Venoms as a platform for human drugs: translating toxins into therapeutics

Cancer Chemotherapy via Natural Bioactive Compounds

BACKGROUND

Cancer-induced mortality is increasingly prevalent globally which skyrocketed the necessity to discover new/novel safe and effective anticancer drugs. Cancer is characterized by the continuous multiplication of cells in the human which is unable to control. Scientific research is drawing its attention towards naturally-derived bioactive compounds as they have fewer side effects compared to the current synthetic drugs used for chemotherapy.

OBJECTIVE

Drugs isolated from natural sources and their role in the manipulation of epigenetic markers in cancer are discussed briefly in this review article.

METHODS

With advancing medicinal plant biotechnology and microbiology in the past century, several anticancer phytomedicines were developed. Modern pharmacopeia contains at least 25% herbal-based remedy including clinically used anticancer drugs. These drugs mainly include the podophyllotoxin derivatives vinca alkaloids, curcumin, mistletoe plant extracts, taxanes, camptothecin, combretastatin, and others including colchicine, artesunate, homoharringtonine, ellipticine, roscovitine, maytanasin, tapsigargin,andbruceantin.

RESULTS

Compounds (psammaplin, didemnin, dolastin, ecteinascidin,and halichondrin) isolated from marine sources and animals such as microalgae, cyanobacteria, heterotrophic bacteria, invertebrates. They have been evaluated for their anticancer activity on cells and experimental animal models and used chemotherapy.Drug induced manipulation of epigenetic markers plays an important role in the treatment of cancer.

CONCLUSION

The development of a new drug from isolated bioactive compounds of plant sources has been a feasible way to lower the toxicity and increase their effectiveness against cancer. Potential anticancer therapeutic leads obtained from various ethnomedicinal plants, foods, marine, and microorganisms are showing effective yet realistically safe pharmacological activity. This review will highlight important plant-based bioactive compounds like curcumin, stilbenes, terpenes, other polyphenolic phyto-compounds, and structurally related families that are used to prevent/ ameliorate cancer. However, a contribution from all possible fields of science is still a prerequisite for discovering safe and effective anticancer drugs.

Snake Venomics: Fundamentals, Recent Updates, and a Look to the Next Decade

Venomic research, powered by techniques adapted from proteomics, transcriptomics, and genomics, seeks to unravel the diversity and complexity of venom through which knowledge can be applied in the treatment of envenoming, biodiscovery, and conservation. Snake venom proteomics is most extensively studied, but the methods varied widely, creating a massive amount of information which complicates data comparison and interpretation. Advancement in mass spectrometry technology, accompanied by growing databases and sophisticated bioinformatic tools, has overcome earlier limitations of protein identification. The progress, however, remains challenged by limited accessibility to samples, non-standardized quantitative methods, and biased interpretation of -omic data. Next-generation sequencing (NGS) technologies enable high-throughput venom-gland transcriptomics and genomics, complementing venom proteomics by providing deeper insights into the structural diversity, differential expression, regulation and functional interaction of the toxin genes. Venomic tissue sampling is, however, difficult due to strict regulations on wildlife use and transfer of biological materials in some countries. Limited resources for techniques and funding are among other pertinent issues that impede the progress of venomics, particularly in less developed regions and for neglected species. Genuine collaboration between international researchers, due recognition of regional experts by global organizations (e.g., WHO), and improved distribution of research support, should be embraced.

Somatostatin venom analogs evolved by fish-hunting cone snails: From prey capture behavior to identifying drug leads

Somatostatin (SS) is a peptide hormone with diverse physiological roles. By investigating a deep-water clade of fish-hunting cone snails, we show that predator-prey evolution has generated a diverse set of SS analogs, each optimized to elicit specific systemic physiological effects in prey. The increased metabolic stability, distinct SS receptor activation profiles, and chemical diversity of the venom analogs make them suitable leads for therapeutic application, including pain, cancer, and endocrine disorders. Our findings not only establish the existence of SS-like peptides in animal venoms but also serve as a model for the synergy gained from combining molecular phylogenetics and behavioral observations to optimize the discovery of natural products with biomedical potential.

Chemo-Selective Cys-Pen Disulfide for Proximity-Induced Cysteine Cross-Linking

Disulfide-rich architectures are valuable pharmacological tools or therapeutics. Besides, a ligand-induced conjugate strategy offers potential advantages in potency, selectivity, and duration of action for novel covalent drugs. Combining the plentiful disulfide-rich architecture library and ligand-induced conjugate via thiol-disulfide interchange would supply great benefits for developing site specific covalent inhibitors. Cysteine-cysteine (Cys-Cys) disulfide bonds are intrinsically unstable in endogenous reductive environment, while cysteine-penicillamine (Cys-Pen) disulfide bonds show satisfactory stability. We envisioned the Cys-Pen disulfide as a potential ligand-induced covalent bonding warhead, and this disulfide could reconstruct with the protein cysteine in the vicinity of the peptide binding site to form a new disulfide. To evaluate our design, protein PLCγ1-c src homology 2 domain and RGS3-PDZ domain were tested as models. Both proteins were successfully modified by Cys-Pen disulfide and formed new disulfides between proteins and peptides. The new disulfide was then analyzed to confirm it was a newly formed disulfide bond between Pen of the ligand and a protein Cys near the ligand binding site. HDAC4 was then chosen as a model by utilizing its "CXXC" domain near its catalytic pocket. The designed Cys-Pen cyclic peptide inhibitor of HDAC4 showed satisfactory selectivity and inhibitory effect.

Design and Ribosomal Incorporation of Noncanonical Disulfide-Directing Motifs for the Development of Multicyclic Peptide Libraries

The engineering of naturally occurring disulfide-rich peptides (DRPs) has been significantly hampered by the difficulty of manipulating disulfide pairing. New DRPs that take advantage of fold-directing motifs and noncanonical thiol-bearing amino acids are easy-to-fold with expected disulfide connectivities, representing a new class of scaffolds for the development of peptide ligands and therapeutics. However, the limited diversity of the scaffolds and particularly the use of noncanonical amino acids [e.g., penicillamine (Pen)] that are difficult to be translated by ribosomes greatly hamper the further development and application of these DRPs. Here, we designed and synthesized noncanonical bisthiol motifs bearing sterically obstructed thiol groups analogous to the Pen thiol to direct the folding of peptides into specific bicyclic and tricyclic structures. These bisthiol motifs can be ribosomally incorporated into peptides through a commercially available PURE system integrated with genetic code reprograming, which enables, for the first time, the in vitro expression of bicyclic peptides with two noncanonical and orthogonal disulfide bonds. We further constructed a bicyclic peptide library encoded by mRNA, with which new bicyclic peptide ligands with nanomolar affinity to proteins were successfully selected. Therefore, this study provides a new, general, and robust method for discovering de novo DRPs with new structures and functions not derived from natural peptides, which would greatly benefit the field of peptide drug discovery.

Antibacterial activities of two potential peptides extracted from Polistes wattii Cameron, 1900 (Vespidae: Polistinae) wasp venom collected at Eastern Province, Saudi Arabia

Alternatives of conventional antibiotics have become an urgent need to control drug-resistant bacteria. Therefore, search for new antibacterial agents has become a trend in several microbiological and pharmaceutical scientific works. Insects, one of the most successful and evolved species on earth is known to be an effective natural source of several medically useful chemicals including antibacterial agents. There is considerable evidence of using wasp venom against medical ailments in several parts of the world. In this work venom from Polistes wattii Cameron, 1900 collected from Eastern Province, Saudi Arabia was evaluated for its antibacterial activities. Such activity was tested against four pathogenic bacteria: two-gram positive Staphylococcus aureus (ATCC 25923) and Streptococcus mutans (RCMB 017(1) ATCC 25175) and two gram-negative (Salmonella typhimurium NCTC 12023 ATCC 14028 and Enterobacter cloacae (RCMB 001(1) ATCC 23355). Also, chemical characterization of wasp venom was done using HPLC and two isolated peptides were sequenced. The result indicates the potent anti-microbial effect of the venom against the four tested bacteria. The most sensitive bacteria were Staphylococcus aureus (ATCC 25923) and Streptococcus mutans (RCMB 017(1) ATCC 25175). The sequence of the two purified peptides indicates that they belong to mastoparan. The study results may pave way to use this wasp venom in future antibiotics especially in controlling skin infection by Staphylococcus aureus.

Harnessing the Natural Toxic Metabolites in COVID-19

SARS-CoV-2 is a novel coronavirus and the cause of the recent pandemic; it is an enveloped β-coronavirus. SARS-CoV-2 appear in the Wuhan City of China for the first time and outspread worldwide quickly. Due to its person-to-person fast transmission, COVID-19 is becoming a global problem. SARS-CoV-2 enter into cells by using ACE2 receptors that are numerous in the lungs and finally can cause acute respiratory distress syndrome (ARDS). Dry cough, sore throat, fever, body pain, headache, GIT discomfort, diarrhoea, and fatigue are some of the COVID-19 symptoms. There is no definite and certain treatment for disease caused by SARS-CoV-2 till now. Some pharmacological effects of toxins, toxoids, and venoms have been proven, and their effects on some diseases have been evaluated. This study aimed to investigate the role of toxins, toxoids, and venom in the pathophysiology of COVID-19 disease.

Therapeutic peptides: current applications and future directions

Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both chemical and biological methods, together with novel design and delivery strategies, which have helped to overcome the inherent drawbacks of peptides and have allowed the continued advancement of this field. A wide variety of natural and modified peptides have been obtained and studied, covering multiple therapeutic areas. This review summarizes the efforts and achievements in peptide drug discovery, production, and modification, and their current applications. We also discuss the value and challenges associated with future developments in therapeutic peptides.

Future Directions for the Discovery of Natural Product-Derived Immunomodulating Drugs

Drug discovery from natural sources is going through a renaissance, having spent many decades in the shadow of synthetic molecule drug discovery, despite the fact that natural product-derived compounds occupy a much greater chemical space than those created through synthetic chemistry methods. With this new era comes new possibilities, not least the novel targets that have emerged in recent times and the development of state-of-the-art technologies that can be applied to drug discovery from natural sources. Although progress has been made with some immunomodulating drugs, there remains a pressing need for new agents that can be used to treat the wide variety of conditions that arise from disruption, or over-activation, of the immune system; natural products may therefore be key in filling this gap. Recognising that, at present, there is no authoritative article that details the current state-of-the-art of the immunomodulatory activity of natural products, this in-depth review has arisen from a joint effort between the International Union of Basic and Clinical Pharmacology (IUPHAR) Natural Products and Immunopharmacology, with contributions from a Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation number of world-leading researchers in the field of natural product drug discovery, to provide a "position statement" on what natural products has to offer in the search for new immunomodulatory argents. To this end, we provide a historical look at previous discoveries of naturally occurring immunomodulators, present a picture of the current status of the field and provide insight into the future opportunities and challenges for the discovery of new drugs to treat immune-related diseases.

Isolation and characterization of five novel disulfide-poor conopeptides from Conus marmoreus venom

Background:

Conopeptides from cone snail venom have aroused great interest related to the discovery of novel bioactive candidates, due to their excellent prospects for the treatment of various health problems such as pain, addiction, psychosis and epilepsy. In order to explore novel biopeptides, we investigated the structure and function of five novel conopeptides isolated from the venom of Conus marmoreus from South China Sea.

Methods:

C. marmoreus crude venom was prepared, fractionated and purified by HPLC system. The primary sequences of the five novel disulfide-poor conopeptides Mr-1 to Mr-5 were identified by comprehensive analysis of de novo MALDI-TOF tandem mass spectrometry and Edman degradation data. In order to investigate their function, these five conopeptides were synthesized by Fmoc-SPPS chemistry, and their biological effects at several heterologous rat nicotinic acetylcholine receptor (nAChR) subtypes (α1β1δε, α3β2, α3β4, α4β2) were determined by electrophysiological technique.

Results:

Five novel disulfide-poor conopeptides were identified and named as follows: Mr-1 (DWEYHAHPKPNSFWT), Mr-2 (YPTRAYPSNKFG), Mr-3 (NVIQAPAQSVAPP NTST), Mr-4 [KENVLNKLKSK(L/I)] and Mr-5 [NAVAAAN(L/I)PG(L/I)V]. None of them contains a disulfide bond. The sequences of conopeptides Mr-2 to Mr-5 do not belong to any category of the known disulfide-poor conopeptides. No significant activity against the above nAChR subtypes were observed for the five conopeptides at 100 µM.

Conclusion:

We purified and structurally characterized five novel disulfide-poor conopeptides from C. marmoreus crude venom and first investigated their nAChR inhibitory effects. This work expanded our knowledge on the structure and function of disulfide-poor conopeptides from this cone snail venom.

Toxic Peptide From Palythoa caribaeorum Acting on the TRPV1 Channel Prevents Pentylenetetrazol-Induced Epilepsy in Zebrafish Larvae

PcActx peptide, identified from the transcriptome of zoantharian Palythoa caribaeorum, was clustered into the phylogeny of analgesic polypeptides from sea anemone Heteractis crispa (known as APHC peptides). APHC peptides were considered as inhibitors of transient receptor potential cation channel subfamily V member 1 (TRPV1). TRPV1 is a calcium-permeable channel expressed in epileptic brain areas, serving as a potential target for preventing epileptic seizures. Through in silico and in vitro analysis, PcActx peptide was shown to be a potential TRPV1 channel blocker. In vivo studies showed that the linear and oxidized PcActx peptides caused concentration-dependent increases in mortality of zebrafish larvae. However, monotreatment with PcActx peptides below the maximum tolerated doses (MTD) did not affect locomotor behavior. Moreover, PcActx peptides (both linear and oxidized forms) could effectively reverse pentylenetetrazol (PTZ)-induced seizure-related behavior in zebrafish larvae and prevent overexpression of c-fos and npas4a at the mRNA level. The excessive production of ROS induced by PTZ was markedly attenuated by both linear and oxidized PcActx peptides. It was also verified that the oxidized PcActx peptide was more effective than the linear one. In particular, oxidized PcActx peptide notably modulated the mRNA expression of genes involved in calcium signaling and γ-aminobutyric acid (GABA)ergic-glutamatergic signaling, including calb1, calb2, gabra1, grm1, gria1b, grin2b, gat1, slc1a2b, gad1b, and glsa. Taken together, PcActx peptide, as a novel neuroactive peptide, exhibits prominent anti-epileptic activity, probably through modulating calcium signaling and GABAergic-glutamatergic signaling, and is a promising candidate for epilepsy management.

Phyto-Phospholipid Conjugated Scorpion Venom Nanovesicles as Promising Carrier That Improves Efficacy of Thymoquinone against Adenocarcinoma Human Alveolar Basal Epithelial Cells

Lung cancer is a dangerous type of cancer in men and the third leading cause of cancer-related death in women, behind breast and colorectal cancers. Thymoquinone (THQ), a main compound in black seed essential oils, has a variety of beneficial effects, including antiproliferative, anti-inflammatory, and antioxidant properties. On the other hand, scorpion venom peptides (SV) induce apoptosis in the cancer cells, making it a promising anticancer agent. THQ, SV, and Phospholipon® 90H (PL) were incorporated in a nano-based delivery platform to assess THQ's cellular uptake and antiproliferative efficacy against a lung cancer cell line derived from human alveolar epithelial cells (A549). Several nanovesicles were prepared and optimized using factorial experimental design. The optimized phytosome formulation contained 79.0 mg of PL and 170.0 mg of SV, with vesicle size and zeta potential of 209.9 nm and 21.1 mV, respectively. The IC50 values revealed that A549 cells were significantly more sensitive to the THQ formula than the plain formula and THQ. Cell cycle analysis revealed that THQ formula treatment resulted in significant cell cycle arrest at the S phase, increasing cell population in this phase by 22.1%. Furthermore, the THQ formula greatly increased cell apoptosis (25.17%) when compared to the untreated control (1.76%), plain formula (11.96%), or THQ alone (13.18%). The results also indicated that treatment with THQ formula significantly increased caspase-3, Bax, Bcl-2, and p53 mRNA expression compared to plain formula and THQ. In terms of the inflammatory markers, THQ formula significantly reduced the activity of TNF-α and NF-κB in comparison with the plain formula and THQ only. Overall, the findings from the study proved that a phytosome formulation of THQ could be a promising therapeutic approach for the treatment of lung adenocarcinoma.

Novel Cysteine Protease Inhibitor Derived from the Haementeria vizottoi Leech: Recombinant Expression, Purification, and Characterization

Cathepsin L (CatL) is a lysosomal cysteine protease primarily involved in the terminal degradation of intracellular and endocytosed proteins. More specifically, in humans, CatL has been implicated in cancer progression and metastasis, as well as coronary artery diseases and others. Given this, the search for potent CatL inhibitors is of great importance. In the search for new molecules to perform proteolytic activity regulation, salivary secretions from hematophagous animals have been an important source, as they present protease inhibitors that evolved to disable host proteases. Based on the transcriptome of the Haementeria vizzotoi leech, the cDNA of Cystatin-Hv was selected for this study. Cystatin-Hv was expressed in Pichia pastoris and purified by two chromatographic steps. The kinetic results using human CatL indicated that Cystatin-Hv, in its recombinant form, is a potent inhibitor of this protease, with a K_i value of 7.9 nM. Consequently, the present study describes, for the first time, the attainment and the biochemical characterization of a recombinant cystatin from leeches as a potent CatL inhibitor. While searching out for new molecules of therapeutic interest, this leech cystatin opens up possibilities for the future use of this molecule in studies involving cellular and in vivo models.

State-of-the-art review - A review on snake venom-derived antithrombotics: Potential therapeutics for COVID-19-associated thrombosis?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent responsible for the Coronavirus Disease-2019 (COVID-19) pandemic, has infected over 185 million individuals across 200 countries since December 2019 resulting in 4.0 million deaths. While COVID-19 is primarily associated with respiratory illnesses, an increasing number of clinical reports indicate that severely ill patients often develop thrombotic complications that are associated with increased mortality. As a consequence, treatment strategies that target COVID-associated thrombosis are of utmost clinical importance. An array of pharmacologically active compounds from natural products exhibit effects on blood coagulation pathways, and have generated interest for their potential therapeutic applications towards thrombotic diseases. In particular, a number of snake venom compounds exhibit high specificity on different blood coagulation factors and represent excellent tools that could be utilized to treat thrombosis. The aim of this review is to provide a brief summary of the current understanding of COVID-19 associated thrombosis, and highlight several snake venom compounds that could be utilized as antithrombotic agents to target this disease.

Evolutionary physiology at 30+: Has the promise been fulfilled?: Advances in Evolutionary Physiology: Advances in Evolutionary Physiology

Three decades ago, interactions between evolutionary biology and physiology gave rise to evolutionary physiology. This caused comparative physiologists to improve their research methods by incorporating evolutionary thinking. Simultaneously, evolutionary biologists began focusing more on physiological mechanisms that may help to explain constraints on and trade-offs during microevolutionary processes, as well as macroevolutionary patterns in physiological diversity. Here we argue that evolutionary physiology has yet to reach its full potential, and propose new avenues that may lead to unexpected advances. Viewing physiological adaptations in wild animals as potential solutions to human diseases offers enormous possibilities for biomedicine. New evidence of epigenetic modifications as mechanisms of phenotypic plasticity that regulate physiological traits may also arise in coming years, which may also represent an overlooked enhancer of adaptation via natural selection to explain physiological evolution. Synergistic interactions at these intersections and other areas will lead to a novel understanding of organismal biology.

A non-lethal method for studying scorpion venom gland transcriptomes, with a review of potentially suitable taxa to which it can be applied

Scorpion venoms are mixtures of proteins, peptides and small molecular compounds with high specificity for ion channels and are therefore considered to be promising candidates in the venoms-to-drugs pipeline. Transcriptomes are important tools for studying the composition and expression of scorpion venom. Unfortunately, studying the venom gland transcriptome traditionally requires sacrificing the animal and therefore is always a single snapshot in time. This paper describes a new way of generating a scorpion venom gland transcriptome without sacrificing the animal, thereby allowing the study of the transcriptome at various time points within a single individual. By comparing these venom-derived transcriptomes to the traditional whole-telson transcriptomes we show that the relative expression levels of the major toxin classes are similar. We further performed a multi-day extraction using our proposed method to show the possibility of doing a multiple time point transcriptome analysis. This allows for the study of patterns of toxin gene activation over time a single individual, and allows assessment of the effects of diet, season and other factors that are known or likely to influence intraindividual venom composition. We discuss the gland characteristics that may allow this method to be successful in scorpions and provide a review of other venomous taxa to which this method may potentially be successfully applied.

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.

Current knowledge, challenges, new perspectives of the study, and treatments of Autism Spectrum Disorder

Over the past 70 years, the understanding of Autism Spectrum Disorder (ASD) improved greatly and is characterized as a heterogeneous neuropsychiatric syndrome. ASD is characterized by difficulties in social communication, restricted and repetitive behavior, interests, or activities. And it is often described as a combination of genetic predisposition and environmental factors. There are many treatments and approaches to ASD, including pharmacological therapies with antipsychotics, antidepressants, mood regulators, stimulants, and behavioral ones. However, no treatment is capable of reverting ASD. This review provides an overview of animal models of autism. We summarized genetic and environmental models and then valproic acid treatment as a useful model for ASD. As well as the main therapies and approaches used in the treatment, relating them to the neurochemical pathways altered in ASD, emphasizing the pharmacological potential of peptides and bioinspired compounds found in animal venoms as a possible future treatment for ASD.

A pain-causing and paralytic ant venom glycopeptide

Ants (Hymenoptera: Formicidae) are familiar inhabitants of most terrestrial environments. Although we are aware of the ability of many species to sting, knowledge of ant venom chemistry remains limited. Herein, we describe the discovery and characterization of an O-linked glycopeptide (Mg7a) as a major component of the venom of the ant Myrmecia gulosa. Electron transfer dissociation and higher-energy collisional dissociation tandem mass spectrometry were used to localize three α-N-acetylgalactosaminyl residues (α-GalNAc) present on the 63-residue peptide. To allow for functional studies, we synthesized the full-length glycosylated peptide via solid-phase peptide synthesis, combined with diselenide-selenoester ligation-deselenization chemistry. We show that Mg7a is paralytic and lethal to insects, and triggers pain behavior and inflammation in mammals, which it achieves through a membrane-targeting mode of action. Deglycosylation of Mg7a renders it insoluble in aqueous solution, suggesting a key solubilizing role of the O-glycans.

Paracelsus' legacy in the faunal realm: Drugs deriving from animal toxins

Given the vast number of venomous and poisonous animals, it is surprising that only relatively few animal-derived toxins have been explored and made their way into marketed drugs or are being investigated in ongoing clinical trials. In this review, we highlight marketed drugs deriving from animal toxins as well as ongoing clinical trials and preclinical investigations in the field. We emphasize that more attention should be paid to the rich supply of candidates that nature provides as valuable starting points for addressing serious unmet medical needs.

Scorpion-Derived Antiviral Peptides with a Special Focus on Medically Important Viruses: An Update

The global burden of viral infection, especially the current pandemics of SARS-CoV-2, HIV/AIDS, and hepatitis, is a very risky one. Additionally, HCV expresses the necessity for antiviral therapeutic elements. Venoms are known to contain an array of bioactive peptides that are commonly used in the treatment of various medical issues. Several peptides isolated from scorpion venom have recently been proven to possess an antiviral activity against several viral families. The aim of this review is to provide an up-to-date overview of scorpion antiviral peptides and to discuss their modes of action and potential biomedical application against different viruses.

An evolution-inspired strategy to design disulfide-rich peptides tolerant to extensive sequence manipulation

Natural disulfide-rich peptides (DRPs) are valuable scaffolds for the development of new bioactive molecules and therapeutics. However, there are only a limited number of topologically distinct DRP folds in nature, and most of them suffer from the problem of in vitro oxidative folding. Thus, strategies to design DRPs with new constrained topologies beyond the scope of natural folds are desired. Herein we report a general evolution-inspired strategy to design new DRPs with diverse disulfide frameworks, which relies on the incorporation of two cysteine residues and a random peptide sequence into a precursor disulfide-stabilized fold. These peptides can spontaneously fold in redox buffers to the expected tricyclic topologies with high yields. Moreover, we demonstrated that these DRPs can be used as templates for the construction of phage-displayed peptide libraries, enabling the discovery of new DRP ligands from fully randomized sequences. This study thus paves the way for the development of new DRP ligands and therapeutics with structures not derived from natural DRPs.

From Poison to Promise: The Evolution of Tetrodotoxin and Its Potential as a Therapeutic

Tetrodotoxin (TTX) is a potent neurotoxin that was first identified in pufferfish but has since been isolated from an array of taxa that host TTX-producing bacteria. However, determining its origin, ecosystem roles, and biomedical applications has challenged researchers for decades. Recognized as a poison and for its lethal effects on humans when ingested, TTX is primarily a powerful sodium channel inhibitor that targets voltage-gated sodium channels, including six of the nine mammalian isoforms. Although lethal doses for humans range from 1.5-2.0 mg TTX (blood level 9 ng/mL), when it is administered at levels far below LD₅₀, TTX exhibits therapeutic properties, especially to treat cancer-related pain, neuropathic pain, and visceral pain. Furthermore, TTX can potentially treat a variety of medical ailments, including heroin and cocaine withdrawal symptoms, spinal cord injuries, brain trauma, and some kinds of tumors. Here, we (i) describe the perplexing evolution and ecology of tetrodotoxin, (ii) review its mechanisms and modes of action, and (iii) offer an overview of the numerous ways it may be applied as a therapeutic. There is much to be explored in these three areas, and we offer ideas for future research that combine evolutionary biology with therapeutics. The TTX system holds great promise as a therapeutic and understanding the origin and chemical ecology of TTX as a poison will only improve its general benefit to humanity.

Therapeutic Inhibition of Acid Sensing Ion Channel 1a Recovers Heart Function After Ischemia-Reperfusion Injury

Background: Ischemia-reperfusion injury (IRI) is one of the major risk factors implicated in morbidity and mortality associated with cardiovascular disease. During cardiac ischemia, the build-up of acidic metabolites results in decreased intracellular and extracellular pH that can reach as low as 6.0-6.5. The resulting tissue acidosis exacerbates ischemic injury and significantly impacts cardiac function. Methods: We used genetic and pharmacological methods to investigate the role of acid sensing ion channel 1a (ASIC1a) in cardiac IRI at the cellular and whole organ level. Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) as well as ex vivo and in vivo models of IRI were used to test the efficacy of ASIC1a inhibitors as pre- and post-conditioning therapeutic agents. Results: Analysis of human complex trait genetics indicate that variants in the ASIC1 genetic locus are significantly associated with cardiac and cerebrovascular ischemic injuries. Using hiPSC-CMs in vitro and murine ex vivo heart models, we demonstrate that genetic ablation of ASIC1a improves cardiomyocyte viability after acute IRI. Therapeutic blockade of ASIC1a using specific and potent pharmacological inhibitors recapitulates this cardioprotective effect. We used an in vivo model of myocardial infarction (MI) and two models of ex vivo donor heart procurement and storage as clinical models to show that ASIC1a inhibition improves post-IRI cardiac viability. Use of ASIC1a inhibitors as pre- or post-conditioning agents provided equivalent cardioprotection to benchmark drugs, including the sodium-hydrogen exchange inhibitor zoniporide. At the cellular and whole organ level, we show that acute exposure to ASIC1a inhibitors has no impact on cardiac ion channels regulating baseline electromechanical coupling and physiological performance. Conclusions: Collectively, our data provide compelling evidence for a novel pharmacological strategy involving ASIC1a blockade as a cardioprotective therapy to improve the viability of hearts subjected to IRI.

Thallium-sensitive fluorescent assay reveals loperamide as a new inhibitor of the potassium channel Kv10.1

BACKGROUND

Ion channels have been proposed as therapeutic targets for different types of malignancies. One of the most studied ion channels in cancer is the voltage-gated potassium channel ether-à-go-go 1 or Kv10.1. Various studies have shown that Kv10.1 expression induces the proliferation of several cancer cell lines and in vivo tumor models, while blocking or silencing inhibits proliferation. Kv10.1 is a promising target for drug discovery modulators that could be used in cancer treatment. This work aimed to screen for new Kv10.1 channel modulators using a thallium influx-based assay.

METHODS

Pharmacological effects of small molecules on Kv10.1 channel activity were studied using a thallium-based fluorescent assay and patch-clamp electrophysiological recordings, both performed in HEK293 stably expressing the human Kv10.1 potassium channel.

RESULTS

In thallium-sensitive fluorescent assays, we found that the small molecules loperamide and amitriptyline exert a potent inhibition on the activity of the oncogenic potassium channel Kv10.1. These results were confirmed by electrophysiological recordings, which showed that loperamide and amitriptyline decreased the amplitude of Kv10.1 currents in a dose-dependent manner. Both drugs could be promising tools for further studies.

CONCLUSIONS

Thallium-sensitive fluorescent assay represents a reliable methodological tool for the primary screening of different molecules with potential activity on Kv10.1 channels or other K⁺ channels.

Neurotoxins in the venom gland of Calommata signata, a burrowing spider

Calommata signata, a burrowing spider, represents a special type of predation mode in spiders, and its utilization of toxins is different from that of web-weaving spiders and wandering spiders. The existing researches on spider toxins are mainly focused on the web-weaving and wandering spiders, but little attention on that of the burrowing spiders. Through transcriptome sequencing of C. signata venom gland and the remaining part as the counterpart tissue, 25 putative neurotoxin precursors were identified. These most neurotoxins were novel because their low similarities with the known sequences except for that of over 50% similarities in four neuropeptide toxins. The 25 neuropeptide toxins were divided into five families according to the constitution of cysteines for the possible disulfide bonds and the similarities of the deduced amino acid sequences. Besides neuropeptide toxins, other potential toxins in the venom gland were also analyzed. Unlike web-weaving spiders and wandering spiders, only a few neurotoxin genes were significantly expressed in the venom gland of C. signata. In the non-peptide toxin genes, only CsTryp_SPc-1, CsPA2-1, CsVa5-2 and four PDI genes were abundantly expressed in the venom gland. The present study provided an improved understanding on the spider toxin diversity and useful information for the exploitation of spider toxins.

Novel Anticancer and Treatment Sensitizing Compounds against Pancreatic Cancer

The isolation of chemical compounds from natural origins for medical application has played an important role in modern medicine with a range of novel treatments having emerged from various natural forms over the past decades. Natural compounds have been exploited for their antioxidant, antimicrobial and antitumor capabilities. Specifically, 60% of today's anticancer drugs originate from natural sources. Moreover, the combination of synthetic and natural treatments has shown applications for (i) reduced side effects, (ii) treatment sensitization and (iii) reduction in treatment resistance. This review aims to collate novel and natural compounds that are being explored for their preclinical anticancer, chemosensitizing and radiosensitizing effects on Pancreatic Ductal Adenocarcinoma (PDAC), which is a lethal disease with current treatments being inefficient and causing serve side effects. Two key points are highlighted by this work: (i) the availability of a range of natural compounds for potentially new therapeutic approaches for PDAC, (ii) potential synergetic impact of natural compounds with advanced chemo- and radio-therapeutic modalities for PDAC.

Advances in venom peptide drug discovery: where are we at and where are we heading?

Introduction: Animal venoms are a complex mixture of bioactive molecules that have evolved over millions of years for prey capture and defense from predators. Venom consists of many different types of molecules, with disulfide-rich peptides being a major component in most venoms. The study of these potent and highly selective molecules has led to the development of venom-derived drugs for diseases such as type 2 diabetes mellitus and chronic pain. As technologies have improved, more bioactive peptides have been discovered from venomous animals. Many of these molecules may have applications as tools for understanding normal and disease physiology, therapeutics, cosmetics or in agriculture.Areas covered: This article reviews venom-derived drugs approved by the FDA and venom-derived peptides currently in development. It discusses the challenges faced by venom-derived peptide drugs during drug development and the future for venom-derived peptides.Expert opinion: New techniques such as toxin driven discovery are expanding the pipeline of venom-derived peptides. There are many venom-derived peptides currently in preclinical and clinical trials that would have remained undiscovered using traditional approaches. A renewed focus on venoms, with advances in technology, will broaden the diversity of venom-derived peptide therapeutics and expand our knowledge of their molecular targets.

Localization and Bioreactivity of Cysteine-Rich Secretions in the Marine Gastropod Nucella lapillus

Marine biodiversity has been yielding promising novel bioproducts from venomous animals. Despite the auspices of conotoxins, which originated the paradigmatic painkiller Prialt, the biotechnological potential of gastropod venoms remains to be explored. Marine bioprospecting is expanding towards temperate species like the dogwhelk Nucella lapillus, which is suspected to secrete immobilizing agents through its salivary glands with a relaxing effect on the musculature of its preferential prey, Mytilus sp. This work focused on detecting, localizing, and testing the bioreactivity of cysteine-rich proteins and peptides, whose presence is a signature of animal venoms and poisons. The highest content of thiols was found in crude protein extracts from the digestive gland, which is associated with digestion, followed by the peribuccal mass, where the salivary glands are located. Conversely, the foot and siphon (which the gastropod uses for feeding) are not the main organs involved in toxin secretion. Ex vivo bioassays with Mytilus gill tissue disclosed the differential bioreactivity of crude protein extracts. Secretions from the digestive gland and peribuccal mass caused the most significant molecular damage, with evidence for the induction of apoptosis. These early findings indicate that salivary glands are a promising target for the extraction and characterization of bioactive cysteine-rich proteinaceous toxins from the species.

Immunological Responses to Envenomation

Venoms are complex mixtures of toxic compounds delivered by bite or sting. In humans, the consequences of envenomation range from self-limiting to lethal. Critical host defence against envenomation comprises innate and adaptive immune strategies targeted towards venom detection, neutralisation, detoxification, and symptom resolution. In some instances, venoms mediate immune dysregulation that contributes to symptom severity. This review details the involvement of immune cell subtypes and mediators, particularly of the dermis, in host resistance and venom-induced immunopathology. We further discuss established venom-associated immunopathology, including allergy and systemic inflammation, and investigate Irukandji syndrome as a potential systemic inflammatory response. Finally, this review characterises venom-derived compounds as a source of immune modulating drugs for treatment of disease.

Effects of pyrethroids on brain development and behavior: Deltamethrin

Deltamethrin (DLM) is a Type II pyrethroid pesticide widely used in agriculture, homes, public spaces, and medicine. Epidemiological studies report that increased pyrethroid exposure during development is associated with neurobehavioral disorders. This raises concern about the safety of these chemicals for children. Few animal studies have explored the long-term effects of developmental exposure to DLM on the brain. Here we review the CNS effects of pyrethroids, with emphasis on DLM. Current data on behavioral and cognitive effects after developmental exposure are emphasized. Although, the acute mechanisms of action of DLM are known, how these translate to long-term effects is only beginning to be understood. But existing data clearly show there are lasting effects on locomotor activity, acoustic startle, learning and memory, apoptosis, and dopamine in mice and rats after early exposure. The most consistent neurochemical findings are reductions in the dopamine transporter and the dopamine D1 receptor. The data show that DLM is developmentally neurotoxic but more research on its mechanisms of long-term effects is needed.

Animal Venoms-Curse or Cure?

An estimated 15% of animals are venomous, with representatives spread across the majority of animal lineages. Animals use venoms for various purposes, such as prey capture and predator deterrence. Humans have always been fascinated by venomous animals in a Janus-faced way. On the one hand, humans have a deeply rooted fear of venomous animals. This is boosted by their largely negative image in public media and the fact that snakes alone cause an annual global death toll in the hundreds of thousands, with even more people being left disabled or disfigured. Consequently, snake envenomation has recently been reclassified by the World Health Organization as a neglected tropical disease. On the other hand, there has been a growth in recent decades in the global scene of enthusiasts keeping venomous snakes, spiders, scorpions, and centipedes in captivity as pets. Recent scientific research has focussed on utilising animal venoms and toxins for the benefit of humanity in the form of molecular research tools, novel diagnostics and therapeutics, biopesticides, or anti-parasitic treatments. Continued research into developing efficient and safe antivenoms and promising discoveries of beneficial effects of animal toxins is further tipping the scales in favour of the “cure” rather than the “curse” prospect of venoms.

Trends in peptide drug discovery

Since the introduction of insulin almost a century ago, more than 80 peptide drugs have reached the market for a wide range of diseases, including diabetes, cancer, osteoporosis, multiple sclerosis, HIV infection and chronic pain. In this Perspective, we summarize key trends in peptide drug discovery and development, covering the early efforts focused on human hormones, elegant medicinal chemistry and rational design strategies, peptide drugs derived from nature, and major breakthroughs in molecular biology and peptide chemistry that continue to advance the field. We emphasize lessons from earlier approaches that are still relevant today as well as emerging strategies such as integrated venomics and peptide-display libraries that create new avenues for peptide drug discovery. We also discuss the pharmaceutical landscape in which peptide drugs could be particularly valuable and analyse the challenges that need to be addressed for them to reach their full potential.

Venom Use in Eulipotyphlans: An Evolutionary and Ecological Approach

Venomousness is a complex functional trait that has evolved independently many times in the animal kingdom, although it is rare among mammals. Intriguingly, most venomous mammal species belong to Eulipotyphla (solenodons, shrews). This fact may be linked to their high metabolic rate and a nearly continuous demand of nutritious food, and thus it relates the venom functions to facilitation of their efficient foraging. While mammalian venoms have been investigated using biochemical and molecular assays, studies of their ecological functions have been neglected for a long time. Therefore, we provide here an overview of what is currently known about eulipotyphlan venoms, followed by a discussion of how these venoms might have evolved under ecological pressures related to food acquisition, ecological interactions, and defense and protection. We delineate six mutually nonexclusive functions of venom (prey hunting, food hoarding, food digestion, reducing intra- and interspecific conflicts, avoidance of predation risk, weapons in intraspecific competition) and a number of different subfunctions for eulipotyphlans, among which some are so far only hypothetical while others have some empirical confirmation. The functions resulting from the need for food acquisition seem to be the most important for solenodons and especially for shrews. We also present several hypotheses explaining why, despite so many potentially beneficial functions, venomousness is rare even among eulipotyphlans. The tentativeness of many of the arguments presented in this review highlights our main conclusion, i.e., insights regarding the functions of eulipotyphlan venoms merit additional study.

Unraveling the structure and function of CdcPDE: A novel phosphodiesterase from Crotalus durissus collilineatus snake venom

This study reports the isolation, structural, biochemical, and functional characterization of a novel phosphodiesterase from Crotalus durissus collilineatus venom (CdcPDE). CdcPDE was successfully isolated from whole venom using three chromatographic steps and represented 0.7% of total protein content. CdcPDE was inhibited by EDTA and reducing agents, demonstrating that metal ions and disulfide bonds are necessary for its enzymatic activity. The highest enzymatic activity was observed at pH 8-8.5 and 37 °C. Kinetic parameters indicated a higher affinity for the substrate bis(p-nitrophenyl) phosphate compared to others snake venom PDEs. Its structural characterization was done by the determination of the protein primary sequence by Edman degradation and mass spectrometry, and completed by the building of molecular and docking-based models. Functional in vitro assays showed that CdcPDE is capable of inhibiting platelet aggregation induced by adenosine diphosphate in a dose-dependent manner and demonstrated that CdcPDE is cytotoxic to human keratinocytes. CdcPDE was recognized by the crotalid antivenom produced by the Instituto Butantan. These findings demonstrate that the study of snake venom toxins can reveal new molecules that may be relevant in cases of snakebite envenoming, and that can be used as molecular tools to study pathophysiological processes due to their specific biological activities.

Engineering of highly potent and selective HNTX-III mutant against hNav1.7 sodium channel for treatment of pain

Human voltage-gated sodium channel Na_v1.7 (hNa_v1.7) is involved in the generation and conduction of neuropathic and nociceptive pain signals. Compelling genetic and preclinical studies have validated that hNa_v1.7 is a therapeutic target for the treatment of pain; however, there is a dearth of currently available compounds capable of targeting hNav1.7 with high potency and specificity. Hainantoxin-III (HNTX-III) is a 33-residue polypeptide from the venom of the spider Ornithoctonus hainana. It is a selective antagonist of neuronal tetrodotoxin-sensitive voltage-gated sodium channels. Here, we report the engineering of improved potency and Na_v selectivity of hNa_v1.7 inhibition peptides derived from the HNTX-III scaffold. Alanine scanning mutagenesis showed key residues for HNTX-III interacting with hNa_v1.7. Site-directed mutagenesis analysis indicated key residues on hNa_v1.7 interacting with HNTX-III. Molecular docking was conducted to clarify the binding interface between HNTX-III and Nav1.7 and guide the molecular engineering process. Ultimately, we obtained H4 [K0G1-P18K-A21L-V] based on molecular docking of HNTX-III and hNa_v1.7 with a 30-fold improved potency (IC₅₀ 0.007 ± 0.001 μM) and >1000-fold selectivity against Na_v1.4 and Na_v1.5. H4 also showed robust analgesia in the acute and chronic inflammatory pain model and neuropathic pain model. Thus, our results provide further insight into peptide toxins that may prove useful in guiding the development of inhibitors with improved potency and selectivity for Na_v subtypes with robust analgesia.

Recombinant PaurTx-3, a spider toxin, inhibits sodium channels and decreases membrane excitability in DRG neurons

Voltage-gated sodium channels are critical for the generation and propagation of action potentials. Gating modifier toxins from spider venom can modulate the gating mechanism of sodium channels and thus have potential as drug leads. Here, we established expression of the gating modifier toxin PaurTx-3, a sodium channel inhibitor found in the venom of the spider Phrixotrichus auratus. Whole-cell voltage-clamp recordings indicated that recombinant PaurTx-3 (rPaurTx-3) inhibited Nav1.4, Nav1.5, and Nav1.7 currents with IC₅₀ values of 61 nM, 72 nM, and 25 nM, respectively. Furthermore, rPaurTx-3 irreversibly inhibited Nav1.7 currents, but had 60-70% recovery in Nav1.4 and Nav1.5 after washing with a bath solution. rPaurTx-3 also hyperpolarized the voltage-dependent steady-state inactivation curve and significantly slowed recovery from fast inactivation of Nav1.7. Current-clamp recordings showed that rPaurTx-3 suppressed small DRG neuron activity. The biological activity assay findings for rPaurTx-3 support its potent pharmacological effect in Nav1.7 and small DRG neurons.

Venom peptides in cancer therapy: An updated review on cellular and molecular aspects

Based on the high incidence and mortality rates of cancer, its therapy remains one of the most vital challenges in the field of medicine. Consequently, enhancing the efficacy of currently applied treatments and finding novel strategies are of great importance for cancer treatment. Venoms are important sources of a variety of bioactive compounds including salts, small molecules, macromolecules, proteins, and peptides that are defined as toxins. They can exhibit different pharmacological effects, and in recent years, their anti-tumor activities have gained significant attention. Several different compounds are responsible for the anti-tumor activity of venoms, and peptides are one of them. In the present review, we discuss the possible anti-tumor activities of venom peptides by highlighting molecular pathways and mechanisms through which these molecules can act effectively. Venom peptides can induce cell death in cancer cells and can substantially enhance the efficacy of chemotherapy and radiotherapy. Also, the venom peptides can mitigate the migration of cancer cells via suppression of angiogenesis and epithelial-to-mesenchymal transition. Notably, nanoparticles have been applied in enhancing the bioavailability of venom peptides and providing targeted delivery, thereby leading to their elevated anti-tumor activity and potential application for cancer therapy.

Venoms as an adjunctive therapy for Parkinson's disease: where are we now and where are we going?

Neurodegenerative diseases, including Parkinson's disease (PD), are increasing in the aging population. Crucially, neurodegeneration of dopaminergic neurons in PD is associated with chronic inflammation and glial activation. Besides this, bradykinesia, resting tremor, rigidity, sensory alteration, and cognitive and psychiatric impairments are also present in PD. Currently, no pharmacologically effective treatment alters the progression of the disease. Discovery and development of new treatment strategies remains a focus for ongoing investigations. For example, one approach is cell therapy to prevent dopaminergic neuronal loss or to slow PD progression. The neuroprotective role of a diverse range of natural products, including venoms from bees, scorpions, snakes and lizards, are also being tested in preclinical PD models and in humans. The main findings from recent studies that have investigated venoms as therapeutic options for PD are summarized in this special report.

Structure-Function of Neuronal Nicotinic Acetylcholine Receptor Inhibitors Derived From Natural Toxins

Neuronal nicotinic acetylcholine receptors (nAChRs) are prototypical cation-selective, ligand-gated ion channels that mediate fast neurotransmission in the central and peripheral nervous systems. nAChRs are involved in a range of physiological and pathological functions and hence are important therapeutic targets. Their subunit homology and diverse pentameric assembly contribute to their challenging pharmacology and limit their drug development potential. Toxins produced by an extensive range of algae, plants and animals target nAChRs, with many proving pivotal in elucidating receptor pharmacology and biochemistry, as well as providing templates for structure-based drug design. The crystal structures of these toxins with diverse chemical profiles in complex with acetylcholine binding protein (AChBP), a soluble homolog of the extracellular ligand-binding domain of the nAChRs and more recently the extracellular domain of human α9 nAChRs, have been reported. These studies have shed light on the diverse molecular mechanisms of ligand-binding at neuronal nAChR subtypes and uncovered critical insights useful for rational drug design. This review provides a comprehensive overview and perspectives obtained from structure and function studies of diverse plant and animal toxins and their associated inhibitory mechanisms at neuronal nAChRs.

Functional and Structural Variation among Sticholysins, Pore-Forming Proteins from the Sea Anemone Stichodactyla helianthus

Venoms constitute complex mixtures of many different molecules arising from evolution in processes driven by continuous prey-predator interactions. One of the most common compounds in these venomous cocktails are pore-forming proteins, a family of toxins whose activity relies on the disruption of the plasmatic membranes by forming pores. The venom of sea anemones, belonging to the oldest lineage of venomous animals, contains a large amount of a characteristic group of pore-forming proteins known as actinoporins. They bind specifically to sphingomyelin-containing membranes and suffer a conformational metamorphosis that drives them to make pores. This event usually leads cells to death by osmotic shock. Sticholysins are the actinoporins produced by Stichodactyla helianthus. Three different isotoxins are known: Sticholysins I, II, and III. They share very similar amino acid sequence and three-dimensional structure but display different behavior in terms of lytic activity and ability to interact with cholesterol, an important lipid component of vertebrate membranes. In addition, sticholysins can act in synergy when exerting their toxin action. The subtle, but important, molecular nuances that explain their different behavior are described and discussed throughout the text. Improving our knowledge about sticholysins behavior is important for eventually developing them into biotechnological tools.

Integrating Top-Down and Bottom-Up Mass Spectrometric Strategies for Proteomic Profiling of Iranian Saw-Scaled Viper, Echis carinatus sochureki, Venom

Saw-scaled or carpet vipers (genus Echis) are considered to cause a higher global snakebite mortality than any other snake. Echis carinatus sochureki (ECS) is a widely distributed snake species, also found across the thirteen provinces of Iran, where it is assumed to be responsible for the most snakebite envenomings. Here, we collected the Iranian specimens of ECS from three different geographically distinct populations, investigated food habits, and performed toxicity assessment and venom proteome profiling to better understand saw-scaled viper life. Our results show that the prey items most commonly found in all populations were arthropods, with scorpions from the family Buthidae particularly well represented. LD₅₀ (median lethal dose) values of the crude venom demonstrate highly comparable venom toxicities in mammals. Consistent with this finding, venom characterization via top-down and bottom-up proteomics, applied to both crude venoms and size-exclusion chromatographic fractions, revealed highly comparable venom compositions among the different populations. By combining all proteomics data, we identified 22 protein families from 102 liquid chromatography and tandem mass spectrometry (LC-MS/MS) raw files, including the most abundant snake venom metalloproteinases (SVMPs, 29-34%); phospholipase A2 (PLA2s, 26-31%); snake venom serine proteinases (SVSPs, 11-12%); l-amino acid oxidases (LAOs, 8-11%), C-type lectins/lectin-like (CTLs, 7-9%) protein families, and many newly detected ones, e.g., renin-like aspartic proteases (RLAPs), fibroblast growth factors (FGFs), peptidyl-prolyl cis-trans isomerases (PPIs), and venom vasodilator peptides (VVPs). Furthermore, we identified and characterized methylated, acetylated, and oxidized proteoforms relating to the PLA2 and disintegrin toxin families and the site of their modifications. It thus seems that post-translational modifications (PTMs) of toxins, particularly target lysine residues, may play an essential role in the structural and functional properties of venom proteins and might be able to influence the therapeutic response of antivenoms, to be investigated in future studies.

Cysteine-Rich Peptides: Hyperstable Scaffolds for Protein Engineering

Cysteine-rich peptides (CRPs) are small proteins of less than 100 amino acids in length characterized by the presence of disulfide bridges and common end-to-end macrocyclization. These properties confer hyperstability against high temperatures, salt concentration, serum presence, and protease degradation to CRPs. Moreover, their intercysteine domains (loops) are susceptible to residue hypervariability. CRPs have been successfully applied as stable scaffolds for molecular grafting, a protein engineering process in which cysteine-rich structures provide higher thermodynamic and metabolic stability to an epitope and acquire new biological function(s). This review describes the successes and limitations of seven cysteine-rich scaffolds, their bioactive epitopes, and the resulting grafted peptides.

Neuropeptide signalling systems - An underexplored target for venom drug discovery

Neuropeptides are signalling molecules mainly secreted from neurons that act as neurotransmitters or peptide hormones to affect physiological processes and modulate behaviours. In humans, neuropeptides are implicated in numerous diseases and understanding their role in physiological processes and pathologies is important for therapeutic development. Teasing apart the (patho)physiology of neuropeptides remains difficult due to ligand and receptor promiscuity and the complexity of the signalling pathways. The current approach relies on a pharmacological toolbox of agonists and antagonists displaying high selectivity for independent receptor subtypes, with the caveat that only few selective ligands have been discovered or developed. Animal venoms represent an underexplored source for novel receptor subtype-selective ligands that could aid in dissecting human neuropeptide signalling systems. Multiple endogenous-like neuropeptides as well as peptides acting on neuropeptide receptors are present in venoms. In this review, we summarise current knowledge on neuropeptides and discuss venoms as a source for ligands targeting neuropeptide signalling systems.

Animal toxins - Nature's evolutionary-refined toolkit for basic research and drug discovery

Venomous animals have evolved toxins that interfere with specific components of their victim's core physiological systems, thereby causing biological dysfunction that aids in prey capture, defense against predators, or other roles such as intraspecific competition. Many animal lineages evolved venom systems independently, highlighting the success of this strategy. Over the course of evolution, toxins with exceptional specificity and high potency for their intended molecular targets have prevailed, making venoms an invaluable and almost inexhaustible source of bioactive molecules, some of which have found use as pharmacological tools, human therapeutics, and bioinsecticides. Current biomedically-focused research on venoms is directed towards their use in delineating the physiological role of toxin molecular targets such as ion channels and receptors, studying or treating human diseases, targeting vectors of human diseases, and treating microbial and parasitic infections. We provide examples of each of these areas of venom research, highlighting the potential that venom molecules hold for basic research and drug development.

Venom of the Red-Bellied Black Snake Pseudechis porphyriacus Shows Immunosuppressive Potential

Venoms act with remarkable specificity upon a broad diversity of physiological targets. Venoms are composed of proteins, peptides, and small molecules, providing the foundation for the development of novel therapeutics. This study assessed the effect of venom from the red-bellied black snake (Pseudechis porphyriacus) on human primary leukocytes using bead-based flow cytometry, mixed lymphocyte reaction, and cell viability assays. We show that venom treatment had a significant immunosuppressive effect, inhibiting the secretion of interleukin (IL)-2 and tumor necrosis factor (TNF) from purified human T cells by 90% or greater following stimulation with mitogen (phorbol 12-myristate 13-acetate and ionomycin) or via cluster of differentiation (CD) receptors, CD3/CD28. In contrast, venom treatment did not inhibit TNF or IL-6 release from antigen-presenting cells stimulated with lipopolysaccharide. The reduced cytokine release from T cells was not associated with inhibition of T cell proliferation or reduction of cell viability, consistent with an anti-inflammatory mechanism unrelated to the cell cycle. Deconvolution of the venom using reverse-phase HPLC identified four fractions responsible for the observed immunosuppressive activity. These data suggest that compounds from P. porphyriacus venom may be potential drug leads for T cell-associated conditions such as graft versus host disease, rheumatoid arthritis, and inflammatory bowel disease.