Intraspecific variation in the venom of the vermivorous cone snail Conus vexillum

Cytotoxicity and apoptosis induction of the marine Conus flavidus venom in HepG2 cancer cell line

Cancer is still an area of continuous research for finding more effective and selective agents, so our study aimed to explore new anticancer medicines from Cone snails' venoms as marine natural products with promising biological activities. Venoms from seven cone snails collected from two locations on the Red Sea coast (Marsa Alam (Ma) and Hurghada (Hu)) were extracted and subjected to SDS for protein concentrations. The venoms of C. vexillum (Ma), C. vexillum (Hu), and C. flavidus were found to have the highest protein concentrations (2.66, 2.618, and 2.611 mg/mL, respectively). The venom of C. vexillum (Ma) was found to be cytotoxic against the lung cancer cell line A549 (IC50 = 4.511 ± 0.03 µg/mL). On the other hand, the venom of C. flavidus showed a strong cytotoxic effect on both liver and lung cancer cell lines (IC50 = 1.593 ± 0.05 and 7.836 ± 0.4 µg/mL, respectively) when compared to their normal cell lines. Investigating the apoptotic cell death of C. flavidus venom on HepG2 cell lines, it showed total apoptotic cell death by 22.42-fold compared to untreated control and arresting the cell cycle at G2/M phase. Furthermore, its apoptotic cell death in HepG2 cells was confirmed through the upregulation of pro-apoptotic markers and down-regulation of Bcl-2 in both gene and protein expression levels. These findings confirmed the cytotoxic activity of C. flavidus venom through apoptotic cell death in HepG2 cells. So, a detailed study highlighting its structure and molecular target for developing new anticancer agents from natural sources is required.Communicated by Ramaswamy H. Sarma.

Prospecting for candidate molecules from Conus virgo toxins to develop new biopharmaceuticals

Background

A combination of pharmacological and biomedical assays was applied in this study to examine the bioactivity of Conus virgo crude venom in order to determine the potential pharmacological benefit of this venom, and its in vivo mechanism of action.

Methods

Two doses (1/5 and 1/10 of LC₅₀, 9.14 and 4.57 mg/kg) of the venom were used in pharmacological assays (central and peripheral analgesic, anti-inflammatory and antipyretic), while 1/2 of LC₅₀ (22.85 mg/kg) was used in cytotoxic assays on experimental animals at different time intervals, and then compared with control and reference drug groups.

Results

The tail immersion time was significantly increased in venom-treated mice compared with the control group. Also, a significant reduction in writhing movement was recorded after injection of both venom doses compared with the control group. In addition, only the high venom concentration has a mild anti-inflammatory effect at the late inflammation stage. The induced pyrexia was also decreased significantly after treatment with both venom doses. On the other hand, significant increases were observed in lipid peroxidation (after 4 hours) and reduced glutathione contents and glutathione peroxidase activity, while contents of lipid peroxidation and nitric oxide (after 24 hours) and catalase activity were depleted significantly after venom administration.

Conclusion

These results indicated that the crude venom of Conus virgo probably contain bioactive components that have pharmacological activities with low cytotoxic effects. Therefore, it may comprise a potential lead compound for the development of drugs that would control pain and pyrexia.

Proteomic analysis of Red Sea Conus taeniatus venom reveals potential biological applications

Background:

Diverse and unique bioactive neurotoxins known as conopeptides or conotoxins are produced by venomous marine cone snails. Currently, these small and stable molecules are of great importance as research tools and platforms for discovering new drugs and therapeutics. Therefore, the characterization of Conus venom is of great significance, especially for poorly studied species.

Methods:

In this study, we used bioanalytical techniques to determine the venom profile and emphasize the functional composition of conopeptides in Conus taeniatus, a neglected worm-hunting cone snail.

Results:

The proteomic analysis revealed that 84.0% of the venom proteins were between 500 and 4,000 Da, and 16.0% were > 4,000 Da. In C. taeniatus venom, 234 peptide fragments were identified and classified as conotoxin precursors or non-conotoxin proteins. In this process, 153 conotoxin precursors were identified and matched to 23 conotoxin precursors and hormone superfamilies. Notably, the four conotoxin superfamilies T (22.87%), O1 (17.65%), M (13.1%) and O2 (9.8%) were the most abundant peptides in C. taeniatus venom, accounting for 63.40% of the total conotoxin diversity. On the other hand, 48 non-conotoxin proteins were identified in the venom of C. taeniatus. Moreover, several possibly biologically active peptide matches were identified, and putative applications of the peptides were assigned.

Conclusion:

Our study showed that the composition of the C. taeniatus-derived proteome is comparable to that of other Conus species and contains an effective mix of toxins, ionic channel inhibitors and antimicrobials. Additionally, it provides a guidepost for identifying novel conopeptides from the venom of C. taeniatus and discovering conopeptides of potential pharmaceutical importance.

The influence of ecological factors on cnidarian venoms

Venom research is often focussed on medical relevance, novel compounds and venom evolution, whilst studying the relationship between a venom and its environment – venom ecology - has been conducted to a lesser extent. Given the projected environmental changes envisioned to occur with global warming, it is pertinent now more than ever, to highlight this topic. Here we review literature examining the influence of ecological factors such as environmental temperature, salinity, ontogeny, geographic location and diet on cnidarian venoms. This review provides an exclusive focus on the cnidarian phylum and encompasses all available published, peer-reviewed literature to our knowledge regarding the ecological factors influencing venom. We find a startling lack of research into the effects of both environmental and biological factors on venoms, with very few to no studies available per category. Importantly, research does exist that suggest these ecological processes may influence other marine or terrestrial venoms, thus we recommend future research is needed to explore this concept in cnidarians.

•

Cnidarian toxins are significantly affected by environment and biology, yet literature on the subject is scarce.

•

Temperature, ontogeny, geographic location and diet can influence cnidarian venoms.

•

Salinity can influence other marine toxins, but literature is lacking for cnidarians.

•

More venom ecology research is needed in medically important species, if medical treatments are to advance.

Combined Proteotranscriptomic-Based Strategy to Discover Novel Antimicrobial Peptides from Cone Snails

Despite their impressive diversity and already broad therapeutic applications, cone snail venoms have received less attention as a natural source in the investigation of antimicrobial peptides than other venomous animals such as scorpions, spiders, or snakes. Cone snails are among the largest genera (Conus sp.) of marine invertebrates, with more than seven hundred species described to date. These predatory mollusks use their sophisticated venom apparatus to capture prey or defend themselves. In-depth studies of these venoms have unraveled many biologically active peptides with pharmacological properties of interest in the field of pain management, the treatment of epilepsy, neurodegenerative diseases, and cardiac ischemia. Considering sequencing efficiency and affordability, cone snail venom gland transcriptome analyses could allow the discovery of new, promising antimicrobial peptides. We first present here the need for novel compounds like antimicrobial peptides as a viable alternative to conventional antibiotics. Secondly, we review the current knowledge on cone snails as a source of antimicrobial peptides. Then, we present the current state of the art in analytical methods applied to crude or milked venom followed by how antibacterial activity assay can be implemented for fostering cone snail antimicrobial peptides studies. We also propose a new innovative profile Hidden Markov model-based approach to annotate full venom gland transcriptomes and speed up the discovery of potentially active peptides from cone snails.

Highlights of animal venom research on the geographical variations of toxin components, toxicities and envenomation therapy

Geographical variation of animal venom is common among venomous animals. This kind of intraspecific variation based on geographical location mainly concerned from envenomation cases and brought new problems in animal venom studies, including venom components regulatory mechanisms, differentiation of venom activities, and clinical treatment methods. At present, food is considered as the most related factor influencing venom development. Related research defined the variational venomous animal species by the comparison of venom components and activities in snakes, jellyfish, scorpions, cone snails, ants, parasitoid wasps, spiders and toads. In snake venom studies, researchers found that antivenom effectiveness was variated to different located venom samples. As described in some snake venom research, developing region-specific antivenom is the development trend. The difficulties of developing region-specific antivenom and theoretical solutions have been discussed. This review summarized biological studies of animal venom geographical variation by species, compared venom components and major biological activities of the vary venom from the same species, and listed the basic methods in comparing venom protein compositions and major toxicity differences to provide a comprehensive reference.

Wasp venomic: Unravelling the toxins arsenal of Polybia paulista venom and its potential pharmaceutical applications

Polybia paulista (Hymenoptera: Vespidae) is a neotropical social wasp from southeast Brazil. As most social Hymenoptera, venom from P. paulista comprises a complex mixture of bioactive toxins ranging from low molecular weight compounds to peptides and proteins. Several efforts have been made to elucidate the molecular composition of the P. paulista venom. Data derived from proteomic, peptidomic and allergomic analyses has enhanced our understanding of the whole envenoming process caused by the insect sting. The combined use of bioinformatics, -omics- and molecular biology tools have allowed the identification, characterization, in vitro synthesis and recombinant expression of several wasp venom toxins. Some of these P. paulista - derived bioactive compounds have been evaluated for the rational design of antivenoms and the improvement of allergy specific diagnosis and immunotherapy. Molecular characterization of crude venom extract has enabled the description and isolation of novel toxins with potential biotechnological applications. Here, we review the different approaches that have been used to unravel the venom composition of P. paulista. We also describe the main groups of P. paulista - venom toxins currently identified and analyze their potential in the development of component-resolved diagnosis of allergy, and in the rational design of antivenoms and novel bioactive drugs.

Variation in Venoms of Polybia Paulista Von Ihering and Polybia Occidentalis Olivier (Hymenoptera: Vespidae), Assessed by the FTIR-PAS Technique

Wasps are able to synthesize toxic compounds known as venoms, which form a part of a mechanism to overcome prey and also to defend their colonies. Study of the compounds that constitute these substances is essential in order to understand how this defense mechanism evolved, since there is evidence that the venoms can vary both intra- and interspecifically. Some studies have used liquid and gas chromatography as a reliable technique to analyze these compounds. However, the use of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) to analyze the variations in venom's chemical profile has been proposed recently. This study evaluated whether the FTIR-PAS technique is effective for assessing the role of environmental factors on intra- and interspecific differences in the venom of the wasps Polybia paulista Von Ihering and Polybia occidentalis Olivier by FTIR-PAS. The colonies were collected in three municipalities of Mato Grosso do Sul, Brazil, in different types of environments. The results showed that the venoms of P. paulista and P. occidentalis differed significantly in profile. In addition, the intraspecific differences in the venom's chemical profile of P. paulista are related to the type of environment where they nested, regardless of the geographical distance between the nests. The FTIR-PAS technique proved to be reliable and effective to evaluate the variations in the venom's chemical profile in social wasps.

Small Packages, Big Returns: Uncovering the Venom Diversity of Small Invertebrate Conoidean Snails

Venomous organisms used in research were historically chosen based on size and availability. This opportunity-driven strategy created a species bias in which snakes, scorpions, and spiders became the primary subjects of venom research. Increasing technological advancements have enabled interdisciplinary studies using genomics, transcriptomics, and proteomics to expand venom investigation to animals that produce small amounts of venom or lack traditional venom producing organs. One group of non-traditional venomous organisms that have benefitted from the rise of -omic technologies is the Conoideans. The Conoidean superfamily of venomous marine snails includes, the Terebridae, Turridae (s.l), and Conidae. Conoidea venom is used for both predation and defense, and therefore under strong selection pressures. The need for conoidean venom peptides to be potent and specific to their molecular targets has made them important tools for investigating cellular physiology and bioactive compounds that are beneficial to improving human health. A convincing case for the potential of Conoidean venom is made with the first commercially available conoidean venom peptide drug Ziconotide (Prialt®), an analgesic derived from Conus magus venom that is used to treat chronic pain in HIV and cancer patients. Investigation of conoidean venom using -omics technology provides significant insights into predator-driven diversification in biodiversity and identifies novel compounds for manipulating cellular communication, especially as it pertains to disease and disorders.

Evaluation of Ceiba pentandra (L.) Gaertner bark extracts for in vitro cytotoxicity on cancer cells and in vivo antitumor activity in solid and liquid tumor models

The stem bark of Ceiba pentandra (L.) Gaertner is claimed to be useful in the treatment of tumors in the southern part of India. This plant possesses a number of sesquiterpenoids and isoflavones which are known for their anticancer properties. The present study was designed to scientifically evaluate the cytotoxic potential of bark extracts in in vitro on Ehrlich ascites carcinoma (EAC), MCF-7 and B16F10 cells and in vivo in EAC (Liquid tumor) model and Dalton's lymphoma ascites (DLA or solid tumor) model. The bark was powdered and extracted successively with solvents viz., petroleum ether (PE), benzene, chloroform, acetone (AC), and ethyl alcohol in the sequential order of polarity. Cytotoxicity of dried extracts was screened on EAC cells by trypan blue assay. Three potent extracts namely petroleum ether, acetone, and ethanol were screened for their cytotoxicity on MCF-7 and B16F10 cells by MTT assay and nucleomorphological alteration by propidium iodide staining. Safe doses of these extracts were evaluated by acute toxicity study in mice. Extracts were found to be safe up to 300 mg/kg in acute toxicity study. Dosage of 1/10th and 1/20th of safe dose i.e., 15 and 30 mg/kg were selected for in vivo study. In the EAC model, both doses of the extracts showed a significant (P < 0.05) improvement in mean survival time and a maximum decline in tumor induced increase in body weight (an indirect measure of tumor weight) by the PE and AC treatment at 15 mg/kg compared to control. In the DLA-model, all extracts at both tested dose levels showed >50 % reduction in tumor weight and a significant reduction (P < 0.05) in tumor volume on the 30th day compared to control. It can be concluded that these extracts possess cytotoxic and antitumor activity.

The role of defensive ecological interactions in the evolution of conotoxins

Venoms comprise of complex mixtures of peptides evolved for predation and defensive purposes. Remarkably, some carnivorous cone snails can inject two distinct venoms in response to predatory or defensive stimuli, providing a unique opportunity to study separately how different ecological pressures contribute to toxin diversification. Here, we report the extraordinary defensive strategy of the Rhizoconus subgenus of cone snails. The defensive venom from this worm-hunting subgenus is unusually simple, almost exclusively composed of αD-conotoxins instead of the ubiquitous αA-conotoxins found in the more complex defensive venom of mollusc- and fish-hunting cone snails. A similarly compartmentalized venom gland as those observed in the other dietary groups facilitates the deployment of this defensive venom. Transcriptomic analysis of a Conus vexillum venom gland revealed the αD-conotoxins as the major transcripts, with lower amounts of 15 known and four new conotoxin superfamilies also detected with likely roles in prey capture. Our phylogenetic and molecular evolution analysis of the αD-conotoxins from five subgenera of cone snails suggests they evolved episodically as part of a defensive strategy in the Rhizoconus subgenus. Thus, our results demonstrate an important role for defence in the evolution of conotoxins.

Effects of geographical heterogeneity in species interactions on the evolution of venom genes

Geographical heterogeneity in the composition of biotic interactions can create a mosaic of selection regimes that may drive the differentiation of phenotypes that operate at the interface of these interactions. Nonetheless, little is known about effects of these geographical mosaics on the evolution of genes encoding traits associated with species interactions. Predatory marine snails of the family Conidae use venom, a cocktail of conotoxins, to capture prey. We characterized patterns of geographical variation at five conotoxin genes of a vermivorous species, Conus ebraeus, at Hawaii, Guam and American Samoa, and evaluated how these patterns of variation are associated with geographical heterogeneity in prey utilization. All populations show distinct patterns of prey utilization. Three 'highly polymorphic' conotoxin genes showed significant geographical differences in allelic frequency, and appear to be affected by different modes of selection among populations. Two genes exhibited low levels of diversity and a general lack of differentiation among populations. Levels of diversity of 'highly polymorphic' genes exhibit a positive relationship with dietary breadth. The different patterns of evolution exhibited by conotoxin genes suggest that these genes play different roles in prey capture, and that some genes are more greatly affected by differences in predator-prey interactions than others. Moreover, differences in dietary breadth appear to have a greater influence on the differentiation of venoms than differences in the species of prey.

Cone snail venomics: from novel biology to novel therapeutics

Peptide neurotoxins from cone snails called conotoxins are renowned for their therapeutic potential to treat pain and several neurodegenerative diseases. Inefficient assay-guided discovery methods have been replaced by high-throughput bioassays integrated with advanced MS and next-generation sequencing, ushering in the era of 'venomics'. In this review, we focus on the impact of venomics on the understanding of cone snail biology as well as the application of venomics to accelerate the discovery of new conotoxins. We also discuss the continued importance of medicinal chemistry approaches to optimize conotoxins for clinical use, with a descriptive case study of MrIA featured.

A 'conovenomic' analysis of the milked venom from the mollusk-hunting cone snail Conus textile--the pharmacological importance of post-translational modifications

Cone snail venoms provide a largely untapped source of novel peptide drug leads. To enhance the discovery phase, a detailed comparative proteomic analysis was undertaken on milked venom from the mollusk-hunting cone snail, Conus textile, from three different geographic locations (Hawai'i, American Samoa and Australia's Great Barrier Reef). A novel milked venom conopeptide rich in post-translational modifications was discovered, characterized and named α-conotoxin TxIC. We assign this conopeptide to the 4/7 α-conotoxin family based on the peptide's sequence homology and cDNA pre-propeptide alignment. Pharmacologically, α-conotoxin TxIC demonstrates minimal activity on human acetylcholine receptor models (100 μM, <5% inhibition), compared to its high paralytic potency in invertebrates, PD50 = 34.2 nMol kg(-1). The non-post-translationally modified form, [Pro](2,8)[Glu](16)α-conotoxin TxIC, demonstrates differential selectivity for the α3β2 isoform of the nicotinic acetylcholine receptor with maximal inhibition of 96% and an observed IC50 of 5.4 ± 0.5 μM. Interestingly its comparative PD50 (3.6 μMol kg(-1)) in invertebrates was ~100 fold more than that of the native peptide. Differentiating α-conotoxin TxIC from other α-conotoxins is the high degree of post-translational modification (44% of residues). This includes the incorporation of γ-carboxyglutamic acid, two moieties of 4-trans hydroxyproline, two disulfide bond linkages, and C-terminal amidation. These findings expand upon the known chemical diversity of α-conotoxins and illustrate a potential driver of toxin phyla-selectivity within Conus.

Systematic interrogation of the Conus marmoreus venom duct transcriptome with ConoSorter reveals 158 novel conotoxins and 13 new gene superfamilies

BACKGROUND

Conopeptides, often generically referred to as conotoxins, are small neurotoxins found in the venom of predatory marine cone snails. These molecules are highly stable and are able to efficiently and selectively interact with a wide variety of heterologous receptors and channels, making them valuable pharmacological probes and potential drug leads. Recent advances in next-generation RNA sequencing and high-throughput proteomics have led to the generation of large data sets that require purpose-built and dedicated bioinformatics tools for efficient data mining.

RESULTS

Here we describe ConoSorter, an algorithm that categorizes cDNA or protein sequences into conopeptide superfamilies and classes based on their signal, pro- and mature region sequence composition. ConoSorter also catalogues key sequence characteristics (including relative sequence frequency, length, number of cysteines, N-terminal hydrophobicity, sequence similarity score) and automatically searches the ConoServer database for known precursor sequences, facilitating identification of known and novel conopeptides. When applied to ConoServer and UniProtKB/Swiss-Prot databases, ConoSorter is able to recognize 100% of known conotoxin superfamilies and classes with a minimum species specificity of 99%. As a proof of concept, we performed a reanalysis of Conus marmoreus venom duct transcriptome and (i) correctly classified all sequences previously annotated, (ii) identified 158 novel precursor conopeptide transcripts, 106 of which were confirmed by protein mass spectrometry, and (iii) identified another 13 novel conotoxin gene superfamilies.

CONCLUSIONS

Taken together, these findings indicate that ConoSorter is not only capable of robust classification of known conopeptides from large RNA data sets, but can also facilitate de novo identification of conopeptides which may have pharmaceutical importance.

Conus vexillum venom induces oxidative stress in Ehrlich's ascites carcinoma cells: an insight into the mechanism of induction

BACKGROUND

It is estimated that venoms of marine cone snails (genus Conus) contain more than 100,000 different small peptides with a wide range of pharmacological and biological actions. Some of these peptides were developed into potential therapeutic agents and as molecular tools to understand biological functions of nervous and cardiovascular systems. In this study we examined the cytotoxic and anticancer properties of the marine vermivorous cone snail Conus vexillum (collected from Hurgada and Sharm El-Shaikh, Red Sea, Egypt) and suggest the possible mechanisms involved. The in vitro cytotoxic effects of Conus venom were assessed against Ehrlich's ascites carcinoma (EAC) cells.

RESULTS

Conus venom treatment resulted in concentration-dependent cytotoxicity as indicated by a lactate dehydrogenase leakage assay. Apoptotic effects were measured in vivo by measuring levels of reactive oxygen species and oxidative defense agents in albino mice injected with EAC cells. Conus venom (1.25 mg/kg) induced a significant increase (p < 0.05) in several oxidative stress biomarkers (lipid peroxidation, protein carbonyl content and reactive nitrogen intermediates) of EAC cells after 3, 6, 9 and 12 hours of venom injection. Conus venom significantly reduced (p < 0.05) the activities of oxidative defense enzymes (catalase and superoxide dismutase) as well as the total antioxidant capacity of EAC cells, as evidenced by lowered levels of reduced glutathione.

CONCLUSIONS

These results demonstrate the cytotoxic potential of C. vexillum venom by inducing oxidative stress mediated mechanisms in tumor cells and suggest that the venom contains novel molecules with potential anticancer activity.

Biochemical and electrophysiological characterization of two sea anemone type 1 potassium toxins from a geographically distant population of Bunodosoma caissarum

Sea anemone (Cnidaria, Anthozoa) venom is an important source of bioactive compounds used as tools to study the pharmacology and structure-function of voltage-gated K+ channels (KV). These neurotoxins can be divided into four different types, according to their structure and mode of action. In this work, for the first time, two toxins were purified from the venom of Bunodosoma caissarum population from Saint Peter and Saint Paul Archipelago, Brazil. Sequence alignment and phylogenetic analysis reveals that BcsTx1 and BcsTx2 are the newest members of the sea anemone type 1 potassium channel toxins. Their functional characterization was performed by means of a wide electrophysiological screening on 12 different subtypes of KV channels (KV1.1-KV1.6; KV2.1; KV3.1; KV4.2; KV4.3; hERG and Shaker IR). BcsTx1 shows a high affinity for rKv1.2 over rKv1.6, hKv1.3, Shaker IR and rKv1.1, while Bcstx2 potently blocked rKv1.6 over hKv1.3, rKv1.1, Shaker IR and rKv1.2. Furthermore, we also report for the first time a venom composition and biological activity comparison between two geographically distant populations of sea anemones.