Inhibition of leukemic U937 cell growth by induction of apoptosis, cell cycle arrest and suppression of VEGF, MMP-2 and MMP-9 activities by cytotoxin protein NN-32 purified from Indian spectacled cobra (Naja naja) venom

Tissue damaging toxins in snake venoms: mechanisms of action, pathophysiology and treatment strategies

Snakebite envenoming is an important public health issue responsible for mortality and severe morbidity. Where mortality is mainly caused by venom toxins that induce cardiovascular disturbances, neurotoxicity, and acute kidney injury, morbidity is caused by toxins that directly or indirectly destroy cells and degrade the extracellular matrix. These are referred to as 'tissue-damaging toxins' and have previously been classified in various ways, most of which are based on the tissues being affected (e.g., cardiotoxins, myotoxins). This categorisation, however, is primarily phenomenological and not mechanistic. In this review, we propose an alternative way of classifying cytotoxins based on their mechanistic effects rather than using a description that is organ- or tissue-based. The mechanisms of toxin-induced tissue damage and their clinical implications are discussed. This review contributes to our understanding of fundamental biological processes associated with snakebite envenoming, which may pave the way for a knowledge-based search for novel therapeutic options.

Ensemble-based molecular docking and spectrofluorometric analysis of interaction between cytotoxin and tumor necrosis factor receptor 1

Cytotoxin (CTX) is a three-finger toxin presents predominantly in cobra venom. The functional site of the toxin is located at its three hydrophobic loop tips. Its actual mechanism of cytotoxicity remains inconclusive as few conflicting hypotheses have been proposed in addition to direct cytolytic effects. The present work investigated the interaction between CTX and death receptor families via ensemble-based molecular docking and fluorescence titration analysis. Multiple sequence alignments of different CTX isoforms obtained a conserved CTX sequence. The three-dimensional structure of the conserved CTX was later determined using homology modelling, and its quality was validated. Ensemble-based molecular docking of CTX was performed with different death receptors, such as Fas-ligand and tumor necrosis factor receptor families. Our results showed that tumor necrosis factor receptor 1 (TNFR1) was the best receptor interacting with CTX attributed to the interaction of all three functional loops and evinced with low HADDOCK, Z-score and RMSD value. The interaction between CTX and TNFR1 was also supported by a concentration-dependent reduction of fluorescence intensity with increasing binding affinity. The possible intermolecular interactions between CTX and TNFR1 were Van der Waals forces and hydrogen bonding. Our findings suggest a possibility that CTX triggers apoptosis cell death through non-covalent interactions with TNFR1.Communicated by Ramaswamy H. Sarma.

The secretory phenotypes of envenomed cells: Insights into venom cytotoxicity

Snake envenomation is listed as Category A Neglected Tropical Diseases (NTD) by World Health Organization, indicates a severe public health problem. The global figures for envenomation cases are estimated to be more than 1.8 million annually. Even if the affected victims survive the envenomation, they might suffer from permanent morbidity due to local envenomation. One of the most prominent local envenomation is dermonecrosis. Dermonecrosis is a pathophysiological outcome of envenomation that often causes disability in the victims due to surgical amputations, deformities, contracture, and chronic ulceration. The key venom toxins associated with this local symptom are mainly attributed to substantial levels of enzymatic and non-enzymatic toxins as well as their possible synergistic actions. Despite so, the severity of the local tissue damage is based on macroscopic observation of the bite areas. Furthermore, limited knowledge is known about the key biomarkers involved in the pathogenesis of dermonecrosis. The current immunotherapy with antivenom is also ineffective against dermonecrosis. These local effects eventually end up as sequelae. There is also a global shortage of toxins-targeted therapeutics attributed to inadequate knowledge of the actual molecular mechanisms of cytotoxicity. This chapter discusses the characterization of secretory phenotypes of dermonecrosis as an advanced tool to indicate its severity and pathogenesis in envenomation. Altogether, the secretory phenotypes of envenomed cells and tissues represent the precise characteristics of dermonecrosis caused by venom toxins.

The myth of cobra venom cytotoxin: More than just direct cytolytic actions

Cobra venom cytotoxin (CTX) is a non-enzymatic three-finger toxin that constitutes 40-60% of cobra venom. Thus, it plays an important role in the pathophysiology of cobra envenomation, especially in local dermonecrosis. The three-finger hydrophobic loops of CTX determine the cytotoxicity. Nevertheless, the actual mechanisms of cytotoxicity are not fully elucidated as they involve not only cytolytic actions but also intracellular signalling-mediated cell death pathways. Furthermore, the possible transition cell death pattern remains to be explored. The actual molecular mechanisms require further studies to unveil the relationship between different CTXs from different cobra species and cell types which may result in differential cell death patterns. Here, we discuss the biophysical interaction of CTX with the cell membrane involving four binding modes: electrostatic interaction, hydrophobic partitioning, isotropic phase, and oligomerisation. Oligomerisation of CTX causes pore formation in the membrane lipid bilayer. Additionally, the CTX-induced apoptotic pathway can be executed via death receptor-mediated extrinsic pathways and mitochondrial-mediated intrinsic pathways. We also discuss lysosomal-mediated necrosis and the occurrence of necroptosis following CTX action. Collectively, we provided an insight into concentration-dependent transition of cell death pattern which involves different mechanistic actions. This contributes a new direction for further investigation of cytotoxic pathways activated by the CTXs for future development of biotherapeutics targeting pathological effects caused by CTX.

In Vivo Toxicity Profile of NN-32 and Nanogold Conjugated GNP-NN-32 from Indian Spectacled Cobra Venom

BACKGROUND

NN-32 toxin, which was obtained from Naja naja venom and showed cytotoxicity on cancer cell lines. As the toxicity of NN-32 is the main hurdle in the process of drug development; hence, we have conjugated NN-32 toxin with gold nanoparticles (GNP-NN-32) in order to decrease the toxicity of NN-32 without reducing its efficacy, GNP-NN-32 alleviated the toxicity of NN-32 in in vitro studies during the course of earlier studies. In continuation, we are evaluating in vivo toxicity profile of NN-32 and GNP-NN-32 in the present study.

OBJECTIVE

To study in vivo toxicity profile of NN-32 and nanogold conjugated GNP-NN-32 from Naja naja venom.

MATERIALS AND METHODS

We have carried out in vivo acute toxicity study to determine LD50 dose of GNP-NN-32, in vivo sub-chronic toxicity for 30 days, haematology, serum biochemical parameters and histopathology study on various mice tissues and in vitro cellular and tissue toxicity studies.

RESULTS

The LD50 dose of GNP-NN-32 was found to be 2.58 mg/kg (i.p.) in Swiss male albino mice. In vivo sub-chronic toxicity showed significantly reduced toxicity of GNP-NN-32 as compared to NN-32 alone.

DISCUSSION

In vitro cellular toxicity studies on human lymphocyte and mouse peritoneal macrophage showed significant inhibition of cells by NN-32 alone.

CONCLUSION

Conjugated GNP-NN-32 toxin showed less in vivo toxicity as compared to pure NN-32.

Cytotoxicity of Snake Venoms and Cytotoxins From Two Southeast Asian Cobras (Naja sumatrana, Naja kaouthia): Exploration of Anticancer Potential, Selectivity, and Cell Death Mechanism

Venoms of cobras (Naja spp.) contain high abundances of cytotoxins, which contribute to tissue necrosis in cobra envenomation. The tissue-necrotizing activity of cobra cytotoxins, nevertheless, indicates anticancer potentials. This study set to explore the anticancer properties of the venoms and cytotoxins from Naja sumatrana (equatorial spitting cobra) and Naja kaouthia (monocled cobra), two highly venomous species in Southeast Asia. The cytotoxicity, selectivity, and cell death mechanisms of their venoms and cytotoxins (NS-CTX from N. sumatrana: NS-CTX; N. kaouthia: NK-CTX) were elucidated in human lung (A549), prostate (PC-3), and breast (MCF-7) cancer cell lines. Cytotoxins were purified through a sequential fractionation approach using cation-exchange chromatography, followed by C₁₈ reverse-phase high-performance liquid chromatography (HPLC) to homogeneity validated with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and identified by liquid chromatography-tandem mass spectrometry (LCMS/MS). The cobra venoms and their respective cytotoxins exhibited concentration-dependent growth inhibitory effects in all cell lines tested, with the cytotoxins being more potent compared to the corresponding whole venoms. NS-CTX and NK-CTX are, respectively, P-type and S-type isoforms of cytotoxin, based on the amino acid sequences as per LCMS/MS analysis. Both cytotoxins exhibited differential cytotoxic effects in the cell lines tested, with NS-CTX (P-type cytotoxin) being significantly more potent in inhibiting the growth of the cancer cells. Both cytotoxins demonstrated promising selectivity only for the A549 lung cancer cell line (selectivity index = 2.17 and 2.26, respectively) but not in prostate (PC-3) and breast (MCF-7) cancer cell lines (selectivity index < 1). Flow cytometry revealed that the A549 lung cancer cells treated with NS-CTX and NK-CTX underwent necrosis predominantly. Meanwhile, the cytotoxins induced mainly caspase-independent late apoptosis in the prostate (PC-3) and breast (MCF-7) cancer cells lines but lacked selectivity. The findings revealed the limitations and challenges that could be faced during the development of new cancer therapy from cobra cytotoxins, notwithstanding their potent anticancer effects. Further studies should aim to overcome these impediments to unleash the anticancer potentials of the cytotoxins.

Anticancer potential of nanogold conjugated toxin GNP-NN-32 from Naja naja venom

Background:

Cancer is the second most common fatal disease in the world, behind cardiovascular disorders in the first place. It accounts for around 0.3 million deaths per year in India due to the lack of proper diagnostic facilities, prevention and treatment. Current therapeutic methods do not provide adequate protection and affect normal cells along with cancerous ones. Thus, there is a need for some alternative therapeutic strategy, preferably from natural products, which have been traditionally used for treatment of various diseases in the country.

Methods:

In this study, we have conjugated purified NN-32 toxin from Naja naja venom with gold nanoparticles and its anticancer potential was evaluated against human breast cancer cell lines. UV-Vis spectroscopy, dynamic light scattering, transmission electron microscopy, atomic force microscopy and zeta potential analysis were the techniques used for characterization of GNP-NN-32.

Results:

GNP-NN-32 showed dose- and time-dependent cytotoxicity against breast cancer cell lines (MCF-7 and MDA-MB-231). NN-32 and GNP-NN-32 induced apoptosis in both breast cancer cell lines. The results of CFSE cell proliferation study revealed that NN-32 and GNP-NN-32 arrested cell division in both MCF-7 and MDA-MB-231 cell lines resulting in inhibition of proliferation of these cancer cells.

Conclusion:

GNP-NN-32 showed an anticancer potential against human breast cancer cell lines. Analysis of detailed chemical characterization along with its cytotoxic property might help to perceive a new dimension of the anti-cancer potential of GNP-NN-32 that will enhance its biomedical function in near future.

Investigating the cytotoxic effects of the venom proteome of two species of the Viperidae family (Cerastes cerastes and Cryptelytrops purpureomaculatus) from various habitats

Animal secretions are of great interest in terms of drug development due to their complex protein and peptide composition. Especially, in the field of therapeutic medications such as anti-cancer drugs snake venoms receive attention. In this study, we address two Viperidae species from various habitats with a particular focus on the cytotoxic potential along with the decomplexation of the venom proteome: the horned desert viper (Cerastes cerastes), native to desert regions of North Africa and the mangrove pit viper (Cryptelytrops purpureomaculatus), found in coastal forests of Southeast Asia. Initial cytotoxic screenings of the crude venoms revealed diverse activity, with the highest effect against SHSY5Y human glioblastoma carcinoma cells compared to other cancerous and non-cancerous cell lines. In-depth cytotoxicity studies of SHSY5Y cells with purified venom fractions revealed heterodimeric disintegrins from C. cerastes venom, which exerted a high cytotoxic activity with IC₅₀ values from 0.11 to 0.58 μM and a disintegrin-like effect on SHSY5Y morphology was observed due to cell detachment. Furthermore, two polyproline BPP-related peptides, one PLA₂ and a peptide-rich fraction were determined for C. purpureomaculatus with moderate IC₅₀ values between 3 and 51 μM. Additionally, the decryption of the venom proteomes by snake venomic mass spectrometry and comparison of the same species from different habitats revealed slight differences in the composition.

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.

Cytotoxic activity of NN-32 toxin from Indian spectacled cobra venom on human breast cancer cell lines

BACKGROUND

Breast cancer is the most common cancer which causes significant morbidity and mortality among women worldwide. Lack of medical facilities for early detection, therapeutic strategies for treatment and side effects due to pharmacological compounds have encompassed the need for new therapies mostly from natural sources. A lot of components have been identified from different snake venoms as therapeutic agents. A group of polypeptides (60-70 amino acid residues) called cytotoxins or cardiotoxins present in an elapid family of snakes have a wide variety of pharmaceutical actions and have the tendency to damage a wide variety of cells including cancerous cells. The aim of the present study was to evaluate the cytotoxic effect of NN-32 protein toxin purified from Indian Spectacled Cobra venom against human breast cancer cell lines (MCF-7 and MDA-MB-231).

METHODS

The NN-32 toxin was purified by ion exchange chromatography and further by RP-HPLC. The potential anticancer effects of the NN-32 toxin on MCF-7 and MDA-MB-231 cells were evaluated using MTT, anti-proliferation, neutral red (NR) uptake and Lactate Dehydrogenase (LDH) release assay.

RESULTS

The ion exchange chromatography showed various peaks among fraction no. 35 showing cytotoxic activity and this fraction showed a single peak with retention time 3.6 mins by HPLC using C18 column. The NN-32 toxin induced cytotoxicity in MCF-7 and MDA-MB-231 cells with the IC₅₀ value of 2.5 and 6.7 μg/ml respectively. The NN-32 showed significant cytotoxicity to both the cell lines along with low cytotoxicity to MCF-10A (normal breast epithelial) cells. The cytotoxic effect was further confirmed by the anti-proliferative, NR uptake and LDH release assays.

CONCLUSION

The purified toxin NN-32 from Naja naja venom showed cytotoxic activity against MCF-7 (ER+) and MDA-MB-231(ER-) cells in both dose dependent and time dependent manner.

Snake venom toxins: toxicity and medicinal applications

Snake venoms are complex mixtures of small molecules and peptides/proteins, and most of them display certain kinds of bioactivities. They include neurotoxic, cytotoxic, cardiotoxic, myotoxic, and many different enzymatic activities. Snake envenomation is a significant health issue as millions of snakebites are reported annually. A large number of people are injured and die due to snake venom poisoning. However, several fatal snake venom toxins have found potential uses as diagnostic tools, therapeutic agent, or drug leads. In this review, different non-enzymatically active snake venom toxins which have potential therapeutic properties such as antitumor, antimicrobial, anticoagulating, and analgesic activities will be discussed.

Venomics, lethality and neutralization of Naja kaouthia (monocled cobra) venoms from three different geographical regions of Southeast Asia

Previous studies showed that venoms of the monocled cobra, Naja kaouthia from Thailand and Malaysia are substantially different in their median lethal doses. The intraspecific venom variations of N. kaouthia, however, have not been fully elucidated. Here we investigated the venom proteomes of N. kaouthia from Malaysia (NK-M), Thailand (NK-T) and Vietnam (NK-V) through reverse-phase HPLC, SDS-PAGE and tandem mass spectrometry. The venom proteins comprise 13 toxin families, with three-finger toxins being the most abundant (63-77%) and the most varied (11-18 isoforms) among the three populations. NK-T has the highest content of neurotoxins (50%, predominantly long neurotoxins), followed by NK-V (29%, predominantly weak neurotoxins and some short neurotoxins), while NK-M has the least (18%, some weak neurotoxins but less short and long neurotoxins). On the other hand, cytotoxins constitute the main bulk of toxins in NK-M and NK-V venoms (up to 45% each), but less in NK-T venom (27%). The three venoms show different lethal potencies that generally reflect the proteomic findings. Despite the proteomic variations, the use of Thai monovalent and Neuro polyvalent antivenoms for N. kaouthia envenomation in the three regions is appropriate as the different venoms were neutralized by the antivenoms albeit at different degrees of effectiveness.

BIOLOGICAL SIGNIFICANCE

Biogeographical variations were observed in the venom proteome of monocled cobra (Naja kaouthia) from Malaysia, Thailand and Vietnam. The Thai N. kaouthia venom is particularly rich in long neurotoxins, while the Malaysian and Vietnamese specimens were predominated with cytotoxins. The differentially expressed toxin profile accounts for the discrepancy in the lethal dose of the venom from different populations. Commercially available Thai antivenoms (monovalent and polyvalent) were able to neutralize the three venoms at different effective doses, hence supporting their uses in the three regions. While dose adjustment according to geographical region seems possible, changes to standard recommended dosage should only be made if further study validates that the monocled cobras within a population do not exhibit remarkable inter-individual venom variation.

Protective effect of Xin Mai Jia ultrafiltration extract on human umbilical vein endothelial cell injury induced by hydrogen peroxide and the effect on the NO-cGMP signaling pathway

The aim of the present study was to evaluate the protective effect of the ultrafiltration extract of Xin Mai Jia (XMJ) on a human umbilical vein endothelial cell (HUVEC) injury model induced by hydrogen peroxide (H₂O₂), by providing experimental data to investigate the mechanism and efficacy underlying the therapeutic effects on atherosclerosis. HUVECs were first injured by H₂O₂ and then varying final concentrations of the Chinese herb extract were added. Effects of the XMJ extract on morphology, activity, monolayer permeability, biochemical indicators, cytokines, endothelial nitric oxide synthase (eNOS) protein content and eNOS gene expression in the HUVECs were analyzed. H₂O₂ significantly promoted HUVEC injury. The XMJ ultrafiltration extract significantly improved the morphological changes in the injured HUVECs. In addition, XMJ treatment increased cell activity and decreased monolayer permeability. The expression levels of intracellular adhesion molecule-1, vascular adhesion molecule-1, interleukin-1 and -6 and nuclear factor-κB decreased, while the expression levels of matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 increased with XMJ administration. Increased levels of nitric oxide (NO), eNOS protein and eNOS gene expression were also observed. Therefore, the XMJ ultrafiltration extract exhibits marked anti-inflammatory effects and antioxidant abilities. These properties significantly inhibited the H₂O₂-induced injury of HUVECs, which may be associated with the NO-cyclic guanosine monophosphate signaling pathway.