Discovery of a selective NaV1.7 inhibitor from centipede venom with analgesic efficacy exceeding morphine in rodent pain models

Animal-derived peptides from Traditional Chinese medicines: medicinal potential, mechanisms, and prospects

ETHNOPHARMACOLOGICAL RELEVANCE

Animal-derived traditional Chinese medicines have a long-standing history in Chinese medicine, which exhibit unique efficacy due to similar structure and function with human tissue. As the major types of constituents that accounted for a relatively high proportion of animal-derived TCMs, peptides with molecular weight between 100 Da and hundreds of thousands of kDa have caught wide attention due to their outstanding bioavailability and excellent specificity.

AIM OF THE STUDY

This review aims to comprehensively delve into the up-to-date research progress in their pharmacology, mechanism, sequence composition, and therapeutic application, laying a solid foundation for future clinical treatment and scientific research.

MATERIALS AND METHODS

Relevant information on the peptides from animal-derived TCMs was collected from scientific literature databases including PubMed, CNKI, literature sources (Ph.D. and M.Sc. dissertations), and Web of Science by using the keywords "Peptides", "Animal", and "TCMs" for gradual screening in the past 30 years.

RESULTS

To date, the peptides from 27 kinds of animal-derived TCMs have been systematically combed. Their pharmacological activity and underlying mechanisms on multiple systems (nervous, circulatory, skeletal, and immune), as well as anti-tumor, antioxidative, and antimicrobial effects, have been sorted out. Besides, the potential safety issues and deficiencies (low bioavailability, imperfect quality management, and toxicity of raw materials) have also been pointed out.

CONCLUSIONS

Comprehensive analysis showed that low development and resource waste accompanied by the inadequate report about the pharmacological activity of most peptides from animal-derived TCMs make it have good research prospects. Although a breakthrough in the field of healthcare products has been made, the development potential for clinical products that bring surprising turnaround will be obtained if the above-mentioned confusions and current needs (improve identification technology and design reasonable dosage forms) are implemented.

Sibanin, a novel black fly-derived Kunitz protease inhibitor, prevents thrombus formation in mice by anticoagulation-antiplatelet duality

Most Kunitz inhibitors exhibit serine protease inhibitory activity, but limited information is available on the regulation of platelet function. Herein, we report the purification and characterization of a novel single Kunitz domain inhibitor (Sibanin) from the salivary glands of the black fly Simulium bannaense. Recombinant Sibanin prolonged activated partial thromboplastin time and prothrombin time, and exhibited high-affinity binding to FXa and elastase with a KD of 5.0 nM and 1.67 nM, respectively. Moreover, Sibanin also shows strong anti-inflammatory and analgesic functions, which would facilitate blood-feeding. Of note, Sibanin markedly suppressed platelet spreading and aggregation, as well as clot retraction. Further studies showed that Sibanin dose-dependently inhibited ADP-induced platelet aggregation by acting on the P2Y12 receptor and blocking its downstream PI3K/AKT/ERK signal pathway. Furthermore, Sibanin also suppressed collagen-induced platelet aggregation by blocking the glycoprotein VI (GPVI) receptor and attenuating the activation of RAP1 signaling pathways. In addition, Sibanin prevented FeCl3-induced arterial thrombosis and carrageenan-induced tail vein thrombosis in mice without inducing a bleeding tendency. Our findings provide new insights into the molecular and functional of Kunitz inhibitors, and will contribute to the understanding of the molecular mechanisms that mediate hematophagous lifestyle of Simulium bannaense.

How to Overcome a Snail? Identification of Putative Neurotoxins of Snail-Feeding Firefly Larvae (Coleoptera: Lampyridae, Lampyris noctiluca)

The larvae of some lampyrid beetles are highly specialized predators of snails. They have been observed to climb on the shells of their prey and use this exposed position to bite and inject secretions potentially originating from the midgut. Besides serving the purpose of extra-oral digestion (EOD), injected compounds also seem to have a paralyzing effect. Up to now, the toxins causing this paralyzing activity have not been identified. In the current study, we provide a first compositional analysis of the midgut secretion from lampyrid larvae, with a focus on identifying putative neurotoxins causing the observed paralyzing effect. For this purpose, we utilized a combined proteo-transcriptomic approach to characterize the compounds present in the midgut secretion of larval stages of Lampyris noctiluca. In terms of the absolute numbers of identified compounds, the midgut secretion is dominated by hydrolyzing enzymes comprising peptidases, carboxylesterases, and glycosidases. However, when considering expression levels, a few rather short cysteine-rich peptides exceed all other compounds. Some of these compounds show moderate similarity to putative neurotoxins identified in the venom of other arthropods and could be responsible for paralyzing effects. In addition to these potential toxins, we provide a list of peptides typical of the midgut secretion of L. noctiluca, supplemented by the corresponding precursor sequences.

Pathology of pain and its implications for therapeutic interventions

Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.

Isolation and structural identification of a potassium ion channel Kv4.1 inhibitor SsTx-P2 from centipede venom

OBJECTIVES

To isolate a potassium ion channel Kv4.1 inhibitor from centipede venom, and to determine its sequence and structure.

METHODS

Ion-exchange chromatography and reversed-phase high-performance liquid chromatography were performed to separate and purify peptide components of centipede venom, and their inhibiting effect on Kv4.1 channel was determined by whole-cell patch clamp recording. The molecular weight of isolated peptide Kv4.1 channel inhibitor was identified with matrix assisted laser desorption ionization-time-of-flight mass spectrometry; its primary sequence was determined by Edman degradation sequencing and two-dimensional mass spectrometry; its structure was established based on iterative thread assembly refinement online analysis.

RESULTS

A peptide SsTx-P2 was separated from centipede venom with the molecular weight of 6122.8, and its primary sequence consists of 53 amino acid residues NH2-ELTWDFVRTCCKLFPDKSECTKACATEFTGGDESRLKDVWPRKLRSGDSRLKD-OH. Peptide SsTx-P2 potently inhibited the current of Kv4.1 channel transiently transfected in HEK293 cell, with 1.0 μmol/L SsTx-P2 suppressing 95% current of Kv4.1 channel. Its structure showed that SsTx-P2 shared a conserved helical structure.

CONCLUSIONS

The study has isolated a novel peptide SsTx-P2 from centipede venom, which can potently inhibit the potassium ion channel Kv4.1 and displays structural conservation.

Wikstroemia indica (L.) C. A. Mey. Exerts analgesic activity by inhibiting NaV1.7 channel

ETHNOPHARMACOLOGICAL RELEVANCE

Wikstroemia indica (L.) C. A. Mey. is traditionally used for the treatment of gastrointestinal disorders, respiratory illnesses, skin infections, and inflammatory conditions. Despite extensive evidence of its biological potential, including antipyretic, antimicrobial, antifungal, anti-inflammatory, and diuretic properties, there are currently no reports indicating its analgesic effects.

AIM OF THE STUDY

Crude extracts from W. indica stems were examined for anti-nociceptive activity. Additionally, an in-depth investigation was conducted to uncover the molecular basis for the possible analgesic phenomenon.

MATERIALS AND METHODS

W. indica stems were subjected to ethanol extraction. To evaluate the in vivo analgesic activity, both chemical and physical-induced pain models were employed. Additionally, single-cell electrophysiological recordings were performed on human embryonic kidney 293T (HEK293T) cells expressing NaV1.7 channel.

RESULTS

Crude extracts derived from W. indica exhibited significant efficacy in mitigating the pain sensation, as evidenced by their substantial effects in both acetic acid-induced and heat-induced pain models. Further screening unveiled osthenol as a key bioactive compound responsible for mediating the analgesic properties of W. indica. Osthenol directly interacts with the pore domain of NaV1.7 channels, leading to channel inhibition. Importantly, this interaction is independent of any changes in the channel gating modifier domain.

CONCLUSION

Both W. indica and osthenol demonstrate potential as effective anti-nociceptive agents in preclinical studies. Their analgesic effects are likely achieved by inhibiting the NaV1.7 channel, which is crucial in pain initiation, transmission, and modulation. These results elucidate the molecular basis of the W. indica as a pain-relieving medication. Additionally, osthenol holds great potential in advancing the development of anti-nociceptive drugs targeting the NaV1.7 channel.

Coevolution with toxic prey produces functional trade-offs in sodium channels of predatory snakes

Seemingly unrelated traits often share the same underlying molecular mechanisms, potentially generating a pleiotropic relationship whereby selection shaping one trait can simultaneously compromise another. While such functional trade-offs are expected to influence evolutionary outcomes, their actual relevance in nature is masked by obscure links between genotype, phenotype, and fitness. Here, we describe functional trade-offs that likely govern a key adaptation and coevolutionary dynamics in a predator-prey system. Several garter snake (Thamnophis spp.) populations have evolved resistance to tetrodotoxin (TTX), a potent chemical defense in their prey, toxic newts (Taricha spp.). Snakes achieve TTX resistance through mutations occurring at toxin-binding sites in the pore of snake skeletal muscle voltage-gated sodium channels (NaV1.4). We hypothesized that these mutations impair basic NaV functions, producing molecular trade-offs that should ultimately scale up to compromised organismal performance. We investigate biophysical costs in two snake species with unique and independently evolved mutations that confer TTX resistance. We show electrophysiological evidence that skeletal muscle sodium channels encoded by toxin-resistant alleles are functionally compromised. Furthermore, skeletal muscles from snakes with resistance genotypes exhibit reduced mechanical performance. Lastly, modeling the molecular stability of these sodium channel variants partially explains the electrophysiological and muscle impairments. Ultimately, adaptive genetic changes favoring toxin resistance appear to negatively impact sodium channel function, skeletal muscle strength, and organismal performance. These functional trade-offs at the cellular and organ levels appear to underpin locomotor deficits observed in resistant snakes and may explain variation in the population-level success of toxin-resistant alleles across the landscape, ultimately shaping the trajectory of snake-newt coevolution.

Molecular mechanism by which spider-driving peptide potentiates coagulation factors

Hemostasis is a crucial process that quickly forms clots at injury sites to prevent bleeding and infections. Dysfunctions in this process can lead to hemorrhagic disorders, such as hemophilia and thrombocytopenia purpura. While hemostatic agents are used in clinical treatments, there is still limited knowledge about potentiators targeting coagulation factors. Recently, LCTx-F2, a procoagulant spider-derived peptide, was discovered. This study employed various methods, including chromogenic substrate analysis and dynamic simulation, to investigate how LCTx-F2 enhances the activity of thrombin and FXIIa. Our findings revealed that LCTx-F2 binds to thrombin and FXIIa in a similar manner, with the N-terminal penetrating the active-site cleft of the enzymes and the intermediate section reinforcing the peptide-enzyme connection. Interestingly, the C-terminal remained at a considerable distance from the enzymes, as evidenced by the retention of affinity for both enzymes using truncated peptide T-F2. Furthermore, results indicated differences in the bonding relationship of critical residues between thrombin and FXIIa, with His13 facilitating binding to thrombin and Arg7 being required for binding to FXIIa. Overall, our study sheds light on the molecular mechanism by which LCTx-F2 potentiates coagulation factors, providing valuable insights that may assist in designing drugs targeting procoagulation factors.

Mammalian neurotoxins, Blarina paralytic peptides, cause hyperpolarization of human T-type Ca channel hCav3.2 activation

Among the rare venomous mammals, the short-tailed shrew Blarina brevicauda has been suggested to produce potent neurotoxins in its saliva to effectively capture prey. Several kallikrein-like lethal proteases have been identified, but the active substances of B. brevicauda remained unclear. Here, we report Blarina paralytic peptides (BPPs) 1 and 2 isolated from its submaxillary glands. Synthetic BPP2 showed mealworm paralysis and a hyperpolarization shift (-11 mV) of a human T-type Ca2+ channel (hCav3.2) activation. The amino acid sequences of BPPs were similar to those of synenkephalins, which are precursors of brain opioid peptide hormones that are highly conserved among mammals. However, BPPs rather resembled centipede neurotoxic peptides SLPTXs in terms of disulfide bond connectivity and stereostructure. Our results suggested that the neurotoxin BPPs were the result of convergent evolution as homologs of nontoxic endogenous peptides that are widely conserved in mammals. This finding is of great interest from the viewpoint of the chemical evolution of vertebrate venoms.

Isolation and Characterization of Poeciguamerin, a Peptide with Dual Analgesic and Anti-Thrombotic Activity from the Poecilobdella manillensis Leech

When Poecilobdella manillensis attacks its prey, the prey bleeds profusely but feels little pain. We and other research teams have identified several anticoagulant molecules in the saliva of P. manillensis, but the substance that produces the paralyzing effect in P. manillensis is not known. In this study, we successfully isolated, purified, and identified a serine protease inhibitor containing an antistasin-like domain from the salivary secretions of P. manillensis. This peptide (named poeciguamerin) significantly inhibited elastase activity and slightly inhibited FXIIa and kallikrein activity, but had no effect on FXa, trypsin, or thrombin activity. Furthermore, poeciguamerin exhibited analgesic activity in the foot-licking and tail-withdrawal mouse models and anticoagulant activity in the FeCl₃-induced carotid artery thrombosis mouse model. In this study, poeciguamerin was found to be a promising elastase inhibitor with potent analgesic and antithrombotic activity for the inhibition of pain and thrombosis after surgery or in inflammatory conditions.

Antihepatoma peptide, scolopentide, derived from the centipede scolopendra subspinipes mutilans

BACKGROUND

Centipedes have been used to treat tumors for hundreds of years in China. However, current studies focus on antimicrobial and anticoagulation agents rather than tumors. The molecular identities of antihepatoma bioactive components in centipedes have not yet been extensively investigated. It is a challenge to isolate and characterize the effective components of centipedes due to limited peptide purification technologies for animal-derived medicines.

AIM

To purify, characterize, and synthesize the bioactive components with the strongest antihepatoma activity from centipedes and determine the antihepatoma mechanism.

METHODS

An antihepatoma peptide (scolopentide) was isolated and identified from the centipede scolopendra subspinipes mutilans using a combination of enzymatic hydrolysis, a Sephadex G-25 column, and two steps of high-performance liquid chromatography (HPLC). Additionally, the CCK8 assay was used to select the extracted fraction with the strongest antihepatoma activity. The molecular weight of the extracted scolopentide was characterized by quadrupole time of flight mass spectrometry (QTOF MS), and the sequence was matched by using the Mascot search engine. Based on the sequence and molecular weight, scolopentide was synthesized using solid-phase peptide synthesis methods. The synthetic scolopentide was confirmed by MS and HPLC. The antineoplastic effect of extracted scolopentide was confirmed by CCK8 assay and morphological changes again in vitro. The antihepatoma effect of synthetic scolopentide was assessed by the CCK8 assay and Hoechst staining in vitro and tumor volume and tumor weight in vivo. In the tumor xenograft experiments, qualified model mice (male 5-week-old BALB/c nude mice) were randomly divided into 2 groups (n = 6): The scolopentide group (0.15 mL/d, via intraperitoneal injection of synthetic scolopentide, 500 mg/kg/d) and the vehicle group (0.15 mL/d, via intraperitoneal injection of normal saline). The mice were euthanized by cervical dislocation after 14 d of continuous treatment. Mechanistically, flow cytometry was conducted to evaluate the apoptosis rate of HepG2 cells after treatment with extracted scolopentide in vitro. A Hoechst staining assay was also used to observe apoptosis in HepG2 cells after treatment with synthetic scolopentide in vitro. CCK8 assays and morphological changes were used to compare the cytotoxicity of synthetic scolopentide to liver cancer cells and normal liver cells in vitro. Molecular docking was performed to clarify whether scolopentide tightly bound to death receptor 4 (DR4) and DR5. qRT-PCR was used to measure the mRNA expression of DR4, DR5, fas-associated death domain protein (FADD), Caspase-8, Caspase-3, cytochrome c (Cyto-C), B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), x-chromosome linked inhibitor-of-apoptosis protein and Cellular fas-associated death domain-like interleukin-1β converting enzyme inhibitory protein in hepatocarcinoma subcutaneous xenograft tumors from mice. Western blot assays were used to measure the protein expression of DR4, DR5, FADD, Caspase-8, Caspase-3, and Cyto-C in the tumor tissues. The reactive oxygen species (ROS) of tumor tissues were tested.

RESULTS

In the process of purification, characterization and synthesis of scolopentide, the optimal enzymatic hydrolysis conditions (extract ratio: 5.86%, IC₅₀: 0.310 mg/mL) were as follows: Trypsin at 0.1 g (300 U/g, centipede-trypsin ratio of 20:1), enzymolysis temperature of 46 °C, and enzymolysis time of 4 h, which was superior to freeze-thawing with liquid nitrogen (IC₅₀: 3.07 mg/mL). A peptide with the strongest antihepatoma activity (scolopentide) was further purified through a Sephadex G-25 column (obtained A2) and two steps of HPLC (obtained B5 and C3). The molecular weight of the extracted scolopentide was 1018.997 Da, and the peptide sequence was RAQNHYCK, as characterized by QTOF MS and Mascot. Scolopentide was synthesized in vitro with a qualified molecular weight (1018.8 Da) and purity (98.014%), which was characterized by MS and HPLC. Extracted scolopentide still had an antineoplastic effect in vitro, which inhibited the proliferation of Eca-109 (IC₅₀: 76.27 μg/mL), HepG2 (IC₅₀: 22.06 μg/mL), and A549 (IC₅₀: 35.13 μg/mL) cells, especially HepG2 cells. Synthetic scolopentide inhibited the proliferation of HepG2 cells (treated 6, 12, and 24 h) in a concentration-dependent manner in vitro, and the inhibitory effects were the strongest at 12 h (IC₅₀: 208.11 μg/mL). Synthetic scolopentide also inhibited the tumor volume (Vehicle vs Scolopentide, P = 0.0003) and weight (Vehicle vs Scolopentide, P = 0.0022) in the tumor xenograft experiment. Mechanistically, flow cytometry suggested that the apoptosis ratios of HepG2 cells after treatment with extracted scolopentide were 5.01% (0 μg/mL), 12.13% (10 μg/mL), 16.52% (20 μg/mL), and 23.20% (40 μg/mL). Hoechst staining revealed apoptosis in HepG2 cells after treatment with synthetic scolopentide in vitro. The CCK8 assay and morphological changes indicated that synthetic scolopentide was cytotoxic and was significantly stronger in HepG2 cells than in L02 cells. Molecular docking suggested that scolopentide tightly bound to DR4 and DR5, and the binding free energies were-10.4 kcal/mol and-7.1 kcal/mol, respectively. In subcutaneous xenograft tumors from mice, quantitative real-time polymerase chain reaction and western blotting suggested that scolopentide activated DR4 and DR5 and induced apoptosis in SMMC-7721 Liver cancer cells by promoting the expression of FADD, caspase-8 and caspase-3 through a mitochondria-independent pathway.

CONCLUSION

Scolopentide, an antihepatoma peptide purified from centipedes, may inspire new antihepatoma agents. Scolopentide activates DR4 and DR5 and induces apoptosis in liver cancer cells through a mitochondria-independent pathway.

Bioactive peptides from scorpion venoms: therapeutic scaffolds and pharmacological tools

Evolution and natural selection have endowed animal venoms, including scorpion venoms, with a wide range of pharmacological properties. Consequently, scorpions, their venoms, and/or their body parts have been used since time immemorial in traditional medicines, especially in Africa and Asia. With respect to their pharmacological potential, bioactive peptides from scorpion venoms have become an important source of scientific research. With the rapid increase in the characterization of various components from scorpion venoms, a large number of peptides are identified with an aim of combating a myriad of emerging global health problems. Moreover, some scorpion venom-derived peptides have been established as potential scaffolds helpful for drug development. In this review, we summarize the promising scorpion venoms-derived peptides as drug candidates. Accordingly, we highlight the data and knowledge needed for continuous characterization and development of additional natural peptides from scorpion venoms, as potential drugs that can treat related diseases.

An Apriori Algorithm-Based Association Analysis of Analgesic Drugs in Chinese Medicine Prescriptions Recorded From Patients With Rheumatoid Arthritis Pain

Chronic pain, a common symptom of people with rheumatoid arthritis, usually behaves as persistent polyarthralgia pain and causes serious damage to patients' physical and mental health. Opioid analgesics can lead to a series of side effects like drug tolerance and addiction. Thus, seeking an alternative therapy and screening out the corresponding analgesic drugs is the key to solving the current dilemma. Traditional Chinese Medicine (TCM) therapy has been recognized internationally for its unique guiding theory and definite curative effect. In this study, we used the Apriori Algorithm to screen out potential analgesics from 311 cases that were treated with compounded medication prescription and collected from “Second Affiliated Hospital of Zhejiang Chinese Medical University” in Hangzhou, China. Data on 18 kinds of clinical symptoms and 16 kinds of Chinese herbs were extracted based on this data mining. We also found 17 association rules and screened out four potential analgesic drugs—“Jinyinhua,” “Wugong,” “Yiyiren,” and “Qingfengteng,” which were promised to help in the clinical treatment. Besides, combined with System Cluster Analysis, we provided several different herbal combinations for clinical references.

Bioactive Peptides and Proteins from Centipede Venoms

Venoms are a complex cocktail of biologically active molecules, including peptides, proteins, polyamide, and enzymes widely produced by venomous organisms. Through long-term evolution, venomous animals have evolved highly specific and diversified peptides and proteins targeting key physiological elements, including the nervous, blood, and muscular systems. Centipedes are typical venomous arthropods that rely on their toxins primarily for predation and defense. Although centipede bites are frequently reported, the composition and effect of centipede venoms are far from known. With the development of molecular biology and structural biology, the research on centipede venoms, especially peptides and proteins, has been deepened. Therefore, we summarize partial progress on the exploration of the bioactive peptides and proteins in centipede venoms and their potential value in pharmacological research and new drug development.

Centipede Venom: A Potential Source of Ion Channel Modulators

Centipedes are one of the most ancient and successful living venomous animals. They have evolved spooky venoms to deter predators or hunt prey, and are widely distributed throughout the world besides Antarctica. Neurotoxins are the most important virulence factor affecting the function of the nervous system. Ion channels and receptors expressed in the nervous system, including Na_V, K_V, Ca_V, and TRP families, are the major targets of peptide neurotoxins. Insight into the mechanism of neurotoxins acting on ion channels contributes to our understanding of the function of both channels and centipede venoms. Meanwhile, the novel structure and selective activities give them the enormous potential to be modified and exploited as research tools and biological drugs. Here, we review the centipede venom peptides that act on ion channels.

Shrew's venom quickly causes circulation disorder, analgesia and hypokinesia

Multiple representatives of eulipotyphlan mammals such as shrews have oral venom systems. Venom facilitates shrews to hunt and/or hoard preys. However, little is known about their venom composition, and especially the mechanism to hoard prey in comatose states for meeting their extremely high metabolic rates. A toxin (BQTX) was identified from venomous submaxillary glands of the shrew Blarinella quadraticauda. BQTX is specifically distributed and highly concentrated (~ 1% total protein) in the organs. BQTX shares structural and functional similarities to toxins from snakes, wasps and snails, suggesting an evolutional relevancy of venoms from mammalians and non-mammalians. By potentiating thrombin and factor-XIIa and inhibiting plasmin, BQTX induces acute hypertension, blood coagulation and hypokinesia. It also shows strong analgesic function by inhibiting elastase. Notably, the toxin keeps high plasma stability with a 16-h half-life in-vivo, which likely extends intoxication to paralyze or immobilize prey hoarded fresh for later consumption and maximize foraging profit.

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.

Antitussive effects of NaV 1.7 blockade in Guinea pigs

Our previous studies implicated the voltage-gated sodium channel subtype NaV 1.7 in the transmission of action potentials by the vagal afferent nerves regulating cough and thus identified this channel as a rational therapeutic target for antitussive therapy. But it is presently unclear whether a systemically administered small molecule inhibitor of NaV 1.7 conductance can achieve therapeutic benefit in the absence of side effects on cardiovascular function, gastrointestinal motility or respiration. To this end, we have evaluated the antitussive effects of the NaV 1.7 selective blocker Compound 801 administered systemically in awake guinea pigs or administered topically in anesthetized guinea pigs. We also evaluated the antitussive effects of ambroxol, a low affinity NaV blocker modestly selective for tetrodotoxin resistant NaV subtypes. Both Compound 801 and ambroxol dose-dependently inhibited action potential conduction in guinea pig vagus nerves (assessed by compound potential), with ambroxol nearly 100-fold less potent than the NaV 1.7 selective Compound 801 in this and other NaV 1.7-dependent guinea pig and human tissue-based assays. Both drugs also inhibited citric acid evoked coughing in awake or anesthetized guinea pigs, with potencies supportive of an NaV 1.7-dependent mechanism. Notably, however, the antitussive effects of systemically administered Compound 801 were accompanied by hypotension and respiratory depression. Given the antitussive effects of topically administered Compound 801, we speculate that the likely insurmountable side effects on blood pressure and respiratory drive associated with systemic dosing make topical formulations a viable and perhaps unavoidable therapeutic strategy for targeting NaV 1.7 in cough.

Venom peptides - A comprehensive translational perspective in pain management

Venom peptides have been evolving complex therapeutic interventions that potently and selectively modulate a range of targets such as ion channels, receptors, and signaling pathways of physiological processes making it potential therapeutic. Several venom peptides were deduced in vivo for clinical development targeting pain management, diabetes, cardiovascular diseases, antimicrobial activity. Several contributions have been detailed for a clear perspective for a better understanding of venomous animals, their venom, and their pharmacological effects. Here we unravel and summarize the recent advances in wide venom peptides across varieties of species for their therapeutics prospects.

Diversity and distribution of the large centipedes (Chilopoda: Scolopendromorpha) in the Phia Oac - Phia Den National Park, Vietnam

The scolopendromorph fauna of the Phia Oac - Phia Den National Park, northernmost Vietnam has been studied. As a result, a total of 17 species in eight genera and three families have been recorded in five different types of habitats (wood forest, bamboo forest, wood-bamboo mixed forest, pine forest, and grassland-shrubs) and from three elevation range (<1,000 m, 1,000–1,600 m, and >1,600 m). Scolopendridae is the most diverse family with nine recorded species. Of the five habitats, most species have been found in wood forests and wood-bamboo mixed forests (11 species each habitat), and at the elevation range of 1,000–1,600 m (15 species). The research also recommended that this number does not reflect the true biodiversity of this region; more intensive surveys are needed to have a better understanding of the scolopendromorph diversity in the Phia Oac - Phia Den National Park.

Identification and Characterization of Novel Proteins from Arizona Bark Scorpion Venom That Inhibit Nav1.8, a Voltage-Gated Sodium Channel Regulator of Pain Signaling

The voltage-gated sodium channel Nav1.8 is linked to neuropathic and inflammatory pain, highlighting the potential to serve as a drug target. However, the biophysical mechanisms that regulate Nav1.8 activation and inactivation gating are not completely understood. Progress has been hindered by a lack of biochemical tools for examining Nav1.8 gating mechanisms. Arizona bark scorpion (Centruroides sculpturatus) venom proteins inhibit Nav1.8 and block pain in grasshopper mice (Onychomys torridus). These proteins provide tools for examining Nav1.8 structure–activity relationships. To identify proteins that inhibit Nav1.8 activity, venom samples were fractioned using liquid chromatography (reversed-phase and ion exchange). A recombinant Nav1.8 clone expressed in ND7/23 cells was used to identify subfractions that inhibited Nav1.8 Na⁺ current. Mass-spectrometry-based bottom-up proteomic analyses identified unique peptides from inhibitory subfractions. A search of the peptides against the AZ bark scorpion venom gland transcriptome revealed four novel proteins between 40 and 60% conserved with venom proteins from scorpions in four genera (Centruroides, Parabuthus, Androctonus, and Tityus). Ranging from 63 to 82 amino acids, each primary structure includes eight cysteines and a “CXCE” motif, where X = an aromatic residue (tryptophan, tyrosine, or phenylalanine). Electrophysiology data demonstrated that the inhibitory effects of bioactive subfractions can be removed by hyperpolarizing the channels, suggesting that proteins may function as gating modifiers as opposed to pore blockers.

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.

Molecular sensors for temperature detection during behavioral thermoregulation in turtle embryos

Temperature sensing is essential for the survival of living organisms. Some reptile embryos can reposition themselves within the egg to seek optimal temperatures, but the molecular sensors involved in this temperature detection remain unknown. Here, we show that such thermotaxic behavior is directly determined by the activation of two heat-sensitive ion channels of the turtle: the transient receptor potential ankyrin 1 (MrTRPA1) and transient receptor potential vanilloid-1 (MrTRPV1). These two TRP channels were found to exhibit distinctive distributions among turtle dorsal root ganglion (DRG) neurons. Additionally, our laser irradiation assays illustrated that the heat activation thresholds of MrTRPA1 and MrTRPV1 are consistent with the mild (28-33°C) and noxious (>33°C) heat determined by behavioral tests, respectively. Further pharmacological studies have demonstrated that ligand-induced intervention of MrTRPA1 or MrTRPV1 is sufficient to mimic heat stimuli or block temperature signaling, causing changes in embryo movement. These findings indicate that the initiation of thermotaxic response in turtle embryos relies on a delicate functional balance between the heat activation of MrTRPA1 and MrTRPV1. Our study reveals, for the first time, a unique molecular mechanism underlying thermal detection: the two TRP channels act as a physiological tandem to control the thermotaxic behavior of turtle embryos.

A plant-derived TRPV3 inhibitor suppresses pain and itch

BACKGROUND AND PURPOSE

Itching is the most frequent pathology in dermatology that has significant impacts on people's mental health and social life. Transient receptor potential vanilloid 3 (TRPV3) channel is a promising target for treating pruritus. However, few selecetive and potent antagonists have been reported. This study was designed to identify selective TRPV3 antagonist and elucidate its anti-pruritus pharmacology.

EXPERIMENTAL APPROACH

FlexStation and calcium fluorescence imaging were conducted to track the functional compounds. Whole-cell patch clamp was used to record itch-related ion channel currents. Homologous recombination and site-directed mutagenesis were employed to construct TRPV3 channel chimeras and point mutations for exploring pharmacological mechanism. Mouse models were used for in vivo anti-pruritus assay.

KEY RESULTS

An acridone alkaloid (citrusinine-II) was purified and characterized from Atalantia monophylla. It directly interacts with Y564 within S4 helix of TRPV3 to selectively inhibit the channel with a half maximal inhibitory concentration (IC₅₀ ) of 12.43 μM. Citrusinine-II showed potential efficacy to attenuate both chronic and acute itch. Intradermal administration of citrusinine-II (143 ng/skin site) nearly completely inhibited itch behaviours. It also shows significant analgesic effects. Little side effects of the compound are observed.

CONCLUSION AND IMPLICATIONS

By acting as a selective and potent inhibitor of TRPV3 channel, citrusinine-II shows valuable therapeutic effects in pruritus animal models and is a promising candidate drug and/or lead molecule for the development of anti-pruritus drugs.

Trp: a conserved aromatic residue crucial to the interaction of a scorpion peptide with sodium channels

Anti-tumour-analgesic peptide (AGAP), one scorpion toxin purified from Buthus martensii Karsch, was known as its analgesic and anti-tumour activities. Trp38, a conserved aromatic residue of AGAP, might play important roles in its interaction with sodium channels. In this study, a mutant W38F was generated and effects of W38F were examined on hNav1.4, hNav1.5 and hNav1.7 by using whole-cell patch-clamp, which were closely associated to the biotoxicity of skeletal and cardiac muscles and pain signalling. The data showed that W38F decreased the inhibition effects of peak currents of hNav1.7, hNav1.4 and hNav1.5 compared with AGAP, notably, W38F reduced the analgesic activity compared with AGAP. The results suggested that Trp38 be a crucial amino acid involved in the interaction with these three sodium channels. The decreased analgesic activity of W38F might result from its much less inhibition of hNav1.7. These findings provided more information about the relationship between structure and function of AGAP and may facilitate the modification of other scorpion toxins with pharmacological effects.

The Pivotal Potentials of Scorpion Buthus Martensii Karsch-Analgesic-Antitumor Peptide in Pain Management and Cancer

Scorpion Buthus martensii Karsch -analgesic-antitumor peptide (BmK AGAP) has been used to treat diseases like tetanus, tuberculosis, apoplexy, epilepsy, spasm, migraine headaches, rheumatic pain, and cancer in China. AGAP is a distinctive long-chain scorpion toxin with a molecular mass of 7142 Da and composed of 66 amino acids cross-linked by four disulfide bridges. Voltage-gated sodium channels (VGSCs) are present in excitable membranes and partakes in essential roles in action potentials generation as compared to the significant function of voltage-gated calcium channels (VGCCs). A total of nine genes (Nav1.1-Nav1.9) have been recognized to encode practical sodium channel isoforms. Nav1.3, Nav1.7, Nav1.8, and Nav1.9 have been recognized as potential targets for analgesics. Nav1.8 and Nav1.9 are associated with nociception initiated by inflammation signals in the neuronal pain pathway, while Nav1.8 is fundamental for neuropathic pain at low temperatures. AGAP has a sturdy inhibitory influence on both viscera and soma pain. AGAP potentiates the effects of MAPK inhibitors on neuropathic as well as inflammation-associated pain. AGAP downregulates the secretion of phosphorylated p38, phosphorylated JNK, and phosphorylated ERK 1/2 in vitro. AGAP has an analgesic activity which may be an effective therapeutic agent for pain management because of its downregulation of PTX3 via NF-κB and Wnt/beta-catenin signaling pathway. In cancers like colon cancer, breast cancer, lymphoma, and glioma, rAGAP was capable of blocking the proliferation. Thus, AGAP is a promising therapy for these tumors. Nevertheless, research is needed with other tumors.

Heterodimeric Insecticidal Peptide Provides New Insights into the Molecular and Functional Diversity of Ant Venoms

Ants use venom for predation, defense, and communication; however, the molecular diversity, function, and potential applications of ant venom remains understudied compared to other venomous lineages such as arachnids, snakes and cone snails. In this work, we used a multidisciplinary approach that encompassed field work, proteomics, sequencing, chemical synthesis, structural analysis, molecular modeling, stability studies, and in vitro and in vivo bioassays to investigate the molecular diversity of the venom of the Amazonian Pseudomyrmex penetrator ants. We isolated a potent insecticidal heterodimeric peptide Δ-pseudomyrmecitoxin-Pp1a (Δ-PSDTX-Pp1a) composed of a 27-residue long A-chain and a 33-residue long B-chain cross-linked by two disulfide bonds in an antiparallel orientation. We chemically synthesized Δ-PSDTX-Pp1a, its corresponding parallel AA and BB homodimers, and its monomeric chains and demonstrated that Δ-PSDTX-Pp1a had the most potent insecticidal effects in blowfly assays (LD₅₀ = 3 nmol/g). Molecular modeling and circular dichroism studies revealed strong α-helical features, indicating its cytotoxic effects could derive from cell membrane pore formation or disruption. The native heterodimer was substantially more stable against proteolytic degradation (t _1/2 = 13 h) than its homodimers or monomers (t _1/2 < 20 min), indicating an evolutionary advantage of the more complex structure. The proteomic analysis of Pseudomyrmex penetrator venom and in-depth characterization of Δ-PSDTX-Pp1a provide novel insights in the structural complexity of ant venom and further exemplifies how nature exploits disulfide-bond formation and dimerization to gain an evolutionary advantage via improved stability, a concept that is highly relevant for the design and development of peptide therapeutics, molecular probes, and bioinsecticides.

Target switch of centipede toxins for antagonistic switch

Animal venoms are powerful, highly evolved chemical weapons for defense and predation. While venoms are used mainly to lethally antagonize heterospecifics (individuals of a different species), nonlethal envenomation of conspecifics (individuals of the same species) is occasionally observed. Both the venom and target specifications underlying these two forms of envenomation are still poorly understood. Here, we show a target-switching mechanism in centipede (Scolopendra subspinipes) venom. On the basis of this mechanism, a major toxin component [Ssm Spooky Toxin (SsTx)] in centipede venom inhibits the Shal channel in conspecifics but not in heterospecifics to cause short-term, recoverable, and nonlethal envenomation. This same toxin causes fatal heterospecific envenomation, for example, by switching its target to the Shaker channels in heterospecifics without inhibiting the Shaker channel of conspecific S. subspinipes individuals. These findings suggest that venom components exhibit intricate coevolution with their targets in both heterospecifics and conspecifics, which enables a single toxin to develop graded intraspecific and interspecific antagonistic interactions.

Conformation-Specific Blockade of αIIbβ3 by a Non-RGD Peptide to Inhibit Platelet Activation without Causing Significant Bleeding and Thrombocytopenia

Bleeding and thrombocytopenia to readministration are the most serious side effects of clinical integrin αIIbβ3 antagonists such as RGD-containing peptides. Here we show that a non-RGD peptide ZDPI, identified from skin secretions of Amolops loloensis, inhibited platelet aggregation induced by agonists, such as adenosine diphosphate, collagen, arachidonic acid, PAR1AP, and integrin αIIbβ3 allosteric activator, and reduces soluble fibrinogen binding to activated platelets without perturbing adhesion numbers on immobilized fibrinogen. Further study showed that ZDPI preferred to bind to the active conformation of integrin αIIbβ3, and thus inhibited c-Src-mediated integrin signaling transduction. In contrast to currently used clinical blockers of integrin αIIbβ3, which are all conformation-unspecific blockers, ZDPI conformation specifically binds to activated integrin αIIbβ3, subsequently suppressing platelet spreading. In vivo study revealed that ZDPI inhibited carotid arterial thrombosis with limited bleeding and thrombocytopenia. A non-RGD peptide which targets the active conformation of integrin αIIbβ3, such as ZDPI, might be an excellent candidate or template to develop antithrombotics without significant bleeding and thrombocytopenia side effects.

Comparative analysis of diverse toxins from a new pharmaceutical centipede, Scolopendra mojiangica

As the oldest venomous animals, centipedes use their venom as a weapon to attack prey and for protection. Centipede venom, which contains many bioactive and pharmacologically active compounds, has been used for centuries in Chinese medicine, as shown by ancient records. Based on comparative analysis, we revealed the diversity of and differences in centipede toxin-like molecules between Scolopendra mojiangica, a substitute pharmaceutical material used in China, and S. subspinipes mutilans. More than 6 000 peptides isolated from the venom were identified by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) and inferred from the transcriptome. As a result, in the proteome of S. mojiangica, 246 unique proteins were identified: one in five were toxin-like proteins or putative toxins with unknown function, accounting for a lower percentage of total proteins than that in S. mutilans. Transcriptome mining identified approximately 10 times more toxin-like proteins, which can characterize the precursor structures of mature toxin-like peptides. However, the constitution and quantity of the toxin transcripts in these two centipedes were similar. In toxicity assays, the crude venom showed strong insecticidal and hemolytic activity. These findings highlight the extensive diversity of toxin-like proteins in S. mojiangica and provide a new foundation for the medical-pharmaceutical use of centipede toxin-like proteins.

Venom-derived modulators of epilepsy-related ion channels

Epilepsy is characterised by spontaneous recurrent seizures that are caused by an imbalance between neuronal excitability and inhibition. Since ion channels play fundamental roles in the generation and propagation of action potentials as well as neurotransmitter release at a subset of excitatory and inhibitory synapses, their dysfunction has been linked to a wide variety of epilepsies. Indeed, these unique proteins are the major biological targets for antiepileptic drugs. Selective targeting of a specific ion channel subtype remains challenging for small molecules, due to the high level of homology among members of the same channel family. As a consequence, there is a growing trend to target ion channels with biologics. Venoms are the best known natural source of ion channel modulators, and venom peptides are increasingly recognised as potential therapeutics due to their high selectivity and potency gained through millions of years of evolutionary selection pressure. Here we describe the major ion channel families involved in the pathogenesis of various types of epilepsy, including voltage-gated Na⁺, K⁺, Ca²⁺ channels, Cys-loop receptors, ionotropic glutamate receptors and P2X receptors, and currently available venom-derived peptides that target these channel proteins. Although only a small number of venom peptides have successfully progressed to the clinic, there is reason to be optimistic about their development as antiepileptic drugs, notwithstanding the challenges associated with development of any class of peptide drug.

Spider venom-derived peptide induces hyperalgesia in Nav1.7 knockout mice by activating Nav1.9 channels

The sodium channels Na_v1.7, Na_v1.8 and Na_v1.9 are critical for pain perception in peripheral nociceptors. Loss of function of Na_v1.7 leads to congenital insensitivity to pain in humans. Here we show that the spider peptide toxin called HpTx1, first identified as an inhibitor of K_v4.2, restores nociception in Na_v1.7 knockout (Na_v1.7-KO) mice by enhancing the excitability of dorsal root ganglion neurons. HpTx1 inhibits Na_v1.7 and activates Na_v1.9 but does not affect Na_v1.8. This toxin produces pain in wild-type (WT) and Na_v1.7-KO mice, and attenuates nociception in Na_v1.9-KO mice, but has no effect in Na_v1.8-KO mice. These data indicate that HpTx1-induced hypersensitivity is mediated by Na_v1.9 activation and offers pharmacological insight into the relationship of the three Na_v channels in pain signalling.

Loss of function of Na_v1.7 leads to congenital insensitivity to pain in humans. Here the authors found that activation of Na_v1.9 can restore nociception in Na_v1.7 knockout mice, revealed by a venom-derived peptide as a probe.

Centipede Venom Peptides Acting on Ion Channels

Centipedes are among the oldest venomous arthropods that use their venom to subdue the prey. The major components of centipede venom are a variety of low-molecular-weight peptide toxins that have evolved to target voltage-gated ion channels to interfere with the central system of prey and produce pain or paralysis for efficient hunting. Peptide toxins usually contain several intramolecular disulfide bonds, which confer chemical, thermal and biological stability. In addition, centipede peptides generally have novel structures and high potency and specificity and therefore hold great promise both as diagnostic tools and in the treatment of human disease. Here, we review the centipede peptide toxins with reported effects on ion channels, including Nav, Kv, Cav and the nonselective cation channel polymodal transient receptor potential vanilloid 1 (TRPV1).

Discovery of aryl sulfonamide-selective Nav1.7 inhibitors with a highly hydrophobic ethanoanthracene core

Nav1.7 channels are mainly distributed in the peripheral nervous system. Blockade of Nav1.7 channels with small-molecule inhibitors in humans might provide pain relief without affecting the central nervous system. Based on the facts that many reported Nav1.7-selective inhibitors contain aryl sulfonamide fragments, as well as a tricyclic antidepressant, maprotiline, has been found to inhibit Nav1.7 channels, we designed and synthesized a series of compounds with ethanoanthracene and aryl sulfonamide moieties. Their inhibitory activity on sodium channels were detected with electrophysiological techniques. We found that compound 10o potently inhibited Nav1.7 channels stably expressed in HEK293 cells (IC₅₀ = 0.64 ± 0.30 nmol/L) and displayed a high Nav1.7/Nav1.5 selectivity. In mouse small-sized dorsal root ganglion neurons, compound 10o (10, 100 nmol/L) dose-dependently decreased the sodium currents and dramatically suppressed depolarizing current-elicited neuronal discharge. Preliminary in vivo experiments showed that compound 10o possessed good analgesic activity: in a mouse visceral pain model, administration of compound 10o (30−100 mg/kg, i.p.) effectively and dose-dependently suppressed acetic acid-induced writhing.

Neuropathic pain: preclinical and early clinical progress with voltage-gated sodium channel blockers

Introduction: Neuropathic pain is a chronic condition that significantly affects the quality of life of millions of people globally. Most of the pharmacologic treatments currently in use demonstrate modest efficacy and over half of all patients do not respond to medical management. Hence, there is a need for new, efficacious drugs. Evidence points toward voltage-gated sodium channels as a key target for novel analgesics.Area covered: The role of voltage-gated sodium channels in pain pathophysiology is illuminated and the preclinical and clinical data for new sodium channel blockers and toxin-derived lead compounds are examined. The expansion of approved sodium channel blockers is discussed along with the limitations of current research, trends in drug development, and the potential of personalized medicine.Expert opinion: The transition from preclinical to clinical studies can be difficult because of the inherent inability of animal models to express the complexities of pain states. Pain pathways are notoriously intricate and may be pharmacologically modulated at a variety of targets; it is unlikely that action at a single target could completely abolish a pain response because pain is rarely unifactorial. Combination therapy may be necessary and this could further confound the discovery of novel agents.

3'-Methoxydaidzein exerts analgesic activity by inhibiting voltage-gated sodium channels

Isoflavones are widely consumed by people around the world in the form of soy products, dietary supplements and drugs. Many isoflavones or related crude extracts have been reported to exert pain-relief activities, but the mechanism remains unclear. Voltage-gated sodium channels (VGSCs) play important roles in excitability of pain sensing neurons and many of them are important nociceptors. Here, we report that several isoflavones including 3'-methoxydaidzein (3MOD), genistein (GEN) and daidzein (DAI) show abilities to block VGSCs and thus to attenuate chemicals and heat induced acute pain or chronic constriction injury (CCI) induced pain hypersensitivity in mice. Especially, 3MOD shows strong analgesic potential without inducing addiction through inhibiting subtypes Na_V1.7, Na_V1.8 and Na_V1.3 with the IC₅₀ of 181 ± 14, 397 ± 26, and 505 ± 46 nmol·L^-1, respectively, providing a promising compound or parent structure for the treatment of pain pathologies. This study reveals a pain-alleviating mechanism of dietary isoflavones and may provide a convenient avenue to alleviate pain.

Parallel Evolution of Complex Centipede Venoms Revealed by Comparative Proteotranscriptomic Analyses

Centipedes are among the most ancient groups of venomous predatory arthropods. Extant species belong to five orders, but our understanding of the composition and evolution of centipede venoms is based almost exclusively on one order, Scolopendromorpha. To gain a broader and less biased understanding we performed a comparative proteotranscriptomic analysis of centipede venoms from all five orders, including the first venom profiles for the orders Lithobiomorpha, Craterostigmomorpha, and Geophilomorpha. Our results reveal an astonishing structural diversity of venom components, with 93 phylogenetically distinct protein and peptide families. Proteomically-annotated gene trees of these putative toxin families show that centipede venom composition is highly dynamic across macroevolutionary timescales, with numerous gene duplications as well as functional recruitments and losses of toxin gene families. Strikingly, not a single family is found in the venoms of representatives of all five orders, with 67 families being unique for single orders. Ancestral state reconstructions reveal that centipede venom originated as a simple cocktail comprising just four toxin families, with very little compositional evolution happening during the approximately 50 My before the living orders had diverged. Venom complexity then increased in parallel within the orders, with scolopendromorphs evolving particularly complex venoms. Our results show that even venoms composed of toxins evolving under the strong constraint of negative selection can have striking evolutionary plasticity on the compositional level. We show that the functional recruitments and losses of toxin families that shape centipede venom arsenals are not concentrated early in their evolutionary history, but happen frequently throughout.

The Latoia consocia Caterpillar Induces Pain by Targeting Nociceptive Ion Channel TRPV1

Accidental contact with caterpillar bristles causes local symptoms such as severe pain, intense heat, edema, erythema, and pruritus. However, there is little functional evidence to indicate a potential mechanism. In this study, we analyzed the biological characteristics of the crude venom from the larval stage of Latoia consocia living in South-West China. Intraplantar injection of the venom into the hind paws of mice induced severe acute pain behaviors in wild type (WT) mice; the responses were much reduced in TRPV1-deficit (TRPV1 KO) mice. The TRPV1-specific inhibitor, capsazepine, significantly attenuated the pain behaviors. Furthermore, the crude venom evoked strong calcium signals in the dorsal root ganglion (DRG) neurons of WT mice but not those of TRPV1 KO mice. Among the pain-related ion channels we tested, the crude venom only activated the TRPV1 channel. To better understand the venom components, we analyzed the transcriptome of the L. consocia sebaceous gland region. Our study suggests that TRPV1 serves as a primary nociceptor in caterpillar-induced pain and forms the foundation for elucidating the pain-producing mechanism.

Newly Discovered Action of HpTx3 from Venom of Heteropoda venatoria on Nav1.7 and Its Pharmacological Implications in Analgesia

It has been reported that Heteropodatoxin3 (HpTx3), a peptidic neurotoxin purified from the venom of the spider species Heteropoda venatoria, could inhibit K_v4.2 channels. Our present study newly found that HpTx3 also has potent and selective inhibitory action on Na_v1.7, with an IC₅₀ of 135.61 ± 12.98 nM. Without effect on the current–voltage (I-V) relationship of Na_v1.7, HpTx3 made minor alternation in the voltage-dependence of activation and steady-state inactivation of Na_v1.7 (4.15 mV and 7.29 mV, respectively) by interacting with the extracellular S3–S4 loop (S3b–S4 sequence) in domain II and the domain IV of the Na_v channel subtype, showing the characteristics of both pore blocker and gate modifier toxin. During the interaction of HpTx3 with the S3b–S4 sequence of Na_v1.7, the amino acid residue D in the sequence played a key role. When administered intraperitoneally or intramuscularly, HpTx3 displayed potent analgesic activity in a dose-dependent manner in different mouse pain models induced by formalin, acetic acid, complete Freund’s adjuvant, hot plate, or spared nerve injury, demonstrating that acute, inflammatory, and neuropathic pains were all effectively inhibited by the toxin. In most cases HpTx3 at doses of ≥ 1mg/kg could produce the analgesic effect comparable to that of 1 mg/kg morphine. These results suggest that HpTx3 not only can be used as a molecular probe to investigate ion channel function and pain mechanism, but also has potential in the development of the drugs that treat the Na_v1.7 channel-related pain.

C-fibers may modulate adjacent Aδ-fibers through axon-axon CGRP signaling at nodes of Ranvier in the trigeminal system

Background

Monoclonal antibodies (mAbs) towards CGRP or the CGRP receptor show good prophylactic antimigraine efficacy. However, their site of action is still elusive. Due to lack of passage of mAbs across the blood-brain barrier the trigeminal system has been suggested a possible site of action because it lacks blood-brain barrier and hence is available to circulating molecules. The trigeminal ganglion (TG) harbors two types of neurons; half of which store CGRP and the rest that express CGRP receptor elements (CLR/RAMP1).

Methods

With specific immunohistochemistry methods, we demonstrated the localization of CGRP, CLR, RAMP1, and their locations related to expression of the paranodal marker contactin-associated protein 1 (CASPR). Furthermore, we studied functional CGRP release separately from the neuron soma and the part with only nerve fibers of the trigeminal ganglion, using an enzyme-linked immunosorbent assay.

Results

Antibodies towards CGRP and CLR/RAMP1 bind to two different populations of neurons in the TG and are found in the C- and the myelinated Aδ-fibers, respectively, within the dura mater and in trigeminal ganglion (TG). CASPR staining revealed paranodal areas of the different myelinated fibers inhabiting the TG and dura mater. Double immunostaining with CASPR and RAMP1 or the functional CGRP receptor antibody (AA58) revealed co-localization of the two peptides in the paranodal region which suggests the presence of the CGRP-receptor. Double immunostaining with CGRP and CASPR revealed that thin C-fibers have CGRP-positive boutons which often localize in close proximity to the nodal areas of the CGRP-receptor positive Aδ-fibers. These boutons are pearl-like synaptic structures, and we show CGRP release from fibers dissociated from their neuronal bodies. In addition, we found that adjacent to the CGRP receptor localization in the node of Ranvier there was PKA immunoreactivity (kinase stimulated by cAMP), providing structural possibility to modify conduction activity within the Aδ-fibers.

Conclusion

We observed a close relationship between the CGRP containing C-fibers and the Aδ-fibers containing the CGRP-receptor elements, suggesting a point of axon-axon interaction for the released CGRP and a site of action for gepants and the novel mAbs to alleviate migraine.

Preparing biomedical students for the unknown: Some unusual challenges for students to help them understand the fundamentals of empirical research

Make teaching challenging again: a pedagogic approach to educate students on how to do science rather than learn about it.

Bottom-Up Proteomic Analysis of Polypeptide Venom Components of the Giant Ant Dinoponera Quadriceps

Ant species have specialized venom systems developed to sting and inoculate a biological cocktail of organic compounds, including peptide and polypeptide toxins, for the purpose of predation and defense. The genus Dinoponera comprises predatory giant ants that inoculate venom capable of causing long-lasting local pain, involuntary shaking, lymphadenopathy, and cardiac arrhythmias, among other symptoms. To deepen our knowledge about venom composition with regard to protein toxins and their roles in the chemical-ecological relationship and human health, we performed a bottom-up proteomics analysis of the crude venom of the giant ant D. quadriceps, popularly known as the "false" tocandiras. For this purpose, we used two different analytical approaches: (i) gel-based proteomics approach, wherein the crude venom was resolved by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and all protein bands were excised for analysis; (ii) solution-based proteomics approach, wherein the crude venom protein components were directly fragmented into tryptic peptides in solution for analysis. The proteomic data that resulted from these two methodologies were compared against a previously annotated transcriptomic database of D. quadriceps, and subsequently, a homology search was performed for all identified transcript products. The gel-based proteomics approach unequivocally identified nine toxins of high molecular mass in the venom, as for example, enzymes [hyaluronidase, phospholipase A1, dipeptidyl peptidase and glucose dehydrogenase/flavin adenine dinucleotide (FAD) quinone] and diverse venom allergens (homologous of the red fire ant Selenopsis invicta) and venom-related proteins (major royal jelly-like). Moreover, the solution-based proteomics revealed and confirmed the presence of several hydrolases, oxidoreductases, proteases, Kunitz-like polypeptides, and the less abundant inhibitor cysteine knot (ICK)-like (knottin) neurotoxins and insect defensin. Our results showed that the major components of the D. quadriceps venom are toxins that are highly likely to damage cell membranes and tissue, to cause neurotoxicity, and to induce allergic reactions, thus, expanding the knowledge about D. quadriceps venom composition and its potential biological effects on prey and victims.

Molecular game theory for a toxin-dominant food chain model

Animal toxins that are used to subdue prey and deter predators act as the key drivers in natural food chains and ecosystems. However, the predators of venomous animals may exploit feeding adaptation strategies to overcome toxins their prey produce. Much remains unknown about the genetic and molecular game process in the toxin-dominant food chain model. Here, we show an evolutionary strategy in different trophic levels of scorpion-eating amphibians, scorpions and insects, representing each predation relationship in habitats dominated by the paralytic toxins of scorpions. For scorpions preying on insects, we found that the scorpion α-toxins irreversibly activate the skeletal muscle sodium channel of their prey (insect, BgNa_V1) through a membrane delivery mechanism and an efficient binding with the Asp/Lys-Tyr motif of BgNa_V1. However, in the predatory game between frogs and scorpions, with a single point mutation (Lys to Glu) in this motif of the frog's skeletal muscle sodium channel (fNa_V1.4), fNa_V1.4 breaks this interaction and diminishes muscular toxicity to the frog; thus, frogs can regularly prey on scorpions without showing paralysis. Interestingly, this molecular strategy also has been employed by some other scorpion-eating amphibians, especially anurans. In contrast to these amphibians, the Asp/Lys-Tyr motifs are structurally and functionally conserved in other animals that do not prey on scorpions. Together, our findings elucidate the protein-protein interacting mechanism of a toxin-dominant predator-prey system, implying the evolutionary game theory at a molecular level.

µ-TRTX-Ca1a: a novel neurotoxin from Cyriopagopus albostriatus with analgesic effects

Human genetic and pharmacological studies have demonstrated that voltage-gated sodium channels (VGSCs) are promising therapeutic targets for the treatment of pain. Spider venom contains many toxins that modulate the activity of VGSCs. To date, only 0.01% of such spider toxins has been explored, and thus there is a great potential for discovery of novel VGSC modulators as useful pharmacological tools or potential therapeutics. In the current study, we identified a novel peptide, µ-TRTX-Ca1a (Ca1a), in the venom of the tarantula Cyriopagopus albostriatus. This peptide consisted of 38 residues, including 6 cysteines, i.e. IFECSISCEIEKEGNGKKCKPKKCKGGWKCKFNICVKV. In HEK293T or ND7/23 cells expressing mammalian VGSCs, this peptide exhibited the strongest inhibitory activity on Na_v1.7 (IC₅₀ 378 nM), followed by Na_v1.6 (IC₅₀ 547 nM), Na_v1.2 (IC₅₀ 728 nM), Na_v1.3 (IC₅₀ 2.2 µM) and Na_v1.4 (IC₅₀ 3.2 µM), and produced negligible inhibitory effect on Na_v1.5, Na_v1.8, and Na_v1.9, even at high concentrations of up to 10 µM. Furthermore, this peptide did not significantly affect the activation and inactivation of Na_v1.7. Using site-directed mutagenesis of Na_v1.7 and Na_v1.4, we revealed that its binding site was localized to the DIIS3-S4 linker region involving the D816 and E818 residues. In three different mouse models of pain, pretreatment with Cala (100, 200, 500 µg/kg) dose-dependently suppressed the nociceptive responses induced by formalin, acetic acid or heat. These results suggest that Ca1a is a novel neurotoxin against VGSCs and has a potential to be developed as a novel analgesic.

Chemical Synthesis, Proper Folding, Nav Channel Selectivity Profile and Analgesic Properties of the Spider Peptide Phlotoxin 1

Phlotoxin-1 (PhlTx1) is a peptide previously identified in tarantula venom (Phlogius species) that belongs to the inhibitory cysteine-knot (ICK) toxin family. Like many ICK-based spider toxins, the synthesis of PhlTx1 appears particularly challenging, mostly for obtaining appropriate folding and concomitant suitable disulfide bridge formation. Herein, we describe a procedure for the chemical synthesis and the directed sequential disulfide bridge formation of PhlTx1 that allows for a straightforward production of this challenging peptide. We also performed extensive functional testing of PhlTx1 on 31 ion channel types and identified the voltage-gated sodium (Na_v) channel Na_v1.7 as the main target of this toxin. Moreover, we compared PhlTx1 activity to 10 other spider toxin activities on an automated patch-clamp system with Chinese Hamster Ovary (CHO) cells expressing human Na_v1.7. Performing these analyses in reproducible conditions allowed for classification according to the potency of the best natural Na_v1.7 peptide blockers. Finally, subsequent in vivo testing revealed that intrathecal injection of PhlTx1 reduces the response of mice to formalin in both the acute pain and inflammation phase without signs of neurotoxicity. PhlTx1 is thus an interesting toxin to investigate Na_v1.7 involvement in cellular excitability and pain.

Novel Approaches to Persistent Pain Therapy

Persistent and neuropathic pain affects >15% of the global population. Apart from being an individual burden to the patient, persistent pain causes considerable subsequent costs in global healthcare systems. Despite the efforts of pharmaceutical companies to develop novel analgesics, pharmacological options for the therapy of persistent and/or neuropathic pain are limited. We discuss here novel approaches to persistent pain therapy that are independent of classical target-based drug discovery, focusing on individualized diagnostic technologies, improvement of existing therapies, and expansion of current pharmacological treatments and future techniques that may broaden pharmacological options for the individual treatment of persistent pain in patients.