the crystal structure and SDS-PAGE of Lys49-PLA₂ remains unknown. In this study, we analyzed a Lys49-PLA₂ homologue from Protobothrops flavoviridis (PflLys49-PLA₂ BPII), by biophysical analyses including X-ray crystallography, SDS-PAGE, native-mass spectrometry, and analytical ultracentrifugation. The results demonstrated that PflLys49-PLA₂ BPII spontaneously oligomerized in the presence of SDS, which is one of the strongest protein denaturants.

Comprehensive Snake Venomics of the Okinawa Habu Pit Viper, Protobothrops flavoviridis, by Complementary Mass Spectrometry-Guided Approaches

The Asian world is home to a multitude of venomous and dangerous snakes, which are used to induce various medical effects in the preparation of traditional snake tinctures and alcoholics, like the Japanese snake wine, named Habushu. The aim of this work was to perform the first quantitative proteomic analysis of the Protobothrops flavoviridis pit viper venom. Accordingly, the venom was analyzed by complimentary bottom-up and top-down mass spectrometry techniques. The mass spectrometry-based snake venomics approach revealed that more than half of the venom is composed of different phospholipases A2 (PLA₂). The combination of this approach and an intact mass profiling led to the identification of the three main Habu PLA₂s. Furthermore, nearly one-third of the total venom consists of snake venom metalloproteinases and disintegrins, and several minor represented toxin families were detected: C-type lectin-like proteins (CTL), cysteine-rich secretory proteins (CRISP), snake venom serine proteases (svSP), l-amino acid oxidases (LAAO), phosphodiesterase (PDE) and 5'-nucleotidase. Finally, the venom of P. flavoviridis contains certain bradykinin-potentiating peptides and related peptides, like the svMP inhibitors, pEKW, pEQW, pEEW and pENW. In preliminary MTT cytotoxicity assays, the highest cancerous-cytotoxicity of crude venom was measured against human neuroblastoma SH-SY5Y cells and shows disintegrin-like effects in some fractions.

First Look at the Venom of Naja ashei

Naja ashei is an African spitting cobra species closely related to N. mossambica and N. nigricollis. It is known that the venom of N. ashei, like that of other African spitting cobras, mainly has cytotoxic effects, however data about its specific protein composition are not yet available. Thus, an attempt was made to determine the venom proteome of N. ashei with the use of 2-D electrophoresis and MALDI ToF/ToF (Matrix-Assisted Laser Desorption/Ionization Time of Flight) mass spectrometry techniques. Our investigation revealed that the main components of analysed venom are 3FTxs (Three-Finger Toxins) and PLA₂s (Phospholipases A₂). Additionally the presence of cysteine-rich venom proteins, 5'-nucleotidase and metalloproteinases has also been confirmed. The most interesting fact derived from this study is that the venom of N. ashei includes proteins not described previously in other African spitting cobras-cobra venom factor and venom nerve growth factor. To our knowledge, there are currently no other reports concerning this venom composition and we believe that our results will significantly increase interest in research of this species.

Effects of Animal Venoms and Toxins on Hallmarks of Cancer

Animal venoms are a cocktail of proteins and peptides, targeting vital physiological processes. Venoms have evolved to assist in the capture and digestion of prey. Key venom components often include neurotoxins, myotoxins, cardiotoxins, hematoxins and catalytic enzymes. The pharmacological activities of venom components have been investigated as a source of potential therapeutic agents. Interestingly, a number of animal toxins display profound anticancer effects. These include toxins purified from snake, bee and scorpion venoms effecting cancer cell proliferation, migration, invasion, apoptotic activity and neovascularization. Indeed, the mechanism behind the anticancer effect of certain toxins is similar to that of agents currently used in chemotherapy. For example, Lebein is a snake venom disintegrin which generates anti-angiogenic effects by inhibiting vascular endothelial growth factors (VEGF). In this review article, we highlight the biological activities of animal toxins on the multiple steps of tumour formation or hallmarks of cancer. We also discuss recent progress in the discovery of lead compounds for anticancer drug development from venom components.

Propensity of crocin to offset Vipera russelli venom induced oxidative stress mediated neutrophil apoptosis: a biochemical insight

Viper envenomation results in inflammation at the bitten site as well as target organs. Neutrophils and other polymorphonuclear leukocytes execute inflammation resolving mechanism and will undergo apoptosis after completing the task. However, the target specific toxins induce neutrophil apoptosis at the bitten site and in circulation prior to their function, thus reducing their number. Circulating activated neutrophils are major source of inflammatory cytokines and leakage of reactive oxygen species (ROS)/other toxic intermediates resulting in aggravation of inflammatory response at the bitten/target site. Therefore, neutralization of venom induced neutrophil apoptosis reduces inflammation besides increasing the functional neutrophil population. Therefore, the present study investigates the venom induced perturbances in isolated human neutrophils and its neutralization by crocin (Crocus sativus) a potent antioxidant carotenoid. Human neutrophils on treatment with venom resulted in altered ROS generation, intracellular Ca(2+) mobilization, mitochondrial membrane depolarization, cyt-c translocation, caspase activation, phosphatidylserine externalization and DNA damage. On the other hand significant protection against oxidative stress and apoptosis were evidenced in crocin pre-treated groups. In conclusion the viper venom induces neutrophil apoptosis and results in aggravation of inflammation and tissue damage. The present study demands the necessity of an auxiliary therapy in addition to antivenin therapy to treat secondary/overlooked complications of envenomation.

Pigment epithelium-derived factor promotes Fas-induced cardiomyocyte apoptosis via its receptor phospholipase A2

AIMS

Cardiovascular diseases cause significant morbidity and mortality worldwide. Recently, our research team demonstrated that a multifunctional cytokine, pigment epithelium-derived factor (PEDF), plays a critical role in regulating myocardial infarction. However, few researchers have studied the molecular mechanisms by which PEDF and its receptors influence the pathophysiology of cardiovascular disease. We tested the hypothesis that PEDF affects cardiomyocyte apoptosis under hypoxic conditions and determined the role that its receptors phospholipase A2 (PLA2) and laminin receptor play in this process.

MAIN METHODS

Cardiomyocytes were isolated from neonatal mice and treated with PEDF under normoxic and hypoxic conditions; then, apoptosis was assessed using Annexin V/PI staining and flow cytometry. Western blotting and immunofluorescence staining were used to detect PEDF receptor expression, and siRNA knockdown of PEDF receptors was performed to determine which receptor was involved in mediating cardiomyocyte apoptosis.

KEY FINDINGS

Our results demonstrated that PEDF increased cardiomyocyte apoptosis during hypoxia via Fas and that PEDF receptors were expressed on cardiomyocyte cell membranes. Furthermore, siRNA experiments indicated that the PEDF receptor PLA2 was responsible for inducing cardiomyocyte apoptosis via the Fas pathway.

SIGNIFICANCE

PEDF promoted Fas-induced cardiomyocyte apoptosis via its receptor PLA2.

Cytotoxic activities of [Ser⁴⁹]phospholipase A₂ from the venom of the saw-scaled vipers Echis ocellatus, Echis pyramidum leakeyi, Echis carinatus sochureki, and Echis coloratus

Fractionation by reversed-phase HPLC of venom from four species of saw-scaled viper: Echis ocellatus, Echis pyramidum leakeyi, Echis carinatus sochureki, and Echis coloratus led to identification in each sample of an abundant protein with cytotoxic activity against human non-small cell lung adenocarcinoma A549 cells. The active component in each case was identified by MALDI-TOF mass fingerprinting of tryptic digests as [Ser⁴⁹]phospholipase A₂ ([Ser⁴⁹]PLA₂). An isoform of [Ser⁴⁹]PLA₂ containing the single Ala¹⁸→ Val substitution and a partially characterized [Asp⁴⁹]PLA₂ were also present in the E. coloratus venom. LC₅₀ values against A549 cells for the purified [Ser⁴⁹]PLA₂ proteins from the four species are in the range 2.9-8.5 μM. This range is not significantly different from the range of LC₅₀ values against human umbilical vein endothelial HUVEC cells (2.5-12.2 μM) indicating that the [Ser⁴⁹]PLA₂ proteins show no differential anti-tumor activity. The LC₅₀ value for [Ser⁴⁹]PLA₂ from E. ocellatus against human erythrocytes is >100 μM and the MIC values against Escherichia coli and Staphylococcus aureus are >100 μM. It is suggested that the [Ser⁴⁹]PLA₂ proteins play a major role in producing local tissue necrosis and hemorrhage at the site of envenomation.

Interactions of PLA2-s from Vipera lebetina, Vipera berus berus and Naja naja oxiana venom with platelets, bacterial and cancer cells

Secretory phospholipasesA₂ (sPLA₂s) form a large family of structurally related enzymes widespread in nature. Herein, we studied the inhibitory effects of sPLA₂s from Vipera lebetina (VLPLA₂), Vipera berus berus (VBBPLA₂), and Naja naja oxiana (NNOPLA₂) venoms on (i) human platelets, (ii) four different bacterial strains (gram-negative Escherichia coli and Vibrio fischeri; gram-positive Staphylococcus aureus and Bacillus subtilis) and (iii) five types of cancer cells (PC-3, LNCaP, MCF-7, K-562 and B16-F10) in vitro. sPLA₂s inhibited collagen-induced platelet aggregation: VBBPLA₂ IC₅₀ = 0.054, VLPLA₂ IC₅₀ = 0.072, NNOPLA₂ IC₅₀ = 0.814 μM. p-Bromophenacylbromide-inhibited sPLA₂ had no inhibitory action on platelets. 36.17 μM VBBPLA₂ completely inhibited the growth of gram-positive Bacillus subtilis whereas no growth inhibition was observed towards gram-negative Escherichia coli. The inhibitory action of sPLA₂s (~0.7 μM and ~7 μM) towards cancer cells depended on both venom and cell type. VBBPLA₂ (7.2 μM) inhibited significantly the viability of K-562 cells and the cell death appeared apoptotic. The sPLA₂s exhibited no inhibitory effect towards LNCaP cells and some effect (8%–20%) towards other cells. Thus, already sub-μM concentrations of sPLA₂s inhibited collagen-induced platelet aggregation and from the current suite of studied svPLA₂s and test cells, VBBPLA₂ was the most growth inhibitory towards Bacillus subtilis and K-562 cells.